I awoke yesterday morning to find an email from a new customer asking if I would give him a second opinion on a gas boiler he had at his rented house in Newcastle. I didn’t realise at the time but the 6am email had come from Shanghai, China, the customer was an English teacher in the Far East!

 Making arrangements

I responded to the email, arranged a visit with the local letting agents and inspected the boiler. The tenant had reported that the boiler was switching on and off every five minutes and on inspection I could see why.

Potterton Prima 30F – combustion safety device

Looking through the spy glass at the flame picture I could see the flame lifting off the burners. These boiler are fitted with an “oxy pilot” pilot light which is designed to shut down the boiler if there is a lack of oxygen in the combustion process – this is what was happening.

The next step was to determine why there was a lack of oxygen and why the pilot light was lifting off the burner causing the thermocouple to cool down and switch off.

Flue problems

In most cases the lack of oxygen is due to flue problems. If a flue is blocked then less air is able to get into the boiler causing combustion problems, but also if the flue is damaged or corroded then exhaust gases can get into the intake of the boiler and as these are primarily CO₂, they starve the boiler of oxygen. Taking a look outside at the flue it could be seen that the terminal had been poorly pointed in but this was a historic fault and the current problem had just arisen so there was more to it that that poor pointing.

Corrosion of the flue

On closer inspection of the flue it was obvious to see the inner exhaust pipe had completely corroded to the point that there was a large airway between the exhaust pipe and the air intake resulting in the boiler breathing in its own exhaust gas. This is likely to cause high levels of CO as the combustion process is compromised by the lack of oxygen and produces CO rather than CO₂.

The boiler was restarted and the CO levels measured to see just how bad the combustion process has become, as you can see the level is very high, 1600 ppm (parts per million) a level that will cause death in 2 hours if the gases were able to get into the house.

I classified the boiler as “At Risk” and disconnected it from the gas supply and issued a warning notice until I was given to go ahead to repair it.

Simple fix

Baxi are aware of this problem and make a simple rectification part (5106693) which neatly fits over the distressed flue pipe. This was purchased, fitted and the CO levels remeasured at 42 parts per million, a much safer level.

The work was completed and the photos sent to Shanghai for approval by the customer who was happy with the work and left a very kind review on Checkatrade – “I can’t thank Richard enough, he’s quite literally a lifesaver, picking up on serious issues missed by a shoddy craftsman obtained by my property manager as I work abroad and rent out my home in Newcastle. He also saved me having to replace the boiler entirely. Thank you, Richard, for your prompt and excellent work as well as the communication, information provided, upfront pricing and photos. It’d be my pleasure to recommend Richard here and I’m definitely keeping his number for any future work as well as sharing it with my family and friends in Newcastle as often as I can.”