New air to water install

[S Davis]

A forum member ask me to post about an air to water heat pump installation I completed recently.
I installed the radiant floor heating system about 20 years ago and the customer just installed Solar and wanted to get away from propane fuel.

The old boiler is staying intact to heat domestic hot water and could be used as backup if necessary. The new system uses a 5 ton Bosch BOVA heat pump outdoor unit and a Noreaire indoor unit with the integrated electric backup, the system heats a buffer tank to supply heat to the radiant floor system.

It heated in heat pump only mode through the 10 degree weather we jus had.

 

[Zwy]

A forum member ask me to post about an air to water heat pump installation I completed recently.
I installed the radiant floor heating system about 20 years ago and the customer just installed Solar and wanted to get away from propane fuel.

The old boiler is staying intact to heat domestic hot water and could be used as backup if necessary. The new system uses a 5 ton Bosch BOVA heat pump outdoor unit and a Noreaire indoor unit with the integrated electric backup, the system heats a buffer tank to supply heat to the radiant floor system.

It heated in heat pump only mode through the 10 degree weather we jus had.

Nice unit, outdoor compensation. How much buffer does it have, 50 gallons maybe?

Any idea on how many Kwh it was using in a day? And how large was PV?

 

[S Davis]

Nice unit, outdoor compensation. How much buffer does it have, 50 gallons maybe?

Any idea on how many Kwh it was using in a day? And how large was PV?

Yes 50 gallons buffer, 2800sqft slab designed for low temp. Don’t know any figures it has been running for a little over a month.

 

[Cmiller]

A forum member ask me to post about an air to water heat pump installation I completed recently.
I installed the radiant floor heating system about 20 years ago and the customer just installed Solar and wanted to get away from propane fuel.

The old boiler is staying intact to heat domestic hot water and could be used as backup if necessary. The new system uses a 5 ton Bosch BOVA heat pump outdoor unit and a Noreaire indoor unit with the integrated electric backup, the system heats a buffer tank to supply heat to the radiant floor system.

It heated in heat pump only mode through the 10 degree weather we jus had.

I have been throwing this idea around for a while.... I currently have a 98 gallon natural gas water heater that runs my infloor heat. What I wish I could do, is have gas keep my water temp at maybe 130ish and allow an air to water heat pump to run when I have excess solar, but I wish to then allow the heat pump to take water temp to 180ish..... but is that kind of water temp even possible with a heat pump like this one you set up? I know the basics of how a heat pump works, but don't know the technical details, and so far my limited research has seemed to suggest that water temps higher than maybe 140ish are possibly not do-able....

Any thoughts...??

 

[S Davis]

I have been throwing this idea around for a while.... I currently have a 98 gallon natural gas water heater that runs my infloor heat. What I wish I could do, is have gas keep my water temp at maybe 130ish and allow an air to water heat pump to run when I have excess solar, but I wish to then allow the heat pump to take water temp to 180ish..... but is that kind of water temp even possible with a heat pump like this one you set up? I know the basics of how a heat pump works, but don't know the technical details, and so far my limited research has seemed to suggest that water temps higher than maybe 140ish are possibly not do-able....

Any thoughts...??

This system will produce 110-115 degree water, most heat pumps do not have the capacity for high temperatures. There are some but very expensive.

 

[Cmiller]

This system will produce 110-115 degree water, most heat pumps do not have the capacity for high temperatures. There are some but very expensive.

Thanks for that reply. That is kind of what I had gathered. Do you know if it is possible to set up heat pumps in series to boost top end temp? Or is the issue mostly related to the temp of the outside air that is being used for the heat source?

 

[S Davis]

Well the energy you absorbed in the first hp is what you would get out of the second plus some heat from the compressor cycle. This unit will put out about 36,000btu but it has a 60,000btu outdoor unit, so larger outdoor coil to operate at lower outdoor temperature.

 

[Cmiller]

Well the energy you absorbed in the first hp is what you would get out of the second plus some heat from the compressor cycle. This unit will put out about 36,000btu but it has a 60,000btu outdoor unit, so larger outdoor coil to operate at lower outdoor temperature.

I see. Got it. Thanks for the info!

 

[Zwy]

Thanks for that reply. That is kind of what I had gathered. Do you know if it is possible to set up heat pumps in series to boost top end temp? Or is the issue mostly related to the temp of the outside air that is being used for the heat source?

I was watching a video on YouTube the other night with Heat Geek and he was talking about a 2 stage heat pump. They work and do get higher temps but come at an efficiency cost. With solar generated power, it might work out but will require a much larger array and storage if off grid. Might be OK with grid tie.

Most of the water heat pumps I've seen will heat to 110°F to 120°F. This is the perfect temp for infloor radiant heat that has lower R value flooring, that is no carpet. This is also why we are seeing the move towards low temp emitters (which infloor radiant is) such as thin panel emitters.

 

[Cmiller]

I was watching a video on YouTube the other night with Heat Geek and he was talking about a 2 stage heat pump. They work and do get higher temps but come at an efficiency cost. With solar generated power, it might work out but will require a much larger array and storage if off grid. Might be OK with grid tie.

Most of the water heat pumps I've seen will heat to 110°F to 120°F. This is the perfect temp for infloor radiant heat that has lower R value flooring, that is no carpet. This is also why we are seeing the move towards low temp emitters (which infloor radiant is) such as thin panel emitters.

I'll have to look up that video.

In my personal scenario, I would primarily (at least at first) be using the heat pump more or less as a dump load for my excess solar. Even a heat pump setup with lower efficiency would still be better than simply using a standard water heating element! My infloor heat is in concrete slab with literally nothing on top, just bare concrete floor, and currently I am just running straight from my gas water heater into the floor tubes with temps probably up at 140ish degrees, but if I would be able to boost the water temps to 180ish degrees, I would probably install a mixing valve to drop the water temps going into the tubes.

Down the road I would love to add enough solar, and possible a water turbine as well, to be able to ditch the gas service completely. That's a long shot and faraway dream though!

 

[Partimewages]

@Cmiller Why do you need such high temperature?

 

[S Davis]

If you need to run such high temperatures you must have a lack of tubing or low flow from too long of loops.

The system in this post is a 4” concrete slab with 5/8” tubing 12” on center and only requires 109 degree water. This is at a 15 degree outdoor temperature with house at 70.

 

[S Davis]

Double post

 

[S Davis]

Here is a small three ton ground source water to water with domestic hot water preheat. Three 120’x5’ deep trench’s with 800’ slinkys.

 

[Partimewages]

I remember those days! We did a loop in early spring one year before leaves on the trees.
2 days later two of us were at the Dr's office for poison ivy! Dug through a whole patch. We learned the roots will gettcha also.

 

[Zwy]

@Cmiller Why do you need such high temperature?

I was going to ask the same thing. Temps under 120°F if infloor only. If he has other high temp emitters such as a plenum heat exchanger but he said infloor radiant.

If the flow is too low or loops too long, you can get hot radiant on one end and cold radiant on the other. The pump speed might not be correct for his loops.

In my case using a wood gasification boiler with thermal storage, you want higher temps to increase the heat capacity of the storage in order to increase the time between batch burns. I may have to use either a 2 stage heat pump or resort to electric elements to really get any heat exchange for a dump load. But I will have 3 tanks and may use 1 with a single stage heat pump to maintain it at 120°F for radiant while run the other 2 tanks when batch burning with the wood boiler. Pull off the larger tanks to charge the small tank when needed using a mixing valve. Plenty of options out there using radiant.