Modcon flue gas smells of gas

rhl

Hi,

I've noticed a condition were on startup we smell gas from the boiler flue pipe just for a moment before we start seeing the white flue gas.

Modcon aqua balance combi boiler.

I replaced the flue gas sensor (which was corroded) and the ignitor -- went ahead and vacuumed out heat exchanger and cleaned per manual.

Refractory is partially worn -- will replace when new part arrives.

Boiler was installed in 2018.

Is this normal? Anything else to check?

Jamie Hall

Are you smelling gas -- or combustion products? Both have an odour, but are quite different.

mattmia2

did you do a combustion analysis on this? Might not be unusual for a small amount of unburned gas to be emitted as it is lighting

HVACNUT

Are you smelling this outside at the exhaust or inside at the boiler?
You might get a good whiff if you're near the exhaust outside on ignition only. Inside, that needs to be checked. Do you have a combustion analyzer and manometer?

EBEBRATT-Ed

Do a combustion analysis. If it lights ok and the combustion test is ok I wouldn't worry about it

rhl

Outside the boiler -- I don't have one personally -- will ask plumber. thank you everyone.

HVACNUT

rhl said:

Outside the boiler -- I don't have one personally -- will ask plumber. thank you everyone.

You don't necessarily need a plumber. A service technician familiar with mod cons and the correct tools is who's needed. Come back and let us know. The tech should leave a printout or email you the combustion report. 

Jamie Hall

You don't necessarily even want a plumber. Not all of them have any idea how to adjust a mod/con...