gas boiler/combi losing pressure

[beerdoctor]

Hello

My son has a combi gas boiler it has lost its pressure(on the gauge) and is leaking water from the overflow,someone said it might need a new seal any ideas anyone

cheers

 

[HorleyMonkey]

It's discharging via the pressure relief, therefore, meaning that he need a gas safe registered engineer to carry out the requisite work. Sorry but on an open forum I won't go into more detail than that.

 

[MANDATE]

The problem is related to the fact it's a combi with a sealed system.
The water when heated expands and the excess water has to go somewhere.
A expansion vessel is provided to accept the water and allow it to retract when cooling down again.
The expansion vessel contains a flexible diaphragm, one side holds 'air' which is charged up like car tyre to 0.8bar. This is before any water pressure is applied. This means the whole of the vessel has no water in it and gives the maximum amount of air for compression.
Your vessel has lost most of its charge, so when you set the water pressure to 1bar the vessel becomes partially or fully filled with water.
Now with little air to compress, the air pressure goes very high, but the PRV kicks in at 3bar and discharges the water. The PRV closes again but during this operation the water pressure drops to about 0.5bar or less and nedd topping up again to start the whole operation over again.
PRVs once opened rarely seal properly and usually need renewing.
So first action is to get the expansion vessel recharged then attend to the PRV

Horley Monkey! Why would a gas safe registered engineer be needed?

 

[bell824]

Horley Monkey! Why would a gas safe registered engineer be needed?

the simple answer is the op says it's a combi boiler and any work required on boiler that a customer cannot carry out themselves (adjusting timers/temp dials) requires the regulation 26.9 to be carried out.
if you are indeed a rgi you will understand what i'm talking about if not then you are working illegally and endangering people by giving out advice that could potentially lead to a dangerous occurance!!!


THAT'S WHY!!!

 

[gaswizzard]

All depends on how reg 26 (9) is interpreted.

 

[beerdoctor]

Hi all

Just an update on boiler troubles,I replaced prv, reset vessel pressures now all o.k

thanks for your help.