I'm looking at a place which utilizes geothermal for HVAC. I have only a very basic familiarity of how they function and I would appreciate the thoughts of anyone with a deeper understanding of such systems, especially anyone with first-hand knowledge of using a residential system. Areas such as operating costs vs conventional HVAC, maintenance, etc.

Thanks!

Ask for records of operating costs.
I don't know much about it either but know someone who did it on a new home build with a contractor that claimed he knew what was doing and they are very dissatisfied and costs are higher than if they had gone with conventional system.
This is in Minnesota, may work better in a warmer climate.

Are they using radiant heat?

Just from my extremely little experience… Virtually none done around here. Lot bigger up front cost and a 10 year or more payback… according to my HVAC guy 3 years ago when I had to replace my 5 ton heat pump. Of course that would vary by location, temperate zone I expect. Too much rock on my lot to use trenches and drilling holes is expensive.

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Originally posted by Prefontaine:
Are they using radiant heat?

No, it uses forced air.

As in anything, properly designed & installed, Water source is a very efficient system. In my opinion, very good option for the cold climate areas. Only way I'd consider a WSHP system is if I was building on a new lot of adequate size and installing a septic system. My BIL did this and laid the lines before the septic lines were installed. The additional expense is the boring for vertical pipe design or digging the horizontal runs. The equipment is typical for commercial spaces, routine air filter changes is basically all that is needed.
As for maintenance costs, upkeep on the water glycol closed loop is minimal, maintaining the corrosion inhibitors is a simple pH check.

It's not as simple as the heating and cooling alone.

Your R value , sun exposure enter into it.

I know my brother averages $170.00 per month bills for his 3500 SQ. Ft. House,

That's summer & winter in eastern Iowa.

Nat. gas, electric , including car charging.

A year after he moved I.
Three of his neighbors hired the same company.

There is a fair amount of geothermal heat in Klamath Falls. I did not have it, only certain parts of town did. One negative was the water was acidic and piping needed replaced every seven years or so. cannot remember the cost but 5-7 thousand sticks in my mind.

Thanks for the replies. Thus far, I haven’t run across anything about the need to replace pipes on a regular basis. Perhaps doing the pH checks as mentioned would prevent the need for that?

R value and sun exposure are both good concerns. Apparently the exterior walls were framed using 2x6’s to allow for more insulation and sun exposure is somewhat minimized by shading from mature trees.

I also just noticed that there is a whole-house fan as well.

[QUOTE]Originally posted by FiveFiveSixFan:
Thanks for the replies. Thus far, I haven’t run across anything about the need to replace pipes on a regular basis. Perhaps doing the pH checks as mentioned would prevent the need for that?

I'm Not following the pipe replacement concern, maybe the ground soil impact to the piping?
Typically the pipe is a poly.
All equipment manufactures have water quality parameters to be maintained. This pertains to the equipment components in contact with the fluid. Corrosion inhibitors will deplete over time, thus the need to check pH annually.Failure to do so, causes the fluid to become acidic.
One question to ask is what product is the system loop filled with?

We have it in our home, it was here when we bought, didn't have a choice. The house is 2x6 constructon with E Glass windows. Our home was built in 2002, until around 2017/18 we didn't have an issue, then it acted up, would not start. The solution was pulling the breaker and then it would be OK for months. That unit was a Climate Master. In 2022 it started to fail, we never really figured out the cause, think it was the pump. We got quotes from two sources and decided to go with Carrier. We ran into issues almost from the start, the unit would struggle to start. The contactor was well known, the largest in the area. Their techs were experimenting with the fix, took almost a year before they replaced all the controls.

The initial purchase had tax rebates, both federal and state. The unit was $15K, came down to $10K with rebates. A conventional system would have been about $8K. We live in the desert, low humidity, it works very well maintaining 78 F in Summer. Our unit is 6 ton, our home 3200 Sq Ft, the electric is around $200/mth. We believe the geothermal saves us quite a bit of money. The new unit is a little louder than the old one but definitely a little more efficient.

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One question to ask is what product is the system loop filled with?

Great question. I'll be sure to look into that. I know the unit is a Water Furnace and it's a closed loop system which utilizes vertical loops. It has a large pre-heater tank which then feeds an electric water heating tank.


UTsig, thanks for the reply. That information is very helpful. It looks like monthly energy costs for this system will be considerably less than I'm accustomed to with either total electric or gas/electric systems.

I had one in my house and have installed several in some of the houses we built.

There are two main types, closed loop and open loop.

A closed loop system can have the poly tubing run one of several ways, in a series of loops buried horizontally in the ground in an open trench, or in a series of wells or even in a body of water deep enough that the water doesn’t get too cold in the winter. All the ones we used ran plain water in them.

On open loop dumps the water in one area, in our case a well, and pulls the water out of an adjacent well. This was done due to space constraints.

If installed correctly a geothermal heat pump can be extremely efficient and the loops in the ground should have an extremely long lifespan. The mechanical components, like any other heat pump can wear out and need periodic replacement.

When I was the warranty analysis manager for a major compressor manufacturer, these systems had higher than average compressor failures.

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...these systems had higher than average compressor failures.

That's interesting. Were you able to determine the cause? Did they have a higher duty cycle than conventional systems? Undersized at the design stage?

I'm also curios of the failure data. Considering typical water source heat pumps are packaged systems, assembled in factory conditions, so the refrigerant side shouldn't be a major factor. As for the other variables, primarily the air flow, water flow and power is the others is a design / commissioning task that should be done ( verified ) at initial startup of the system. ( obviously properly designed, as in the ability to maintain the loop temperature within the manufacturers spec.
Older models typically only had two safeties, a high refrigerant pressure and a flud loop freeze protection switch. The newer units I've worked on can have a very elaborate control / system protection for anything out of the compressor envelope of normal operation.

So we “sorta” deal with this. (Lots of heat transfer fluids)

The biggest issue is to be willing to trade efficiency for corrosion and freeze protection.

Be sure the system never pumps against closed valve. (At work, you “know” when the FNG decided to close both valves instead of open both valves.

We have lots of non-potable ground water which works very well to just dump waste heat.

If NG is available, I think it would have to be the cheapest.

Any local sources of fuel? Sawdust pellets, cherry stones, etc?

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If NG is available, I think it would have to be the cheapest.

It's total electric.

Lots of confusing information in these posts. It sounds like the FiveFiveSix is dealing with a closed loop geothermal heat pump system. Others have mentioned corrosion, geothermal ground water, etc. That’s referring to an open loop system. Hvactech seem to also be dealing with these closed loop systems. Basically the ground loop is either horizontal (drilled) or vertical (trenched) and acts as your heat exchanger, and you don’t have that unsightly condenser outside. A pump circulates the fluid through the closed loop of piping (most often HDPE high density poly ethylene) with your electric heat pump. It is an extremely efficient system, but overall cost to operate and efficiency depends on where you are geographically located. I spent a lot of time engineering this stuff once upon a time. It is not new tech, but the design expertise/knowledge and efficiency of the heat pumps have improved a good amount over the years. If it’s already installed, for me it would be a no brainer. The downside of ground sourced geothermal HVAC is the installation cost/payback (depending on size of system and geographic location).

quote:

Originally posted by Mutiny:
Lots of confusing information in these posts. It sounds like the FiveFiveSix is dealing with a closed loop geothermal heat pump system. Others have mentioned corrosion, geothermal ground water, etc. That’s referring to an open loop system. Hvactech seem to also be dealing with these closed loop systems. Basically the ground loop is either horizontal (drilled) or vertical (trenched) and acts as your heat exchanger, and you don’t have that unsightly condenser outside. A pump circulates the fluid through the closed loop of piping (most often HDPE high density poly ethylene) with your electric heat pump. It is an extremely efficient system, but overall cost to operate and efficiency depends on where you are geographically located. I spent a lot of time engineering this stuff once upon a time. It is not new tech, but the design expertise/knowledge and efficiency of the heat pumps have improved a good amount over the years. If it’s already installed, for me it would be a no brainer. The downside of ground sourced geothermal HVAC is the installation cost/payback (depending on size of system and geographic location).

You are quite right, Mutiny. It's a pre-existing vertical closed loop geothermal system with no outside condenser.