Geothermal Problems


Old 01-03-08, 07:54 AM
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Geothermal Problems

I have a command Air 4ton unit and have been using my well water and dumping into my pond. It has worked great, but for economy, two years ago I put a 2200' loop using 11/2 black Plastic pipe buried 50+ inches. I am using Ethylene Glycol. I copied my friends loop he had installed twenty years ago. (Same furnace absolutly no service problems.)
I have two Grundfos Pumps. One to push away from the unit the other to pull.
The system works fine in the cooling system, but the Compressor kicks off when the outside temp. is about 35 Degrees. Everything goes to back up heat strips. I talked to a local Heating Co who first told me I shouldn't use glycol. and that it is freezing outside after it leaves the coils. I need the mixture to go much lower(I was at -9 degrees
I put 55 gal more glycol in got down to -20 degrees. Didn't help.
Another Guy told me to put a third pump on to push the system faster and that I have "to much glycol mixed in". I should be at 10 degrees mix. I installed a third pump.
No difference. Any Ideas Guys? Thanks Brian
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Old 02-16-08, 08:33 AM
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Brian, I'm a bit new to geothermal and in proccess of installing one here. From the research I've done thus far it appears there may flow problems. I am going to use an open loop source from a well that supplies 56F water continously. Since you didn't have this problem before you switched from an open loop and now it is showing up with the closed loop, did you change any flow settings when you switched to closed loop? Check the mfg requirements for your system in their manuals (most manuals are online now) for these things: gpm required, pressure drop accross heat exchanger (HX) temp drop accross HX, these readings are telling us what is going on as heat is extracted from heat in the loop. I recall that most mfg's talk about some timing issues before the compressor starts after the loop field starts flowing. There may be something you have to change in your control box as far as startup delays. I doubt if you have freezing issues when your loop is +50" deep.

Next thing, did you do any HX cleaning while using open loop and/or before changing to closed loop. Most Heating/Cooling ppl don't want to deal with open loop because of water quality issues and scaling problems in HX. A good hot vinagar soaking and flushing of HX every 6 months will prevent HX problems. Usually scaled HX issues can be detected through the P/T and flow readings talked about above as long as you know the mfg specs when unit was new.

One other thing, no expert here; but not sure why any more than one pump would be needed in a closed loop. Is glycol mix a bit much? Maybe it is too thick and effecting flow. Good luck, and keep us updated.
Old 02-16-08, 11:05 AM
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Ill go with how long did you run this on well water?? Have you ever cleaned the heat exchanger??? Id do this first there is some cleaners for water cooled coils . Check out Calgon and Virginia liquid scale remover.Also Nu-coil water coil cleaner. ID also cut down some on the glycol mixed .
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