Geothermal questions

[davesl708]

I have the dual tank with DHW. Very happy with the setup. My brand is Water Furnace.
The buffer tank w/o the DHW on maintains 95 degrees in the winter when the heating is operating. This feed the hot water heater. Lot cheaper heating 95 deg. to 130 deg. than 55 deg. to 130.

When family is here I turn on the DHW. Never a shortage of hot water with 100 gals. available and the DHW going.

My house is total electric. My high bill in summer is $65 and high in winter is $165. I have a six person hot tub that runs year round.
With the 30% energy tax credit my system with the vertical wells cost about the same as a high end gas/electric HVAC and no noise outside unit.
My energy cost were cut in half by getting rid of gas and not running an outside unit.

The system runs on 30amp 220v and can run the system on a generator if needed. Have never had a power failure yet.

 

[buckeyefarmer]

Buffer tank, as the others have said.

 

[s219]

We have a single Rheem Marathon hooked up to the geo system (ClimateMaster 22). The geo unit pulls water off the bottom of the tank (from what would normally be the drain port), runs it through the de-superheater heat exchanger, then delivers the water back into the tank through the top "cold" input. I can't give pros or cons of single versus dual tanks based on real experience since I don't have any -- we only went single because that's what the geo installer recommended for our setup. I believe dual gives you more options however.

 

[LD1]

Thanks everyone. I have pretty much decided on the buffer tank for efficiency. Maybe I wasnt that clear in my post this morning.

The question is really about the second tank hooked to the electric, and weather or not a tank type is better than a tankless. and weather a 13kw or 18kw tankless is a better option. And weather those will actually keep up with reasonable demand in the months that the geo is not needed?

 

[davesl708]

Thanks everyone. I have pretty much decided on the buffer tank for efficiency. Maybe I wasnt that clear in my post this morning.

The question is really about the second tank hooked to the electric, and weather or not a tank type is better than a tankless. and weather a 13kw or 18kw tankless is a better option. And weather those will actually keep up with reasonable demand in the months that the geo is not needed?

My geo operates year round. The hot water is 50 gal. electric with 50 gal. buffer tank feeding 85 to 95 degree water. With 5 people in the house hot water has not been an issue. My geo people used my old gas water heater as the buffer tank.

 

[techman]

The biggest disadvantage of a single tank system is temperature. The desuperheater takes the heat from hot freon at the compressor outlet. When compressor head pressures are low (a good percentage of cooling and some during heating) there is not a very high temperature extracted. If the WH is near or above the desuperheater temp (mass of freon times the temp) there will be no heat added to the HW heater. In other words if the desup generates 80 or 90 deg, it will do nothing to add to the HW heater which is at 120-130 deg. Many new design geo units have a temp switch that will not run the desup pump when the temp is not high enough.

With a second tank you are generally working with a lower water temp so heat is easier to add to the water. Any temp added to the preheat tank are BTUs that directly benefit the main tank by having warmer water coming in and therefore does not need to be heated as much. Just thermodynamics at work.

paul

 

[jk96]

You might also consider the expense of service for the on-demand water heater. Maybe they're more reliable now. When we built a few years ago our plumber talked us out of one. He didn't have one and said he wouldn't install one in his home due to the high number of service calls he has for them.

 

[LD1]

Techman, I understand how a twin tank works. I am not even considering a single electric tank tied to the desuperheater.

And as far as BTUs go, a second uninsulated tank, even if you don't have geo, would also help. Allow your 45 degree ground water to warm up to house temp of 70 prior to going into the main tank. Same theory, just not as much benefit as the desuperheater.

My focus now is on either:
1. Dual tanks
2. Single buffer tank + on demand heater in lieu of second electric tank

 

[buckeyefarmer]

For the loops, I'm happy with my non pressurized.

Find a local supply house that deals with geo. There is one online, up in sugar creek ohio.