Looking at j0sh411's second photo (https://www.geoexchange.org/forum/attachments/dsc_0116-jpg.1915/) the pipe looks like it is marked HDPE.
It is HDPE. Just a different size. Nice look Stickman. Ohio does not care what you bury. PE is polyethylene. HD is tufter. Think trash bags. Plastic Bison along I-90.
Here's another Wrench to throw into the mix that I just found. Another Contractor sent me this I completely forgot about it. Maybe It will shed some light on the subject. If you look it shows heat and cooling loads.
Sorry my mistake. I was thrown off by the statement on the Terra Source website that the pipe and fittings are tested to 100 PSI. 3608 SRD9 HDPE is pressure rated at 200 PSI. The operating cost estimate above appears to be more a guesstimate.
OK, the SDR 9 pipe has 2 issues. But... 1) the wall is thicker and therefore transfers lesser heat (resistance goes up). But making some general assumptions for ground conductivity (1.0) and some diffusivity (0.67) etc, assuming that you have as short runs within in the basement as possible, and you get as much of the 500' in the ground as you can (lets say 450' of it, 2 x 25' for the runs to the outside), you should have enough pipe in the ground to support 50,000 btus of heating load. You should be OK. You have 31% more pipe than you need which compensates for the lesser heat transfer of the SDR9 pipe. You must be 10ft off center for the trenches, 7 ft deep, and the pipe going out and the one coming back must be at least 2 ft apart in the trenches. 2) Flow: Also your flow is OK since you only flow 2 gpm per loop, your Reynolds number is a bit low at around 2000, but still OK. The good part is that you get by with a single 26-99 despite the smaller lumen. So you should take one pump out or return it for a 1 single pump flow center. That will save you the pumping power. In other words the SDR9 pipe is not ideal, but due to having more pipe in the ground, you mostly compensate for it. Again, this is the best I can do without having more local knowledge. Hope this helps
The header, I was told to make a max of 10 ft from the house. Technically i should have about 430 ft out of the 450 in the ground. Where the HP is going may be a foot on the other side of the block wall. So I believe I should be ok.
The type of soil that is at my place is bennington. https://soilseries.sc.egov.usda.gov/OSD_Docs/B/BENNINGTON.html
Apparently you have 500 of pipe for each circuit, if you go 25ft to and from the heat pump you have 450ft feet left. If you fan out from the house wall, soon or later you will be at 10ft of center for your trenches. I question that the contractor actually did a manual J, I don't think he showed it to you. The numbers look too much as he plugged them in the operational cost estimate what he thought they would be, but I don't want to be judging him without knowing the facts. 80 KBTUs of heating load sound too unrealistic for a building you are describing, with the upgrades. Silty clay is perfect soil for horizontal slinkies, no complaint there.
With 3 trenches and 6 loops the 4 pipes would be only 1 foot apart at the bottom of the trench. Should 2 be at bottom and 2 be 5 feet deep?
I'm going to go 7ft deep. 250' long 10' on center. The contractor which supplied those operating cost did in fact do a Manual j. He went over it with me I just can't remember any of the loads. The system which I purchased the guy did not do manual j. I'm guessing just went off of my sq ft. I'm not doing slinkies either just a 4 pipe u bend. One on the bottom the other 2 ft on top of it. Hope that helps
I do question if he actually did one, or if he only showed you one....The numbers he is presenting to you don't add up. If you do a 4 pipe u-bend and the second circuit is 2 ft on top of the first one, your system will perform significantly less than if you put everything at 7ft, since now the pipes are stealing heat from each other. I urged you before to listen closely if you want help! Your pipe itself is performing significantly less than the same length SDR 11 pipe. Thus you have lesser safety margins. If you now further reduce the heat exchange by putting 4 pipes in each trench, instead of 2 pipes in each trench, you are adding to the risk of failure! I was trying to help to allow you to keep the SDR 9 pipes you have already purchased.
OK, one 500ft pipe going out 250ft, u-bend, coming back 250ft in the same trench (minus the pipe run into the building) at least 2ft apart from the pipe going out. All at 7ft depth. Next trench is 10ft to the side, correct? 6 trenches total?
10 ft on center yes. 7 ft deep. 250 up 250 back one 500 ft coil per side of each trench. Supply 7ft return 2ft on top of it on each side. 3 trenches.
