A GAME-CHANGER IN COMBI WATER HEATING

Lochinvar has long been an industry leader in commercial boilers—and now we’re bringing that engineering excellence to residential combi boilers.

The wall mount EPIC® combi boiler you know and trust is now available in floor standing models.

What Makes EPIC a superior choice?

· Easy To Install, Set Up and Service

· Delivers Hot Water Faster

· Display Screen Uses Text, Not Codes

· Better Technical Support and Training

· 10:1 Turndown Ratio

· Floor and Wall mount available

· Advanced Electronic Control -

20 air changes per hour at 50 Pascals (about 0.00725 psi) of air pressure differential. A well-sealed new house could have air leakage in the range of 1 to 4 air changes per hour at 50 Pascals pressure difference (ACH/50).

And a super-tight house, built to current Passive House standards, must not exceed an air leakage rate of 0.7 ACH/50.

Experience has shown that the “natural” air infiltration rates of buildings will be approximately 1/20 th of those established by blower door testing at 50 Pascals differential pressure. Thus, a house with 4 ACH/50 blower door test rating will have a natural air leakage in the range of 0.2 air changes per hour.

You won’t suffocate in such a house, but you’re unlikely to find the air quality provided by air leakage acceptable. Fry up some bacon on Monday, and you’ll still smell it on Wednesday. I could cite more examples of this air quality problem, based on other “facilities” in the house, but I’m confident you get the idea.

Grab It While You Can

The contemporary approach to providing fresh air while at the same time not adding substantially to the home’s heating load, is to install a heat recovery ventilator (HRV), or in some cases an Energy Recovery Ventilator (ERV). Both of devices create two air flows: one brings outside air into the building, and the other exhausts “stale” inside air back outside. Both air streams are generated by small blowers within the ventilator.

During the heating season, the stream of incoming cool (or cold) outside air absorbs heat from the warmer exhaust air stream. This exchange takes place within the heat exchange “core” of the ventilator, through which both air streams simultaneously pass, but never mix.

Typical heat recovery efficiency is in the range of 70%. Thus, the fresh air requirement is met using about 70% less thermal energy that would otherwise be needed if the air was simply blown into and out of the building with ventilation fans and no heat exchange.

During the cooling season, the outgoing stream of cool (but “stale”) inside air absorbs some heat from the incoming warm (but fresh) outside air. Again, the fresh air requirement of the building is met, but the energy penalty associated with fully cooling and dehumidifying the incoming air to desired indoor temperature and humidity is greatly reduced.

Energy recovery ventilators (ERVs) provide similar functions to heat recovery ventilators (HRVs). The difference is that ERVs can also exchange moisture (in vapour form) between the ingoing and outgoing air streams.

In winter, some of the moisture in the outgoing (higher absolute humidity) air stream is transferred to the incoming (low absolute humidity) air stream. And in summer, some of the moisture in the incoming (higher absolute humidity) air stream is transferred to the (lower absolute humidity) outgoing stream.

This moisture exchange helps maintain a comfortable (and healthy) indoor relative humidity in winter and it also reduces the latent cooling load in summer.

Add On

So, what does this have to do with hydronics?

Well, in combination with an air-to-water heat pump, or a geothermal water-towater heat pump, heat recovery ventilation becomes another part of the “total solution” package you can offer. That package includes heating, cooling, domestic hot water and ventilation.

For example, consider a relatively simple system that provides multiple zones of space heating using panel radiators, and “whole house” cooling using a ducted chilled water air handler.

It also provides domestic water heating using energy from both the heat pump and an electric resistance backup heater. Figure 1 (on the opening page) shows one concept for such a system.

The heat pump maintains the buffer tank between some upper and lower temperature limits. Those limits could be set points or determined using outdoor reset control. Some air-to-water heat pumps have integrated controls that allow either.

The variable-speed pressure-regulated circulator operates continuously during the heating season. Warm water passes through any panel radiator with a partially-open or fully open thermostatic radiator valve. A system that is simple, elegant and even “wireless.”

The motorized diverter valve routes heated fluid from the heat pump to the buffer tank. This flow path is only open when the heat pump is operating.

The path between ports AB and A close as soon as the heat pump turns off, preventing reverse thermosiphoning from the tank.

This valve operation also prevents flow returning from the distribution system from passing through the heat pump when it’s off.

The large coils inside the buffer tank preheat domestic water. The temperature rise of the water depends on the fluid temperature maintained in the tank’s shell, the surface areas of the internal coils, and the rate at which domestic water flows through the coils.

If the tank shell temperature is maintained close to the desired domestic hot water delivery temperature it’s possible that over 90% of the total temperature rise can occur through the coils.

The remaining temperature rise is handled by a tank-type electric water heater, or a tankless electric water heater

If the buffer tank temperature is based on outdoor reset control, the auxiliary water heater will need to contribute more energy for domestic hot water during milder outdoor temperatures.

Continued on MH10