Half way through constructon in SW Montana, with below zero temperatures, our 6Ton GSHP seems to have developed a mind of it's own. Any suggestions from the pros would be appreciated. This is what I know for sure: The heat pump, after cycling, generally three times, shuts down to the LOCK OUT mode, evident from the red lock out mode light. The 2 blinks from the red code light inside the unit would indicate, according to the manual, a LOW PRESSURE SWITCH issue. Generally, the unit had been running fine since installation three months ago, but with dropping temps (not sure if that has anything to do with it) the unit has been shutting down when the buffer tank reaches 65-66 degrees when it was originally set to shut down at 90 degrees. The GSH contractor is currently "researching" the problem, but seems unsure of the next step toward further trouble shooting of final resolution of the problem. Where do we go from here? By the way, this is a horizontal closed loop system. Much thanks for your input.

Sucecreek - I'm only an owner of a GSHP, and no expert, but I know there is more info required to help. Can you tell us:

- Water to Water or Water to Air?
- Loop description - length, depth, configuration etc?
- The water temp entering and leaving unit form the loop? From the buffer tank?
- Pressure in entering and leaving the unit for the loop?
- Air temps entering and leaving the unit?
- Manufacturer/model of the unit?
- Is the error display a Comfort Alert by Emerson?
- What happens if you turn of the DeSuperheater?

Posting these details will help the experienced techs help you. I'm interested in learning the solution as well.

john

The info requested above is right on.

In addition consult your Owners Manual or perhaps list the Complete model number of your machine here. Look to see if it has a FreezeStat installed. If that is the case, low EWT could cause it to open. They are typically in series with the low pressure switch, LPS which would throw the Low Pressure fault code.

Also, tell us if the system has anti-freeze in the ground loop.

Dick

John, Will have to get back with you on some of those questions. At this point we do not have the 3Ton air unit or desuperheater hooked up. It is a water to water heat pump. Eight 700 foot loops were install at 6 and 8 feet deep, with 2 foot backfill, actual trench being approx 350 feet. The unit is the GeoComfort GT or GW Series, I believe. Just received a call from the heating contractor, he's willing to come take a look. Will try to find out more about ingoing and outgoing temps since I don't have the tools. Thanks John

A $9.00 electronic meat thermometer will get your temps for you. Just tape it to the line you want to measure.

this is a guess, but it sounds similar to a problem I had with a furnace install in our old house.  Keep in mind, it was a furnace, not a heat pump.  Ours acted similarly, & tripped a pressure switch.  After lots of research, it was determined that the intake air was restricted because of the run from the furnace to the outside wall.  Once we took the pvc pipe off & let it pull in the basement air, it ran fine.  This was, of course causing combustion issues, which are not applicable with gshp's, but maybe it can give you a direction to start looking?

Thanks jerkylips. Interesting. I'll gather up some temps in a bit. I have every reason to think, having assisted, that the ground loops were properly installed. I'm also sure that the properly mixed glycol mixtures are flowing adequately through the ground loops and to the radiant floor system. I suspect the FREEZE STAT or LOW EWT may be the issue. Thanks again for the responses. Will keep everyone posted. sucecreek

More info: Geo Comfort Model GWSR072 Type No. A10CC Serial No. S08083298 410A HVAC guy should be showing up shortly.

Yes the ground loop does have anti-freeze. Tried my meat thermometer, think I'll need to shop for a more sensible one. Dogs are barking, must be the GS guy. Thanks, JC

The only time I had our lockout like that was when one of the valves was shut off on the field side. So my guess is either the intake or outgoing side have no flow, either a bad / tripped pump, or something is just plugged.

Ok, this is the scoop....... or it least what I understand of what the problem "was" (I think)....... we're still working on the
solution. Apparently, because the basement became so cold, due to heat loss from the upper levels of the house (it's and ICF foundation), the system was working overtime to heat the slab, ultimately, causing the ground loop temp to drop to the 30 to 35 degree range which caused the low pressure switch to shut down the hp. Not sure to what extent the ground loop mixture was "jellied" due to the cold temps further disrupting proper flow. By closing and opening ground loops over a two hour time period, with the unit in cooling mode, in other words, "reversed," we have been able to get the HP to cycle from 55-60 degress in the buffer tank.
So, at this point, we're simply heating the basement slab back up slowly (as if there was any choice) and letting the loop area return to a more normal temp...... it least thats the current stratagy. I think the key to all this was the incoming ground water temp. Had I picked up on that earlier, I could have diagnosed the problem sooner. I'm currently wondering at what temp do most
FREEZE STAT units kick in. Thanks for your replies.

A Montana closed loop system should have substantial antifreeze protection in the loop fluid, and the unit should be configured so as not to trip out on low loop water temperature down to 15-20 F or so.

It may be that you have a freeze-protected closed loop but the installer neglected to change the freeze protection setting from the manufactuer's default of open loop / non-antifreeze (~30F) to closed loop w/ antifreeze (~15 F)

You generally don't want to use a geothermal system to heat a house during construction. Instead an alternate portable system is recommended that can deal with the excessive heat loads. Otherwise, you risk dropping your loop field temps to a point that they can't recover until the cooling season.

-Adam

While I agree that a geo system isn't the best choice for construction heating it shouldn’t have had an issue even with the loop in the 20's. I would find out what it was that jelled and make sure it won't freeze again. Once construction is done and someone inadvertently left a window open or was somehow broken, you wouldn't want you field to freeze up trying to keep up and then shut down heat pump and have the whole house freeze.