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Geothermal heat pump question


AHI in AR
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I am getting ready to inspect a home next week with a closed-loop geothermal system. Geo systems are extremely rare around here, and this will only be my second one. The first one was about 10 years ago or so as best I can recall. Are there standardized guidelines regarding expected/ proper temp differentials in cooling mode?

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I am getting ready to inspect a home next week with a closed-loop geothermal system. Geo systems are extremely rare around here, and this will only be my second one. The first one was about 10 years ago or so as best I can recall. Are there standardized guidelines regarding expected/ proper temp differentials in cooling mode?

Kevin, although the engineering is slightly different on the condenser side of the system, the air temperature differentials on the evaporator side should be the same as any other residential, centrally ducted, split system that you've inspected.

Marc

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Kevin, you can expect about the same delta from geothermal systems that you get with other systems. But . . . the whole temperature differential method for determining whether an A/C system is operating correctly is iffy, at best.

Lots of things can screw up the delta: improper ductwork, a dirty coil and/or filter, closed registers. If it's warm outside--80 degrees or above--all you really have to do is check the refrigerant lines. If the suction line is cold and sweating, and the liquid line is warm, the system's working like it's supposed to. You can also shoot the lines with an infrared thermometer. If everything INSIDE the house is okay, the delta of the refrigerant lines will pretty closely mirror what you're gonna get within the interior.

I'm not saying I never check the temperature of the supply-air swooshing out of the register, I always do, but if it's twelve or thirteen degrees rather than the 15-20 degrees we were taught to look for, that's not always a sure sign that there's something wrong with the system.

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Id like to see atleast 20-25 degree drop across the coil on any cooling system myself

Based on what standard? What do you say when it's 19°.

personal experiance,lots of years servicing equipment [^]

if its less than a 20 degree drop i start checking pressures and temps on lineset

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I am getting ready to inspect a home next week with a closed-loop geothermal system. Geo systems are extremely rare around here, and this will only be my second one. The first one was about 10 years ago or so as best I can recall. Are there standardized guidelines regarding expected/ proper temp differentials in cooling mode?

Use a digital psychrometer at the inlet and a regular thermometer at the outlet and use the attached chart. The differential is highly dependent on the humidity of the indoor air.

Of course, the filters have to be in place and both the filters and the coils must be clean or the whole process is a waste of time.

- Jim Katen, Oregon

Download Attachment: icon_adobe.gif Temperature _Differential_Chart_Carrier.pdf

75.91 KB

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  • 2 weeks later...

I've always heard 14 - 21, but I don't have a source.

I've always used the same range.. 14 ~ 22 degs F unless it's only, say, 62~70 outside then, it may be a little lower.

Would you guys only recommend checking this geothermal unit in one mode (heating or cooling based upon the season) like we do for air source units?

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I'm in the habit of checking both heat and cool functions, regardless of whether is an all electric, gas powered, heat pump or geothermal. There are defects that can occur that would allow a heat pump system to cool but not heat.

Marc

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