Gas Boiler Safety Valve

Hi

Our gas boiler after it starts up and is running for a bit (10min) has started to blow water/steam out of the safety valve. It makes a loud grating noise ( like a train on a track) and then the safety valve pops and the water releases. This is now a regular occurance with the system.

I had the Pottertan service man come and look at it but he said he didnt know what was wrong with it.

Its about 6 yrs old and was regulary maintained.

Does this mean theres something seriously wrong with it.. the radiators work fine and there are no air locks in the central heating so far.

any ideas would be gratefull.

thanks
c7

Is it a closed system with a valve to top up the water from mains pressure? This is the case in many new developments esp. apartments because there is no height or space for a gravity feed expansion tank. If so someone may have opened the valve and left it open. In any case its a job for a professional as if the relief valve is venting the coils have been overpressured and need to be tested.


There should be a pressure guage on the front of the boiler.

If its reading a considerable pressure when cold then watch if it goes way over towards the red when running as the pressure will increase when hot.

Anyway if its gas then by law it must be serviced by a Bord Gais certified fitter.

thanks for the reply.

by coincidence it all started happening after the last service by a boird gas approved company.i'd say its only a coincidence but i know i will not get this company back again.

im sure its a closed system and the last person who came out was doing something at the top of the unit like venting it or something like that.

would it help to bleed the system if there is the chance of some airlock or does this matter.

suppose its best to get a professional out..any recommendations?

I've had High Speed Gas out to do work for me and was happy with them.

An airlock should'nt cause overpressure of itself but bleeding will reduce the system pressure provided its not connected to the mains with an open valve. I really think you need a professional though. If its only overpressure a plumber may suffice but anything done to the boiler itself must be done by a certified gas engineer.

Are you topping up the water in the system after it blows.
At cold the pressure gauge at the front of the boiler should read approx 1 bar or slightly below.
As the heat comes on this should rise to under 3 bar. If it goes over 3 bar the pressure release valve should blow.
Inside the boiler there should be a red pressure vessel that is supposed to control the pressure in the system. If this is faulty the water has no place to expand and so blows the valve.
Air locks in the system wouldn't cause this.
Where are you based?