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A way to temper geotherm loop
We have a job that has five geothermal heat pumps.The units currently have no supplemental electric heaters.The issue is when the temperature gets cold outside the loop temperature goes down as well.I was there today, and the water entering the units was 47 degrees.With this low of water temperature we get supply air temperatures in the mid to high 80's.My question is does anyone know the best way to temper the loop temperature so there would be higher water temperatures entering the units.Either with a supplemental boiler, and heat exchanger or other means.The entire system is about ten years old,Our company did not install it so I do not know if it is a vertical,or horizontal loop.The house does have natural gas, and the homeowner would rather not install electric heaters in the units.Thanks to all.
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Wilson Services, Inc
Northampton, MA
www.wilsonph.com
[email protected]
I have at least 2 houses with 2 WA HP's. Both owners say they have never used the supplemental heaters. If they get turned on accidently they might call because they smell the dust burning off and think something is wrong. Both of these are pump and dump well water @ 50-55 degrees. That 3 to 8 degrees must make the difference.
More houses with only a single zone WWHP might need supplemental heaters on occasion. The 2 zone houses have oversized capacity with the logic applied that in AC season one unit may cover the requirements.
Would slowing down the blower deliver air temps that are more tolerable?
NG preheat of inlet water would really make that ModCon condense, max efficiency and give you some really hot air. IMHO
Is this house tight and well insulated, or is it kinda tight and sort of insulated?
Seems odd you can't heat with 47 degree water, you're sure the hp units are ok?
I can heat my home with my geothermal system with 40 degree water. I'm in Massachusetts. Of course I use my radiant heating instead.
Wilson Services, Inc
Northampton, MA
www.wilsonph.com
[email protected]
So it's basically two pipe....two pumps on each hp?
Wilson Services, Inc
Northampton, MA
www.wilsonph.com
[email protected]
I certainly would not add a boiler to the ground loop if you have 47 deg entering water temp. Also, at the end of the day, a Geo unit is not a furnace. The air will be cooler. Actually, the cooler the supply air is, the more efficiently the compressor will run due to decreased head pressure and increased mass flow rate. The desired supply air temp is always a balance between comfort, efficiency and of course, it has to be high enough to effectively meet the heat load at desired indoor temp.
ramermechanical.com
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Before you add refrigerant, if you think that may cause it, run it in the cooling mode for 10 to 15 minutes to warm up the water loop for a bit. The units we have are usually pushing 90 to 95 degree air.
Your 47 degree loop temp doesn't sound all that bad at all. I would leak check those units. Also are you measuring discharge air directly at the unit? If you are taking the measurement at a vent in the space, compare it with one directly at the unit connection. You may need to consider duct insulation. Just a few ideas.
Are you moving enough fluid thru the coil, outlet temp drop should show some drop. Or a refrigerant issue? Air flow too high?
If I am missing something please tell me, thanks.
Langans Plumbing & Heating LLC
732-751-1560
Serving most of New Jersey, Eastern Pa .
Consultation, Design & Installation anywhere
Rich McGrath 732-581-3833
Now thinking out loud - Using boiler you would have to heat the water from the below design temperature to the design temperature. Otherwise the heat would start going to the ground. Right? Otherwise pick up the entire heat add load on the boiler and shut off the flow to the wells. Please correct anything that I wrote that doesn't make sense.
I wonder if adding a well is the best answer.
I can't imagine that turning down the air flow would do anything but make the situation worse.
I know of a similar situation further north where the heat pumps are just not heating sufficiently on design days (<10 deg). Common piping, one pump, I would assume the loop design was more like 32 deg.
BTU = GPM x Delta T x 500 if your using water with methanol.
Closed loop units should get about 3 GPM per ton and open loop should see about 1.5 GPM per ton.
We design our loops to run down to 35 deg so there is no reason that 47 deg shouldn't work for you. This must be one big house to get five units.