I dug the trenches per the contractor's specs and he installed the loops. There are 5 trenches. Each is 150 f. long each, 5 f. wide, dug to 5 1/2" f. deep, then 6" of screened clay-containing material on the bottom, then 800 f. of 3/4" Charter Plastics Geothermal tubing in loops that touch but do not overlap, then 1 f. of the screened material on top, then backfilled. The site is in Northeast Pennsylvania. The ground has a high clay content. I thought I was getting 5 tons but I'm seeing numbers on the internet in terms of number of feet of tubing per ton which causes me to think I have more than 5 tons. Does 5 tons sound right or do I have more? If I have more, but only go with a 5 ton unit, is that a problem?
How does 800' of pipe fit in to 150' of trench? Just trying to figure out your layout - not be an @$$ More is not a problem. Moisture content?
5 tons sounds about right. Your slinky trench is a bit shallow, but you have a longer pitch. You should be good with 5 tons. NE PE usually has a good moisture content.
The 800' of pipe was formed with a jig into 4' 9" diameter circles which lay right next to each other. The circles touch but they don't overlap at 2 points which I've seen in images of other loops. There is one manifold trench so the return line runs back to the beginning. With about 20' at both ends that enter the mainifold trench, the circles filled the 150' trench perfectly. The moisture content of the clay ground is at least medium and might be considered high. The clay smears easily if that means anything.
Yes the circle diameter is 4' 9" and the pitch is 4' 9" so they don't overlap; it's like 2 circles next to each other that touch at one point.
http://www.sbgeothermal.com/images/ow-slinkyloop.jpg Is this what your field looks like, but with larger coils that do not overlap? your loops are that close to each other too?
I think you have more than 5 tons. I live on the shores of lake Erie west of Cleveland, Ohio. I am not sure why the directions included 800' of 3/4" pipe. From a pumping stand point using a manifold, one only needs to count one loop and the transportation piping for one of the loops in adding up the total head to over come at the GPM required for the system. If one looks up what the resistance of a given size pipe is times the length, then doing the math, one can buy the smallest pump possible. You maybe OK at 800' per loop, but I would have to look it up. The bigger the pipe the less the pumping power to move the BTUs. How many tons do you need/want. Mark
I should read these threads from the front each time, but I do not. I think my brain remembers it all. Next life I will order the biggest auto defrag brain possible. Jerry that field will do 5 tons on a cake walk. It my go as high as 10 tons with good piping. MHO and MPO Mark
Mark: I wanted 5 tons. If you say I may have 10, once the HVAC system is up and running, is there any way of figuring out based on actual performance how many tons I'm using and whether there's excess tons in the ground? If there's excess tons, I'd like to use them to heat a detached garage/workshop with loft I'm building in the future. Jerry
