3,500 PPM CO

Alan (California Radiant) Forbes

I was doing a Triangle Tube recall on a PA250 today. Everything went well until the combustion analysis. The high CO count destroyed the CO sensor in my Testo 300. Colleagues have said replace the burner. Others have said to check the orifice size, if any, but I don't see one shown anywhere. Anyone with experience with this here?

mattmia2

was here like a log of carbon extruding out the vent?

Steamhead

Sounds like not enough air.

ChrisJ

https://forum.heatinghelp.com/discussion/204111/3-500-ppm-co

Are you sure the analyzer didn't just fail on it's own causing an abnormally high reading? Perhaps it was already acting flakey at the start?

GGross

I had this happen one time and someone (me) sent me the wrong venturi. I hit 9k and shut it down, my analyzer took about 3 days to clear I thought the sensor was toast but it was not! This was on an original series PS solo boiler

HydronicMike

Unless burners are misaligned, I'd double check input. Underfired is a usual cause for high CO, as is impingement. On furnaces, cracked heat exchanger is another culprit.

Alan (California Radiant) Forbes

@mattmia2 No, but the exhaust run is about 80' long.

@Steamhead We had the cover off and all the doors open to the outside, so there was plenty of air. We tried to find where the fresh air pipe termination was, but couldn't.

@ChrisJ I thought the same thing, but there was a previous technician who got the same results.

@GGross I'll check the venturi.

@HydronicMike That's novel. I'll clock the meter.

Gene: Looking at parts diagrams, it was interesting that the same burner and gas valve fit 3 different size boilers. Only the venturi changes.

GGross

That looks like the correct venturi number, 051 at the end

I think that model added an orifice for propane conversion, I do not think there was one installed for natural gas but i had a lot less hands on time with that exact model

the propane conversion kit instructions for that one don't mention removing a natural gas orifice, just adding the propane one

Alan (California Radiant) Forbes

Thanks, Gene.

The PA 155, 175 and 250 all use the same burner and gas valve. Just curious, If the wrong venturi was installed on this PA 250 boiler, wouldn't it just fire at a lower rate? It shouldn't have this high CO aberration.

GGross

https://forum.heatinghelp.com/discussion/comment/1892338#Comment_1892338

i still have the old failed venturi and the incorrect replacement . I use them as visual aids when needed, or to remind me of one of my biggest blunders lol

The little pathway the fuel takes is also different for each model, so in my case I had one that the venturi opening was about 2x what it should be on the air side, and take a look at how much more fuel could probably get through the fuel side (opened these up quite a bit so you can see the opening better) So what I think was happening is that way too much fuel was getting in my burner resulting in very incomplete combustion. Not sure how thats happening with yours though assuming that venturi is correct, and you didn't remove any orifice or orifice gaskets.

Alan (California Radiant) Forbes

Yes, I see that the gate is much larger in the first photo. What a difference! I'll check on mine when I go back in April as the owners are away on vacation.

I see in the second photo that the plastic in the venturi was destroyed.

mattmia2

maybe finding the intake and making sure it is ok is important or checking that the equivalent length of both is in spec. is there something that failed in the recalled parts that made it soot up and it is now burning off that soot?