central heating question - non boaty

[ShipsWoofy]

Thought I would ask here as lots of experts in different disciplines on this forum.

Last week during the strongest winds our hot water went off. We have a combi boiler. It had tripped the pressure valve. When I checked the pressure for the central heating it had dropped just below 1000. A quick scout around the house showed no leaking radiators and no water around boiler.

So I added more water and bled the system. The next evening the boiler made a right racket, similar to turning a tap on after the main has been shut down, loads of air in the system thinks I. Boiler tripped again. Did the same as before.

It has been fine since. So my question, I can accept air in the mains might cause problems, but why should this affect the central heating, which as I understand is a closed pressure system. Is this a sign of something else going awry and should I seek to have the boiler serviced, or can it be just one of those things?

Sorry for a non boaty type question.

 

[alruss]

We need the make and model of combi boiler to start, but should be able to help.

 

[pete]

Hi
If the boiler locked out because the pressure had fallen below the minimum you did the right thing by repressurizing it ,normally to 1 bar with the system cold (depends on the model, follow users instructions) You are right- air in the mains will not affect your rads as they are on a sealed system the noise may well be down to air in the system, If you lost pressure where has the water gone? how long since you last checked it ?
Is the pressure ok now ? there will be an expansion vessel in the boiler usually red with a diapragm in it and if this leaks you will initially lose pressure then when you top it up, the extra water has nowhere to expand to on heating up so the pressure will go up to around 3 bar then vent through the blow off pipe (usually through the outside wall.)
The expansion vessel will also have a shraeder valve on it to charge the dry side of the diapragm, if this has been leaking the air will have escaped and again there is nowhere for the water to expand to if this valve lets out water the diapragm has gone if its air it wants to be charged to around .8 bar but the heating system pressure must be reduced to zero before you do this.

This info is general but boilers and specs may vary CHECK YOUR INSTRUCTIONS
Good luck

 

[lyc]

Had same problem to 9 year old system and had the red expansion vessel changed yesterday.

The internals of red expansion vessel were kaput and had filled up with water.

Lot of noise to the system and the black pressure needle had gone off the scale when running.

 

[sonarbell]

Mine needs regular topping up( once a month ) still cant find the leak, but hey who cares, It keeps on running ....... Has done for 3 years since new boiler installed. Old Rad system just a new boiler.

 

[ShipsWoofy]

It is a Worcester 240.

It has been fine now for about 9 days, the pressure has not moved. From what others have said, if the accumulator had failed it would not hold pressure at all.

It has been years since the boiler has been looked at, I also can not find an overflow pipe, it is on an internal wall so I would imagine the pipe would be visible at some point. The boiler was in the house when I bought it.

 

[bob_tyler]

On my Worcester, I had a similar problem. At first I thought that there was a blockage somewhere between the boiler & the rads. Flushed through, very dirty at first. It worked for a while but pressure sometimes dropping, until it stopped Central Htg altogether. Discovered that diverter valve (just behing the pump) was faulty. Changed valve (£66+VAT) and has all worked perfectly since.

Bob