Thread: Ben's Garage
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Old 11-03-16, 09:18 AM   #9
jeff5may
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Quote:
Originally Posted by Daox View Post
Does anyone have any good info on using an air source heat pump to heat hydronics? I was talking with Ben the other day about this and he hasn't been able to find any good info. I know we have a bunch of people doing heat pump water heaters, but this is a bit different.
Building your own out of what have you is not impossible. AC Hacker, Randen, and Aquario all have discussion threads detailing their custom builds. The general principles used in the smaller units remain the same, but instead of using a portable or window unit, you would be using a larger outdoor ASHP unit with defrost control. For the condenser, you could run a buffer tank with a submerged heating coil in it, or a refrigerant-to-water heat exchanger with or without a buffer tank.

The major manufacturers all offer air-to-water heat pump systems now. The main two types of systems are monobloc (packaged, single unit with water pipe/hose connections) and split (separate indoor and outdoor units). Some of the bigger name brands are listed here:

Daikin Altherma

Maritime Geothermal Nordic ATW

Fujitsu Waterstage

Panasonic Aquarea

A new technology being used in some of these systems is generically known as enhanced vapor injection (EVI). The term describes a new compressor design that has 3 ports instead of 2: suction, injection, and discharge. The injection port is used to add cool vapor (at intermediate pressure) at a certain point inside the compressor. This has the effect of increasing the capacity of the compressor at high compression ratios without wasting energy or overheating the compressor. This is especially useful when heating during frigid outdoor conditions, where the low suction pressure needed to run the evaporator effectively limits raw BTU output.

EVI heat pump technology


EVI technology is kind of like the polar opposite of VSI (variable speed inverter) technology. A VSI compressor changes the speed of the compressor to match the heat load, saving energy by lowering the compression ratio and power draw (when it is running slower). An EVI compressor boosts the output of the compressor by feeding itself higher suction pressure. The newest compressor designs include both technologies, and the manufacturers are really talking up the performance of these new systems.
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