Heat-pump water heater paired with hydronic air handler?
Does anyone have any experience pairing a heat-pump water heater (GE, Rheem) with a hydronic air handler (First Co., Rheem)?
We have a 1956 raised 1,800-sq-ft. home with 3875 cfm50 which we are hoping to reduce to 1568 cfm50 (70% of .35ACH). Ducts are asbestos, so we are getting rid of them and will get leakage to 6% or better with R-8 ducts. R-38 attic & R-19 crawl.
Current Manual J heat loss is 57,000 BTUH. I’d like to cut that at least in half. Mild coastal climate, so no cooling.
Owners are installing a 2-kW grid-tied PV system which would offset some of the heat pump. I’ve sold them on the idea of getting rid of their old gas furnace & water heater.
Even though there are just two people, I’m worried that the HPWH won’t keep up with both the DHW demand and the air handler. This is new to me, so any help would be appreciated.
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Don't do it.
First of all, where would this heat-pump water heater be located? If it is indoors, then you certainly can't use it for space heating. The heat-pump water heater steals space heat in order to make hot water, so you would never get ahead. The machine would be trying to rob Peter to pay Paul, and would be cooling the house at the same time that it attempted to heat the house. Eventually the electric-resistance element would kick on, and the homeowner would end up with high electric bills (and almost undoubtedly, a cold house).
If you want to use an air-source heat pump to heat the house, that's fine. Either choose a ducted model manufactured in the U.S. -- the Lennox XP14 is worth considering -- or a few ductless minisplit units from Japan or South Korea.
Your point about having the water heater in the house is well taken, but why is this a bad idea generally? The concept seems sound, if the heat pump draws heat from outside, but you seem to think it's a non-starter regardless.
You're right that in a warm climate, a heat-pump water heater can be placed in a garage.
However, the heat-pump water heaters you listed can barely manage to meet the domestic hot water needs of a house. When several family members take successive showers, these heaters kick into electric-resistance mode. You can't expect these water heaters to also supply space heat because they don't have the capacity.
If you want to use a heat pump for space heating, plenty of manufacturers will sell you equipment designed for precisely that purpose. What you are looking for is an air-source heat pump.