Problem with boiler

carlgren

Hi,

New house. Installed new viessmann BH1K-150 boiler. Boiler worked fine for several days on the radiant side. I was in the process of removing air from my DWH side and the boiler fired and blew back. From then on anytime it fires it's blows back a little and then runs fine.

Checked with Viessmann and they suspected my gas pressure was dropping low on initial start up and then coming back up.

Called the gas fitter back to check the pressure. Turns out that I was getting 2psi at the boiler valve. He checked further and the two gas regulators he installed were both putting out 2psi. He checked the one outside and it was 2psi, as it should have been. Both inside regulators are stamped .7 to 11"wc but both putting out 2psi. The other regulator is for our gas stove that hasn't been installed yet.

He's going to get new regulators on Monday and we'll see if they work. He also discovered that the new BBQ regulator he installed is leaking on the case.

SO my question is what is the likelihood that I'm now going to have to replace the gas valve on my new boiler? The valve is over 1K. The boiler was running fine after the initial startup but there is no getting around that it was being exposed to 2psi for possibly up to 3 days from when I initially fired it.

thanks

Don

mattmia2

Did the same contractor install the regulators and the boiler? Did they both work under the same general contractor if not?

carlgren

nope, he installed the regulators and ran the line to the boiler. I installed the boiler and flipped the switch. He pressure tested everything (with air) but didn't check gas pressure as he wasn't on site when I commissioned the boiler. I think the assumption in the industry is that when you install a regulator it will provide gas at the set point it's supposed to and not act like it isn't even there.

In hindsight I should have had him put his gauge on the valve at the boiler to check the pressure when he hooked the line to the boiler.

HVACNUT

Whoever commissioned the boiler should've checked lockup and running pressures at startup. After the visual inspection and checking zone cycling, I cycle the boiler with the gas valve off to put the boiler into an ignition fault. Only then do I open the gas valve to check check pressures at lockup and startup. I haven't met a mod con yet that didn't need a tweak on the throttle screw to dial in proper CO2. A combustion test would've shown an obvious issue.

Jamie Hall

https://forum.heatinghelp.com/discussion/comment/1816311#Comment_1816311

Problem. It sounds as though @carlgren commissioned the boiler. Without checking the gas pressures… in which case…

Ironman

Was the air pressure test done with the regulators installed? If so, and if the test pressure was above 5 psi, then that could have blown the regulators.

carlgren

Yes, I commissioned the boiler without checking the pressure. I assumed it was done when the gas was connected to the boiler. My mistake on that for sure. The air pressure test was done without the regulators installed. I wasn't in the house when they were installed following the air pressure test and the connection was done on the boiler. I wrongly assumed he checked the actual gas pressure at that time. Since he put in a brand new regulator yesterday and it was also reading 2psi to me indicates his supplier has a bad batch of regulators.

The question was…..is it a safe bet the gas valve should be replaced or can they survive a few days over pressure? My guess is it needs to be replaced. My thoughts is it survived for the first 40 or so starts and then when we got the first poof on startup that was the end of it.

EBEBRATT-Ed

What @Ironman said if the gas pressure test was done withe the gas valve and regs under pressure they are likely toast. You plumber/gasfitter should have know thei. You should never turn the gas on to an appliance if there was any doubt about the pressure in the gas line it needs to be checked.

Ironman

The gas control valve should never be subjected to more than 1/2 psi pressure. The internal regulator in it will be damaged if it is.

There’s often a warning label or printing on it which says so.

I’m not convinced that your gas guy knows what he’s doing.

carlgren

OK, thanks. I figured it was going to have to be replaced.

First issue is to get regulators that work properly then I'll deal with the damage to the boiler. Unfortunately where I live the choices for this kind of work are pretty slim. Hopefully I can find someone better to do the work on the boiler.

thanks for the help everyone. You confirmed my suspicions. I screwed up and the gas fitter I hired also screwed up.