Greetings to all: trenching question,

[gwdixon]

That is a valid point I am concerned about. You do need to have good soil contact to get the thermal transfer. When I only had to dig 4' deep and 30 inches wide I ran my plate compactor over the pipe. My friend and I were discussing this yesterday. Excavating 4 ft. deep then digging 4 ft. with the backhoe may be the better route, just adds more work to the job.

For the OP with the smaller pipe and trench I wonder if using a power washer to help pack might do the trick? Weather permitting he could in a sense water pack the crack in a few lifts working to the surface.

Darn, beat me to the water/mud idea. The mud would seem to create a pipe packing even in rocky soil and have 100% contact.

Not sure where he lives in Suisun Valley but some of the areas are in the Sacramento River Delta so the soil is quite fine and packable. However, there are rocky places in higher ground.

 

[showcattle]

I'd hire someone who does directional drilling with one of these JT25 Directional Drill | Ditch Witch. Hardly any soil disturbance.

 

[JFoy]

fandango99: I know exactly what you're talking about as I was planning to do the same type of project for a house I was going to build. Do you know what your soil temps are at 5ft vs. 6ft? It may be that 5ft will still work for you and that would be much easier as it opens up more lower end machines. As a DIY project, this is going to take some time - well, a lot of time. Since it is liquid, a 1 x 600ft line would work just as well as a 6 x 100ft line and would be easier to trench. It would actually be better to put in the 1 x 600ft line when you consider that the temp near the out-from-the-house side will heat up in the summer with the interior temp air. That means the soil will start storing the heat. As the summer progresses, the distance from the house will increase. By putting in the 1 x 600ft line, the soil temp at the 500ft mark will still be cool at the end of the summer. Of course, that will work against you in the winter unless you can run the flow backwards to take advantage of the heat at the 100ft mark. Anyway, aside from OSHA regs and the like, check into the soil temp at 5ft and see if that still works for you. If you do it, tell us about it a year from now.

 

[jenkinsph]

JFoy,
Six feet is shallow as is, to get steady state mean temperatures requires a depth of about 30 feet in depth. I dug out an area today 50x60x 2.5 depth with my box blade about 275 yds. Will finish this weekend to get to the 4' depth. Then use the backhoe to dig an additional 4' deep to install the pipe. While this seems like a lot more work the 8' depth will provide a more stable temperature. Hoping for plus or minus 6 degrees F.

Whether the OP should use a single 600' run or 6) 100' runs is debatable. I am no expert but from the research I have done the length of most tubes should be limited to about 125' in length. Every thing I have read about recommends the multiple run scenario.

 

[2458n]

As a Local 18 Operating Engineer I have ran trenchers and directional boring machines. Cheapest way to do what you want would be done by using a Vermeer 7x11 boring machine. It would come with 400 ft. of drill rod. Can go to 10ft. plus deep level off and run out 400 foot. Hook a swivel onto your pipe and pull it back. If you want two lines in a joint trench, hook on a small reamer and pull both lines back together. Your paying for the length not the depth. If you need 600 foot make another hole and do a additional 200 connecting everything together. In Ohio you run around 55 degrees at 5 foot. Geothermal is the way to go.

 

[texas42]

I'm not a geothermal expert, but did have a ground source heat pump in a house I built in 1991. I did a lot of research on the subject back then. I had a 4 ton unit and choose a 750 well with 1500 feet of 1 inch pipe in a loop in the well. Water table was 20 foot down so I had about 1450 of pipe submerged in water at ground tempature year round. Back then it was suggested if you go with a horizontal loop to be at least 8 foot deep to get to a ground tempature that was not effected by heat or cold of the seasons. I think, but don't know for sure, for a horizontal loop you need to be deep enough to be in moist soil so you are disapating the heat/cold from the loop. Dry soil will not do that. When I sold that property people could not believe how cheap it was to heat/cool a 3400 sq ft house by that geothermal unit.