Saunier Duval F30E?

Sounds very much like your expansion vessel is NG. This is the large red disc item inside the rear of the boiler. Inside it is a strong diaphragm, one side is pressurised and the other allows the expanding hot water from the heating side to fill the vessel, then as the heating cools the pressurised side pushes the cooling waster back into the system. If the diaphragm fails then the water is pushed out via the overflow outlet usually not noticed, but look for traces of water around the external overflow pipe outside. There is a real easy way to DIY check this with no gas risk etc. Remove the large upper front panel from the boiler, and on the top (normally RHD side) of the expansion vessel is a valve, same as a car type with a cap on it. Remove the cap and for a second press the pin in the centre of the valve down, only thing that should come out is compressed air. If you have water coming out then the vessel is NG and the internal diaphragm is ruptured. This will then need a gas fitter, to either replace, or as I did for ease, add another external expansion vessel, took the gas fitter less than an hour to do. They just tapped into the heating pipes right by the boiler and added a small expansion tank. Long term the inside of the original tank may corroded through and begin to drip, mines still OK after 5 years so not much concern there. Cost for the whole repair was less than £100 as I say 5 years ago.

Dokka Watson
February 2015

I have the same boiler snd facing the same problem. Losing presure every time that the heating comes on. When the heating goes of the presure goes below 0.5 bar. Any ideas. I think that the expansion vessel needs replacing. I would appreciate if any one could help thanks.

Daniel
November 2014

Hi i have had nothing but probs with mine , new pcb in placr noe its showing F14 and i am lost what to do cheers Andy

Andrew Hogg
April 2011

If this helps anybody else with the same problem, this is the reply I got from Saunier Duval, I've not got anyone to check mine yet so don't know if it works.

It is certainly not something we come across regular, however i believe you have a problem with Expansion, the problem maybe the expansion vessel has lost its air charge this should be 0.5bar approx 10psi alternatively the pipe feeding it maybe partilally blocked, with that said thou the Safety valve to the outside of the property must be releasing.

Gary
February 2009

Gary

Like you, I also have the same boiler and am having the same issues. Initially it started we had to change the main PCB. I have since replaced the pressure release valve, but to no avail.

Would appreciate a response from anyone that has had and rectified this problem.

Thanks

Neil
January 2009