MODERN HYDRONICS 2016 SPRING
BOILER PLANT REVITALIZATION: POINTS TO PONDER
A FRESH PERSPECTIVE ON FLOW VELOCITY PUMP SIZING HOW TO GET IT RIGHT
a publication of
MOISTURE CONTROL FACTS PRODUCT SHOWCASE COMBINED INSTALLATIONS: HEALTH & SAFETY CONSIDERATIONS
CONTENTS MH4 FLOW CONTROL
IS THE WATER MOVING TOO FAST?
New perspectives on a long-standing question. BY JOHN SIEGENTHALER
MH10 RADIANT COOLING
THE LOGIC OF MOISTURE MANAGEMENT
Condensation is not the dark side of chilled water and radiant cooling systems. BY ROBERT BEAN
MH14
PRODUCT SHOWCASE
MH22 PUMPS GETTING IT RIGHT
Sizing a pump is a relatively easy exercise. BY STEVE GOLDIE
MH26 COMBINED SYSTEMS
MIXING HYDRONIC HEATING WATER WITH POTABLE WATER
Designers and installers must be aware of potential issues when considering heat sources. BY LANCE MACNEVIN
MH28 BOILERS
REPLACING BOILERS IN EXISTING BUILDINGS
Boiler replacement in existing buildings is sometimes viewed as an easy task, but if it is done right, it can be challenging. BY MIKE MILLER
MODERN HYDRONICS
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MODERN HYDRONICS HPAC_Feb_Fastform.indd 1
SPRING 2016
| MH3
2016-01-27 2:48 PM
>>Flow Rates
IS THE WATER MOVING TOO FAST? New perspectives on a long-standing question. BY JOHN SIEGENTHALER
O
ne question about hydronic heating that pops up over and over again is this: If the water moves too fast through a hydronic circuit, will the heat it holds be unable to “jump off” as the stream passes through a heat emitter? The answer, from the standpoint of heat transfer alone, is no. But rather than just take my word for it, let’s see why this is true.
mated using complex calculations dependent on variables such as the physical properties of the fluid, geometry of the surface and the speed of the fluid. But you do not have to be a math wizard to understand how the process works. Instead, picture flow moving along the inside of a tube as shown in Figure 1. A thin “boundary layer” of fluid creeps along the inner wall as the bulk of the fluid moves at higher speeds down the “core” of the flow stream. Figure 1 Flow moving along inside of tube
CONVECTION COUNTS The heat output from any hydronic heat emitter is governed by all three modes of heat transfer. For example, before a radiant floor can release heat into the room by thermal radiation and to a lesser extent natural convection, that heat must pass through the floor materials and tube wall by conduction. Before this happens the heat must pass from the fluid stream to the tubing wall by convection. Thus, heat output from a radiant floor or any other hydronic heat emitter is dependent on the convective heat transfer between the water stream and inner wall of the heat emitter. The surface contact area, the temperature difference between the fluid and the wetted surface, and the convection coefficient, govern convection. The latter can be estiMH4 | SPRING 2016
MODERN HYDRONICS
tube wall boundary layer of slow moving fluid limits convection velocity profile of fluid Note low velcoity near tube wall
"core" of flow stream
heat flows from water, through boundary layer, tube wall, into surrounding material
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Modern Hydronics
CHECK IT OUT You can see this effect in the thermal ratings for many types of heat emitters. For example, the heat output of fintube baseboard is often listed for arbitrary flow rates of one gallon per minute (gpm) and four gpm. The output at four gpm will always be slightly higher than at one gpm (all other conditions being the same). Years ago, the Hydronics Institute in the U.S. developed the following formula for estimating the increased heat output of fin-tube baseboard for flow rates above one gpm.
Figure 2 Estimate of baseboard heat output 1.1
Heat output multiplier
1.09
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1.06 1.05 1.04 1.03 1.02
1
2 3 4 5 6 7 8 9 10 flow rate through baseboard (gpm)
Next, go look up the output ratings for fan- or blowerequipped convectors. Just in case you do not have a catalogue handy, the output of a small wall convector operating at a fixed inlet water temperature is plotted in Figure 3. Figure 3 Output of a small wall convector operating at a fixed inlet water temperature 4500 4000
WHERE:
The graph in Figure 2 shows how this formula estimates the heat output of baseboard at flow rates up to 10 gpm. Although there is a definite increase in heat output with increasing flow, the magnitude of the increase is quite small. For example, increasing flow from one to four gpm only increases heat output about six per cent.
1.07
1
Qf = heat output at flow rate f (Btu/hr/ft) Q1 = heat output at flow rate of 1 gpm (Btu/hr/ft) f = flow rate through baseboard (gpm) 0.04 = exponent
Here is an example: Assume the rated heat output of a fin-tube baseboard is 550 Btu/hr/ft at 180F water temperature and flow rate of one gpm. Estimate the output of this baseboard at a flow rate of five gpm and the same 180F water temperature.
1.08
1.01
Heat output (Btu/hr)
Because fluid molecules in the boundary layer do not aggressively mix with those in the core of the flow stream, they give up heat to the tube wall and cool down more than fluid molecules in the core. This limits the rate of heat transfer to the tube wall, especially if the flow is laminar rather than turbulent. You could even think of the boundary layer as a thin layer of “liquid insulation” between the heat contained in the core of the flow stream and the cooler tube wall. The higher the flow rate through the tube, the thinner the boundary layer and the less it restricts heat transfer between the core and the tube wall. Thus, all other things being equal, higher flow rates always increase convective heat transfer, and this boosts heat output for any hydronic heat emitter.
3500 3000 2500 2000 1500 1000 500 0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 water flow rate (gpm)
Once again, you find that increasing the flow rate through the coil increases heat output. As was the case with baseboards, the increase is slight at higher flow rates. You will also find heat output increases at higher fan speeds. This occurs for the same reason as on the water-side of the heat emitter; faster flows reduce the thickness and thus the thermal resistance of the boundary layer between the bulk air stream and the surface of the coil. How about radiant floor circuits? The graph in Figure 4 shows the upward heat output of a 250-foot long circuit of 1/2-inch PEX tubing embedded at 12-inch spacing in a fourinch bare concrete slab. The supply water temperature is 110F. The only thing that is changing is flow rate.
MODERN HYDRONICS
continued on MH6 SPRING 2016
| MH5
>>Flow Rates continued from MH5
to-water efficiency of 25 per cent provides flow and head, the electrical power needed to operate this one circuit can be calculated as follows:
Figure 4 Upward heat output Upward heat output (Btu/hr)
8000 7000 6000 5000 4000
WHERE:
3000
W = required electrical power input to circulator (watts) f = flow rate (gpm) ∆P = pressure drop (psi) 0.25 = assumed wire-to-water efficiency of circulator (decimal per cent)
2000 1000 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 Circuit flow rate (gpm)
Increased flow rate again results in increased upward heat output. The gains are much more noticeable at lower flow rates than at higher flow rates. At 0.2 gallons per minute, only 10 per cent of the maximum flow rate shown on the graph, the circuit releases about 44 per cent of the maximum heat output. Increasing flow from one to two gpm only increases heat output about 11 per cent.
THE OTHER SIDE OF THE STORY Hopefully you are convinced that the heat output of any hydronic heat emitter increases with increasing flow rate. From the standpoint of heat transfer only, faster flow is always better. However, heat transfer is not the only thing that needs to be considered when designing hydronic systems. Issues such as head loss, piping erosion and system operating costs also play a role in selecting flow rates and subsequent piping/circulator hardware. Here is where the downside of high flow velocity becomes apparent. One very significant drawback to high flow rate is sharply increased operating cost. Any time there is flow through a piping component, there is head loss and that head loss has an associated circulator input wattage. Thus, every hydronic component has an operating cost. Here is an example of how quickly that operating cost can climb as flow rates are increased. Take the 250-ft. by ½ in. PEX floor heating circuit previously discussed. Operating at one gpm and 110 F supply temperature, this circuit releases 7117 Btuh. Bumping the flow rate to two gpm with the same supply temperature increases heat output to 7902 Btuh (a modest 11 per cent increase). The circuit’s head loss at one gpm is 9.98 ft. The pressure drop corresponding to this head loss is 4.3 psi. Assuming a small wet-rotor circulator operating with a wireMH6 | SPRING 2016
Assuming the circuit operates for 3000 hours a year in an area where electricity costs $0.10/kWhr, the annual electrical operating cost of this single circuit is $2.24, probably less than you paid for your last hamburger. Now, let’s double the flow rate through the circuit to two gpm. The circuit’s head loss climbs to 33.58 ft. and the corresponding pressure drop is 14.4 psi. Assuming the same circulator efficiency, the electrical power required to operate the circuit climbs to 50 watts. The annual electrical operating cost for this one circuit using the previously assumed conditions is now $15. The added annual cost to operate this circuit at two gpm rather than one gpm is $12.76. Keep in mind this is for one circuit and one year. Assuming 10 identical circuits operating for 20 years with electricity inflating at four per cent per year, the total added operating cost is staggering.
WHERE: CT = total operating cost of a period of N years ($) C1 = first year operating cost ($) i = inflation rate on annual cost (decimal per cent) N = number of years in life cycle Spending $3,800 more in electricity to achieve an 11 per cent boost in heat output (with a corresponding 11 per cent added fuel required to produce this heat) just does not make sense.
WEARING THIN Another effect associated with increased flow velocity is the potential for erosion of copper tubing. According to a re-
MODERN HYDRONICS
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>>Flow Rates continued from MH6
port published by the National Association of Corrosion Engineers, sustained flow in copper tubing should not exceed four feet per second to avoid potential erosion issues. This corresponds to the velocity limit often imposed to avoid objectionable flow noise for pipes routed through occupied spaces. According to one reference, PEX tubing can withstand sustained flow velocities in excess of 90 feet per second at elevated temperatures without damage. However, such velocities are completely beyond the range of practical system design from the standpoint of head loss, flow noise and operating cost. My suggestion is to size PEX tubing for maximum flow velocities in the range of four feet per second. Figure 5 lists the flow rates corresponding to flow velocities of four feet per second for common sizes of copper, PEX, and PEX-AL-PEX tubing. It also lists the flow rates associated with flow velocities of two feet per second. These minimum flow rates are recommended to provide air bubble entrainment. Figure 5 Flow rates corresponding to flow velocities
Tubing size / type
3/8" copper
MINIMUM Flow rate
MAXIMUM Flow rate
based on 2 ft/sec (gpm)
based on 4 ft/sec (gpm)
1.0
2.0
1/2" copper
1.6
3.2
3/4" copper
3.2
6.5
1" copper
5.5
10.9
1.25" copper
8.2
16.3
1.5" copper
11.4
22.9
2" copper
19.8
39.6
2.5" copper
30.5
61.1
3" copper
43.6
87.1
3/8" PEX
0.6
1.3
1/2" PEX
1.2
2.3
5/8" PEX
1.7
3.3
3/4" PEX
2.3
4.6
1" PEX
3.8
7.5
1.25" PEX
5.6
11.2
1.5" PEX
7.8
15.6
2" PEX
13.4
26.8
3/8" PEX-AL-PEX
0.6
1.2
1/2" PEX-AL-PEX
1.2
2.5
5/8" PEX-AL-PEX
2
4.0
3/4" PEX-AL-PEX
3.2
6.4
1" PEX-AL-PEX
5.2
10.4
MH8 | SPRING 2016
THINK AVERAGES Finally, if you still think the water can move too fast for the heat to jump off, consider the following situation as a practical rationale that this is not the case. A fin-tube baseboard is operated at three different flow rates, but with the same 180F entering water temperature, and the same surrounding air temperature (see Figure 6). Figure 6 Fin-tube baseboard at three flow rates
Tin = 180 ºF
Tout = 160 ºF
low flow average water temperature = 170 ºF
Tin = 180 ºF
Tout = 170 ºF
medium flow average water temperature = 175 ºF
Tin = 180 ºF
Tout = 178 ºF
high flow average water temperature = 179 ºF
At the low flow rate the temperature drop across the heat emitter is 20F and thus the average water temperature in it is 170F. When flow is boosted to the medium level the outlet temperature rises to 170F and hence the average water temperature inside the heat emitter is 175F. Finally, when the flow rate is boosted to the high level, the outlet temperature of 178F is a mere 2F below the inlet temperature. The average water temperature is 179F. In every case the average water temperature inside the heat emitter increased as flow increased. Increasing the average water temperature inside any heat emitter always increases heat output. There is just no way around the physics of this situation.
SAY IT AIN’T SO The next time you hear someone lament that their system is not releasing sufficient heat because the water is flowing too fast through the heat emitters, please use what has been discussed here to convince them otherwise. Also, be sure they understand the consequences of excessive flow rates. Hundreds and even thousands of dollars are usually at stake. John Siegenthaler, P.E., is a mechanical engineering graduate of Rensselaer Polytechnic Institute and a licensed professional engineer. He has over 34 years experience in designing modern hydronic heating systems. Siegenthaler’s latest book, Heating with Renewable Energy, was released last month (see p55 or visit www.hydronicpros.com for more information). MODERN HYDRONICS
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>>Radiant cooling
and radiant cooling panels is a straw man argument; regardless of HVAC system type, moisture must be managed for biological concerns, hydrolysis, dimensional stability of hygroscopic materials, and preservation of materials, respiratory comfort, and thermal comfort. Condensation becomes a moot point if you control moisture for these reasons (setting aside discussions around pipe insulation, infiltration, and so on). Let’s look at each of these conditions.
Condensation is not the dark side of chilled water and radiant cooling systems.
1. BIOLOGICALS
BY ROBERT BEAN
T
here is no shortage of articles describing the risks and jeopardies of using chilled water and radiant cooling systems, and how these systems cause condensation. It seems that mysterious aliens with a hidden agenda handed out scripts to industry authors instructing them to repeat in a James Earl Jones voice, “Luke, be wary of the radiant cooling systems – it shall condense and rain upon the galaxy.” To this I reply: What are the facts? Here is a serving of universal logic for critics of chilled water and radiant cooling systems: 100 per cent of all condensation problems in buildings conditioned exclusively with refrigerated air, did not have a chilled water radiant cooling system to blame. We do not hear Darth Vader voices from the “refrigerated air only” camp. Only bad designers and bad installers can be held accountable for sweating refrigerated air-based systems because good designers and good installers would never let moisture become a problem. Good designers and installers spend hours evaluating moisture loads and assembling building and HVAC components properly so sweating does not occur. But apparently with chilled water and radiant cooling the good logic of moisture management gets tossed to the far corners of the galaxy because evidently only bad designers and bad installers are permitted to work on these systems. That is definitely dark side thinking. It is time to stop holding radiant cooling and chilled water systems to some unreasonable double standard and talk about the real problem, which is moisture. Moisture is the root of all that is good and bad in the universe. It is an equal opportunity offender and does not discriminate between HVAC system types. Statistically one is far more likely to find moisture problems in refrigerated air systems than chilled water radiant systems due to the installation ratio of air over water. Here are six reasons why condensation with chilled water
MH10 | SPRING 2016
Without moisture control, numerous biological risks develop which support the growth of bacteria, viruses, fungi (moulds) and mites. According to a ASHRAE Transaction, Human Exposure to Humidity in Occupied Buildingsi and the ASHRAE Handbooks, humidity at less than 30 per cent or more than 60 per cent can introduce higher multiple microbial risk factors. As noted in the Environmental Protection Agency (EPA) Indoor Air Plus program, “You have to control humidity to below 60 per cent RH.” You will also find support from the medical community on this range. Stephanie H. Taylor, M.D. states, “The movement and infectivity of bacterial, viral, and fungal organisms vary with the RH of the air…” This is supported by Dr. R.L. Dimmick from the Naval Biological laboratory (NBL), Univ. CA, Berkeley who said, “Moisture content may, indeed, be the most important environmental factor influencing the survival of airborne microbes.” Figure 1 Indirect health effects of RH
Taylor goes on to say, “Maintaining the relative humidity of hospital indoor air between 40 per cent and 60 per cent can significantly decrease healthcare associated infections.”ii In addition to ASHRAE, the EPA and NBL this position is supported by numerous authoritative organizations including the Canadian Centre for Occupational Health & Safety, Health Canada and ACCA and The Indoor Environment & Energy Efficiency Association.
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2. HYDROLYSIS Hydrolysis is a water-based reaction that is used to break down certain chemicals. Studies by Dr. Richard L. Corsi, University of Texas (Austin), show paint emissions (specifically HC-O-O) are affected by rising relative humidity.iii Matthews et al, noted that changing the indoor conditions from 68F (20C) and 30 per cent relative humidity (RH) to 79F (26C) and 60 per cent RH would result in two to fourfold increases in formaldehyde concentration for the same air change rate. Hodgson et al, stated in its study on the topic, “This suggests that indoor humidity has a substantial impact on formaldehyde emission rates and concentrations.”iv
tions have substantially different relative humidity requirements…Specimens with metal components may benefit from RH levels that are as low as possible. Organic artifacts require more moderate RH levels to prevent desiccation or embrittlement. Most specimens benefit from RH levels that are moderate and stable to prevent physical damage that can be caused by wide climatic shifts. Generally, recommendations for museum environments are given as to [sic] 50 per cent while attempting to minimize dramatic swings to between 40-60 per cent, even if broad seasonal trends are hard to avoid.” viii
5. RESPIRATORY COMFORT Research showing the effects of high and low humidity on respiration discomfort supports the humidity ranges above. In one study the least amount of people dissatisfied (PD) at 10 per cent, corresponds to space conditions of 20 per cent to 60 per cent relative humidity for a temperature range between 68F (20C) and 78F (26C). Increases in discomfort were observed during increases in relative humidity at a given air temperature. For example, at 72F (22C) there is a 10 per cent increase in people dissatisfied going from approximately 40 per cent RH to 65 per cent RH; and an additional 10 per cent dissatisfaction going from 65 per cent RH to 80 per cent RH.ix,x
Figure 2 Effect on hygroscopic material
3. DIMENSIONAL STABILITY OF HYGROSCOPIC MATERIALS
6. THERMAL COMFORT
When hygroscopic materials such as wood are operated in an uncontrolled environment their moisture content can fluctuate. Such changes lead to dimensional instability due to shrinking and swelling. Both Canada Mortgage and Housing Corporation’s Wood Frame Envelopes Best Practice Guidev and Forest Products Laboratory’s (U.S. Department of Agriculture/Forest Services) Wood Handbookvi provide for the ideal “in service” wood moisture content as between six per cent and 14 per cent. This ideal in-service range corresponds to relative humidity between 40 per cent+/-10 per cent and 60 per cent+/-10 per cent at temperatures typical for space heating and cooling.
Two authoritative documents addressing humidity and thermal comfort are ANSI/ASHRAE Standard 55 and ISO 7730. At the humidity conditions defined in points 1 through 5, indoor climate engineers will meet the requirements of both the ASHRAE and ISO Standards. Figure 3
4. PRESERVATION OF MATERIALS According to the Image Permanence Institute (IPI), a university-based non-profit research laboratory devoted to preservation research, at approximately 73F dry bulb, “no risk” conditions exists for chemical decay of organic materials between 25 per cent RH and 35 per cent RH for a dew point condition between 45F and 59F.vii The American Museum of Natural History regarding preservation and temperature and relative humidity says this; “Different types of collecWWW.HPACMAG.COM
MODERN HYDRONICS
continued on MH12 SPRING 2016
| MH11
>>Radiant cooling continued from MH11
FINAL THOUGHTS Now that you have 60 per cent RH as recommended maximum, do you know what the sea level dew point is at say a 75Fdb? It is 60F. What is the lowest temperature a radiant floor cooling system should operate at? It is 66F. That would be a six degree Fahrenheit safety margin – far more than required by good engineering practice. If you have made it this far you should conclude that there is zero logic in stating unequivocally, “don’t use chilled water and radiant cooling systems because of moisture concerns.” It is a silly statement. You must provide moisture control regardless of the HVAC type for the six reasons outlined above.xiii With chilled water systems the control of space moisture is done with a dedicated outdoor air system. Noted DOAS expert Stanley A. Mumma, Ph.D., P.E., Fellow ASHRAE, Professor Emeritus of Architectural Engineering, Penn State University states, “The DOAS approach effectively eliminates biological contaminants and inadequate ventilation. It also avoids building-wide distribution of indoor chemical contaminants.”xiv The need for a hybrid with two systems, one for ventila-
tion and one for cooling is actually a good thing. Indoor air quality and energy specialists will attest that dedicated ventilation with radiant cooling provide superior control and efficiency over dual duty air only systems. In commercial systems Rumsey and others have demonstrated these hybrid systems can also be installed for less cost.xv So hybrid systems can enable better air quality, better comfort, better efficiency and for some projects – a lower capital cost. Controlling moisture is a fundamental principle. It enables the use of chilled water and radiant cooling systems without going off the deep end on condensation concerns. Condensation is not the dark side of chilled water and radiant cooling systems – moisture is. Take care of the moisture and you take care of the dark side. Robert Bean, who is president of Indoor Climate Consultants Inc., is a Registered Engineering Technologist in building construction through the Association of Science and Engineering Technology Professionals of Alberta and a Professional Licensee in mechanical engineering through the Association of Professional Engineers, Geologists and Geophysicists of Alberta. References
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iS terling E M, Arundel A, Sterling T D., 1985 CH-85-13 No 1, ASHRAE Transactions, 1985, Vol 91, Pt 1. 11p. ii Taylor, S.H. (2014) Infectious Microorganisms Do Not Care About Your Existing Policies. Engineered Systems <http://www.esmagazine.com/articles/96849-infectiousmicroorganisms-do-not-care-about-your-existingpolicies> accessed Jan. 2016 iii Corsi, R.L., 2013. Relative humidity and paint emissions (HC-O-O). Building Energy & Reactivity Complex Interactions. Simple Solutions, IAQ 2013 – Environmental Health in Low Energy Buildings – Vancouver, BC, Canada October 17th, 2013 iv Hodgson, A.T., et al. 2004. Volatile Organic Compound Concentrations and Emission Rates Measured over One Year in a New Manufactured House. Lawrence Berkeley National Laboratory. <http://www.osti.gov/scitech/servlets/purl/838617> accessed Jan. 2016 v Wood Frame Envelopes: Best Practice Guide. Canada Mortgage and Housing Corporation. 1999. <http://www.naturallywood.com/sites/default/files/CMHC-BestPractice-Guide-Wood-Frame-Envelopes.pdf > accessed Jan. 2016 vi W ood Handbook. Forest Products Laboratory. U.S. Department of Agriculture/Forest Services) http://www.fpl.fs.fed.us/products/publications/several_pubs.php?grouping_ id=100 accessed Jan. 2016 vii Image Permanence Institute. <https://www.imagepermanenceinstitute.org/ environmental/research/preservation-metrics> accessed Jan 2016 viii Temperature and Relative Humidity (RH). American Museum of Natural History.<http:// www.amnh.org/ourresearch/natural-science-collections-conservation/generalconservation/preventive-conservation/temperatureand-relative-humidity-rh >Accessed Jan. 2016 ix Toftum, J., Jørgensen, A.S., Fanger, P.O. 1998. Upper limits of air humidity for preventing warm respiratory discomfort, Energy and Buildings, Volume 28, Issue 1, August 1998 x Fang L, Clausen G, Fanger PO. Impact of temperature and humidity on the perception of indoor air quality. Indoor Air 1998; 8:80–90. xi ANSI/ASHRAE Standard 55 Thermal Environmental Conditions for Human Occupancy xii I SO 7730 Ergonomics of the thermal environment -- Analytical determination and interpretation of thermal comfort using calculation of the PMV and PPD indices and local thermal comfort criteria. xiii Setting aside discussions on duct and pipe insulation. xiv http://www.healthyheating.com/DOAS/DOAS_Introduction.htm#.VpbI3PkrL9g xv S astry, G., Rumsey, P. 2014. VAV-vs- Radiant-Side-By-Side-Comparison, ASHRAE Journal, vol. 56, no. 5, May 2014. < https://www.ashrae.org/resources--publications/ periodicals/ashrae-journal/features/vav-vs--radiant-sideby- side-comparison> Additional resources can be found at www.hpacmag.com, search radiant cooling and condensation.
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range of static pressures.
dronic heating and cooling applications. The ProPEX ASTM F1960
www.ecovisionsales.ca/ecosmart.htm
expansion fitting offering includes a complete line of tees, elbows, couplings and transition fittings as well as a flange adapter kit. New
Viessmann’s Vitocrossal 300, CU3A is a
PEX pipe cutting tools and larger sizes of PEX-a Pipe Support (a steel
compact, floor standing stainless steel
channel that enables hanger spacing similar to that of copper for
condensing boiler suited to retrofits and
suspended-piping applications) are also available.
cast-iron boiler replacements in residen-
www.uponor.ca
tial and small commercial applications. Operating features include quiet opera-
The HBX Wi-Fi zoning system allows users to remotely control multiple
tion and 95 per cent AFUE efficiency and
zones within a living space. The system incorporates a ZON-0550 along
high temperature operation up to 90C
with a two-wire THM-0300 programmable thermostat and Wi-Fi commu-
(194F). High water volume extends burn-
nication ThermoLinx module. Each zone can be viewed or configured from
er run time and reduces cycling. Units do
smartphone or tablet devices. The ZON-0550 has the capability to con-
not need a dedicated boiler pump or low
trol up to four zones plus fancoil control, with expansion of up to four
loss header. www.viessmann.ca
additional zone units that communicate wirelessly, for a maximum of 20 zones. It is suited to retrofits, as well as new installs. It incorporates a
The RAUPEX Speed radiant over-
system pump output, auto changeover, intermittent fan control and two
pour fastening system from RE-
demand outputs. The Wi-Fi lzoning app is free to download for both Apple
HAU allows contractors to install
and Android. The app provides the capability to control comfort for mul-
heating pipe in overpour and con-
tiple locations in real time. www.hbxcontrols.com
crete installations. O2 barrier pipe with hook-and-loop wrap is walked on to the mat, which has an adhesive backer that attaches to a range of different thermal insulation, concrete and plywood materials. The pipe can be detached and repositioned. The ½ in. pipe is offered in 300 and 1000 ft. (91.4 and 304.8 m) coils and the 3-mm. thick mat is offered in 3.1 by 52.9 ft (0.93 by 16.13 m) rolls. www.na.rehau.com/speed
continued on MH16 MH14 | SPRING 2016
MODERN HYDRONICS
WWW.HPACMAG.COM
GET COMFORTABLE WITH HIGHER EFFICIENCY. Up to 99% with Lasting Durability. Engineered for high performance with ultra-reliability, RBI commercial boilers and water heaters are as strong as they are diverse. From 199 to 5,000 mbh, RBI has the solutions to any application. rbiwaterheaters.com
Futera III
>>Products continued from MH14 The Stiebel Eltron Accelera 300 heat pump water
Roth X-PERT S5 5-layer pipe consists of a
heater is designed to extract up to 80 per cent of its
layer of ethylene vinyl alcohol polymer
energy requirements from the energy in the air around
(EVOH) sandwiched between two layers of
it. Its compressor and fan consume one kWh of elec-
DOWLEX 2344 polyethylene copolymer
tricity to generate the heat equivalent of three to five
resin and two layers of adhesive for long-
kWh. It runs on one 15 amp. 240 V breaker. It has an
term hydrostatic design strength. The outer
80 gallon capacity, an energy factor of 2.73 and power
layer of DOWLEX 2344 also provides a pro-
input of 2.2 kW with annual power consumption of
tective shield for the oxygen barrier. PE-RT pipe has a DIN 4726 oxygen
1391 kWh/year. A roll-bond wrap-around condenser
barrier to prevent corrosion of ferrous components, or the premature
prevents refrigerant contamination of the water and in
breakdown of inhibitors in propylene glycol antifreeze systems. The pipe is
conjunction with the glass-lined tank, mitigates hard
rated for 100 PSI at 180F and 200 PSI at 73F. www.roth-usa.com
water problems. Engineered to satisfy 90 per cent of hot water needs, the heat pumps feature an electric booster element at the top of the
Lochinvar Knight heating boiler is offered in mod-
tank for periods of high demand. www.stiebel-eltron-USA.com
els 80 000 to 285 000 Btuh. Boilers of one or more sizes can be combined into a single cas-
SpacePak’s Solstice Extreme air-to-water re-
cade. Installations can be fine tuned using an in-
verse cycle heat pumps use hydronics as the
ternal cascading sequencer with multiple pro-
primary source for heating and cooling de-
grammable system efficiency optimizers. Features
mands. Units can be installed at ground level,
also include outdoor reset for each temperature
on rooftops or in remote locations. The con-
loop and programmable post purge to allow pumps
denser coil is larger than standard units and
to operate after a call has been satisfied. The boil-
operates with a COP of up to four. Designed for
ers permit up to 100 ft. of air intake and 100 ft. of
heating in colder climates, the heat pump produces up to 48 000
exhaust vent with 3 in. PVC, CPVC, polypropylene
Btuh at 0F at 140F heating supply. www.spacepak.com
or stainless steel pipe. www.lochinvar.com Caleffi’s suite of magnetic separation products address problems caused by ferrous oxide debris found within hy-
Products are available through:
dronic systems. The debris, which is abrasive and often microscopic, is created from the oxidation of iron or steel
Canada (except Quebec):
materials. It can deposit onto heat exchanger surfaces and accumulate in other components including circulators, wreaking havoc caused
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by reduced thermal efficiency and premature equipment wear. The dirt separator removes these dirt particles, collecting them in a large collection chamber from which they can be flushed, even while the system is in operation. The devices are designed to remove the smallest particles, with very low head loss. www.caleffi.com Navien is introducing their next generation combi-
In Quebec:
boiler, the NCB-E. Navien’s NCB series is unique in
Trilex Inc.
house heating system while also providing the do-
1-450-582-1184
ment, now with a Grundfos pump, an integral air vent,
that, as one unit, it is capable of providing a whole mestic hot water output of a stand-alone tankless water heater. The NCB-E will be a rolling replacea PRV top connection, a quieter fan and a new front cover bevel design. www.wholehousecombi.com
continued on MH18 MH16 | SPRING 2016 HPAC_Feb_Aquatech.indd 1
MODERN HYDRONICS 2016-01-20 3:13 PM
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>>Products continued from MH16
The FlexCore fire tube boiler from RBI has a conical shaped tube sheet coupled with rounded rectangular fire tubes to allow for even heat transfer at all levels of the heat exchanger. The coolest water enters opposite of the down-fired burner, optimizing efficiency in low temp condensing applications. Available in 1500 and 3000 MBH, the boiler offers a 96.8 per cent thermal efficiency rating by AHRI with 5:1 combustion turndown on individual units. HeatNet 3.0 with touch screen technology provides a control platform capable of integrating the unit into various applications including variable primary systems. Complimentary online boiler system monitoring is available. HeatNet Online allows users the ability to change set points and trend boiler plant performance, as The Amvic expanded polystyrene insulated
well as receive updates by text or e-mail. www.rbiwaterheaters.com
radiant PEX panel has nubs, which form a “mushroom” shape to lock 3/8 in., 1/2 in., 5/8
Weil-McLain Canada’s Evergreen high-efficiency condensing boiler deliv-
in., 3/8 in. and 1 in. PEX piping firmly in place.
ers up to 96.5 per cent AFUE. The boiler is suited to large residential and
The pex piping is inserted into the oversized,
light commercial applications and is available in 220, 299, 300 and 399
four sided tongue and groove interlock sys-
MBH sizes. Floor or wall-mountable, it features a stainless steel heat
tem by walking on the tube. Once inserted
exchanger, quick setup with 10 presets, and an easy-to-use setup wizard
the pipe will be properly positioned and seat-
for single and multiple boiler installations. Features include zone stack-
ed in the panel where it can be encased in
ing for up to 24 programmable zones with no external panel required, low
concrete. The panels are available in residen-
NOx (less than 20PPM certified), common combustion air venting and
tial and commercial styles.
two network and two local priorities per network boiler system.
www.amvicsystem.com
www.weil-mclain.ca/products/evergreen
MH18 | SPRING 2016 HPAC_Feb_Tamas.indd 1
MODERN HYDRONICS
continued on MH20
WWW.HPACMAG.COM
2016-01-26 1:15 PM
>>Products continued from MH18 The Tamas Hydronic VFD booster pump
The Webstone Add-
package can be assembled in many
A-Gauge tool allows
configurations. It is programmable for
installers to utilize
up to five pumps. The control box that
an
is attached to the package frame
connection to quick-
comes with LED operational lights and
ly add a gauge port
manual override switches that can be
to any system. Mod-
set to automatic (VFD run), or manual
els
(full output), or in the off position.
bottom or centre-
These features allow servicing without
back mounted tem-
having to compromise the building load.
perature and/or pressure gauges (sold separately).
www.tamashydronic.com
The tool features a 1/8 in. capped bleeder and is con-
existing
hose
accommodate
structed from lead-free CleanBrass and guaranteed for life. www.webstonevalves.com
Viega’s MegaPress system for installing schedule 5 - schedule 40 black iron pipe is designed to make secure connections in less than seven seconds. More than 200 fittings are available
tekmar has unveiled an app
ranging in sizes from ½ in. to 2 in., including el-
and online tool to assist us-
bows, couplings, reducers, tees, reducing tees,
ers in designing their own
threaded adapters, caps, flanges and unions.
snow and ice melting solu-
The fittings use a stainless steel grip ring with
tions. Users enter their de-
an EPDM sealing element. The system can be
sign parameters and instant-
installed under flow conditions.
ly
www.viega.us/7333.htm
information they need to
receive
the
specific
specify the correct control Grundfos’s Comfort hot water recirculation
solution, prepare a quote,
pump with AutoAdapt features three operation
and successfully complete
modes. The AutoAdapt mode learns, stores and
an installation. The tool pro-
adapts operation time to the consumption pat-
vides access to mechanical and electrical drawings
tern of the homeowner. The temperature mode
(including packages for 28 different applications), a bill
keeps the water temperature within an automat-
of materials, and manuals and literature on tekmar
ically detected range in the individual system.
snow and ice melting controls.
The 100 per cent mode lets the pump run con-
www.tekmarControls.com
stantly at full speed. www.grundfos.ca Taco SFI series pumps’ bearing
NTI’s Vmax gas boilers
frame design features sealed-
have a fully modulat-
for-life bearings that meet indus-
ing burner with a 6.5:1
try requirements for a minimum
turn-down
L 10 life of 60 000 hours. Op-
stainless steel down-
tional, re-greaseable bearings
fired heat exchanger
are available. A slip-on shaft
and a field convertible
sleeve facilitates seal mainte-
gas system. The units
nance in the field. The dry shaft
include a built-in pri-
design eliminates contact with
mary loop, circulator
the circulating fluid, so corro-
and high-energy spark
sion-resistant shaft materials
ignition as standard
are generally not required. The
features. Maximum in-
pumps also feature flush seal line taps, allowing the installation of a filter to protect the
put is 110 000 Btuh. A
seal from non-condensable particles. Pressure tappings on suction and discharge connec-
Plus version is available with a built-in indirect water
tions are provided as a standard feature. www.TacoComfortSolutions.com
heater. www.ntiboilers.com
MH20 | SPRING 2016
MODERN HYDRONICS
ratio,
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>>Pumps
Getting it right Sizing a pump is a relatively easy exercise. By Steve Goldie
T
troubleshooting makes up a large part of my job. When things do not seem to be working quite like they should be in a hydronic system, I am often the guy who gets the call. No heat calls, not enough hot water calls, too much noise calls; whatever the issue, I will visit the site to determine what the problem is. Many of the calls start something like this; â&#x20AC;&#x153;that (boiler, pump, hot water tank, and so on) you sold us is a piece of junk.â&#x20AC;? I admit, even with the most stringent quality control procedures in place, every manufacturer will occasionally ship a dud, but the issues are most often the result of improper installation or application, rather than faulty equipment or components. One of the most common components in a hydronic system is also one of the most often maligned: the simple circulating pump. The circulator is the heart of a hydronic system and it has the job of moving the heating or cooling fluid throughout the system. If you have no flow, you have no heating or cooling. As we will see however, no heat or no flow does not always mean the pump is no good. Circulators in closed loop hydronic systems are typically centrifugal pumps. The centrifugal pump transfers mechanical energy from the motor to the fluid through the rotating impeller. The fluid flows from the inlet to the
MH22 | SPRING 2016
impeller centre and out along its blades. The centrifugal force increases the fluid velocity causing an increase in the fluid pressure from the pump inlet to its outlet. They do not so much create pressure, rather they create a pressure differential and when this differential is greater than the friction resistance (head loss) in the piping, the fluid moves. How much fluid can be moved and how much head pressure is created is a function of many factors such as the rotational speed of the impeller, the size and diameter of the impeller and the horsepower of the motor. All of this data is calculated and plotted on graphs or pump curves. I am not going to go into a detailed explanation of these as I am sure most, if not all of you, are somewhat familiar with pump curves. In addition, I do not believe the problems I see with pump sizing are the result of people misreading pump curves. Issues with pumps usually occur when they are sized without the correct information, or when something in the distribution piping, or the piping itself prevents them from doing their job properly. Sizing a pump is a relatively easy exercise. Pumps are sized with two critical pieces of information: how much fluid do you want to move (flow) in gallons per minute (gpm), and how much pressure do you need to overMODERN HYDRONICS
Figure 1 The pump curve shows how the pump will perform with varying head or flow requirements. Courtesy Bell & Gossett
come, typically measured in feet of head. Flow and head pressure; that is the information wholesalers need in order to provide you with the correct circulator. This is the data represented on the two axis of a pump curve. As shown in Figure 1, the x axis (vertical) shows total head while the y axis (horizontal) shows flow capacity, typically in gpm. All too often customers ask for a pump sized by horsepower alone. This is problematic as there can be quite a range of varying duty points with the same horsepower, and identical duty points can be achieved with multiple horsepowers. As an example, if you were in looking for a 1/6 horsepower pump, I could give you one that could supply eight gpm at 28 feet of head, or a different one that could supply 45 gpm at five feet of head. Which one would be correct, if either? One can deliver relatively low gpm at a high head while the other can deliver lots of gpm at a relatively low head. If you remember nothing else, remember that pumps are sized by flow and head, not by horsepower or pipe size. If you are working on a new construction project this information
continued on MH24 WWW.HPACMAG.COM
>>Pumps continued from MH22
“If you remember nothing else, remember that pumps are sized by flow and head, not by horsepower or pipe size.”
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should have been calculated and appropriately-sized pumps should have been selected by the mechanical engineer or designer. If the pump selection is up to you then calculate based on how many Btus you want to move. Use the universal hydronic formula, GPM = Btuh/(500x T). So, if you want to move 100 000 Btuh at a 20 degree T, that would be 10 GPM (100 000/ (500x20)). For the head pressure, if you have a reasonable estimate of the total length of piping and number of fittings in the piping, calculating the head pressure is also quite simple. If you choose a circulator with this information and it does not seem to be doing the job, you need to look for another reason. Is the pipe size too small? Are the lines fully bled of air? I have lost count of the number of times I have been called to a job with flow issues and the contractor swears up and down that all the air is out. Sure enough, when I get there I discover the problem is an air lock. Remember, a closed loop circulator does not create a lot of positive pressure, it creates a pressure differential across its inlet and outlet. This differential is easily absorbed by trapped air and it does not require a lot of air to lock up a circuit. A bubble the size of a dime could potentially stop the flow in a ½" circuit. It is somewhat understandable when you encounter what appears to be a flow issue to assume the circulator may be the culprit. I urge you not to be too hasty in installing a larger pump. I often see components that have boiler connection sizes that are much smaller than the pipe size
MH24 | SPRING 2016 HPAC_Feb16_Centrotherm_CSA.indd 1
MODERN HYDRONICS 2016-02-01 1:54 PM
required to deliver the amount of Btus they are rated for. Plate heat exchangers and indirect hot water tanks are two common examples. The undersized connection will only be a problem if the installer fails to upsize the connected piping to match the Btu load they are hoping to deliver. The pinch point at the connection will only create a slight increase in head pressure and will not significantly impair flow as long as the accumulated piping is sized correctly. I wish I had a dollar for every time I have seen a scenario where the indirect tank does not deliver the expected recovery, the tank gets blamed, then the boiler gets blamed, and finally, the pump gets blamed. There is a lot of blaming going on until the pipe size is corrected, and low and behold, all of a sudden the pile of junk boiler, tank and pump suddenly perform just as advertised. Getting it right can be as simple as following the manufacturer’s instructions, following good piping practice, and having all the correct information. Guessing on things such as pump and pipe sizing will ultimately cost you time and money and possibly business. Let’s take the extra time we need to do it properly the first time. Steve Goldie learned his trade from his father while working as plumber in the family business. After 21 years in the field, he joined the wholesale side of the business in 2002. His expertise is frequently called on to troubleshoot systems and advise contractors. He can be reached at sgoldie@nextsupply.ca. WWW.HPACMAG.COM
>>Combined systems
Mixing hydronic heating water with potable water Designers and installers must be aware of potential issues when considering heat sources. By Lance MacNevin
W
e know that hydronic radiant heating is a comfortable technology, so efficient that a heated floor can often satisfy a building’s heat loss with low-temperature fluid, even below 115F (46C). This gives radiant heating systems the flexibility to work with a variety of heat sources, including water heaters, subject to codes and local requirements. In fact, CSA B214/12 allows combined space and waterheating applications, as long as the water heater is “designated by the manufacturer for use in dual-purpose applications” and meets specific product standards. This application of a water heater provides an inexpensive source of warm water for smaller radiant heating systems, reducing the up-front cost of a separate heat source. However, installers should be aware that building a combined hydronic and potable system, whereby the potable water contacts hydronic heating components such as pipes, fan coils, valves, expansion tanks and manifolds, could create potential health and safety issues. Some of those issues follow. Certain hydronic heating components are not intended or certified for use with potable water. These items can include radiators, pipes and fittings, fan coils, mixing valves, expansion tanks or distribution manifolds. Such items are not necessarily marked as “Non Potable”; the absence of a “Potable Water” mark may be the only clue provided as to the item’s intended purpose. These hydronic components might contain lead within the brass alloys; trace amounts of cutting oil that are OK in hydronic systems but not OK in drinking water; or other materials that are not approved for drinking water contact. That is why CSA B214-12 says, “All piping, components, and heat-transfer devices in contact with the potable water shall be intended for use in potable water systems.”1
01
MH26 | SPRING 2016
Therefore, do not assume that any product sold for hydronics is automatically tested and approved for use with potable water. If non-potable components are installed so that plumbing water flows through them, then this type of installation most likely would violate regulations, may contaminate drinking water, and may void product warranties. Fresh water usually contains lots of dissolved oxygen and disinfectants such as chlorine or chloramines. Some hydronic components can be corroded or otherwise damaged by contact with these substances. For example, if you install an iron-body mixing valve or circulator in a combined system, that component could start to rust immediately. A rubber or plastic hydronic valve seal or gasket could be attacked by disinfectants in the fresh water and cause a leak. Or, the plastic tubing itself might not be intended for contact with hot chlorinated water (although most are) and might fail prematurely. When building a combined system, the installer must verify that each component is approved and recommended for use with potable water to avoid premature product failure. The bacterium legionella pneumophila is found in both potable and non-potable water systems, especially with stagnant water between 95F (35C) and 122F (50C). Legionella can cause legionnaires’ disease or legionellosis, a severe, often lethal, form of pneumonia that occurs primarily when steam or vapour containing legionella is inhaled. The disease was named in 1976, when American Legion members who attended a Philadelphia convention suffered from an unusual pneumonia (lung infection). Legionella is in the news again these days, with several outbreaks identified in large cities, and innocent victims perishing. Our society is vulnerable, and our plumbing industry must do what it can to protect the public. In a potable-hydronic system with a shared water heater,
02
03
MODERN HYDRONICS
WWW.HPACMAG.COM
Modern Hydronics
the water from the heating distribution system will inevitably mix with domestic hot water whenever the heating system is activated. After longer periods of inactivity, such as after the summer, the heating water has been stagnant for weeks or months, allowing more time for legionella to multiply. This situation has the potential to expose users of the domestic hot water to legionella bacterium through showers and other hot-water uses. To help prevent this, CSA B214-12 requires that “a means shall be provided to prevent the stagnation of potable water in a hydronic heating system by recycling or flushing the contents not less than once every 24 h.”2 However, if the timer used to mix the water fails or is deactivated, there is the potential for serious health risks. Studies show that flushing a water system to effectively kill legionella requires water temperature over 160F (71C) throughout the entire piping network for at least 30 minutes; at lower temperatures, some bacteria remain protected inside the biofilm lining the pipes. However, supplying water this hot through radiant tubing embedded in concrete may damage the concrete or any flooring it contacts, and similar risks apply to other radiant installation techniques. Proper flushing is not a great option from the heating system’s perspective. Not to mention, it may be dangerous to have the water heater set to a temperature above 160F for any duration.
RISKS AND BENEFITS
“ …do not assume that any product sold for hydronics is automatically tested and approved for use with potable water.”
Combined space and water-heating installations where the plumbing system shares a heat source and water with the hydronic distribution system are allowed in certain circumstances using specifically-approved equipment. This arrangement can reduce the up-front cost of building a small radiant heating system. On the other hand, designers and installers of these combined systems must be aware of the potential issues. Concerns can be avoided by using a dual-purpose water heater where the potable and hydronic water do not mix, or by using approved heat exchangers to separate the potable water from the hydronic fluid.
Lance MacNevin, P.Eng. is the director of engineering for the Plastics Pipe Institute’s Building & Construction Division and a member of CSA’s B214 Technical Committee. MacNevin is a mechanical engineering graduate of the University of New Brunswick. He may be reached at lmacnevin@plasticpipe.org. For more information about legionnaires’ disease, visit http://legionella.org/ or Health Canada’s information at www.hc-sc.gc.ca/ewh-semt/air/in/qual/legionnaire-eng.php.
REFERENCES CAN/CSA-B214-12 - Installation code for hydronic heating systems, Third Edition, www.shop.csa.ca
1,2
Online Learning – from the masters Mastering Hydronic System Design
Expert Instructor: John Siegenthaler • Online: March 21 - May 29, 2016 MASTERING HYDRONIC SYSTEM DESIGN
Learn how to design state-of-the-art systems for residential and light commercial buildings that deliver unsurpassed comfort, efficiency and reliability. During Mastering Hydronic System Design, John Siegenthaler provides a detailed discussion of the design elements underlying modern hydronic heating systems. It presents both design concepts and design tools for optimizing hydronic heating systems in a variety of contemporary applications. For more information and to register visit www.hpacmag.com/siggy
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| MH27
>>Boilers
Photo Laars Heating Systems
Replacing boilers in existing buildings
When making the boiler selection, be aware of the application that the boiler needs to service.
Boiler replacement is sometimes viewed as an easy task, but it can be challenging if it is done right. BY MIKE MILLER
T
here is an opportunity to provide some additional value for the customer when it comes to boiler replacement. Doing it right will also set you apart from the competition. Think about the factors that will impact the overall investment for the replacement. Also consider the future operating efficiency and the extended life cycle of the equipment. If the boiler seems to have failed prematurely, investigate the cause of the failure first. Was the failure related to flow, short cycling, piping or age? If the issue is not age related, spending the time at this point to identify and eliminate the cause of the failure will ensure that your customer is happy. What you should not do is replace a failed boiler with a like unit without considering the following points.
EQUIPMENT SIZING When a boiler needs replacing, do not assume that it was originally sized based on the appropriate building load. In fact, heating equipment used to be commonly oversized and grossly oversized in some cases. Apart from unnecessarily high operating costs, oversizing may have been a contributing factor to the premature boiler replacement. The building may have undergone upgrades over its lifetime such as better windows, additional insulation, upgrades to the distribution piping and so on, that could impact the overall heat loss of the building. It pays to do a proper heat loss analysis based on the current building envelope. You may MH28 | SPRING 2016
find that a smaller heating plant output capacity can get the job done now. Perhaps the building was upgraded, but no changes were made to the heat emitters? Terminal units (fan coils, baseboard and radiators) in the building might be oversized for the upgraded building envelope. The fluid delivery temperature required to heat this building on the coldest day of the year may be lower than when the system was originally designed. That could impact what type of replacement boiler you choose.
WHAT IS THE APPLICATION? Be aware of the application that the boiler needs to service. Does the system have many high temperature loads, which require setpoint operation for the majority of time? Those could include large domestic hot water heating needs, pools, spas, maybe even fan coils; anything that requires fluid to be delivered at 170F to 180F for a bigger part of the operating season. If that is the case, then a non-condensing boiler may be suitable in this application.
ABOUT CONDENSING Condensing occurs when the flue gas condenses. Different boiler and/ or system designs and larger system fluid Ts may either promote condensing at higher return temperatures than that or prevent them at lower temperatures. Always consider the boilerâ&#x20AC;&#x2122;s design and noted operating benefits. The addition of a proper condensate drain is required. MODERN HYDRONICS
If there is no significant reason for a boiler to be operating at high temperatures for the majority of its operating life, a condensing boiler may be what you want to use. Condensing boilers operate much more efficiently in the long run if they are able to operate in condensing mode the majority of the time. Condensing occurs when the boilerâ&#x20AC;&#x2122;s return fluid temperature is at or below 130F. Traditionally, smaller non-condensing boilers are on/off boilers, where larger non-condensing boilers can be staged or modulating with the use of power burners or modulating gas trains. Smaller condensing boilers typically come standard with modulating capabilities, which enables higher operating efficiencies.
NUMBER OF BOILERS Depending on the size of the boiler being replaced and available space in the mechanical room, it may make sense to replace a single boiler with two (or more) smaller boilers, which equal the same Btuh requirement. The benefit of multiple boilers includes some redundancy when not at design condition. The total boiler plant is designed to heat the building at the coldest day of the year, which represents maybe two or three days a year in all. Multiple boilers allow you to match the boiler plant output to the buildingâ&#x20AC;&#x2122;s needs year round. For example, if you are replacing a boiler with two smaller boilers that are
continued on MH30 WWW.HPACMAG.COM
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>>Boilers continued from MH28
on/off firing, each of the boilers would provide 50 per cent of the load. Three boilers would provide 33 per cent of the load. If the replacement boiler is a single modulating boiler, then depending on the boiler turndown ratio, the boiler can match its output anywhere between the minimum boiler modulation output to a maximum of 100 per cent. Some newer boilers may provide up to a 10 to 1 turn down ratio, meaning the boiler could operate anywhere between 10 per cent to 100 per cent of its output. Many other modulating boilers have a turn down ratio of 5 to 1, allowing them to operate through a range of 20 per cent to 100 per cent of the needed output.
CONTROL SYSTEM Is there a control system that is managing the boiler plant based on the building’s needs? If there is, the control system will have to be factored into the decision making process. Consider its ability to deal with the number and types of boilers you are opting for. The proposal you put together may include a controls upgrade as well. The cost of that upgrade could be minimal in comparison to the payback or life cycle costing of the new heating plant. Controls are an invaluable part of any heating plant. If there is not a control system in place by now, there should be. The most basic addition a control should provide is the ability to reset the fluid water temperature delivered to the building based on outdoor temperature as it directly relates to the heat loss of a building. If you opt for multiple boilers, pick a controller that can stage the types of boilers selected (modulating or on/off or maybe a combination thereof) and provides additional logic such as boiler rotation (on equal run time). For non-condensing boilers the conMH30 | SPRING 2016
trol would provide boiler return fluid temperature protection through the operation of a mixing device. If the building had multiple boilers to begin with and only one of them failed, then a staging controller needs to have the ability to exclude the older lower efficient boiler(s) from the rotation of the newer and higher efficient boiler(s).
PIPING/PUMPING/VENTING Depending on the boiler type, you may or may not be able to pump the full system flow through the boiler(s) directly. Many of the newer low mass boilers need to be hydraulically decoupled from the main building loop, especially when multiple boilers make up the total building capacity. In that case, the primary loop flow is equal to the system requirement where the flow through the boiler is a fraction, depending on how many boilers there are. For example, given a 20F deltaT between supply and return, three equal sized boilers in a 600 000 Btuh system would flow 20 GPM each to a total primary loop system flow of 60 GPM (GPM = Btuh/(deltaT x 500)). Hydraulic separation is accomplished through a low loss header or a set of two closely spaced tees (primary/ secondary), or other engineered fittings that serve the same purpose. Whatever the device, it physically decouples the generation equipment from the building system. Now each boiler can have the right size pump that it needs to ensure adequate flow through that boiler’s heat exchanger and the ability to control the pump’s output based on the boiler’s start-up sequence requirements. The boiler’s venting and combustion air requirements may have changed with the introduction of a new device. Always check the boiler manufacturer’s instruction manual for proper implementation. MODERN HYDRONICS
MORE DETAILS TO ATTEND TO While you are replacing the boiler, also check on some of the following components to ensure the longevity for your newly installed device. Verify the functionality of the existing expansion tank. You can verify its operation by watching the system’s pressure gauge when the boiler(s) fire. Its purpose is to capture a system’s pressure increase resulting from the expansion of the fluid when heated. If the expansion tank is operational, the pressure gauge on the system would maintain its fill pressure. If it failed, the pressure in the system will increase, or even pop the pressure relief valve. Make sure that there is a functional device in the system that can capture the air and dirt in the system, particularly since the boiler plant was just worked on. Air and/or dirt introduced during that process can be detrimental to the new or existing components. It is always an advantage to have a device in place that can continuously remove dirt and air from a closed loop system with potentially ferrous components. Some boiler manufacturers are very strict about the fluid quality and may require specific inhibitors and supplements to be used. That should be verified with the boiler manufacturer. There is a lot to think about, but if you get the replacement right a trouble-free system won’t be eating up the time you could use to develop business and increase profits. Take the time to properly assess the boiler situation – the payback is worth it. Mike Miller is director of sales, building services with Taco Canada Ltd. and is also chair of the Canadian Hydronics Council. Contact him at hydronicsmike@ taco-hvac.com. WWW.HPACMAG.COM
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