Ground Source Heat Pump

[fazerman]

I've been in the trade since 1988, worked on a few heat pumps in my day, never really cared for them in Colorado.
We are planning a rather large addition on our campus. The engineers are really pushing for ground source heat pump. Based on the numbers I've seen, they are pretty efficient. I don't know anyone running this system in there building. Any advice on these systems?

Questions

Any ground source heat exchanger failures
Broken pipes
Ground movement
Reliability

Any technicians out there run into issues on this system?

Thanks

[junkhound]

I have GSHP in own house, 5 T copeland scroll compressor, 78 ft tube in tube evaporator, condenser from old carrier 7.5 T ac. Measured COP of 5.6. 55C water in, 34C water out.

The evaporator is shop built, 3/4" Cu pipe in 1-1/4" pvc water in annular space..

I did have one massive evap failure after 3 years. Circulating pump failed as had used an old pump sitting in the shop, Only had 2 thermocouples on the PVC pipe. Froze solid, spit pipe, had to replace.
Redid the undertemp shutdown circuit, used 10 NTC resistors and custom designed comparator vs. tc limit switch. Also installed better pump.

Other than that trouble free for the last 19 years. I did use a large commercial contactor vs. typical whimpy residential sized contactor so no failures there.

I had installed this system just before our 2001 6.9 earthquake, no problems then.

[TechmanTerry]

Interested in reading a little about the subject?

[BALloyd]

I would get more than one opinion on the sizing of the ground loop to make sure it is sized adequately. Then make sure someone does not try to save money by going with a smaller loop.

Been in way too many buildings where the ground loop is too small.

Also the one building I did work in that had an open loop required cleaning all the time due to the soil composition in the area.

Sent from my SM-G965W using Tapatalk

[pecmsg]

I've been in the trade since 1988, worked on a few heat pumps in my day, never really cared for them in Colorado.
We are planning a rather large addition on our campus. The engineers are really pushing for ground source heat pump. Based on the numbers I've seen, they are pretty efficient. I don't know anyone running this system in there building. Any advice on these systems?

Questions

Any ground source heat exchanger failures
Broken pipes
Ground movement
Reliability

Any technicians out there run into issues on this system?

Thanks

Ground source heat pumps are extremely efficient but!

Whats the ground you have to drill into?
Whats the cost per ft for a well?
How deep is the water table?
You will need 2 wells supply and return.
In Colorado water is a mineral just like gold, silver, lead. Who owns those rights?

When you add all the extra costs in that environment I don't think you'll see a return on investment for many many years!

Peconic Landing in Greenport NY tried it for there facility.
https://www.peconiclanding.org/
The field they laid war not big enough and the wells didn't produce the GPM expected. 1 by 1 they went air to air heat pumps with electric back up. (Greenport has a private electric company)

[Chev5372]

The size of the field in important don’t undersize it. The shafts are vertical and don’t take up any room. Parks , parking and ball fields can be built over the top. The type of soil is key as well sand, decomposed granite have a lot of air in them and that will not allow heat transfer as well as plain old dirt or clay.
We have two schools with each of the problems. One may have to add a cooling tower and boiler to correct.


Sent from my iPhone using Tapatalk

[71CHOPS]

I've had several ground source systems, but they were all closed loop. They pumped glycol through the ground with another heat exchanger between that and the building loop.

An open ground loop (using ground water) will end being a nightmare....regardless of what the experts tell you.

Also, vertical wells are gonna be better than a horizontal loop. Horizontal aren't really that deep and are more affected by soil quality. Plus, customers like to build things like parking lots on top of horizontal loops, without calculating the additional heat gain from the hot asphalt in the summer. Then you end up struggling to maintain loop temps in the hot months.

If you can get closed loop, WELL designed by someone that actually knows what they're doing, you'll have a decent system.

As far as brands of equipment, be careful, a lot of the large tonnage water source heat pumps are custom built. I've worked on several brands that were all poorly designed. Being custom, it takes a lot of tweeking to get them to not eat compressors regularly. I'm talking 20-50 ton units with plate and frames. The small units (1-3 tons) seem to do well with pretty much any brand, as long as you keep the loop temps under control. If you can't maintain the correct loop temps, you'll end up losing compressors on the small ones too.

Building loop design and balancing is very important for the small ones too. Otherwise, you'll end up with spots that have poor flow rates.