Bolier not filling up/ No pressure

[whelzer]

HI,

Last night I bled two upstairs rads, they were hot instantly and all was cosy. This morning (now!) heating is not "coming on" and the pressure on the front panel is showing zlich!..

Any help much appreciated:

Sequence of events:

Spoke to plumber (installer) on phone as was told:

Opening filling value
Bled rads
Close valve

no need to turn off system, minor probem blah, blah.

I done exactly this, but was called away just after bledding second rad (neighbours window put in!!!!!!!), came back after 30 odd mins and closed valve - rads were fine.

Background - 3 month old brand new sealed gas system, no problems so far.

Can't get hold of plumber and its f'ing freezing.

I read a load of previous posts on these boards put not sure what the prob is.

Ian

 

[breezer]

sounds like you let it over fill and it has blown via the pressure relief valve

try refilling, this time do not GO AWAY (and hope you have caused no damage)

 

[whelzer]

Ta for the reply - whats blown?

When I switch on heating I can hear the bolier "attempting" to start but nothing, no pressure, no ignition.

Ian

 

[MANDATE]

Combi boilers will only operate if there is water pressure in the sealed system.
It needs to about 1.5 bar when cold and this will rise to about 2.2 bar when the water has become hot and expands.
When you bled the radiators some or all your pressure was lost.
When you open the filling loop too quick or for too long the pressure will go up until the pressure relief valve opens ( about 3 bar) when all the pressure is lost again.
Just open the filling loop slowly and observe the pressure on the gauge.
If you set the pressure to 1.5 bar while the water is hot you can expect it to drop when it goes cold and it might drop to a point that prevents the boiler from flashing up.

 

[oilman]

[/quote]

It needs to about 1.5 bar when cold and this will rise to about 2.2 bar when the water has become hot and expands.

Surely it doesn't need to be that high for modern boilers. That's 50 feet when cold

 

[COG]

As Oilman says, thats high , most low water pressure switches work at 0.5 bar +/- 10% and if it was a low water pressure switch tripped it would not let you get as far as "attempting to start" as you would not want to run a pump with no system pressure,.Check that have not got a manual overheat re set button, it should be labelled, sometimes on top of the boiler (stupid place)

 

[whelzer]

Hi,

Thanks for all the replies.

Plumber eventually came round after 4 days with no heating (should have got someone else in). He simply switched the boiler feed on to the mains for a minute or two "to blow out the system", then changed it back to the filling loop. No damage done and cosy once more.

Ian

 

[MANDATE]

Hi Ian.
Just out of interested, what pressure is your boiler now at when not operating.(cold)?
I bled a friends very small radiator last week and the pressure dropped from 1.35 bar to 1.25 bar and I have opted to leave it at this pressure.

 

[whelzer]

Its 1.25...

Ian