underground piping for pressurized boiler

[jdurant]

Hey Eric, and fellow boiler folk,

I am getting ready (this spring) to run underground pipe from my boiler (royall boiler in garage) to my house. I spoke to a guy ( Boiler manufacturer) about this and he recommended to run insulated copper pipe underground. He stated that if the power goes out and the blower is not on that the unit can buildup to much pressure, back flow, and can blow out the pex tubing (he said that the pipe balloons out). Can I prevent this by using and automatic zone valve? I want to use this so that it can gravity feed the water during a power outage. Is pex that touchy? The guy (rick) said copper pipe can take the pressure more. Do you have any suggestions on where to buy insulated copper pipe? I thought about making my own (copper tubing, foam insulation, in pvc pipe) I just want to do this right. I want a pressurized boiler because they last.

 

[jebatty]

Something's not making sense. Home boilers (I think) all are low pressure to start with, 12 lbs or so, and mine has a 30 lb pressure relief valve. Second, an overheat loop, gravity loop being best to deal with power out, is essential. If the overheat loop is adequately sized, there will be no pressure buildup of any significance, as heat will be dissipated. Third, pex is rated for more than 30 lbs, and the pressure relief should handle any problem.

One way to forestall a problem is to do a pressure test on the pex before finishing the install. My guess is that the crimp connections are more likely to be at fault than any failure in the pex itself, although I've never used it myself. If copper ever leaks, it's at the solder connections (but of course, I never have a cold solder joint).

 

[BrownianHeatingTech]

Your system needs a 30-psi relief valve, piped to discharge at a safe place. That way, if the pressure builds, it has some place to go.

Pex is superior to copper in underground use, since frost and other things can't break it (due to far greater flexibility than copper has).

Joe