Saunier Duval moves between 0.5 and 2.6 bar!

[srdegnan]

Hi

Have moved into Partner's flat and she has a very old Saunier Duval F30E combi. Never seen one before.

Pressure will move between 0.5 and 2.6 bar without any topping up of the system. When below 0.6 boiler will not start. I'm use to a little expansion and contraction when heating is on but this is something else!

Any suggestions appreciated. I appreciate upon reading this and other forums the boiler is best placed in a bin ... which is where it will be going in short order. However I need a tactical fix for a few weeks at least!

Cheers

 

[ianmcd]

Expansion vessel problem

 

[Poisonata]

As Ian correctly stated sounds highly suspicious of the expansion vessel. Either needs re pressurising or the internal bladder has breached / needs replacing. To re pressurise locate the expansion vessel (fairly large, round, relatively flat (but not always)) normally situated at the rear of the boiler. Somewhere on it you'll find a valve that closely resembles a car tyre valve, used to introduce air into the internal bladder. You'll need to check the exact pressure this needs to achieve & introduce air when the boiler has been off for some time (pressure dropped to lowest). Any introduction of air into a deflated bladder will improve the problem. If the bladder is breached you'll simply hear a bubbling sound. Good way to check is depress the valve centre pin momentarily (as if to release air). Water comes out > replace vessel is only option.

 

[Poisonata]

P.S. Do not be tempted to find the first valve that resembles a car tyre valve & start pumping air into it. Make sure it's the one directly connected to the expansion vessel. Else you may end up blowing air into the boiler auto bleed valve.