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Air to water heat pump to boiler...
Short story, sorry if this is in the wrong forum. I am a retired GC who does energy/solar consulting. I hav e a client in a Victorian era house, heated with a cast iron boiler and cast iron radiators. (Hot water, Nat gas) Client is interested in changing to a enter system. His primarily interest is to use a heat pump, supplied by his roof top net metered solar system. I have suggested an air to water heat pump (we are in the Pacific N.W where a “coldest” design temp is ~25f, but 35f is a more normal overnight low).
As I said, I am not an HVAC professional, but I understand the technology, just not the fine design details. My plan would be to mate a heat pump to a Mod/con boiler, running the heat pump into a heat exchanger and a buffering tank, controlled with a outdoor reset. What I don’t understand how if you are running water into the buffer tank at an ideal Delta of ~120f, how do you use this to add heat to a more usable 140-160f for the radiators to be effective. The client wants to retain the radiators. (If this we’re not the case, I would suggest a minisplit system.
What I don’t have is a good contractor/design engineer who can do a custom design in what in this market is a cutting edge installation. The local boiler/HVAC contractor came in, never having heard of such a system, and simply suggested installing a new Buderus or Weil/McLean old fashioned cast iron boiler, of a size that is roughly 3 times as big as my load calcs would suggest. (Not going to even consider that contractor!). Why would anyone suggest a cast iron boiler for a moderate climate, when a mod/con with out door reset is so very much more efficient?
So, does anyone have a resource to find a good design engineer to work through the design/efficiency curves for me? In principle it should be pretty simple, but one needs a good baseline expertise.
Thanks in advance for any advice,