I have a newly installed, and just commissioned, Ferolli 35C condensing boiler in a new house in France. It worked fine for a week and then I shut it down. It runs underfloor heating and hot water. I restarted it after about 5/6 weeks and it runs for a while reaching operating temperatures. It then builds up pressure inside and goes bang. The casing visibly expands each time. The frequency increases, the' bang ' gets louder,and the temperature drops 3 degrees before recovering- so I shut it off. I am not sure if it is steam trying to escape, or the pilot is going out and the gas is exploding on hitting the hot boiler. Please help. Am I in danger of the whole boiler exploding? The maintainance company ,and the plumber say its " bizarre". Trouble is I will have to run the boiler again for them to see the problem, which is probably not a good idea!!!

Robert Welton, December 2006

The boiler has been running too hot, and has melted the blades on the fan. Hopefully the boiler will now be set up properly! The flue has been installed to the manufacturers instructions, but the technician here says that the angle of the flue should be slightly more than 90 degrees to allowed the water condensed from the steam to return to the boiler.

rob, February 2007

Thanks Lee
The flue is around 600 to 800 mm long with a 90 degree bend. The engineer has returned and changed the electrodes but the fan then completely jammed. So you are right, the fan was probably the original problem. I did not install the boiler, but I will check the flue installation instructions ( in French! ) tomorrow, and take your advice about having it set up and monitored.

Thanks Again
Robert

robert, February 2007

you have a flue/fan/combustion problem.Need to know how long is the flue length. Restrictors used?
sounds as if the gas air mixture is incorrect and the boiler needs a good commissioning engineer. At this stage it would require a stripping down to check flue ways are clear and that all flue aspects have been correctly carried out to manufacturers instructions. Then you can go to the next stage of setting up correctly and monitoring the result.

lee S. Wales, January 2007