Wrapped up trench, bury and backfill operations on my new horizontal closed loop located in Eastern Oregon for new construction. Design was 250 feet to an outside buried manifold and quantity six , 700 foot 3/4 inch hdpe loops branching off the manifold. Due to the distance between the house and buried manifold I went with 2 inch hdpe header to reduce head loss. Soil is water saturated silt and clay with a ground temperature of 52 degrees. With a five ton heat pump, I am way over designed on the loop field. I did this to increase entering water temp in the winter months, provide redundancy and allow installation of an additional heat pump in the future. Step one was to core drill the stem wall to allow passage of the 2 inch hdpe into the crawl space. I drilled 4 inch hole and purchased link sealers to fill the void between 2 inch and the core drill. All I can say is core drilling a 4 inch hole through a 12 inch stem wall is a bitch, two holes took about a half day. Next we trenched and buried 2 inch at 5 feet deep through a swamp area from the house to the manifold area. I have my own excavator and skid steer and a three foot bucket was used with effort to keep the supply and return lines as far apart in the trench as possible. Lines were landed in a manifold area where we would terminate the 3/4 inch loop lines and fuse the lines to a purchased hdpe manifold in ‘first in , last out’ fashion. Being a cheap individual, the uncoiler for the 3/4 inch loop lines was strictly a homemade affair. It did work. Trench and bury for the 3/4 inch loop lines took 4 hours each so the entire process was a week long effort, working in the evening and on weekends. We used the same three foot bucket with supply and return lines at 5 feet deep on opposite sides of the trench. No particular problems were encountered and you can see we have a very nice soil for heat exchange. Costs were $2200 for hdpe pipe and related accessories , $2000 for labor. Obviously having my own equipment was a godsend. Your mileage may vary. Next steps are to fuse the manifold and pressure test.
Thus the rational for 2 inch header. Higher up front cost , more difficult to install but head loss reduction compared to standard 1 1/4 header is significant.
Your most awesome loop field is truly awesome! Good on you for the DIY effort! We love pictures, keep us posted as you progress. Eric
Continue on with the installation. Socket fusion of 2 inch header and 3/4 inch loop lines to manifold based on ‘first in, last out’. Installers cleverly utilize their commercial scaffolding to keep themselves out of the groundwater. All connections completed. Back in the crawl space, a pressure test of the entire assembly to 100 psi using air looks good ! Next step - connect 2 inch header pipe to flow center. Prepare to power flush ground loop assembly using flush cart.
Since we were rigged up for pressure test, decided to go ahead and retest the lines to the manifolds and in floor heating loops. It had been a while since gypcrete was poured and the lines tested. And tile / wood floor installation is on the near horizon. Turned out we had a failure Tracked down to the in floor radiant loop associated with a downstairs shower enclosure. Plumbers apparently nicked the hydronic line with a saw while installing water lines to the thermostatic and diverter valves. So chipped out some of the gypcrete to gives us a long enough piece of hPex tubing to place a repair splice down in crawl space. The tile folks will patch the missing gypcrete with mortar when tile is installed. Morale of the story, test your hydronic lines often during construction.
I love testing. Finding leaks you can fix along the way are just part of construction. Having leaks after completion are a PITA, and hard to fix. Eric
