High CO Readings on Baxi Combi 105 HE

[Johnnyboy1]

Hi, Can anyone help?

During a landlords inspection carrying out a Flue Gas Analysis I found exceptionally high CO readings, more than 750 PPM. Readings are satisfactory with combustion case removed or if appliance is on minimum output ie. with gas valve solenoid wire removed.

Gas rate and burner pressure ok. Cleaned out burner and primary heat exchanger. Have checked flue, appears to be clear. Air intake has no POC. contamination with appliance running. Have replaced secondary heat exchanger/condensing unit and associated seals.

Am Now cosidering changing fan in case running slow or POC's leaking up air impellor shaft and back into case instead of going out of the flue.

Starting to run out of ideas. If anyone has any ideas or has come across this problem before i would be grateful to hear from them.

[Alpha man]

Has it got a long flue?

[Toddyplumb]

Have had it a couple of times both were flue joints apart.

[Johnnyboy1]

No more than 1 metre...

[Johnnyboy1]

Thanks, I will go back through and have a closer inspection of flue...Flue is less than 1 meter long so no actual joints to speak of...I had the same problem last year and ended up handing job to Heatteam and they said they replaced the secondary heat exchanger/condensing unit which worked....