Wisconsin Geothermal system performance & problems in private home

Hello:

Although Geothermal is certainly not the easiest installation, the ultimate results after many adjustments and apparent system failures are quite impressive.

The system is 5 ton with 15kw resistance heat back-up for a 2600ft home with a rating of 60,000BTU heat loss/hr. In a cold climate with pipes a minimum of 4 ft deep but in most places more than that (up to 6 feet), the temperature specs were within allowable limits for incoming and outgoing lines.

At -22.5C (-8.5F) the system was still cycling on and off, easily keeping up with the frigid temperatures. At -24.9C (-12.8F) there was no cycling off but also no drop in inside temperature, maintained in both cases at 21.1C (70F).

Initial problems were noise from the fan because the installer vented 2 ducts from the plenum with only about 6-7ft distance to the vent next floor up. This was corrected by moving them to come off the main duct.

Shut downs occurred randomly due to overloading the system that turned out to be either a) the desuperheater was used exclusively to heat water, pulling too much heat from the system or b) the electric resistance heat was locked out at the lowest temperature of -15C (5F). It seems more likely that "a" is correct as it was too much load for the system at low outside temperatures. By leaving the hot water element turned on this problem was solved, the desuperheater working as assisted not principle heat.

Bill

 

Bill:

More input> What do you wish to learn?

Mark

 

"Shut downs occurred randomly due to overloading the system that turned out to be either a) the desuperheater was used exclusively to heat water, pulling too much heat from the system or b) the electric resistance heat was locked out at the lowest temperature of -15C (5F)"
Neither add up. How is your DSH plumbed? What is the fault code for lockouts?

 

Hi Mark.

Thanks for replying.

Unrelated to my entry I'd really like to know what you would suggest regarding draining the DSH when we are away for an extended period. There is no drain at the low point within the system (inside heat pump) to facilitate this and what I've done is attach a drain on the lowest DSH line coming out of the heat pump. This drains a lot out (about 12 liters) but there is still some at the low points which I expel best I can with a compressor (2.5hp 4.2 gal).

Is it advised to install a drain hole within the DSH system at its lowest point? or are there any other ideas. I'm not so keen on putting anti-freeze solution in our water supply lines.

Thanks.

 

Hi Joe: Thanks or replying.

The DSH is plumbed directly into the hot water tank with incoming at tank top, outgoing at bottom. There are no bypasses so that the DSH is always activated when system is running.

I'm not sure what you mean by a fault code (I've checked some of the literature on the Waterfurnace Legend but came up dry) unless you mean the thermistor which is set for 15F for closed loop. Pressure was checked along with temperature of lines and everything came up to specs. The climate here can be extremely cold and perhaps the system is undersized but I doubt it since it kept up even at -24.9C (-12.8F). I thought that perhaps the TX valve was malfunctioning with maybe an intermittent fault. I know that Johnson Controls had a recall on this part due to sticky valve restricting flow and causing malfunctions.