Rehau RAUPEX PEXa RAUGEO Ground Loop System

belated response

Hey guys,

I work at REHAU and came across this thread from last year. Truthfully, I really liked reading through it and you all bring up some very good points to consider when choosing between PEXa and HDPE.

One question I have though, in response to Eric's post from 9-24-2010 - why don't you include the cost of the drilling? If all you really need is 0.81 tons of cooling (or any multiple of that), you could simply drill 160 ft loops instead of 200 ft loops. By not drilling the extra 40 ft, you are saving your customer those drilling costs. You start to break even around the $13/ft mark.

Another positive is if you're close to the house, you could use a 210' loop and use the remaining 50 ft (in keeping with the above example) to run directly into the house with no fittings.

Of course if you need to drill bigger boreholes, more grout is needed. But in the area I'm in (Northern VA, MD, PA), drillers are drilling 5" or 6" bores anyway. Installing two loops actually decreases the grout required.

I'm not a driller, so my reasoning might not hold from your perspective, but I thought I'd add my 2 cents!

- Chris

P.S. I agree, do not buy the rehau weights. They are simply a carry-over from the geothermal program in Germany. I don't know if they sell any there or not (probably not).

 

High Chris,
Welcome.

The single biggest differance in drilling cost is between mud rotary and air drilling. From your post the area you serve sees intermittant mud rotary at best, and predominantly air rotary. When doing mud rotary the typical residential bore is 3.5 to 4 inches. A 200' bore can be drilled, loop installed, and grouted in about 38 minutes. The cost for that is 6.00 per foot.
When you do air rotary the size of the bore hole is controlled by the size of the hammer. The smallest economical hammer is 6 inch in diameter.
I did not include the cost of the drilling because that is an unfair comparison based on lithology. For mud rotary I used cost of materials only for the roi on results to level the field. That being said I will be the first to admit that if I have to pay for a larger bore, I am going to stuff all the pipe that will fit in it, down the hole.
Eric

 

I designed and helped install

The loops at Zach's home in Albany. The delta-P issue turned out to be a non-issue when properly sized pumping was applied. I have been using remote but accessible manifolds for years. It is all in the piping design and pump sizing.

Mark