When I use my CH and set the pressure to 1 bar it rises to just above 2.5 bar and nears the red. There is also some leaking from the boiler itself causing the boiler pressure to reduce slightly over the period of a week or so which I top up from time to time. Reading other articles suggests that the pressure in the expansion vessel may be low hence the over increasing of the working pressure when the CH is on. Would someone confirm this and tell me how to increase the air pressure on my Saunier Duval Combitek F23E

Chris, December 2007

You mentioned that there was a leak from the boiler itself. I s that still there if so that will drop the pressure. Providing the pressure does not exceed 3 bar the ex tank needs no attention. The pressure increase is relative to the amount of water in the heating system. Only re pressurise if the outlet pipe is leaking.

bendan, March 2008

THE LEAK IS NOT THE EXPANSIONTANK.
The pressure increases as the system warms up. This is contained in the ex tank. The tank only needs refilling if the working pressure exceeds 3 bar and the safety valve opens. I F THIS IS THE CASE A BICYCLE PUMP WILL DO THE JOB.

t, February 2008

The increase in pressure on the gauge is relative to the amount of water in the heating system. If the pressure is getting higher than it used to then maybe the expansion tank is at fault. It has lost it`s air pressure. Isolate the boiler from the heating system by turning off the flow and return valves on the fixing jig,drain the boiler, remove the dust cap from the expansion tank,attach a bicycle pump and pump out the water in the tank through the safety valve. Pressurize the tank to half a bar. open the isolating valves and fill to one bar. The leak could be from several places,more info required.

bendan, December 2007

Thanks for the information 'b' you have been very helpful.

chris, December 2007

you can try to pump the pressure up but you must drop the
pressure in the heating system to zero first
as for replacing the tank if its at the back of the boiler
the boiler will have to come out, so it will cost quite a lot,
how ever I think you will be able to fit an in line expansion
tank on the heating return pipe it will cost a lot less.

b, December 2007

Thank you 'b' for the information.

I can see some water on the valve! How much would it cost to replace the expansion tank and is it a complicated job?

In the mean time can I pressurise it to 0.5 bar as suggested or will the problem remain until the expansion tank is replaced?

Chris, December 2007

you should see a valve on the top of the expansion tank
you can use a car foot pump to pump up the pressure
it should 0.5 bar without any pressure in the heating system
if water comes out of the valve the expansion tank needs
replacing.

b, December 2007