Heating & Air Conditioning Design Dilemma

Mini split plus hydronic

6 years ago

hey yall, im trying to figure this one out. Electricity rates are high where i live and I want to save money long term. My house has infloor hydronic throughout and is expensive to run. I was thinking about putting in a mini split to save money but figure it would prevent my infloor from turning on and keeping the floors warm.

My question is: Do you think I can run the infloor system using some kind of sensor that measures only the floor temp, keep that at a minimum temp (say, 19 degC) and then use the mini split to heat the ambient temp to the desired setpoint (22 Deg C)? That way the floor doesnt have the burden of heating up the whole house, just the floor.

Featured Answer

armoured

6 years ago

It would technically work in the sense that you'd be pumping in heat at the higher efficiency of the minisplit. I fear though that you'd never quite be happy with the feel as the benefit of the hydronic in-floor is consistent temp radiated throughout.

If off electricity the 'standard' way - not uncommon in Europe - to get what you're after would be e.g. an air to water heat pump (or a ground source). It is more expensive of course and I understand may be hard to find in USA (although you say C so maybe you're not there?). In coldest outdoor temps you would still be running off of electric resistance heat (you could possibly keep your current boiler as backup).

Because target output temperature not very high for infloor radiant, it can be reasonably efficient, but depends on your climate too.

Too many issues but I'd not rush into your minisplit approach. Air to water heat pump would at least be in line with original design.

There are newer tech solutions being developed (e.g. CO2 heat pumps, 'big in Japan' as they say), but not yet common or widespread.

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Comments (7)

katinparadise
6 years ago
bump
armoured
6 years ago
Is your boiler on gas or electric? Do you need air conditioning?
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steve
Original Author
6 years ago
Its electric. Maybe use air conditioning couple times a year. Not a huge concern
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Patricia Colwell Consulting
6 years ago
IMO hydronic floor heating works best when you set the temp and leave it, what happens is the mass heats and retains the temp. We have hot water heating (not in floor) and I find once the whole space is to temp the boiler just comes on to keep that , if I fool with it it takes too long to bring to temp again. You will find the fewer rugs you have the better the system works too. I really am not sure how adding another electric heating system would lower costs.
steve
Original Author
6 years ago
The mini split is many times more efficient than the electric boiler. It has a COP around 2.5 as opposed to 1.
fsq4cw
6 years ago
I basically agree with ‘armoured’ approach, although water temperature for in-floor is dependent on pipe spacing.

I would suggest at least looking into an integrated air-to-water heat pump for in-floor with hydronic fan coil or hi-wall heating and cooling and using your existing electric boiler for backup.

Nordic Air-To-Water Heat Pump

IMPO

SR