Free cooling guide C O O L I N G I N T E G R AT I O N I N LO W ENERGY HOUSES
01 | 2013
Table of contents
1. Introduction to the concept of free cooling ...3 The need for cooling in low-energy houses.............4 Comfort and energy efficiency – the best fit for low-energy houses ............................................4 Investing for the future – the design of a low-energy house ...................................................5 2. Cooling loads in residential buildings .............6 Factors influencing the sensible cooling load ..........6 Factors influencing the latent cooling load .............7 The effect of shading ..............................................7 Room variation .......................................................8 Duration of the cooling load ..................................8 Required cooling capacity .......................................9 3. The ISO 7730 guidelines .................................10 Optimal temperature conditions............................10 Draught rate .........................................................11 Radiant asymmetry ...............................................11 Surface temperatures ............................................12 Vertical air temperature difference ........................12 4. Capacity and limitations of radiant emitter systems ..............................................13 Heat flux density...................................................13 Thermal transfer coefficient ..................................13 Dew point limitations ............................................13 Theoretical capacities of embedded radiant cooling ......................................................14 5. Ground heat exchangers .................................15 Ground conditions ................................................15 Ground heat exchangers .......................................16 Ground temperature profile...................................17 Primary supply temperatures.................................17 Dimensioning of ground heat exchangers for free cooling .....................................................17
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6. Free cooling in combination with different heat sources ....................................19 7. Choosing and dimensioning the radiant emitter system ................................................20 Capacity of different radiant emitter systems ........20 Radiant floor constructions and capacity ..............22 Radiant ceiling constructions and capacity ...........24 Capacity diagrams .................................................24 Regulation and control..........................................26 The self-regulating effect in underfloor heating ..27 Functional description of Uponor Control System .................................................................27 Component overview ............................................29 8. Uponor Pump and exchanger group (EPG6) for ground sourced free cooling.....................29 Dimensions ...........................................................30 Pump diagram.......................................................30 Control principle ...................................................31 Installation examples.............................................33 Operation of Uponor Climate Controller C-46 .......36 Operation mode of Uponor Climate Controller C-46 .....................................................36 Dew point management parameters and settings .................................................................37 Heating and cooling change-over: external signal .......................................................38 Heating and cooling change-over: Uponor Climate Controller C-46 ............................38
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1. Introduction to the concept of free cooling
Free cooling is a term generally used when low external temperatures are used for cooling purposes in buildings. This guide presents a free cooling concept based on a ground coupled heat exchanger combined with a radiant heating and cooling system. A ground coupled heat exchanger can for example be horizontal collectors, vertical boreholes or energy cages. A radiant system means that the floors, ceilings or walls have embedded pipes in which water is circulated for heating and cooling of the building. Under floor heating and cooling is the most well know example of a radiant system. A radiant system combined with a ground coupled heat exchanger is highly energy efficient and has several advantages. In the summer period, the ground coupled heat exchanger provides cooling temperatures that are
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lower compared to the outside air. The radiant system operates with large surfaces, which means it can utilize the temperatures from the ground directly for cooling purposes. The result is that free cooling can be provided with only cost being the electricity required for running the circulation pumps in the brine and water systems. No heat pump is required. In the heating season the system is operated using a heat pump. As the ground temperature during winter is higher compared to the outside air temperature, the result is improved heat pump efficiency (COP) compared to an air based heat pump. In addition, the radiant emitter a system (under floor heating) operates at moderate water temperatures in large surfaces which further improves the heat pump COP.
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The need for cooling in lowenergy houses Today, there is a high focus on saving energy and utilising renewable energy sources in buildings. The energy demand for space heating is reduced by increased insulation and tightness of buildings. However, increased insulation and tightness also increase the cooling demand. The building becomes more sensitive to solar radiation through windows and becomes less able to remove heat in the summer. More extreme weather conditions further contributes to the cooling needs and together with an even more increased consumer awareness of having the right indoor climate, the need for cooling also in residential buildings will become a requirement. Optimal architectural design and shading will help to reduce the cooling need, but
Comfort and energy efficiency – the best fit for low-energy houses Using shading will help to reduce the cooling demand. However, this forces occupants to actively pull down the shades e.g. when leaving the house. Also, shading will block daylight which increases electricity consumption on artificial light, and shading will block the view which may not be in the interest of the home occupant. In fact many architects state that energy efficiency and comfort may conflict when defining comfort in a broader sense, such as the freedom to design window sizes, spaciousness with increased ceiling height, daylight requirements and the occupant’s tendency to utilise open doors and windows. All such requirements put increased demands on the HVAC applications. Ground heat exchangers combined with radiant systems is the only “all-in-one” solution, with the ability to provide both heating and cooling. Such systems are more cost efficient and simpler to install than having to deal with a separate heating and cooling systems.
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simulations and practical experience show that such measures alone will not eliminate the cooling need. Space cooling is needed, not only in the summer, but also in prolonged periods during spring and autumn when the low angel of the sun gives high solar radiation through windows. In order to meet the energy frame requirements of the building regulations, space cooling can be provided by utilising renewable energy sources such as ground heat exchangers for cooling purposes in conjunction with a radiant system with embedded pipes in the floor, wall or ceiling. Cooling needs will differ between rooms and are highly influenced by direct solar radiation. Rooms with larger window areas and facing the south will generally have higher cooling requirements. In periods with high cooling loads, active cooling is normally required during both day and night time.
Furthermore, radiant systems are able to heat at a low supply temperature and cool at a high supply temperature. This fits perfectly to the typical operating temperatures of a ground coupled heat exchanger. Furthermore, the connected heat pump will be able to run more efficiently and thereby consume less electricity. In addition, a radiant system provides no draught problems and provides an optimal temperature distribution inside a room. Last but not least, radiant systems provide complete freedom in terms of interior design, as no physical space is occupied inside the room. Even more important when looking at the lifetime and property value of a house, such systems have very low maintenance need and a lifetime that almost follows the lifetime of the building itself. In today’s uncertain environment of future energy prices, free cooling and ground coupled heat pumps provides a high stability on the future energy costs of the building in question. It will most certainly meet today’s and future building regulations even in a scenario where future property taxation would be linked to energy efficiency. Hence, it is an investment that helps to maintain and differentiate the future property value.
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Investing for the future – the design of a low-energy house A radiant system, e.g. underfloor heating and cooling, coupled to a ground source heat pump, provides optimal comfort with high energy efficiency both summer and winter. In addition, due to the increased tightness requirements in low-energy houses, a ventilation system is necessary to maintain an acceptable indoor air quality. In order to keep the ventilation system energy efficient, it should be coupled to a heat recovery ventilation (HRV) unit to minimise heat losses through the air exchange.
Energy sources for cooling There are several alternative HVAC applications available for cooling purposes. A district heating connection is an energy efficient option for space heating, but cannot be used for cooling purposes. Alternative means of cooling could be an air-to-water heat pump, but no “free cooling” can be extracted from such a system, hence cooling can only be provided with the heat pump running causing a higher electricity consumption. Purely air-based systems like split units can also act as a cooling system but as can be seen from the picture below, the efficiency is considerably lower than for water-based cooling systems.
DKK/m2
25
20
Energy class
15
Correlation between average property m2 prices and energy class 10
The figure above shows the correlation between property prices and the energy efficiency level of the property in Denmark. Properties with energy class A or B are on average 6% more expensive than energy class C and 17% more expensive than energy class D.
5
0
Air to air heat pump
Air to water heat pump
Brine to water heat pump
Free cooling
European seasonal energy efficiency ratio (ESEER) for different cooling systems. ESEER is defined by the Eurovent Certification Company and calculated by combining full and part load operating conditions.
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2. Cooling loads in residential buildings
The design cooling load (or heat gain) is the amount of energy to be removed from a house by the HVAC equipment, to maintain the house at indoor design temperature when worst case outdoor design temperature is being experienced. As can be seen from the figure above, heat gains can come from external sources, e.g. solar radiation and infiltration and from internal sources, e.g. occupants and electrical equipment.
Factors influencing the sensible cooling load •
Windows or doors
•
Direct and indirect sunshine through windows, skylights or glass doors heating up the room
•
Exterior walls
Two important factors when calculating the cooling load of a house are:
•
Partitions (that separate spaces of different temperatures)
• •
•
Ceilings under an attic
•
Roofs
•
Floors over an open crawl space
•
Air infiltration through cracks in the building, doors, and windows
•
People in the building
•
Equipment and appliances operated in the summer
•
Lights
sensible cooling load latent cooling load
The sensible cooling load refers to the air temperature of the building, and the latent cooling load refers to the humidity in the building.
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Factors influencing the latent cooling load Moisture is introduced into a room through: People
•
Equipment and appliances
•
Air infiltration through cracks in the building, doors, and windows Transmission (Sensible)
To reduce the cooling load from solar gains, the most efficient and sustainable way is to use passive measures. From an architectural point of view, shading can be created by building components and by using blinds. Depending on the type of blinds used, the solar gain can typically be reduced with up to 85% with external shading. The figures below show a building simulation example conducted on a low-energy single family house, where using different shading factors have been applied.
Solar Radiation (Sensible) Total sensible
(Sensible) Air Ventilation
(Latent)
Lighting
(Sensible) (Sensible)
Equipment
CONDITIONED S PA C E
Internal heat gain
External heat gain
•
The effect of shading
Cooling Load
Total latent
(Latent) (Sensible) People (Latent)
Internal gains in residential buildings are limited to the people normally occupying the space and household equipment. In national building regulations, the load for internal gains in ordinary residential buildings is often mentioned (3-5 W/m2). In residential buildings, the cooling load primarily comes from external heat gains, and mostly from solar gains through windows and doors, transmission through wall and roof, and infiltration through the building envelope/ventilation.
Without shading; cooling loads up to 60 W/m2.
The figure below shows that about 2/3 of the cooling load comes from the solar radiation. Shading factor 50%; cooling loads up to 40 W/m2. 2%
5% 3% 10%
13%
52%
15%
Heat from air flows
Heat from lighting
Heat from occupants (incl. latent)
Heat from daylight (direct solar)
Heat from equipment
Heat from windows (including absorbed solar) and openings
Heat from walls and floors (structure)
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Shading factor 85%; cooling loads up to 25 W/m2.
As can be seen from the figures above, even with the most efficient shading factor, the cooling load still amounts to 25 W/m2.
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Room variation There is a big variation in the cooling load from room to room, caused by the architectural design of the building. Large window areas facing the south and west are needed for daylight requirements and winter heat gains, but they also incudes high summer cooling loads. As a result of large south facing window areas, the cooling demand in south facing rooms are higher than in the north facing rooms. In addition, the desired temperature levels of each room may differ ranging from the highest temperature requirements in the bathroom, to the lowest temperature requirements in the bedroom.
No window opening, no HRV by-pass Open windows, no HRV by-pass
8500
8000
7500
7000
6500
6000
5500
5000
4500
4000
3500
3000
2500
2000
1500
Open windows, with HRV by-pass UFH, no opening window
500
37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19
1000
The figures below show the duration of over-temperature with different shading and ventilation strategies. The data originates from a full year building simulation of a low-energy single family house in Northern European climatic conditions (Denmark).
Temperature [°C]
Duration of the cooling load
Time [h]
Time [h]
8
No window opening, no HRV by-pass Open windows, no HRV by-pass
8500
8000
7500
7000
6500
6000
5500
5000
4500
4000
3500
3000
2500
2000
1500
Open windows, with HRV by-pass UFH, no opening window
500
Temperature [°C] 8500
8000
7500
7000
6500
6000
5500
5000
4500
4000
3500
3000
2500
2000
1500
Open windows, with HRV by-pass UFH, no opening window
37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19
1000
No window opening, no HRV by-pass Open windows, no HRV by-pass
500
37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19
1000
Temperature [°C]
Without shading; over-temperature up to 2 300 hours per year.
Time [h]
Shading factor 50%; over-temperature up to 1 100 hours per year.
Shading factor 85%; over-temperature up to 800 hours per year.
The simulations show that without active cooling there will be a significant amount of time with overtemperature (assuming that the maximum temperature allowed is 26 °C). All the cases also show that with radiant floor cooling, it is possible to keep the temperature below 26 °C all year round. National
building regulations across Europe have already started to implement maximum duration periods of overtemperature. In Denmark, the requirement in the 2015 standard is that a temperature above 26 °C is only allowed for maximum 100 h during the year and above 27 °C for maximum 25 h during the year.
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Required cooling capacity Based on the peak load calculations of the building, the heating and cooling system can be designed. The HVAC system should be designed to cover the worst case (peak load). The ďŹ gures below show an example of the variation of the needed capacity to cover the heating and cooling loads.
As can be seen, the cooling capacity peaks are actually higher (up to 4 kW), than the heating capacity peaks (up to 3.5 kW) under any shading conditions (excluding domestic hot water). Although, the heating period still remain longer than the total cooling period, it is interesting to note that the cooling period extends into early spring and late autumn.
Required heating and cooling capacity 5000
5000
Cooling Heating
4000
2500
December
October
November
September
July
August
December
October
November
September
July
August
June
May
0
April
500
0
March
1000
500
January
1500
1000
June
2000
1500
May
2000
3000
April
2500
3500
March
3000
January
Capacity [W]
3500
February
Capacity [W]
4000
Cooling Heating
4500
February
4500
Low energy building, shading in-between windows. Window opening and HRV by-pass are used during cooling season
Low energy building, no shading. Window opening and HRV by-pass are used during cooling season
5000
Cooling Heating
4500
Capacity [W]
4000 3500 3000 2500 2000 1500 1000 500
December
October
November
September
July
August
June
May
April
March
January
February
0
Low energy building, external shading. Window opening and HRV by-pass are used during cooling season
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3. The ISO 7730 guidelines In order to provide thermal comfort, it is necessary to take into account local thermal discomfort caused by temperature deviations, draught, vertical air temperature difference, radiant temperature asymmetry, and floor surface temperatures. These factors can influence on the required capacity of the HVAC system.
Optimal temperature conditions
PMV and PPD
Dissatisfied [%]
PPD
The PMV is an index that predicts the mean value of the votes of a large group pf persons on a seven-point thermal sensation scale (see table below), based on the heat balance of the human body. Thermal balance is obtained when the internal heat production in the body is equal to the loss of heat to the environment.
PMV
PMV
Predicted mean vote
PPD
Predicted percentage dissatisfied [%]
+3
Hot
+2
Warm
+1
Slightly warm
0
Neutral
-1
Slightly cold
-2
Cool
-3
Cold
Seven-point thermal sensation scale
10
The PPD predics the number of thermally dissatisfied persons among a large group of people. The rest of the group will feel thermally neutral, slightly warm or slightly cool. The table below shows the desired operative temperature range during summer and winter, taking into consideration normal clothing and activity level in order to achieve different comfort classes. Comfort requirements
PPD Class [%]
Temperature range
PMV [/]
Winter 1.0 clo 1.2 met [°C]
Summer 0.5 clo 1.2 met [°C]
A
< 6 - 0.2 < PMV < + 0.2
21-23
23.5-25.5
B
< 10 - 0.5 < PMV < + 0.5
20-24
23.0-26.0
C
< 15 - 0.7 < PMV < + 0.7
19-25
22.0-27.0
ISO 7730 basically recommends a target temperature of 22 °C in the winter, and 24.5 °C in the summer. The higher the deviation around these target temperatures, the higher the percentage of dissatisfied. The reason for the different target temperatures is because that the two seasons apply different clothing conditions as can be seen in below figure:
Predicted Percentage of Dissatisfied [%]
EN ISO 7730 is an international standard that can be used as a guideline to meet an acceptable indoor and thermal environment. These are typically measured in terms of predicted percentage of dissatisfied (PPD) and predicted mean vote (PMV). PMV/PPD basically predicts the percentage of a large group of people that are likely to feel “too warm” or “too cold” (the EN ISO 7730 is not replacing national standards and requirements, which always must be followed).
Metabolic rate: 1.2
Basic clothing insulation: 0.5
Basic clothing insulation: 1.0
Operative temperature [°C]
Operative temperature for winter and summer clothing
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Radiant asymmetry When designing a radiant ceiling or wall system, make sure to stay within the limits of radiant asymmetry. As can be seen in the figure below, the radiant asymmetry differs depending on the location of the emitter system, and whether it’s used for heating or cooling.
Maximum air velocity, 0.5 m from wall [m/s]
Radiant systems are low convective systems and will not create any problems with draught. However, down draught from a cold wall can put a limitation to the system. A cold wall can create draught as we know from windows. When designing wall cooling, the velocity on the air need to be within the recommendation (Class A is 0.18 m/s). 0.4
Recommended comfort limit for sedentary persons
0.35
Dissatisfied
Draught rate
With the insulation levels typically used today, radiant asymmetry does normally not cause any problems due to the moderate heating and cooling load the emitter has to perform. However, especially when using ceiling heating, a calculation must be made for a given reference room.
0.3 0.25 0.2
Floor temperature
0.15
Δt (wall-room) 0.2
3.0 K 4.0 K 5.0 K 6.0 K
0.05
Local discomfort caused by warm and cool floors
7.0 K 8.0 K 9.0 K 10.0 K
0 0.5
1
1.5
2
2.5
3
Height of cool wall [m]
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3.5
4
4.5
When designing radiant cooling systems, the dew point is normally reached before radiant asymmetry problems occur. Can be calculated according to ISO 7726.
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Surface temperatures
0,1 - 1,1 m
For many years, people have chosen underfloor heating systems as the preferred emitter system, because of the perceived comfort of walking on a warm floor. Similarly, the question is if the occupants complaint about discomfort when utilising the floor to remove heat (cooling).
0
9
18
27
36
45
54
63
[°F]
80 60
2,5
B
2 1,5
A
1 0,5 0
Warm ceiling
40
Dissatisfied [%]
Vertical air temperature difference [K]
3
2
Cool wall
4
6
8
10
ΔT floor surface room
20
Cool ceiling
Warm wall
Correlation between the temperature difference floor surface to room and the vertical air temperature difference (Deli, 1995).
10 8 6 4
2
1 0
5
10
15
20
25
30
35
[°C]
Radiant temperature asymmetry [°C]
According to ISO 7730, the lowest PPD (6%) is found at a floor temperature of 24 °C. A typical floor cooling system will have to operate with a minimum floor temperature of 20 °C, where the expected PPD would still be under 10%. As will be seen later, such floor temperatures still provide a significant cooling effect, due to the large surface area being emitted.
Vertical air temperature difference
The study concludes that up to a ΔT 8K, the comfort category is still A. This would equal a floor temperature of 20 °C and a dimensioned room temperature of 28 °C. The dimensioned room temperature must be below 26 °C and similarly above a floor temperature of 20 °C in order to reach comfort class B. Hence, the vertical air temperature difference will in practice not cause a indoor climate below category A. As the pictures below show, different emitter systems provide different temperature gradients in a room. Clearly, a radiant heating system in the floor provides a temperature gradient closest to the ideal. Similarly, a radiant cooling system in the ceiling provides a temperature gradient closest to the ideal.
The comfort categories are divided into A, B and C depending upon the difference between the air temperature at floor level and at a height equivalent to a seated person. As can be seen below, the temperature difference must be under 2°C in order to reach category A. 18
Category
Vertical air temperature difference a °C
A
<2
B
<3
C
<4
20
22
24
26
[°C]
Ideal heating Radiant ceiling heating
Underfloor heating External wall radiator heating
Vertical temperature profile with different emitter systems
a) 1,1 and 0,1 m above floor
A study done by Deli in 1995 shows the correlation between the ΔT floor surface/room (difference between the floor surface temperature and the dimensioned room temperature) and the vertical air temperature difference. 18
20
22
24
26
[°C]
Radiant floor cooling
Radiant ceiling cooling
Radiant wall cooling
Temperature profile radiant cooling
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4. Capacity and limitations of radiant emitter systems
Heat flux density The ability of a surface to transfer heating or cooling between the surface and the room, is expressed by the heat flux density. According to EN 1264/EN 15377, the values below can be used to express the heat flux density.
Floor heating, ceiling cooling: q = 8.92 (θs,m - θi)1.1 Wall heating, wall cooling:
q = 8 (| θs,m - θi |)
Ceiling heating:
q = 6 (| θs,m - θi |)
Floor cooling:
q = 7 (| θs,m - θi |)
Where q
2
is the heat flux density in W/m
θs,m is the average surface temperature (always limited by dew point) θi
is the room design temperature (operative)
Thermal transfer coefficient The thermal transfer coefficient is an expression of how large an effect per m2 the surface is able to transfer to the room, per degree of the temperature difference between the surface and the room. The figure below shows the thermal transfer coefficient for different surfaces for heating and cooling respectively. Surface heating and cooling
[W/m2K] Thermal transfer coefficient
All emitter systems, whether it is pure air-based, radiators or pure radiant systems, are bounded by their ability to transfer energy. The capacity of any radiant emitter systems is limited by the heat flux density, which differs depending on the location of the emitter, i.e. floor, wall or ceiling. The heat flux density can be used to calculate the capacity of the emitter, also known as the thermal transfer coefficient. Specifically regarding cooling, any radiant emitter will need to work within the dew point limitations in order to avoid moisture on the surface and within the construction.
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Heating Cooling 10
5
0
Ceiling
Floor
Wall
Due to natural convection, the floor provides the best thermal transfer coefficient for heating while the ceiling provides the best thermal transfer coefficient for cooling.
Dew point limitations In order to secure that there is no condensation on the surface of the emitter in the room the supply water temperature should be controlled so that the surface temperatures of the emitter always is above dew point. In the diagram below, the dew point temperatures can be found under different levels of relative humidity (RH):
Dew point temperature [°C]
24 23
Room temp. 26 °C Room temp. 25 °C Room temp. 24 °C Room temp. 23 °C
22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 40
45
50
55
60
65
70
75
80
Relative humidity RH [%]
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Emitter surface and humidity Design temperatures for cooling systems are specified according to the dew point. The dew point is defined by the absolute humidity in the room and can be estimated from the relative humidity RH and the air temperature. The cooling capacity of the system is defined by the difference between the room temperature and the mean water temperature.
Theoretical capacities of embedded radiant cooling Taking both ISO 7730 (surface temperatures, radiant asymmetry, and down draught) and the dew point limitations into account, the following surface temperature limitations exist.
Distribution pipes and manifolds In any cooling system where you have distribution pipes or manifolds you have to be aware of that these parts of the system also have a risk of condensation because they sometime operates below the dew point. Insulation of distribution system is often necessary in order to avoid condensation.
Design temperature
40
Heating
35
Cooling
30 25 20 15
Floor
Parimeter
Ceiling
Wall
Surface temperature limitations
With these surface temperature limitations in mind, the maximum capacities of different radiant emitter systems can be calculated. The results are shown in the figure below. 200
Heating and Cooling Capacity [W/m2]
For radiant floor cooling a minimum surface temperature of 20 °C is required, which means that only when the relative humidity exceeds 70% in the room, the risk of condensation occurs, because that corresponds to a relative humidity of 100% at the emitter surface. Radiant cooling from the ceiling is limited by the radiant asymmetry between the surface of the emitter and the room temperature recommendation is that it should not exceed more than 14 K. For standard conditions (26 ºC, 50% RH) the surface of the emitter usually reaches the dew point before the radiant asymmetry limit.
Temperature [°C]
45
Often standard design parameters for cooling systems are an indoor temperature of 26 °C and a relative humidity of 50%. At the dew point, condensation will occur on the emitter surface. In order to avoid condensation, the emitter surface temperature has to be above the dew point temperature.
180
Heating Cooling
160 140 120 100 80 60 40 20 0
The design supply water temperature of the system depends on the type of surface used, the design indoor conditions (temperature and relative humidity) and the cooling loads to be removed. It should be calculated to obtain the maximum cooling effect possible from the system. The capacity and mean water temperature for radiant floor cooling depends on the floor construction, pipe pitch and surface material. To have the highest possible capacity of the system you should design your floor construction so the surface temperature is equal to the minimum temperature of 20 °C. The capacity and mean water temperature for radiant cooling from the ceiling is calculated, or can be read directly, in the capacity diagram of the cooling panels. To have the highest possible capacity of the system you should design as close to the dew point as possible.
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Floor
Parimeter
Ceiling
Wall
Maximum heating a cooling capacities
In theory, the highest heating capacity can be achieved from the wall. Since space is limited due to windows and other things hanging on the wall, the real heating capacity from walls is significantly reduced. Hence, the biggest capacity can be achieved by heating from the floor, and cooling from the ceiling. In practice, either a floor system or a ceiling system is installed and used for both heating and cooling. A floor system should be chosen if the heating demand is dominant and a ceiling system should be chosen if the cooling demand is dominant.
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5. Ground heat exchangers
Ground conditions When planning the use of ground heat exchangers, the ground conditions are of fundamental importance. Determining the ground properties, with respect to the water content, the soil characteristics (i.e. thermal conductivity), density, specific and latent thermal capacity as well as evaluating the different heat and substance transport processes, are basic pre-requisites to determine and define the capacity of a ground heat exchanger. The dimensioning has a significant impact on the energy efficiency of the heat pump system. Heat pumps with a high capacity have unnecessary high power consumption when combined with a poorly dimensioned heat source. With a higher water concentration in the ground, you get a better system capacity. Horisontal collectors are hence depending on the ground’s ability to prevent rain water from mitigating downwards due to gravitation. The smaller the corn size in the soil, the better the ground can prevent rain water from gravitation. Hence clay will provide a better performing ground heat exchanger than sand. Vertical collectors are depending
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on being in contact with ground water. Hence the depth of ground water levels has an important impact on the performance of a vertical ground heat exchanger. In addition to the water concentration, different ground types have different thermal conductivity. For example rock has a higher thermal conductivity than soil, so ground conditions with granite or limestone will give a better performing ground heat exchanger than sand or clay.
Soil type Clay/silt, dry
Thermal conductivity (W/m K) 0.5
Clay/silt, waterlogged
1.8
Sand, dry
0.4
Sand, moist
1.4
Sand, waterlogged
2.4
Limestone
2.7
Granite
3.2
Source: VDI 4640
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Ground heat exchangers With ground heat exchangers, a distinction is made between horisontal and vertical collectors. These can be further classified as follows: Horisontal: • •
The suitability of the different collectors depends on the environment (soil properties and climatic conditions), the performance data, the operating mode, building type (commercial or private), the space available and the legal regulations.
Horisontal or surface collectors Energy cages
Vertical: • •
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Boreholes Energy piles and walls
Horisontal collectors
Energy cages
Collectors installed horisontally or diagonally in the upper five meters of the ground (surface collector). These are individual pipe circuits or parallel pipe registers which are usually installed next to the building and in more rare cases under the building foundation.
Collectors installed vertically in the ground. Here, the collector is arranged in a spiral or a screw shape. Energy cages are a special form of horisontal collectors.
Boreholes
Energy piles
Collectors installed vertically or diagonally in the ground. Here one (single U-probe) or two (double U-probe) pipe runs are inserted in a borehole in U-shape or concentrically as inner and outer tubes.
Collectors build into the pile foundations that are used in construction projects with insufficient load capacity in the ground. Individual or several pipe runs are installed in foundation piles in a U-shape, spiral or meander shape. This can be done with pre-fabricated foundation piles or directly on the construction site, where the pipe runs are placed in prepared boreholes that are then filled with concrete. Most often energy piles are used for larger commercial buildings.
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Ground temperature profile The figure below shows a generic temperature profile in the ground for each season during the year. Temperature (earth’s surface) [°C] 0
0
5
10
15
20
Depth in soil [m]
5
10
15
1. May 1. November 1. August
20 5
10
15
20
Temperature (depth) [°C]
The closer to the ground surface, the higher the influence from the outside temperature and solar radiation. Hence not surprisingly, the highest temperatures are found in late summer and the lowest temperatures in late winter. The reason for the temperatures being higher in late autumn than late spring, has to do with the ground’s ability to store energy. After a warm summer period, the ground remains relatively warm during the autumn. Ground temperatures stabilize below 10-15 m. It is clear from these ground temperature profiles that the cooling capacity is higher below 15 m. Hence vertical collector systems provides a better cooling capacity than horisontal collector systems.
Primary supply temperatures The temperatures mentioned in the previous section are often referred to as the undisturbed ground temperature. Depending on the thermal resistance between the collector and the surrounding ground, the temperature of the fluid in the collector will be higher than the surrounding ground.
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The first thing to decide is whether the ground heat exchanger shall be used for heating only or for both heating and cooling. As demonstrated in this guide, new built low energy houses will often have substantial cooling loads. It is therefore highly recommendable to use the ground heat exchanger for free cooling in the summer period. A combined use for heating and cooling also balances of the ground temperature during the year and leaves the ground environment undisturbed. Existing guidelines for dimensioning ground heat exchangers are typically based on the peak load for the heating demand. But in order to ensure that adequate cooling capacity is available in the summer season, it is recommend doing a design check for the maximum cooling load as well.
1. February
0
Dimensioning of ground heat exchangers for free cooling
Dimensioning for the heat load should be done based on the peak load for space heating plus the domestic hot water need. As a heat pump is used for covering the heat load, the COP of the heat pump on the coldest day (design day) should be applied in the design calculation. In addition to this, the specific characteristic of the chosen heat exchanger and the thermal conditions in the ground must be taken into account. Dimensioning for the cooling load should be done based on valid information of the maximum cooling load in the building. Free cooling operates without a heat pump. It is therefore vital that the thermal capacity of the ground heat exchanger is able to fully cover the max cooling load (no COP is included). In residential buildings in Northern Europe the cooling need will normally be covered with the capacity derived from the heating requirements. But a design check is always recommended. In special cases in residential buildings and typically in office buildings, the cooling need will be dominant and thus the design driver. In such case vertical collectors are normally recommended as the deeper ground temperatures are sufficiently stable and independent of surface temperature and solar radiation. If a horizontal system is chosen, the space requirements can be a capacity limitation. Designing for inadequate cooling capacity on the warmest summer days may then be necessary compromise, but should be evaluated carefully.
17
Dimensioning examples data (thermal conductivity etc.) from local databases or authorities. The figures below show the capacity for different collectors.
In order to dimension ground heat exchangers certain information has to be considered. First of all an estimation of the physical properties of the ground is needed. Normally its possible to obtain local ground
Horisontal collectors
*) Energy cage; normal height is 2.0 m, and XL height 2.6. Required depth is 4 m.
Pipe size Capacity cooling
Energy cage
Vertical collectors
25, 32 and 40 mm
Normal 32 mm
XL 32 mm
40 mm
7-28 W/m2
800-1120 W
1000-1500 W
30-70 W/m
17-20 °C
14-17 °C
10-13 °C
10-13 °C
Dimensioning temperature, supply/return
Flow and pressure drop in the collector different from the physical properties of pure water. The table below shows the required flow of often used brines for providing different cooling capacity.
When the cooling need is defined, the flow can be calculated. When using ground collectors, the water used has to be mixed with anti-frost liquid. Hence, the specific heat capacity and density in the brine is Cooling need [kW] 2 3 4 5 6
Ethanol Flow [kg/s] 0.16 0.24 0.32 0.40 0.48
Monoethylenglyciol Flow [l/s] 0.15 0.23 0.31 0.38 0.46
When calculation the pressure loss in the collector the flow is divided equally up in the number of loops. For vertical collectors the total pressure loss is normally very low hence the pressure is equalized and it is only the pressure loss in the feeding pipe has an influence. For horisontal collectors and partly energy cages the pressure loss has to be calculated in order to be sure that the pump will be able to circulate the water through the collector and the cooling exchanger including manifolds and valves.
Flow [kg/s] 0.18 0.27 0.36 0.45 0.54
Propylenglycol
Flow [l/s] 0.19 0.28 0.38 0.47 0.56
Flow [kg/s] 0.17 0.26 0.34 0.43 0.51
Flow [l/s] 0.18 0.27 0.36 0.45 0.54
In the diagram below, the pressure loss in the ground collector should be maximum 34 kPa at the dimensioning conditions, and the ground collector should be dimensioned so that the pressure loss in each loop is less than 34 kPa. Pump diagram Available pressure for the primary circuit. Pressure loss [kPa] 50
Example: 4 kW installations Horisontal collector extraction power
40
15 W/m2
30
CP2 CP1
20
Liquid
Monoethylenglycol
Total flow
0.38 l/s, 1.37 m3/h
Diameter of collector
Ø 32 mm
10
18
0
0
0.5
1
1.5
2
2.5
3
Rate of flow [m3/h]
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6. Free cooling in combination with diďŹ&#x20AC;erent heat sources The illustrations below shows a ground heat exchanger combined with a radiant system in heating mode and cooling mode. In this example a ground sourced heat pump is providing heating to domestic hot water (DHW), space heating, and for heating up the incoming ventilation air. This could of course be utilized with other heat sources such as boilers or district heating. Free cooling is provided through a special pump and exchanger group (see chapter 8) that supplies cold water/brine from the ground heat exchanger directly to the radiant emitter system and possibly the incoming ventilation air. In cooling mode, the heat pump will only be active for domestic hot water generation.
Heating mode, the free cooling is deactivated
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As one can see from the grey connection lines the pump and exchanger group is not active in heating mode. Similarly, the connection lines from the heat pump (or any other heat source) to the emitter systems are inactive in cooling mode. If a boiler or district heating system is used as heating source, the ground heat exchanger will only work during cooling (also known as a bivalent system). If a ground source heat pump is used as heat source, the ground ground heat exchanger will work both during heating and during cooling (also known as a monovalent system).
Cooling mode, the free cooling is activated
19
7. Choosing and dimensioning the radiant emitter system Embedded emitters are the key to any radiant system. In order to have an energy efficient and comfortable solution, the emitter system has to be designed to the construction but also to the task it has to solve. There are many types of constructions for floor, wall and ceilings. Uponor offers emitters that can meet the requirements of all types of installations. All emitters are able to provide heating and cooling. However, some emitters are more efficiently than others. The most efficient cooling system is placed in the ceiling, but the heating efficiency is lower whereas an emitter system in
Floor installation
Wall installation
the floor has the highest heating efficiency, but with a lower cooling efficiency. Another important factor is the supply water temperature. Radiant emitter systems operate on a relatively low temperature for heating, and a relatively high temperature for cooling. A radiant system should be designed for the lowest possible temperature for heating and the highest possible temperature for cooling. This secures a heating/cooling system with high energy efficiency and optimal conditions for the heating and cooling supply.
Ceiling installation
Capacity of different radiant emitter systems In order to calculate the capacity of the radiant emitter, it is important to know the construction in which the embedded emitter is integrated, including the surface material on top of the construction. In general, there are three factors that influence on the capacity of a radiant emitter system: • Thermal resistance in the surface construction RB • Pipe pitch, i.e. the distance between the pipes T • Thermal conductivity in the construction material In practice, this means that when designing the floor construction, the performance of the radiant system can be optimised by choosing the right construction, pipe layout and surface material.
20
Example: floor construction
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Y = Specific thermal output qc [W/m2] X = Temperature difference between room and cooling medium [θc K]
Thermal resistance in the surface construction The thermal resistance in the surface construction has a big influence on the performance of the emitter. In the diagram, an example of a cooling curve where different thermal resistance values from 0.00 to 0.15 m2K/W are shown. The curve shows that higher resistance gives a lower capacity. All constructions with embedded radiant emitter systems will have a surface resistance that has to be considered. In order to get the highest efficiency, the resistance value has to be as low as possible.
RλB = 0 qCN (RλB = 0)
RλB = 0.05 RλB = 0.10
RλB = 0.15
qCN (RλB = 0.15)
ΔθCN
Field of characteristic curves of a cooling system
Pipe pitch, i.e. distance between the pipes
45
40
The diagram shows the capacity of a concrete floor construction with =1.8 W/(mK), and with different kinds of surface material. The diagram illustrates the variation of the capacity depending on the pipe pitch. A short distance between the pipes, gives a higher capacity and vice versa. For a combined heating and cooling system, it is recommended to use a relatively small distance 300 mm between the pipes, in order to utilise free cooling and maintain an even surface temperature.
35
Thermal output q [W/m2]
The pipe pitch, i.e. the distance between the pipes in the embedded construction, not only has an influence on the capacity, but also on how equal the surface temperature is. This is especially important from a comfort perspective.
30
25
20
15
10 0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
Pipe spacing T [m]
θm 15.5 °C, 14 mm parquet
θm 18.5 °C, 14 mm parquet
θm 15.5 °C, 7 mm parquet
θm 18.5 °C, 7 mm parquet
θm 15.5 °C, 10 mm tiles
θm 18.5 °C, 10 mm tiles
Floor surface temperature limit 20 °C
Thermal conductivity in the construction The thermal conductivity in the construction has an effect on the system’s ability to distribute heating and cooling in the thermal mass. A construction with a low thermal conductivity requires a smaller pipe pitch, in order to obtain an equal surface temperature variation.
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For dry constructions, high performance material like heat distribution plates in aluminium or similar are used to ensure optimal heating and cooling distribution.
21
Radiant floor constructions and capacity using a relatively short distance between the pipes, and a surface material with a low thermal resistance.
Radiant floor systems are far more common than ceiling or wall systems, and can be used for cooling and heating. A radiant floor system can be installed in wet constructions using concrete and screed, and in dry constructions with heat emissions plates.
In the figure below, an overview of the capacity in the most common floor installations is shown with mean water temperatures of 15.5 °C and 18.5 °C corresponding to supply temperatures of 14 °C and 17 °C with a T of 3 K over the emitter loops. Figures are based on a room temperature of 26 °C and a surface temperature of 20 °C.
A radiant floor has a cooling capacity of up to 42 W/m2 limited by a surface temperature of 20 °C. The most efficient installation is in a wet construction with concrete or screed, because of its high heat conductivity,
Surface material Tiles 10 mm, = 1.0 W/mK
Floor installation
22
Surface material Wood 14 mm parquet, = 0.014 W/mK
Installation principle
Cooling effect q [W/m2] θm 15.5 °C
Cooling effect q [W/m2] θm 18.5 °C
Cooling effect q [W/m2] θm 15.5 °C
Cooling effect q [W/m2] θm 18.5 °C
Wet floor installation
42
40
33
24
Installation integrated in construction
42
40
33
24
Installation on the joists
28
20
27
19
Dry floor installation
28
20
27
19
Installation between the joists
24
17
18
14
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Radiant wall constructions and capacity Radiant wall systems are typically used as a supplement to floor and ceiling emitter systems for rooms with a higher need for cooling/heating. Instead of dimensioning the floor or ceiling system according to the room with the highest peak load, it can be designed according to the average and the peak room(s) can be supplemented with a wall emitter.
by a surface temperature of 17 °C, in order to be within the limits of radiant asymmetry and to prevent draught. In the figure below, an overview of the capacity of the most common wall systems is shown with mean water temperatures of 15.5 °C and 18.5 °C corresponding to supply temperatures of 14 °C and 17 °C with a T of 3 K over the emitter system. Figures are based on a room temperature of 26 °C and a surface temperature of 20 °C .
A radiant wall system will be limited by the architecture and by the furnishing. Radiant wall systems have a cooling capacity of up to 60 W/m2 (active area) limited
Surface material Plaster 10 mm, = 0.7 W/mK
Wall installation
Installation principle
Cooling effect Cooling effect q [W/m2] q [W/m2] θm 15.5 °C θm 18.5 °C
Dry wall installation
Wet wall installation
Stud wall installation
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60
Surface material Plaster 11 mm, = 0.24 W/mK
Surface material Plaster 11 mm, = 0.23 W/mK
Cooling effect q [W/m2] θm 15.5 °C
Cooling effect q [W/m2] θm 18.5 °C
Cooling effect Cooling effect q [W/m2] q [W/m2] θm 15.5 °C θm 18.5 °C
45
32
45
42
34
23
Radiant ceiling constructions and capacity Radiant ceiling systems are the most efficient systems for cooling, but can also be used for heating. Ceiling systems have originally been developed for office environments, but are also available for residential constructions using wet plaster or dry gypsum panels.
attention has to be taken for adequate dew point control. In the figure below, an overview of the capacity in the most common ceiling systems is shown, with mean water temperatures of 15.5 °C and 18.5 °C corresponding to supply temperatures of 14 °C and 17 °C with a T of 3 K over the emitter system. Figures are based on a room temperature of 26 °C and a surface temperature of 16 °C.
Radiant ceiling systems have a cooling capacity of up to 97 W/m2. It is important to note that especially for ceiling cooling, the surface temperature of the system is in peak often very close to the dew point. Special
Surface material Plaster 10 mm, = 0.7 W/mK
Ceiling installation
Installation principle
Cooling effect Cooling effect q [W/m2] q [W/m2] θm 15.5 °C θm 18.5 °C
Wet ceiling installation
75
Surface material Plaster 11 mm, = 0.24 W/mK
Surface material Plaster 11 mm, = 0.23 W/mK
Cooling effect q [W/m2] θm 15.5 °C
Cooling effect Cooling effect q [W/m2] q [W/m2] θm 15.5 °C θm 18.5 °C
Cooling effect q [W/m2] θm 18.5 °C
55
Dry ceiling installation
Suspended ceiling installation
59
97
42
67
Capacity diagrams Uponor offers a wide range of embedded emitter systems adapted to different kinds of constructions in the floor, wall or ceiling. Whenever the choice of system has been selected, detailed diagrams can be used in order to make the planning of the capacity. The diagram and example on next page shows a floor construction with the cooling and heating output of the emitter system.
Dimensioning diagram for cooling Analogue to dimensioning for heating, the following parameters must be considered:
3. Pipe pitch, i.e. centre distance between the pipes T [cm] 4. Difference between room temperature and mean water temperature θc. = θi - θc [K] 5. Recommended minimum surface temperature (20 °C) 6. Difference between room temperature and surface temperature θv - θr, m [K] If three of the parameters above are known, the remaining parameters can be calculated using the diagram to the right.
1. Cooling effect of the radiant area qc [W/m2] 2. Thermal resistance in the surface construction RB [m2 K/W]
24
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100 T 15
Thermal output heating qH [W/m2]
T 25
80
=θ Δθ
T 30
= Ðθ
15
K
i
H
80
H
60
10 K 8K
40
40
6K =4K Δθ = θ Ðθ
20
C
i
20
C
0
0
T 0,05
0,10
30
T2
5
T
20
T 15
Heating
T 10 T cm 10 15 20 25 30
qH W/m2 98,6 96,3 93,0 87,3 81,3
Δθ H,N K 15,9 18,1 20,3 22,0 23,6 0
25
0,15
T
Thermal resistance RB [m2 K/W]
60
Thermal output cooling qc [W/ m2]
T 20
T
20
T
T 10
15
Cooling
T cm 10 15 20 25
qC W/m2 34,8 39,8 27,5 24,5
Δθ C,N K 8 8 8 8
0,05
0,10
0,15
Dimensioning example for cooling Estimating the dimensioned supply water temperature θV, Ausl.
Calculated:
θr, m = i - 4.3 K
Given:
qc
θr, m = 21.7 °C
θi = 26 °C RB = 0.05 m² K/W
(O.K., as this is above the recommended minimum surface temperature (20 °C)
Chosen pipe pitch = Vz 15 T: θv - θH = 2 K
θV, calc. = θi - θc - (θv- θR)/2 θV, calc. = 26 - 9 - 2/2 θV, calc. = 16 °C
= 29 W/m²
Read from the diagram: θc = 12 K
θr, m - θi = 3.9 K
Note: The required cooling effect can only be achieved if the median surface temperature and the dimensioned supply temperature are above the dew-point. In order
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to avoid condensation, a supply water controller such as Uponor Climate Controller C-46 is needed.
25
Regulation and control room control causes the room with the highest demand to determine the heating or cooling supply to a full zone, resulting in over temperatures and unnecessary high energy consumption.
The purpose of a control systems is to keep one or more climate parameters within specified limits without a manual interference. Heating and cooling systems require a control system in order to regulate room temperatures during shifting internal loads and outdoor temperatures. Good control systems adapt to the desired comfort temperatures while minimising unnecessary energy use.
An individual room control system is much preferable in order to meet room specific load variations and individual comfort requirements. Due to high variations in the individual room loads in low-energy buildings, an individual room control system is also required to minimise the energy consumption.
In residential buildings two different types of controls principles are common; zone control and individual room control. In a zone control system, the temperature is controlled in a common zone consisting of several rooms and heating and cooling is supplied evenly to the full zone. Not all national building codes allow zone control systems as they have major shortfalls with comfort as well as energy consumption.
The basic principle in an individual room control system is that a sensor measures the room temperature and regulates the heating or cooling supplied to the space controlled in order to meet a user defined temperature set point. The most well-know examples are radiators with thermostatic valves and underfloor heating systems with room thermostats.
In low-energy buildings there will in particular be high variations in the individual room heating and cooling loads (see figure 5.2). This means that lack of individual
In addition, room by room regulation provides the possibility to shut down cooling in a specific room, such as a bathroom or a room without cooling loads.
Room 1
Living room
Kitchen
21°C
21°C
18°C
Bedroom
Bath 1
Room 3
21°C
22°C
21°C
Entrance
18°C 20°C
Typical desired temperature (set points) in a single family house.
26
Room 2 Bath 2
22°C
Typical variation between individual room heat demands in a low-energy house.
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The self-regulating effect in underfloor heating
Functional description of Uponor Control System
Radiant floor heating and cooling benefits from a significant effect called ”self control” or “self regulating effect”. The self regulating effect occurs because the heat exchange from the emitting floor is proportional to the temperature difference between the floor and the room. This means that when room temperature drifts away from the set point, the heat exchange will automatically increase.
Individual room control with traditional on/off functionality
The self regulating effect depends partly on the temperature difference between room and floor surface and partly on the difference between room and the average temperature in the layer, where the pipes are embedded. It means that a fast change of the operative temperature will equally change the heat exchange. Due to the high impact the fast varying heat gains (sunshine through windows) may have on the room temperature, it is necessary that the heating system can compensate for that, i.e. reduce or increase the heat output. Low-energy houses will largely benefit from the self regulating effect, because the temperature difference between floor and room will be very small. A typical low-energy house has on average for the heating season a heat load of 10 to 20 W/m² and for this size of heat load, the self regulating effect will be in the range of 30 - 90%. °C 27
= Floor surface temperature
26
= Room temperature 25
Uponor’s Dynamic Energy Management control principle is an advanced individual room system based on innovative technology and an advanced self learning algorithm. Instead of a simple ON/OFF control, the actuators on the manifold supplies the energy to each room in short pulses determined based on feedback from the individual room thermostats. Uponor Control System DEM is self learning and will remember the thermal behavior of each room. This ensures an adequate and very accurate supply of energy, which means better temperature control and energy savings. Higher temperature
+
Saved energy when using Uponor DEM technology
Actuator on/off
Thermostat set point 20 °C
23 22 21
Individual room control with DEM technology
c cooling = -10.5 W/m2
c
24
For a radiant floor heating and cooling system, the control is normally split up in a central control and individual room controls. The central control unit is placed at the heat source. It controls the supply water temperature according to the outside temperature based on an adjustable heat curve. The individual room control units (room thermostats) are placed in each room and controls the water flow in the individual underfloor heating circuit by ON/OFF control with a variable duty cycle. Its done according to the set-point by opening and closing an actuator placed at the central manifold.
b a
Lower temperature
b heating = 13.9 W/m2
Lost energy when using Uponor DEM technology
Uponor DEM technology
-
20
Time
a heating = 19.1 W/m2 19
Self-regulating effect. UFH/C outputs for different temperatures between room and floor surface.
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Time
Typical behaviour in a heavy floor construction, where Uponor DEM technology ensures that a minimum of energy is lost to the construction. Compared with traditional on/off regulation, saving figures between 3-8% can be obtained.
27
Zone control When using zone control for a radiant ďŹ&#x201A;oor heating and cooling system, the central controller is normally placed at the heat source. It controls the supply water temperature according to the outside temperature based on an adjustable heat curve. The manifold system
has no actuators and normally the system works at a constant ďŹ&#x201A;ow with temperature regulation based on a reference thermostat is placed in one of the main rooms.
I-76 C-46 C-46
C-56
230 V AC
C-56
C-56
230 V AC
H-56 M
T-54
T-55 T-75
24 V DC M
230 V AC
Simple zone control, the central controller provides a regulated supply temperature based on the outdoor/indoor temperature.
28
M
Individual room control, the central controller provides a regulated supply water temperature based on the outdoor/indoor temperature and the room thermostat controls the room temperature by using actuators.
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8. Uponor Pump and exchanger group (EPG6) for ground sourced free cooling The Uponor Pump and exchanger group, EPG6, is designed for a separate cooling supply and temperature control for ground source free cooling. The EPG6 is pre-mounted and ready to install in the installations. Together with the Uponor ground collectors it is ready to provide free cooling for radiant emitter systems. The EPG6 can be integrated in HVAC installations for applications a separate supply of cooling needs to be provided through a heat exchanger (e.g. from a ground collector). The EPG 6 is controlled by Uponor Climate Controller C-46, which is able to adjust the secondary temperature supplied to the emitter
system and interact with the Uponor Control System used to control the emitter system. Uponor Climate Controller C-46 is also able to control the temperature according to the dew point, in order to prevent condensation. The primary side of the system is driven by a circulation pump, to circulate the fluid in the brine circuit and a 3-way mixing valve for controlling the primary flow, in order to maintain the correct temperature on the secondary side. The exchanger that exchanges the brine from the ground circuit with the water in the emitter system is designed for a capacity up to 6 kW.
Secondary circlet, to emitter system 6 5
7
Component overview
8
4
3
2 9
10
1
11
Primary side, ground collector or other cooling supply
2
3 way mixing valve Kvs 7 m3/h Primary circulation pump Grundfos Alpha 2L 26-60
3
Filling and air valve G ¾”
4
Heat exchanger 6 kW SWEP ESTH x 40/1P-SC-S 4 x ¾”
5 6
Ball valve with integrated check valve and thermometer Rp 1” Ball valve with integrated thermometer Rp 1”
1
7
Sensor pocket (supply)
8
Blind piece 180 mm G 1¼” for secondary circulation pump
9
Filling valve G ¾”
10
Uponor Climate Controller C-46
11
Primary connection Rp 1¼”
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Primary side The primary side of the system (ground collector) is connected to the EPG6 and will work as the heat sink. The mixing valve (1) will adjust the flow of the primary side and is controlled by the Uponor Climate Controller C-46 (10), which opens and closes the valve to the adjusted supply temperature on the secondary side measured by the supply sensor (7). The primary pump (2) will circulate the fluid in the brine circuit through the exchanger (4) and will shut down when there is no request from the secondary control system. The filling and air valve (3) is used to fill up the primary system with brine. Connection to an expansion tank and safety valves can be done on the connection valve (9).
Secondary side The secondary ball valves (5 and 6) are shutting down the secondary side of the system, and have a ball valve (5) including a check valve to prevent backflow in the system. The blind piece (8) can be replaced by a circulation pump, if no other pump is used for the secondary side. The secondary pump has to be connected to the Uponor Climate Controller C-46 (10).
29
Dimensions 230
360 Rp 1
80
580
Rp 1
Rp 1¼
Rp 1¼ 125
Pump diagram Available pressure for the primary circuit 50
Pressure loss [kPa]
40
30
CP2 CP1
20
10
0 0
0.5
1
1.5
2
3
2.5 3
Flow rate [m /h]
30
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Control principle
Primary control – cooling
Controls is required for the primary system as well as the secondary system.
The primary control of the cooling system is provided by the EPG6 which includes the Uponor Climate Controller C-46 that manages:
Since the primary control of the heating mode is separated from the primary control of the cooling mode, the change-over between heating and cooling must be defined. This can be done either automatically if a communication interface can be setup between the Uponor Climate Controller C-46 and the heat source or through a manual switch if it is not possible to setup a communication interface. Because a radiant emitter system can act for both heating and cooling, the secondary system can be controlled by one system as described below.
Secondary control – heating and cooling For the secondary control of the emitter system, Uponor recommends to apply individual room control, in order to provide energy efficiency and comfort. The individual control system also secures that cooling can be deactivated in single rooms/zones, e.g. in bathrooms where cooling might not be required. The Uponor Control System offers a long range of benefits for the user and can be integrated with the primary controller for cooling, Uponor Climate Controller C-46.
•
the supply temperature of the system
•
pump management of primary and secondary pumps
•
change-over between heating and cooling
•
dew point management with up to six wireless dew point sensors (Uponor Relative Humidity Sensor H-56)
In order to eliminate the risk of condensation on the emitter surface, dew point management is an essential part of the cooling system. The relative humidity sensors measure the relative humidity and the temperature in the room, and Uponor Climate Controller C-46 uses the data to calculate the dew point. Thereby, it is able to secure that the supply water temperature never gets too low, and that no condensation will occur on the emitter surface.
H-56
T-54
C-56
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T-55
T-75
I-76
31
Hydraulic change-over between heating and cooling
32
Uponor recommends using a diverting valve in the secondary heating/cooling distribution system, which opens and closes when changing between heating and cooling. The diverting valve is controlled by the Uponor
Climate Controller C-46 either directly through a 24 V actuator or through a relay for a 230 V actuator. The diverting valve is activated by the change-over signal between the heating and cooling modes.
Heating mode
Cooling mode
In heating mode, the free cooling system is deactivated. Hence, no pumps are running and the diverting valve is closed (the ďŹ&#x201A;ow goes straight through).
In cooling mode, the free cooling system is activated. Hence, pumps are running and the diverting valve is open. An internal circuit is secured for the heat source for producing domestic hot water.
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Installation examples Brine to water heat pump with Uponor EPG6 A diverting valve (7) is used to switch the flow direction in the hydraulic system between heating and cooling (diverting valve to open when cooling is activated).
The system diagram illustrates a Uponor free cooling installation using a ground collector and Uponor EPG6 in combination with a brine to water heat pump for space heating and domestic hot water.
When switching between heating and cooling, the heat pump must be in a position where it only produces domestic hot water (typically “summer mode” can be used).
The EPG6 (3) is connected to a Uponor ground collector (1) on the primary side of the free cooling installation. If more than one ground loop is installed, a manifold can be used to connect the ground loops.
The Uponor Climate Controller C-46 can send an external signal to the heat pump when switching between heating and cooling or it can be done manually with a relay switch. Contact the heat pump manufacturer in order to check the possibilities.
The secondary side of the EPG6 is connected to the heating pipe system before the manifold of the radiant system (4).
4
TW
6
3
7 9
M
5 2
1
8
1
Ground collector
2 3
6
Domestic hot water tank
Brine to water heat pump
7
Diverting valve
Uponor EPG6 with Uponor Climate Controller C-46
8
Non return valve
4
Radiant emitter system
9
Secondary circulation pump
5
Buffer tank
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Condensing boiler with Uponor EPG6 The system diagram illustrates a Uponor free cooling installation using a ground collector and Uponor EPG6 in combination with a gas/oil boiler for space heating and domestic hot water.
When switching between heating and cooling, the boiler must be in a position where it only produces domestic hot water (typically “summer mode” can be used).
The EPG6 (3) is connected to a Uponor ground collector (1) on the primary side of the free cooling installation. If more than one ground loop is installed, a manifold can be used to connect the ground loops.
The Uponor Climate Controller C-46 can send an external signal to the boiler when switching between heating and cooling or it can be done manually with a relay switch. Contact the boiler manufacturer in order to check the possibilities.
The secondary side of the EPG6 is connected to the heating pipe system before the manifold of the radiant system (4).
In the example below, a solar collector is supporting the boiler for space heating and domestic hot water but is not interacting with the cooling system.
A diverting valve (7) is used to switch the flow direction in the hydraulic system between heating and cooling (diverting valve to open when cooling is activated). 4
6
7
3
8
2 5
M
1
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1
Ground collector
5
Solar tank
2
Condensing boiler
6
Solar panel
3
Uponor EPG6 with Uponor Climate Controller C-46
7
Diverting valve
4
Radiant emitter system
8
Secondary circulation pump
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Free cooling with Uponor EPG6 Please note that a circulation pump (180 mm) has to be added to the EPG6 in order to circulate the secondary circuit. There is a blind piece on the EPG6 that can be replaced with a pump.
The system diagram illustrates a Uponor free cooling installation using a ground collector and Uponor EPG6 as a stand-alone system. The EPG6 (3) is connected to a Uponor ground collector (1) on the primary side of the free cooling installation using the same supply line as to the heat pump. If more than one ground loop is installed, a manifold can be used to connect the ground loops.
The activation of the EPG6 cooling module can be done automatically through the Uponor Climate Controller C-46 included in the EPG6 or through another external signal through the climate controller.
The secondary side of the EPG6 is connected to the heating pipe system before the manifold of the radiant system (4). 3
2
M
1 1
Ground collector (or bore hole)
2
Uponor EPG6 with Uponor Climate Controller C-46
3
Radiant emitter system
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Operation of Uponor Climate Controller C-46
Operation mode of Uponor Climate Controller C-46
Uponor EPG6 is delivered integrated with Uponor Climate Controller C-46. It is important that the settings and parameters are programmed to fit the designed system. A detailed user manual describes all settings and parameters.
Two possible operation modes for cooling are described below. The most typical operation mode of Uponor Climate Controller C-46 is heating and cooling mode when the controlled radiant system is used for both heating and cooling emitter. In the case where a radiant ceiling or wall system is installed purely for cooling purposes, the operation mode is set to cooling mode. This could apply to an example where cooling is needed in an energy renovated house with radiators.
Operation mode heating and cooling of Uponor Climate Controller C-46 When having a combined heating and cooling system where you change between heating and cooling, the climate controller always have to be in heating and cooling mode, even though the climate controller is not used as the primary controller for heating.
Operating mode Heating Heating and cooling Cooling Wizard – great installation guide When Uponor Climate Controller C-46 is started for the very first time, it guides the installer to make the necessary primary settings of the system. Wizard helps you step by step through the installation process. On the display, the installer can read all about the set-up and what to do next. The installation wizard is also started after changing or resetting the operation mode. Quick menu – gives easy access to basic settings Made for end-users: The quick menu consists of a series of screens easily accessible from the Uponor screen. These screens display readings for daily use. If the Uponor Climate Controller C-46 is set to installer access level, it is also possible to modify some parameters. Main menu – all informations and settings on the whole The main menu and all its sub-menus are used for displaying any accessible information, parameter settings, and selecting operating modes that are accessible in the system.
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Uponor > Main menu > Control settings > Advanced control > Operation mode. Note that the startup wizard will start when changing mode.
Heating min./max. supply Uponor Climate Controller C-46 In the case of combined heating and cooling system, where you can change between heating and cooling, the climate controller C-46 must always be set to Heating and cooling mode, even when the climate controller is not used as primary controller for heating. In this case the heating setting in the climate controller must be neutralized as follows:
Min./max supply Min 5.0 °C
Max 8.0 °C
Uponor > Main menu > Control settings > Heating > Min./max supply OK, also covered in startup wizard.
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Cooling mode only
Dew point margin
If the system works as a stand alone cooling system without any change over between heating and cooling, cooling mode is chosen:
Operating mode Heating Heating and cooling Cooling Uponor > Main menu > Control settings > Advanced control > Operation mode. Note that the startup wizard will start when changing mode.
1
Uponor > Main menu > Control settings > Cooling > Dew point
The functions require Uponor Relative Humidity Sensor H-56 and can handle up to six sensors, placed in different rooms/zones. The sensor mode function allows to decide which value to use in the dew point calculation. It can be set as an average or maximum value of the sensor. For cooling application, it is always recommended to use the maximum sensor mode.
Dew point management parameters and settings In the operation mode cooling, indoor compensated supply with dew point control will help you to prevent condensation problems if the actual condition in the room/zone is different from the design criteria. The supply water set point is referring to the design supply temperature of the system, and is the absolute minimum temperature that the Uponor Climate Controller C-46 will provide. The supply temperature should be set according to the design of the emitter system, taking into account the limitations factors, such as surface temperature and dew point.
Supply setpoint 14.0 °C
Uponor > Main menu > Control settings > Cooling
The function also allows using a dew point margin as an extra safety to compensate for having the variation in room conditions, occupation of the room, etc. The dew point margin can be adapted to the installation. A smaller margin will improve the cooling power, while a larger margin will reduce the risk of condensation. The installation needs to be checked after startup and re-configuration. If condensation occurs, the dew point margin must be increased.
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Sensor mode Average Maximum
Uponor > Main menu > Control settings > Cooling > Sensor mode
Resulting supply water temperatures The dew point control is activated if the cooling supply setpoint is below the calculated dew point. The function overrules the cooling supply setpoint, and automatically adapts the temperature according to calculated dew point based on the measured room temperature and humidity of the room/zone. The resulting supply water temperature is the calculated dew point + the dew point margin. Uponor Climate Controller C-46 calculates the dew point using data from Uponor Relative Humidity Sensor H-56, i.e. relative humidity and temperature. It is displayed in the quick menu.
Calculated dew point 18.3 °C
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Heating and cooling changeover: external signal
Bus master
When having a combined emitter system for heating and cooling, the change-over between heating and cooling system can be managed by Uponor Climate Controller C-46 or through it. The climate controller has several options for how to switch between heating and cooling. The most common is to use the general purpose input (5 and 6) in the climate controller, to control that the system should switch from heating to cooling. The general propose input is a contact sensing input that can be connected to a relay in the heat source or a manual switch. The heating and cooling change-over behavior needs to be configured in Uponor Climate Controller C-46. The hydraulic change-over with the diverting valve is managed by the general purpose output (11 and 12) that sends out a free signal using a dry contact output.
Reset
1 2
3 4
5 6
G H I J
C-56 230 V
Uponor > Main menu > Control settings > H/C switchover > Bus master
General purpose output Inactive H+C commands Fault signalling Uponor > Main menu > General settings > General purpose output > Mode
Heating and cooling changeover: Uponor Climate Controller C-46
7 8 9 10 11 12
μ 2A 24VAC/DC
1
Indoor and outdoor Supply water temp. General purpose input
K L
5 6 V ~ 50 Hz
+ -
N L 230 V ~ 50 Hz
0-10V
24 V
L μ2A 230 V ~
N
5
4 3
2
1
Heat pump Pump 3 Diverting valve 4 Actuator 24 V 5 Relay (e.g. Uponor 1000517) 2
Change-over between heating and cooling can also be handled by Uponor Climate Controller C-46, either automatically using the indoor-outdoor temperature controlled switch-over, or a manual command. When the change over from the climate controller is activated, the hydraulic change-over with the diverting valve is managed by the general purpose output (11 and 12) that sends out a potential free signal. At the same time, the same signal can be used through a relay to send a signal to the heat source. The automatic change-over indoor, outdoor and trigger parameters have to be selected in the climate controller, as well as the function of the general purpose output.
Contact closing output from the best source or from manual switch. The supplier of the heat source will be able to give guidelines of which signal is available. Reset
1 2
5 6
7 8 9 10 11 12
μ 2A 24VAC/DC
1
G H I J
C-56
Activating the general purpose output needs to be configured in Uponor Climate Controller C-46.
3 4
230 V
K L
5 6
V ~ 50 Hz
+ -
N L 230 V ~ 50 Hz
0-10V
24 V
L μ2A 230 V ~
H/C switchover
N
5
Bus master Bus slave No bus
2
230 V Uponor > Main menu > Control settings > H/C switchover
1 2 3 4 5
4 Heat pump 3 Pump Diverting valve Actuator 24 V Relay (e.g. Uponor 1000517)
The heat source must be able to receive potential free signal, i e sense a dry contact closure. The supplier of the heat source will be able to give guidelines of which signal is available
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H/C switchover Bus master Bus slave No bus
The secondary pump can also be connected through the Uponor Climate Controller C-46, but the pump relay has a limit of 100 W for the primary and the secondary pump. The primary pump has a maximum consumption of 45 W. Hence, 55 W is left for the secondary pump. An alternative is to connect the secondary pump to the secondary controller, i.e. Uponor Controller C-56.
Uponor > Main menu > Control settings > H/C switchover
Bus master Indoor and outdoor Supply water temp. General purpose input
Reset
1 2
3 4
5 6
7 8 9 10 11 12
C-56
μ 2A 24VAC/DC
Uponor > Main menu > Control settings > H/C switchover > Bus master
5 6
230 V
General purpose output
DEM
Inactive H+C commands Fault signalling Uponor > Main menu > General settings > General purpose output > Mode
Pump management EPG6 The EPG6 is equipped with a Grundfoss circulation pump Alpha 2L 25-60 for circulation of the primary brine circuit. The pump is powered up through the Uponor Climate Controller C-46 and prepared for pump management. The actuator for the three-way mixing valve is also powered by the climate controller and connected to the control signal. The signal adjusts the valve and secures the correct supply temperature using the supply sensor which is also pre-installed in the EPG 6.
Pump management
Internal control Bus control Always on Uponor > Main menu > Control settings > Advanced control > Pump management
In order to get the correct operation of the mixing valve, motorised valves have to be selected in Uponor Climate Controller C-46. The pump management also has to be selected in the climate controller and in order to get optimal control, “bus control” is selected. The bus control will react on the secondary control system and the pump will stop if there is no demand to the zones.
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2012-12-18_UK Production: Uponor AB, IC/EL, Virsbo; Sweden
Uponor Corporation www.uponor.com Uponor reserves the right to make changes, without prior notiďŹ cation, to the speciďŹ cation of incorporated components in line with its policy of continuous improvement and development.