High Co levels 400+ on 28i RSF combi

[ed209]

Hi am getting extremely high CO reading, using test point that connects to fan via silicone tube as vertical flue fitted, new fan fitted by other last year so could be that not sealed/missing gasket, or flue gaskets as everything else as Mi's
Burner removed and cleaned etc.
Going back tomorrow as ID today
any other suggestions please

 

[Last Plumber]

Hi am getting extremely high CO reading, using test point that connects to fan via silicone tube as vertical flue fitted, new fan fitted by other last year so could be that not sealed/missing gasket, or flue gaskets as everything else as Mi's
Burner removed and cleaned etc.
Going back tomorrow as ID today
any other suggestions please

Test air intake with FGA to check there are no combustion products. That should rule out the flue seals

 

[ed209]

Unfortunately no test point for air, this is over 15 years old with unpainted aluminium vertical flue

 

[Stoney Ground]

Hi am getting extremely high CO reading, using test point that connects to fan via silicone tube as vertical flue fitted, new fan fitted by other last year so could be that not sealed/missing gasket, or flue gaskets as everything else as Mi's
Burner removed and cleaned etc.
Going back tomorrow as ID today
any other suggestions please

Lower BP to see if CO drops

 

[hammers4spanner]

15 years old!!!

If it was a car you'd bin it

 

[Last Plumber]

Unfortunately no test point for air, this is over 15 years old with unpainted aluminium vertical flue

Burner pressure ok ?
Fan speed good ?
How is it with case off ?

 

[ed209]

Fan speed ok, BP as per mi's as is gas rate
Good blue flames no evidence of crack in burner, haven't checked with cover off will do that tomorrow

 

[Last Plumber]

What is ratio CO/CO2 ?

 

[ed209]

0.0064

 

[Last Plumber]

0.0064

Why are you worried ?

You could clean the fan blades but tbh, it's possibley always burnt like that. This is an older type boiler than today's don't forget.

Today, fan speed controls gas rate ( to put it simples ), so the flue gases are always fairly similar ( within reason ). The boilers like the one you are working on are not as balanced. A lot of them had one or two fan speeds but had a modulating burner.

You won't always get as stable a reading on those as you will on modern boilers.

However, the ratio is below the ' we need to worry ' levels.

 

[ed209]

sorry should have been 0.0640 going back today will confirm that
In fact please disreguard that figure until i confirm, WB said max CO permissible was 250 and it went up to over 600ppm

 

[Last Plumber]

sorry should have been 0.0640 going back today will confirm that
In fact please disreguard that figure until i confirm, WB said max CO permissible was 250 and it went up to over 600ppm

Ah!

You got a low CO2 count too then ?

Like I said before, check fan blades are clean, run it with case off and check flue gases ( if it safe to do so), it could be a blockage in the air intake !. It could be a partial blockage in flue, quite a few aluminium exhaust flues corroded and had a build up of corrosion inside. If that is the case, it is also possible that the air and flue gases can mix, ( via a hole in exhaust),giving bad readings.

Also, check for things like flue restrictors. Some ( and I can't remember on yours because it's been a while) had a 'air in', restrictor that should be removed if you where using vertical or lengthy flues.
All part and parcel of what I said before about fan speeds etc.

Let us know how you go on.

 

[ed209]

All sorted the inner flue tube had been partly pulled out the offset elbow, this could have happened when a new fan was fitted approximately 8 months ago (not by me) as the lugs that secured inner to outer were snapped off. Every thing was text book with this boiler including flame picture so it shows its a good idea to FGA even standard efficiency boilers, which I tend to do anyway as it leaves a big blank section on the LGSC and service form other wise

 

[Last Plumber]

All sorted the inner flue tube had been partly pulled out the offset elbow, this could have happened when a new fan was fitted approximately 8 months ago (not by me) as the lugs that secured inner to outer were snapped off. Every thing was text book with this boiler including flame picture so it shows its a good idea to FGA even standard efficiency boilers, which I tend to do anyway as it leaves a big blank section on the LGSC and service form other wise

I agree and we'll done for being thorough, there should be more engineers about who care about what they're doing.