Add heat for ground souce heat pumps?

[carlosgw]

Has anyone run into a situation where the installed wells (or ground loop) was insufficient for the heat add for a ground source heat pump system? (northern climate)
What was done to rectify?
I'm looking at a small building that has been installed for over ten years but just does not heat well on very cold days.
The owner is not going to install any additional wells and does not want to use any electric heat if at all possible.

 

[Drazen]

yes, it happens all the time.

add the boiler.

the other option is to dig new well or to recondition soil all around loops, and small house owner will never ever have payback on investment.

 

[GMcD]

What Drazen said. Here in Canada there are a number of early adopters' efforts that resulted in permafrost being formed due to value engineering the ground loops and just plain poor ground loop/borehole designs. There is also a way to recharge the ground using solar thermal panels depending on the solar location and hours of sunshine. Google Drakes Landing in Okotoks Alberta as an example.

Here in the Pacific NW in a fairly mild climate, it's still heating dominated, and a peaking boiler/hot water generator is still needed.

 

[carlosgw]

Thanks for the replies.
When you add a boiler, do you work it out so you are raising the temperature of the water as it comes back from the wells up to the design temperature?
For example if the design temperature is say 35 deg and it is coming back at say 30, add heat via heat exchanger to get the design temperature corrected?

BTW it is currently set up with control valves on the branches to the heat pumps (there are 6 heat pumps 1-1/2 - 3 tons). The pump does not run unless there is a call for heat (or cooling). So the water can sit in the ground loops. I can't decide if this is good or bad.

The problems with the system I am looking at include no record of the wells and no supply and return temperature records (no sensors).

 

[GMcD]

It sounds like you have water to air type heat pump units? In that case, yes, you'll likely have to add heat to the condenser (source) water loop if that is falling too low as the heat pumps are extracting heat. I don't think the fact that the condenser water can sit in the loop without circulating is necessarily a bad thing, since it will allow the water temperature to at least exchange heat with the ground while it sits there. However, if the ground has been subjected to a lot of freezing in the past, and the soil conductivity isn't good, it may take a while for the ground temperatures to come back up to a more stable temperature.

 

[chicopee]

I don't know where you are located in the northern regions, however if your building is isolated away from natural gas deliveries, think about installing a forced air roof mounted propane heater. Heating the ground water with a boiler is in my opinion senseless and really inefficient as an overall heating system.
.

 

[urgross]

Evacuated tube solar hot water heater might be an option.

 

[Ziggypump]

You are wanting a Hybrid geothermal system. What is the loop temperature in the winter? It is possible the heat pumps were sized incorrectly for the water temperature provided to them. But it is also possible that the setback temperature is too great. A heat pump system should have a 5 deg F setback temperature max. Otherwise it takes too long to get the space up to occupied temperature, and everyone is miserable.

To do this right, a load calculation needs to be run. Determine the required loads and temperatures needed, and verify if the existing equipment is correct.

If you don't run calculations, add the boilers and pray that it is enough.

 

[LittleInch]

"...but just does not heat well on very cold days.
The owner is not going to install any additional wells and does not want to use any electric heat if at all possible. "

What else does the owner want - a car that does 1000 miles to the gallon?

The owner either needs to wrap up warmer, install a wood burning stove or just accept that you can't get something (heat) from nothing (no heat available in the ground because it is "very cold").

Depends on the details of your system as to where the most feasible place is to add heat - a diagram or two would help.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[willard3]

Do a thorough heat gain/loss. Then you'll know what is undersized.