Combi Boiler Pressure Drop

[liamconnolly]

Ok, newbie entering the scene...

Hi All,

The prob. started on wtues night when i bled some air of my farthest rad. initially all went well, rad. filled with hot water smiles all round.

within 30 mins the heating had shut down and refused to start up again and no hot water was available. I could hear boiler fire so knew pilot was not problem.

Took advice at work which suggeswted i shoudl crank pressure to free the diverter valve. retunring home i opened the grub screw on the hot water pipe and heard the pipes/system immediately fill with water (heating system switched on) and i kept valve open until i knew all rads warm and pressure correct.

This morning awoke to find that the heating had once more shutdown (hot water available tho) so again bled off a bit more air in the rads. and filled the pressure to 0.7 bar as recomm. in the boiler door notes.

All fine and well. retunred home from work this evening to find pressure of system was at 0 and rads obviously would not warm up. again opened up grub screw and let hot water filter thru until i got to the 0.7 bar. fear i shall be repeating this in the morning.

should i be increasing pressure with the system off?
where could the water be going to drop the pressure so significantly?
Anyone got any advice?

Details of system are:

Glowworm Swiftflow 80 gas combi. (small red cistern sits on floor beneath - is this an expansion cistern?); radiators throughout.

Thanks in advance,

Liam

 

[ollski]

Took advice at work which suggeswted i shoudl crank pressure to free the diverter valve.

You mean you opened up the filling loop to mains water pressure?, if so the pressure relief valve will have opened and dumped the water through the pipe outside. Trouble is the valve will not be seating back down properly and your pressure will be escaping through there. You could try opening the pressure relief again and hope it reseats better, but chances are it will need replacing. Swiftflows expand a lot don't pressure them cold to over .75bar.

 

[liamconnolly]

Hmm, i wouldn't have though the pressure releif valve would need to let off any excess pressure/water as the water would surely be filling the system back up to the pressure previously experienced when there was air in the radiators...

Is it correct to let water into the system after bleeding air off? if so have i used the right valve to let mains water in or is there some other way?

I'm sure it can't bee to much pressure blowing a a valave as the gauge has never gone beyond the recommended 0.7 bar.

 

[ollski]

I'm struggling to get my head round what you are doing really, you refill the system cold and top up via the 2 taps on a braided hose connecting water mains to heating circuit pipe.

 

[Bahco]

Fill to 0.7 bar, bleed all your rads , and then refill if necessary.
See if you are still losing pressure. It could be your expansion vessel needs pumping up. if so do this with the system empty

 

[gasman]

Check for any evidence of recent water discharge on floor outside where the PR pipe should be sticking out the wall Sometime there is a build up of rust/grit etc that builds up under the pressure relief valve seating. It only has to lift once and it wont seal water tight again. You need to check your exp vessell is charged to the correct pressure. if it's not you will need to re-pressurise it with a foot pump, normally around .7 to 1 bar. make sure you open up the system when you re-press it so it is not creating it's own pressure. And replace the pressure relief valve

 

[liamconnolly]

bit more to add...

just found i wasn't adding water by the filling loop but instead the valve screw in the hot water outward circulation pipe.

the system seems to be strange in that it has a expansion cistern fitted beneath. i have found the filling loop attached to this.

seemingly the system drops pressure on the gauge when programme is off. when advance button is presseed the pressure rises on the gauge to the .7 bar. is this correct? or shoul di expect constant pressure?

should i add water by the filling loop when the system is at idle and the gauge at zero?

 

[gasman]

This means that you're boilers exp vess is knackered and the one you describe is a remote one (same thing). When the system is cold put water into the system via the fill loop to 1 bar. When the heating is on this will rise to poss 1.5 ,2 as this indicates the pressure of the system when the water has expanded. Water expands 5% when heated to 80 deg[/img][/quote][/code]