Prima F crazy burner behaviour!

[gassafe]

Just been to a potterton prima F, it starts fine, but after around a minute, the burner starts trying to cut out, the flame is lifting off burner etc before it eventually cuts out! I thought the gas valve was failing and not keeping gas open but its a constant 9 Mbar!

Upon checking the outside terminal to check the fan is staying on I noticed the last 3 inches of flue has rotted through at the bottom! Would this be enough to cause my crazy gas burner flame picture? I have never seen this before on a burner with holes in inner flue!

Is it easy to fit a new inner flue, or is it not worth it on this old thing?

 

[Millsy 82]

Yes it would be enough and its very common on these. You can get a flue remedial kit for them its dead simple to do takes about 20 mins to fit it.

 

[mfgs]

As has been said the flue remedial kit is very easy to fit unless the screws on the terminal have been cemented over when sealing the flue. It is literally three screws to take terminal off and slide new kit over the old inner flue.

 

[Reg Man]

What's happening is the products of combustion are re-entering the boiler through the defective flue, depleting the O2 and causing the burner to search for air, hence the lift off. Bet your bottom dollar the combustion is rank too. Huge amount of CO if you ECGA it.

 

[zeebeedee]

Over 6000 ppm usually when they go. Flame stays blue though just dances all.over the place!

 

[Reg Man]

Over 6000 ppm usually when they go. Flame stays blue though just dances all.over the place!

That's because the flame is searching for air.