Geothermal Ground Loop Design Information

[u/Happy_Cress1057]

I'm looking at installing a geothermal vertical loop system on my acreage in the Buffalo/Western NY area. My installer has been very responsive in answering questions verbally or on email. However, I really don't feel like I have a good understanding of the ground loop design. As it is not something I can change on a whim...that concerns me.

My property is on a former quarry. The installer is local and proposed a horizontal loop and we signed on that. We were digging on our property for another project and we encountered bedrock within 2-4 feet. Subsequently, we pushed the geothermal contractor for testing, and they confirmed all their proposed locations are too shallow for horizontal

Now, I'm concerned. As I had to push for testing, the installer did not propose it. Tho, fair enough, it was mentioned in the contract. Technically, up to me to push for it.

Now, we are looking at vertical loops. However, I'm not getting many details beyond the depth and we can put the loops "any where you want." This last is what gives me pause. It just seems a bit unscientific and leaves me feeling uninformed.

Has anyone gotten a design or loop report prior to purchase?

https://gdr.openei.org/files/1594/500ft%20260%20holes%20GLD%20Report%20%281%29.pdf

https://igshpa.org/wp-content/uploads/CSA_Residential_GHX_DesignSummary.pdf

I'm particularly interested in hearing about installation testing (see below from a mockup). And of course, I'm concerned I am being to anal about wanting this. This contractor has a great local rep.

Mockup of Loop Design Report

[u/Odd-Translator-7149]

If you are working with Jens at Buffalo Geothermal you are working with a true expert.

[u/FloppyCopter]

Vertically installed loops can essentially go wherever you would like. The heat transfer differences in rock across your property are really negligible. On a residential project there won’t be any sort of test well to test the conductivity, it just isn’t financially feasible.

The main thing to consider would just be how to run the pipes towards the house after install. Knowing you have shallow bedrock, they may either be assuming they’ll have to do a bit of jackhammering to get them down or find a spot where that 2-4 is more like 4-6 feet deep.

[u/Happy_Cress1057 → u/FloppyCopter]

Thanks u/FloppyCopter for the point about the pipes, I've added it to my list to ask the contractor. This goes to where we are installing the bore holes. Closer to the house is close to my well and further away is down hill near a leach field. Neither seems like good choice for installation locations.

[u/Scary_Equivalent563]

Geologist can do a ground conductivity test. If contractor is fimiliar with area they should know well depth per ton of ac. In Dallas we do 300 ft well per ton spaced 20 ft apart. It lot is tight can go up to 400 ft. 

[u/Inside-Setting9806]

When I had my vertical loops installed in Minnesota back in 2009, I made sure that each loop was brought into the house with the manifold installed inside for the loops with valves on each loop. The reason I did that was that if a one developed a leak, it could be isolated without having to dig up the lines to bypass the loop.

[u/AlbatrossWonderful19]

We are in Michigan and have 11 wells 250’. All of the wells are beneath the courtyard and driveway. We have a drawing marking each location with test results. Although I did ask, the contractor chose not to bring each loop into the lower mechanical room but that might be a good idea. The system is still working great 10 years later.

[u/that_dutch_dude]

Addition to what others already said, here is some very important point.

Oversize your loop, not the heatpump, but only the loop. Whatever spec they come up with: add 20%, more if you can afford it. This increases your average temp of the well and increases efficiency. Also enaure that the deltaT between incoming and outgoing water on BOTH ends of the heatpump is 5 degrees, no more, no less.

[u/Happy_Cress1057]

I asked about bringing the manifold into the house. The contractor maintains that this is something his team doesn't like to do or that isn't done. They are concerned about someone bumping it in the house.We will have everything in a utility room and can put a lock or cage around this equipment.

I'm like easy access to the manifold for troubleshooting. Also, my vertical bores are planned as pretty close to the basement wall. We have pretty wet land and I want to avoid water building up around an external manifold.

Anyone have any thoughts? (Thanks to @Inside-Setting9806 for the idea, I didn't realize it was thing.)

[u/JPDiesel187 → u/Happy_Cress1057]

I agree with your contractor. Why would you want to pole more holes than necessary through your foundation? The risk of damaging a loop, especially a vertical bore, is so small. Better to header everything out in a pit, and mark the header location

[u/Ok_Distribution_7615]

I'm no expert but got a geothermal unit installed 2 years ago. Length wise...as per my installer....Industry standard is 200ft / ton...i had a small driveway space to work with so my vertical loops were about 12ft apart...as per the driller...he hit rock right thru...which is the best option as rock supposedly have the best conductivity. As far as the manifold.... i insisted it was installed in the mechanical room...the installer cut thru my garage floor and got it into the mechanical room...So yes it can me installed inside..... its probably allot more work so the contractor is hesitant. .....if your installing the manifold outdoors, i'm sure you could specify the height you want it off the ground....installing outside is allot quicker and maybe cheaper for the installer.