I’m doing an addition for a customer where there is no mechanical space in the architects drawings. Heat is all hydronic radiant, AC is forced air.
i originally thought geothermal but am getting bad pricing.
So now I was thinking about mini splits which can have in ceiling cassettes and can also produce radiant temperatures, but I have no experience with the air-to-water, just articles I’ve read which may be manufacturers smoke.
However since it would be much easier to run line sets in this addition then ducts, and the unit would be outside where it isn’t seen – so it seems a perfect solution if it works well …
… Anyone done air-to-water with success?
Replies
Awesome way to go. Very efficient. Use a quality manufacturer. Samsung, trane, Mitsubishi, etc.
Are you suggesting that you use a conventional mini-split to heat air and use that hot air to heat water?
No, there are air-to-water heat pumps but I've never seen or heard of them being used.
https://www.hpacmag.com/features/heat-pumps-in-hydronic-systems/
I hope your customer has deep pockets. Why not use an air to air high SEER mini-split/ They are super efficient and very quiet. Air to water heat exchangers were all the rage around here 25 years ago. "Free" hot water and a more efficient AC system except that they didn't work and needed a lot of maintenance. I took the one off my house 13 years ago.
well thats good to know
... radiant is a must, so the question is how and I just wanted to know if this was an option, but doesn't seem so ... thanks all
I recently came across these guys, and am contemplating putting one in my house.
https://www.chiltrix.com/
If you go with air over water I believe you will need a tank with a heat exchanger in it. However, I believe if you install an air/air to unit you just have a small compressor unit outside the building. Find of like hotel room heater/air conditioner but with a much much quieter indoor fan.
If you have gas available then a demand type water heater is the only way to go. In Europe one heater often fills both functions.
What about liquid-to-liquid. Then the in-floor heat would work and the AC would have to be high-mount gravity cooling plates. As an architect, it's pretty obvious to me that you need to go back to the architect for specific directions on how to accomplish what they have in mind, and there are obvious aesthetic considerations here.
I'm an architect, builder, and energy nerd. I am mystified at the lack of education, or interest in state of the art practices to solve some of the most pressing issues we face in these trades and society at large.
We designed & built a net-zero energy residence using air/water heat pump as the source. We used radiant panels (home grown) and a radiant masonry wall as the primary distribution for both cooling loads and heating. Air was used only for mechanically induced ventilation and dehumidification.
These systems work. Radiant sourced cooling and heating when used in a high performance envelope confer a comfort level unmatched by air systems and at a greatest efficiency level. Only a geo-source heat pump can top this performance.
First cost is the measure most will apply without consideration of why it is that we build houses. Our bad.
Climate stress should also be analyzed when choosing any air source heat pump.
Inefficient housing should be energy upgraded before an HVAC system modernization.
Do you have any details on your design I can learn from?
re: radiant is a must
Customer wishes?
Then the AC would be straight air-air minisplit with indoor unit in ceiling or high on wall.
For the radiant, have only used water-water and water-air hieat pumps and those were custom design (DIY)
What jurisdictions for codes are you in? If allowable (say in Germany) you could go with direct hx, e.g. copper tubes in floor and use R290 refrigerant (or even just bbq propane). Have built a 5 ton unit water-water for own use for under $500 parts.
As already said by florida, if you are not HVAC and vapor cycle system savvy, need deep pockets.
Another option would be heat pump water heater as source. Or 2.
@David80503 what units are you using. I know of chilltrix, and several in Canada, but they need back up for low temps. In Sweden there are units that have no need for back up. I'm hoping that, with more incentives and interest they will become available here. I'm always on the look out for these.
Trane recently introduced an air-to-water heat pump based on mini-splits. 70C at 0C outdoor, 60C at -15C outdoor.
https://www.pv-magazine.com/2024/02/08/trane-debuts-air-to-water-heat-pumps/