Hi, I recently had geothermal installed in our new retrofit home. The house was built in 1971 and is around 3500 square feet. We had geo installed in early July. There are two 3 ton Climate Master split units. One for upstairs and one for downstairs. There were two wells dug, each shy of 500 feet, lopped in series. The main question I have that I would like to hear from others or the experts is if there is an approximation of how much kWh should be used on average per month or annually for a system of this size working as it should? Second question, given the common knowledge that hot air rises, does it cause any problems or increased bills that we are setting downstairs to 68 and upstairs to 66 24/7? It seems that the downstairs unit is running a lot more than upstairs, any issues with that? Should temp be set the same for both zones or is it not a big deal? Thanks in advance! I am in lower NY just North of the city. Winter temps are starting to drop! I am praying the electric heat strips never have to kick on! So far the systems have been holding the temperature.

We have not experienced any problems with different thermostat settings.  We minimize the run time difference by closing the upstairs doors and having a remote thermostat inside one of the bedrooms.  Airflow has not been a problem in our house with the doors closed.

Your air filter on the downstairs unit may need changing more often than the upstairs unit, but I wouldn't consider that a problem.  Unless otherwise managed, the heat strips on the downstairs geothermal unit may engage if that system can't keep up with the increased load from upstairs.  Depending on your air conditioning needs, things may be reversed in the summer (with the upstairs unit running more.)

Usually not a problem if these are different zones not open to each other. Then a different thermostat setting is a problem.

The problem appears to be that you have (2) 500ft boreholes looped together in series, which would mean that 2000ft of pipe is in series. That is a significant problem for your flow. What size pipe do you have in the ground? 2" diameter?

The only way to estimate KWh usage is knowing your specific load calcuation, a 3 ton unit in my area will use around 4,000 KWh's per year... once again depending on load calculation but I am in Portland Oregon.

If the stairwell is open, you will have a problem, if not, then not so much. With the open stairwell and higher downstairs setpoint, as you have noticed, the downstairs unit will do most of the work. Wither the single well is sufficient to do what both wells were designed to do, I will leave to the geo experts.

"I am praying the electric heat strips never have to kick on!"
This comment suggests a hole in your geo education and your installer's. No reason, I don't expect you are going to need auxilliary heat with 6 tons for 3500SF.

"There were two wells dug, each shy of 500 feet, lopped in series."
This suggests a hole in your installer's education as well.

KW usage would depend on out door temps and actual manual J heat load for the house.

Posted By joe.ami on 01 Dec 2013 09:34 AM

... KW usage would depend on out door temps and actual manual J heat load for the house.

I think you meant to say "kWh" (assuming air flow is reasonably well designed, as is water loop flow)?

Best regards,

Bill

"There were two wells dug, each shy of 500 feet, lopped in series"

This can't be right, If it is you will likely be spending more in pumping penalties(over the course of the year) than a right sized system's use of aux heat.

Heat load would definitely be needed to even ballpark energy usage

Posted By geodude on 01 Dec 2013 05:43 PM
"There were two wells dug, each shy of 500 feet, lopped in series"

This can't be right, If it is you will likely be spending more in pumping penalties(over the course of the year) than a right sized system's use of aux heat.

Heat load would definitely be needed to even ballpark energy usage

I pointed that out before, but everyone is concerned about the load. The fact is that even if the load is OK, this loop will either not perform, or cost way too much pumping to perform. Either way, the loop is an issue. Which brings up the question again: What size is your pipe?

"I think you meant to say "kWh" (assuming air flow is reasonably well designed, as is water loop flow)?"
Bill we already know water loop is not designed well (assuming OP is correct about the field). There is too much we don't know to predict energy consumption but if the description of the project is correct, we can assume it is not optimized.

Penalty for pipes in series are going to be based on many things such as type of pump, pipe diameter, antifreeze etc. If one has a variable speed flow center and methyl antifreeze and the system is designed in a way that laminar flow is acceptable, it will be much less consequential that if a PSC flow center needs to create turbulent flow with prop. gly. antifreeze. (though we may also assume someone piping in series may not be a student of variable speed flow centers).