Heating Pex Blew

redtyde

Hello.
I have seen a couple of postings about heating PEX blowing and I just had this happen.
See pic below.

It was originally installed in 2005 and just burst today.
Any thoughts on why this would happen?

JUGHNE

How hot was the water temp?
How far to any support on the right side?
Looks a little saggy.

redtyde

Thanks for quick response Jughne.
180 degrees is the water temp tos a hydro heating unit.
Its about 18" from the brass fitting to the main wooden support beam where its attached.

kcopp

What is the boiler???? Looks like 220*+ water temps to me....

redtyde

Its a Carrier with Weil Mclain burner. I know its 180, or at least that is what the gauge is showing me after I I closed off this zone and fired up the system again. Also gauge at 15 PSI.

Tinman

Aquastats and temperature gauges that come with new boilers are inaccurate at best. Just one of the reasons I would NEVER use Pex in a high temp application.

Solid_Fuel_Man

Agree with @Stephen Minnich I've preached the same thing on wood/coal/pellet fires boilers. One overheat and the results can be catastrophic.

Is there any way to confirm the max temp other than aquastat settings and boiler gauge?

Mark Eatherton

Yeah, no. I have literally MILES of this stuff out there, and have never seen a failure like this on my systems. I have seen this type of failure where the boiler was run away and producing steam. I can tell by the deformities of your tubing that it was well above steam. I also saw this kind of damage when I mistakenly applied heat (torch flame) to a kink trying to get the kink out of the pipe. Forgot it was under 100 PSI test pressure... Made a heck of a noise when it blew.

You may have been seeing 180 F water temperatures when the system was running, but when you shut it down quickly, there is still a lot of heat left in the refractory, and it can create drift heat significantly hotter than 180. Probably softened the tubing and the pressure blew it. Need to see more pictures of the system to which it was connected to give a clearer idea.

ME

Ironman

I have to ask: is that a piece of Qest or just discolored pex. Judging by the tear, it looks like Qest.

kcopp

Looks like Uponor/ Wirsbo to me. The fittings are the expansion type. The system water discolored the inside.

Zman

Mark Eatherton said:

Yeah, no. I have literally MILES of this stuff out there, and have never seen a failure like this on my systems. I have seen this type of failure where the boiler was run away and producing steam. I can tell by the deformities of your tubing that it was well above steam. I also saw this kind of damage when I mistakenly applied heat (torch flame) to a kink trying to get the kink out of the pipe. Forgot it was under 100 PSI test pressure... Made a heck of a noise when it blew.

You may have been seeing 180 F water temperatures when the system was running, but when you shut it down quickly, there is still a lot of heat left in the refractory, and it can create drift heat significantly hotter than 180. Probably softened the tubing and the pressure blew it. Need to see more pictures of the system to which it was connected to give a clearer idea.

ME

I agree that this one flashed to steam.
I have seen the exact same damage where the insulation contractor applied spray foam too quickly with the system under air test. Talk about a hot mess...

redtyde

UPDATE - So after getting the PEX repaired and heat going again, root cause is still undetermined and I have had (3) contractors give me (3) different reasons as to why they feel the PEX failed.

The PEX that burst feeds a hydro-heating system in an unconditioned attic space. There was speculation that the coils froze. (It was cold and windy on the day it happened, it got down to 13 degrees). Although keep in mind this unit was installed in 2005 and has never had this type of issue before.

Another contractor states that it couldn't have been freezing coils as he would expect the copper in the coils to split before the PEX bursting.
After the PEX repaired and a pressure test was done, coils were fine with no leaks.

My question, even if there was some type of blockage in that line, does a circulatory pump have that kind of horsepower to build that much PSI?

Do we put in glycol to avoid the possibility of freezing coils?

Tinman

3 contractors and not one of them suggested iron pipe for near boiler piping?

redtyde

No, As a matter of fact one of my questions was how far off the boiler can you start PEX. I thought you had to be so many feet away from the boiler but I may have been mixing up my domestic hot water PEX. ALL of them said you can go directly to the boiler.

Bob Bona_4

Logic dictates using iron or copper near the boiler for stability for the pumps/valves/service components. After that, pex away.

Zman

I am thinking the boiler got low on water and overheated, it then got a shot of cold water which immediately flashed to steam creating the temp and pressure needed to cause that kind of damage. Just a theory...
Some more pictures of the boiler piping would help determine the cause. Does the boiler have automatic fill and/or low water cutoff?

Mark Eatherton

I think you had a stuck aquastat, and it could happen again.

As for antifreeze yes, but unless you want to go to the expense of setting a heat exchanger and related equipment, you will need to fill the whole house heating system with it.

As I and others have said, it would be nice to see more of the near boiler piping...

ME