Air-to-Water Heat Pump for Heating, Cooling, and Hot Water
My gas boiler is 25 years old, and still working fine but it will die some day. I am also trying to get off of fossil fuels. Existing cast iron radiators are oversized at water temps as low as 140*F. Please see attachment below for how I arrived at that. I live in Maryland, stick built 1925 1 1/2 story house. The basement is Not in the conditioned zone. I have now almost completely insulated the basement ceiling. Conditioned area is 1275 Sq Ft. Outdoor design temp 15*F, indoor 68*F, and 95/75 during the summer. HDD is about 2853. Moderatly humid, 40 grains difference. Winter ACH 1 per hour; summer .5 per hour. 3 occupants, plus dog. 1 pellet stove in Living room, tight.
Total heating load 25,399 BTU/h and cooling load 18,314 BTU/h.
And here I just found what must be an error , under Energy Cost Analysis manual J show 4500 HDD, and only 1250 CDD. Eai.gov shows 2853 HDD for South Atlantic, and 1964 for cooling. I ran the Manual J my self.
My room by room calc. shows my lossiest room at 4942 heat loss at design temp and my radiator emits 7560 at 140* water. All my existing room are like that. I know Air/water heat pumps only give out 130-140* water, but it seems I should be fine with that. The idea comes from John Siegenthaler at HPAC.
This involves use of a buffer tank, with a coil for DHW, but I still don’t know how that would work in the summer, and a fan coil unit for forced air cooling.
I have had energy audit s done, and I am trying to finish up on those recommendations, and it seems I will need a mechanical engineer to design the system.
Is there any reason why this could not work?
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