3,500 PPM CO

Alan (California Radiant) Forbes · March 20

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 · March 20

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

Steamhead · March 20

Sounds like not enough air.

ChrisJ · March 20

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 · March 20

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 · March 20

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 · March 20

@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 · March 20

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 · March 20

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 · March 20

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 · March 20

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 · March 20

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?

EBEBRATT-Ed · March 20

Not likely the intake as he had the doors open and the intake would be pulling room air. I messed up my analyzer more than once and taught myself to pull it if the CO shoots up otherwise your standing there and can't do anything.

mattmia2 · March 20

oh, it is one of the ones that uses the cabinet as the intake connector?

tim smith · March 20

Alan, was the burner replaced or at least cleaned. Also the heat x tubes may be clogged and obstructing flow of gas/air through heat x creating dirty burn.

Alan (California Radiant) Forbes · March 24

Just cleaned. I'll be replacing the burner when I go back.

Thanks for suggesting to clean the HX tubes. I'll do that with your silfos trick.

Alan (California Radiant) Forbes · April 3

I'll be returning to the job later this morning to check and replace the burner and venturi as necessary. I will also clock the boiler on high fire and clean the HX. After looking up the installation guidelines for the exhaust/fresh air piping, it's obvious that the actual length exceeds what is permitted for this Solo 250. The combined length is probably 80 feet, not counting any fittings. Three inch pipe.

Alan (California Radiant) Forbes · April 3

We just finished the service. We clocked the boiler at 250K, so no problem there. The burner and HX were pristine and on first glance, the venturi was in good shape. But then I noticed that the adjustment screw was retracted all the way, so the problem seems that the burner was getting too much gas.

I could have tried dialing down the venturi, but I had a new one and I didn't want to di*k around with a device that may have something else wrong with it.

The boiler is working fine now. CO numbers come in at 60-70 ppm on high fire.

3,500 PPM CO

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