Heat pump for Radiant floor advice

[Flexia]

Im looking into the idea of doing radiant for my garage that will be 26x44. I ran loop cad and it came up with just under 16000btu that I will need to heat with. Also I will have 4 loops around 290ft long. I was at the lunber yard the other day and they had a 50gallon heat pump hybrid water heater for 500. Its a rheem hp50. I couldn't pass it up being mark down to 1/4 of the price. Will this be able to provide heat for me or did I jump the gun on the purchase? Location is ne ohio if you need it

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[Montysmith]

sorry I've no idea into the issue you have raised here instead looking of the same solution as you are this is why I'm here to this forum area looking for some apt reply to get a clue about from where to start for an efficient end....

 

[yeldogt]

The problem you are going to have is two fold. The HP WH's I have looked at use a panasonic 9000btu HP unit coupled to a standard resistance type heater - that will not be enough. Also: can I assume that the HP will be in the same space as that being heated? If so the surrounding heat goes into the water and the cold air will be exhausted back into the space being heated?

You will be using the resistance strip to heat the space -- and depending on the your electric costs -- that may or may not work.

I have a friend that put one in his old house in PA. The basement holds the boiler and was always on the warm side in winter and he always ran a dehumidifier in the basement during the summer. Now the HP WH is almost enough in the summer as a dehumidifier and he is able to capture some of the wasted warmth in the heating season for the HW.


The HP WH's look to be a great option for those in the south to put in a hot garage where the cold air is a benefit all year

 

[Highbeam]

Sorry, you jumped the gun. Good price for a HPWH but not the right device to use in the shop for floor heat since the water heater steals room heat to heat the water.

There is currently no readily available device that uses heat pump technology to heat water for radiant floor heating. Other than the all-on-one units, there is very little out there for domestic water heating either. Plan on wood boiler, electric resistance, or gas boiler.

I am saddened by the lack of technology in this area. The minisplit heat pump systems for heating air are excellent in terms of efficiency, cost, and availability but nobody has applied this to water heating with success.

Is 16000 really all you think you need? That is about what a normal 4500 watt water heater element puts out.

 

[walrus]

Sorry, you jumped the gun. Good price for a HPWH but not the right device to use in the shop for floor heat since the water heater steals room heat to heat the water.

There is currently no readily available device that uses heat pump technology to heat water for radiant floor heating. Other than the all-on-one units, there is very little out there for domestic water heating either. Plan on wood boiler, electric resistance, or gas boiler.

I am saddened by the lack of technology in this area. The minisplit heat pump systems for heating air are excellent in terms of efficiency, cost, and availability but nobody has applied this to water heating with success.

Is 16000 really all you think you need? That is about what a normal 4500 watt water heater element puts out.

I believe Nyle Corporation in Maine is close to putting out a heat pump "boiler"

 

[Flexia]

I attached the heat loss summary from loop cad if you want to take a look.

The building is going to be 26x44x12 with r19 in the walls and r30 in the ceiling. And 2 in slab insulation. 2 Over head 9x8 insulated doors and one man door.

From what you are saying it will cool the air some and that's why its a bad idea? I thought about that and i am going to be having it mounted on a shelf about 6ft high so the cooler air will stay up top. Or is it not enough power for what I need?

 

[Flexia]

Well I checked back up on loop CAD and it had 10' walls and im doing 12' So I guess that bumps my btu's to 19000.

 

[KenB]

The other issue you should consider is how fast you'll need to reheat the water. This so-called recovery capacity is much higher for tankless heaters and boilers, which makes them preferable for hydronic heating. The unit you purchased is rated at a maximum 21 gallons per hour at a 90F temperature rise, which won't be nearly enough to keep up with a system that circulates water (or glycol-water mix) at a few gallons per minute.

This link contains some references I found useful while researching my system: http://www.garagejournal.com/forum/showthread.php?t=140533.


Ken

 

[theoldwizard1]

Also: can I assume that the HP will be in the same space as that being heated? If so the surrounding heat goes into the water and the cold air will be exhausted back into the space being heated?

From what you are saying it will cool the air some and that's why its a bad idea? I thought about that and i am going to be having it mounted on a shelf about 6ft high so the cooler air will stay up top. Or is it not enough power for what I need?

Yeldogt is 100% correct ! You will be heating the floor and cooling the air, and the Second Law of Thermodynamics says you will always loose !

The basics of a heat pump are it moves "heat" (or "cold") from one area to to another. The basic assumption is that those areas are heavily insulated from one another. Windows air conditioners (and and A/C unit is a type of a heat pump) work because the move hot air from inside the house to outside the house. How well do you think it would work if you ducted that hot exhaust air back into the house ? That is effectively what you are doing.

I have a friend that put one in his old house in PA. The basement holds the boiler and was always on the warm side in winter and he always ran a dehumidifier in the basement during the summer. Now the HP WH is almost enough in the summer as a dehumidifier and he is able to capture some of the wasted warmth in the heating season for the HW.

The HP WH's look to be a great option for those in the south to put in a hot garage where the cold air is a benefit all year

Looking at it from a slightly different angle (but actually saving the same thing Yeldog is saying) you want to install such a device where there is a (near) infinite source of FREE heat so that you can move that heat into the floor via the water. A possible bonus (in the case of his PA friend) is cooling/dehumidification.

 

[Flexia]

Thanks for the advice. I will be looking into different heat sources now. I like the idea of electric heat because of not having an open flame. But I dont like the cost factor of electric. I thought I found a medium with the hpwh but I guess not

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[Rickcnc]

This looks like a possible solution, I sent the Ontario contact an email, but didn't get a response.

http://www.ecologix.ca/products/cold-climate-heat-pumps/air-to-water-heat-pump/