insulating OWB lines

[hondaracer2oo4]

I have a 100 foot run from the boiler to the house. I went with the spray foam in the ground method. I dug a 30 inch deep trench shovel width. I dropped 4 one inch pex lines and had a closed cell spray foam guy come and just spray right in the hole. We lifted the pipes out and he sprayed about 3 inches in the bottom of the trench. we then dropped 2 of the lines down seperated, he sprayed again then we dropped the last 2 lines and he sprayed again. The closed cell foam is tough stuff. He also sprayed my boiler for me and the cost was $500. My pex lines cost about $400 if I remember right. If I had gone with the thermopex or something similar it would have been $1200 and I would have only had 2 one inch lines, not enough water flow after my heat calculations. So this was pretty much my only option that was reasonable in price. I lose 1-2 degrees from the boiler to the house Ive run two seasons now with no issues.

 

[sw18x]

Thanks. I'm going with the thermopex, I'll pay a little more for ease of installation at this point. With the thermopex I can dig above the existing lines without disrupting them, and leave the domestic hot water lines in place. That turns a week long project into a day.

 

[taxidermist]

do you have 2 sets of pipes running in the ground? 1 for DHW and 1 for the HX?

Why in the world would you change 1 set but keep heating the ground with the other?


I would run 1 set new and switch to a DHW heat exchanger in your house.

Just because you dont want your water any hotter dosent mean you are being efficient by heating the ground.

Just my 2 cents.

Rob

 

[sw18x]

For the amount of time the DHW spends traveling back and forth underground I don't think it will ultimately make that much difference how often the OWB fires. You're right, installing a heat exchanger in the house for the DHW is a more efficient option, but I'll use up my full budget on the Thermopex (or at least what I'm willing to pay). Right now, leaving the DHW lines buried where they are is a lot simpler solution.

 

[taxidermist]

Not sure of your plumbing but if your DHW runs all the time to heat your tank in your house then thats a lot of BTU heating the ground.

I use Logstore pex for my underground 150'.If I was to do it again I would use 1.25 pex and spray foam with closed cell foam.

With 1.25 pex you can use a lot smaller pump.


Rob

 

[sw18x]

DHW only runs as needed - i.e. when you turn on the hot water, it pulls water into the indoor hot water tank from the coil in the OWB, there's no pump just on demand with water pressure.