it would just be 3.14 x 3 or 9.42 ft tubing / 3 ft of pipe +3 ft of the return along side it correct. so for 800 ft of pipe a trench of 74' long should gobble up most of the pipe and allow 74' of return as well as the 16' to hit manifold. do you count the pipe in the manifold trench as still gaining heat . i read somewhere you should stay below 750 in pipe length is that correct or will 800 be ok. would you go with 36 inch pitch or 18 inch if you had the room. it only shortens the trench about 10FT. I worry ab out creating a dead zone if i use 18 in a cold winter. do i worry too much.

Posted By rikmeister on 27 Sep 2011 01:23 AM
do i worry too much.

yep

is the 800 ft ok joe

we use 800' slinkies

800ft and 18" pitch end up to be 100' of trench. make sure they all have the same lenght. Don't use much shorter trenches, you reduce the pitch which allows the slinkies to steel too much heat from each other. And yes.....you worry too much.

do you use mostly 18 inch pitch or 36 inch.

we use 36" pitch and 500' coils

so if i use 6 trenches with 500ft of 36 in. pitch i would need 6 connections on the header for the 3000 ft of pipe and it would be around 100 ft long or 4 trenches 100 ft long using 18 pitch and 800ft length coils and only 4 connections. my problem is the yard size i have 107ft. length and only 78ft depth. after i allow for the header trench . i can run one at most 100 ft long stright the others would have to be a lazy L .

500' at 36" pitch will give you as much BTU exchange as 800' at 18" pitch according to my loop software.

I have used slinky loops with 1000 ft coils of pipe at a 10" pitch with great success.  The problem with longer runs of pipe is the amount of pumping power required to overcome friction losses.  Unless the flow rates are low, I would recommend using 1" DR 11 HDPE pipe.

Earth Fire Energy Inc.
www.earthfire-energy.ca