Solar and Heat Pump

Larry Weingarten

Do you know at what temperature the solar is activated to do space heating? Getting the tank "hot enough" could mean 130* or nearly anything. I'd set it to work when the top of tank temperature was about 5* above indoor temp. A differential control might work nicely. Anything the solar can add should be used. Sounds like it is all or nothing at present.

Yours, Larry

Wayco Wayne_2

I have a customer

who has a house with lots of solar panels and a 500 gallon storage tank in the basement. Presetnly they have a forced air heat pump with a hot water coil on the inlet of the Air Handler that if the tank gets hot enough, will shut off the outdoor condensing unit and heat with the hot water. They called me today asking to upgrade the heat pump system since it is getting old. I'm wondering what the best way to upgrade is. Would some sort of water source heat pump stretch out the storage or am I messing with fire? Any ideas welcome. WW

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Wayco Wayne_2

Let me rephrase

Customer has 24 solar panels going to a 500 gallon storage tank. Air source heat pump has a hot water coil on the return duct side of the Air Handler to heat air whenever water in tank is hot enough. Is there a better way to integrate the solar with the forced air heat pump system???? WW

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Kevin_in_Denver_2

heat pumps & solar

In the interest of KISS principles, I wouldn't change the strategy. I know from experience that you don't want to put in a water source heat pump that draws off the solar tank. If you have an extended cloudy period, the solar tank is drawn down to 35F and then resistance heat kicks on. With the air-to-air heat pump, at least you can draw heat from the outside air under these conditions.

Just a couple more observations. Assuming 4x8 panels, that solar tank is grossly undersized. Solar storage usually runs 1-3 gallons per sq. ft. of collector area.
Also, the solar tank can be drawn down to 75F, as Larry says. The heat pump should boost the air temp. to prevent cold drafts.

David Woycio

Size?

How much sq. ft coll. area?

Size of coil and how many rows?

Muliple fan speed in furnace?

BTU heat loss?

Vent damper?

Pump size to fan coil?

Using water in storage tank or coils?

Mike Dilling

solar coils and heat pumps

I would not place the hot water coil "up-stream" of the heat pump, but down stream. The cooler the return air entering the heat pump coil the better it performs. I would re-locate the hot water coil to "downstream" or after the heat pump coil for better system performance.With the coil downstream, you can run the heat pump and the solar at the same time. this would stretch out the storage. I would run some calcs to see what water temp was necessary to heat the house at an average OA Temp and then set up some sort of control that allowed the heat pump to run when the water temp was equal to or less than that temp. When ever the water temp was hight enough, run just the solar. As far as a water source unit, you could replace the air source with a water source closed loop, but I wouldn't try and have the solar heat the water source loop, the gain in efficiency and capacity would not reduce operating costs to as low a level as the straight solar would. Let us know what you decide to do and how it turns out! Good luck!

Wayco Wayne_2

As I was waking up

this morning, I am guessing I must have dreamed about this job, since I was thinking of a set up where when the water was hot enough, using the hydro coil, when it cooled down too much for that using a water source heat pump, and back up electric heat after that if needed. whadaya think? WW

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"