how to repair my vokera linea 24 boiler?

my boiler pressure rises to between 2 and 3.5 bars with the heating comes on and starts to drip water from the boiler,
to stop this when it happens i have to turn the heating down to below 15c with the thermostate in the living room which results in the radiators cooling down making my house quite cold!!
also when the heating is off the pressure drops to 0.5 bars meaning i have to top it up to 1/1.5 bars again starting the whole problem off again!!
is this something i can do myself or do i need a gas fitter??
please help as the cold weather is just around the corner!!
thanks,
neil

neil, October 2007

the problem with my boiler is a constant loosing preasure. The valve at the top of the expansion vessel is leaking water.even when the preasure gauge is at 1-1.5 bar.should it be leaking or not or should it be air coming from this valve not water? Does it need a new new expansion vessel ? Engineer has been here and tried to sort it out and couldnt find the problem. I m a plumber and used to be a gas engineer but not been used to a combi boilers. Any ideas what we could tell the engeneer to sort this problem out?

john, January 2010

looks like you have a water leak from the boiler and not a radiator, try to find the leak put your pressure up to 3 bar if you find the leak from a component on the boiler go for it, drain your system down and repair, it might be your safety valve overpressure weeping if you need that replace simple task, the same as any water leak repair, the gas side better leave to the experts,i have just had my sons leaking from the heat exchanger a bit of an unexpected leak but got to replace the exchanger

Davie, November 2007

looks like you have a water leak from the boiler and not a radiator, try to find the leak put your pressure up to 3 bar if you find the leak from a component on the boiler go for it, drain your system down and repair, it might be your safety valve overpressure weeping if you need that replace simple task, the same as any water leak repair, the gas side better leave to the experts,i have just had my sons leaking from the heat exchanger a bit of an unexpected leak but got to replace the exchanger

Davie, November 2007

Sounds like your expansion vessel has gone kaput. You could try re-pressurising it as it may have lost it's pressure. If you look in the manual (on page 54 Linea insallation & servicing instructions if you have it)-when looking at the boiler from above- right at the back is a large whoopee cushion looking thing. This is the expansion vessel. It is designed to take up the increase in presuure as the water in the system gets hot & expands.(A good analagy would be-BUT DON'T TRY THIS- if you sealed the spout on a kettle as it boiled what would happen to the lid with all the steam? It would blow it off. This is what your boiler is trying to avoid by throwing the water through the overflow to stop it exploding) On the top is a car tyre valve-top it up to about 15psi when the boilers cold & not in service. If's it's below give it a go & see how you get along. If it's already got pressre it's probably knackered. Your looking at around £85 just for the part not including fitting.

The reason you keep having to top it back up is because the expansion is not being taken up & the pressure release valve ( a safety part designed to stop a wonky boiler blowing up) starts throwing the water out of the system at 3 bar. Loss of water equals top-up.

You could cut the cost by fitting an auxilillary expansion vessel the look like an orange drum about a foot & a half tall & are a lot cheaper usually than original equipment boiler vessels. a 12 litre one is around £25 with the mounting bracket.

If all this sounds gobledy-gook discuss it with your service engineer.

Hope this helps
Steve

Steve Bedford, November 2007