Combi boiler losing pressure and hot water cold quickly

alpenbowl · 6 Dec 2016

Hi,

I have recently moved into a new house that is fitted with a 15 year old Vokera Linea Max LPG combi boiler.

1st Issue
Original problem was the hot water when run went cold relatively quickly for a boiler that size that contains around 58litres inside the boiler ready to go.

I ran the hot water tap today and found that the central heating outlet pipe got hot, I suspect the diverter valve sticking??? can anyone confirm or point out any other issues?

2nd Issue
While I was running the hot water to fault find I noticed the boiler pressure had dropped from 1 bar to 0.5 bar. I have put the central heating on and its now back up to 1 bar on its own.

Any ideas what is causing the above problems and are they linked?

ianmcd · 6 Dec 2016

your diverter valve needs a service kit installed, with the boiler off and cold set the pressure to 1.5 Bar, this will alter when there is a demand as the pump will start and the pressure reading on the guage will change and will rise slightly as the boiler gets hot , this is normal and nothing to worry about

alpenbowl · 6 Dec 2016

Thanks ianmcd.

Will get a service kit for the diverter. What about the motorised valve do they tend to break often?

As for the pressure change. I agree that it does rise slightly under normal CH operations, issue with mine was the pressure dropped from 1 bar to 0.5 bar with the hot water running

ianmcd · 6 Dec 2016

The actuator heads are very robustand usually very reliable but I have seen them damaged by water when the front end seal on the divertor valve is passing and the water gets into the motor, they are easy enough to test and its something you could do your self with the heating on open a hot tap and listen to hear if you can hear the motor moving its a sort of grinding noise then a click

alpenbowl · 12 Dec 2016

Hi, bringing this thread up as about to change seals on the diverter valve and noticed the black schrader valve dust cap
like a car valve was leaking after running the hot water tap. Is this a auto vent for the pump? Looks like it has been leaking for a while but as I said we have not long moved in to the house.

Should this be tight or backed off? Starting to think the 15 year boiler could do with a proper service as mention in the previous post the boiler does lose pressure when hot water is run.

ianmcd · 12 Dec 2016

That is not a shraeder valve and yes it is an automatic air valve, usually draining the boiler and cleaning them stops them from passing they have a small float operated valve inside them and are supposed to let air out and then seal but they leak all the time , as a temp measure just screw the black cap down and if you need to release air at any time before you sort it just unscrew it again till the air is released

alpenbowl · 12 Dec 2016

Thanks again ianmcd.

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Combi boiler losing pressure and hot water cold quickly

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