Round 2, Insulated Underground Pipe

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MyOutdoors

Member
May 12, 2008
111
Lempster, NH
Well, since I made the fatal mistake of rushing into my OWB install last season, I put in 1" pex which was undersized for my application, I also went with a BHS pipe which I found to lose quite a bit of BTU's. So I'm chaulking this up as a costly lesson that hopefully people in my situation can learn from.

My thought now is that I will install 1-1/4" pex in a a 3-4' trench. I believe I'm going to go with the DYI Tiger foam kits. I'm going to separate the pex 2" with a rigid foam block. What type/brand of pex should I use for the best actual ID". How much foam should I put down below/side/above pex. Any and all suggestions would be much appreciated since this is the last time I want to do this!
 
From the reading I've done on this site on this topic it sounds like most people will run (2) 1" lines instead of (1) 1-1/4" line. 1-1/4" pex can be very expensive. I'm sure others will chime in as well.

Good luck with your retrofit!
 
I'm interested in this as well.

Tip: you might want to change the thread heading to something more descriptive. "Round 2" might not catch the eyes of the right people...
 
I,m no expert on the pipe size but i have sprayfoamed quite a few of these setups. You will save some money by finding a contractor to do the spraying. Those kits are quite expensive. I usually put 6" closed cell foam all the way around the pipes.
 
I called a local contractor and they quoted me 2k for 165' of 3" foam on all sides. That's way to steep to do it that way. Tiger foam goes for $610 for 600 bdft. for there DIY kit. Add that to the cost of 2 1 1/4" pex and they DIY option looks to be alot better and less expensive. I'm going to try and call a different contracor as well. the one I spoke with didn't have much experience with spraying pipe in trenches.

I've also run into this product which is local and I can pick up for $1250. This would be for 112 cu ft.

http://www.dritherm.com/index.html
 
I know most people like to calculate based on 20°F delta T, but it looks like if you based your calcs on 40°F delta T you may be alright. This essentially doubles the BTU's you can carry. I know nothing about BHP pipe quality.

Since this is a OWB and not a gasser your not worried about getting the BTU's away from the boiler to storage, but simply to the end user.

Tim
 
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