5T Vertical, 1 hole at 250', U coils are 300'
My contractor (SW Ohio) has drilled the first of 3 holes, hit solid limestone at 20' all the way to 250'. U loop coils were just delivered and are 300' vs. 250'.
Should I have them drill the next two the additional 50' (wells are 16' apart, straight line). Will be reverse return and there would be 2@ 300' and 1 at 250 (already in well).
Tubing is 160 psi, 1". Grout is bentonite slurry.
So, is the extra 100' worth asking for more drill time (which won't be alot of cost...and I bought the crew lunch)...
What do you folks think... Crew will return at 8AM EST tomorrow...
I replied to your PM but wanted to repost here so others could see. In most cases the benefits do not outweigh the cost when boring vertically. The additional 100' while you say it won't cost alot you will also never see a return on that investment even after the 30% tax credit assuming the loop and load calc were done correctly first. Usually rock is a much better/faster transfer of heat than dry soil and even heavy moist soil but I also am not familiar with limestone. Glad to hear you went ground source, this is a decision you will NOT regret and it is a wonderful investment.
Travis and the group,
Thanks for the PM and feedback...
I will hear from the contractor in the morning... I should have clarified (to the forum) that this is a WF Envision 5T (water to air), two speed with ECM and DSH. Heat load is 49kbtu cooling and 89kbtu heating (HVAC-Calc). Duct work being done on trunks and adding return/supply for the 5T (old system was 4T air to air HP). Using dual Marathon 50 gal per suggestion of Travis and others (vs. a single 105 gal tank)...
Original plan was 5x 150' using 3/4" U loops, the driller changed to 3x at 250' with 1" tube (160psi) as the drilling was simple (no issues) and we hit limestone at 20'.
I will let the forum know what the driller/contractor feels is the best option..
Thanks ALL, this forum is really a blessing to both the consumer as well as to fellow contractors/professionals...
PPJ Inv. (Cincinnati, OH)
I would worry about having 1 loop shorter than the others, water/glycol will take the path of least restance so the shorter loop may have a higher flow rate and starve the long loops. Someone smarter than I could do the friction calcs and tell you how much the short loop will steal from the long loops.
Assuming the design of the loops was correct at 250 I would make them all 250 and not chance it unless I had some solid numbers to back up the change.
Kevin, thanks for the input...
I think they are using methenol but I just heard from the 'planner' from the contractor, they are planning on re-using the excess 1" on other tasks... so we are staying at 3x @ 250'...
The limestone does make a good conductor. We hit it all the time here in Louisville, ky area. The shorter well would've caused some issues but the reverse return would have helped that. I know we install one 200' bore per ton here. 3/4 pipe. I think I would question the number of bores even with 1 inch pipe. Have seen units not perform well or at all when loops fields are cut that close. Just my opinion....
If 5x150'/ton was sized correctly and transfer heat efficiently, then 3x250' will not change the outcome at all!
I usually cut our bore hole count down to save time of rig setup/break down on a jobsite. I Prefer doing 3x300'x1" loops then doing 5x180'x1" loops. Saving time on the jobsite will lower the final price to the customer by cutting the labor hours lower, and in NJ each borehole needs its own permit from the NJDEP too.