Combi Boiler Problem

[paddyk]

Hi. We have a Vokera Linea 24 Combi boiler and on the guage the water pressure sholud be between 1.0 and 1.5 bar. There is a red line on the guage at 4.0 bar.
The guage at present is reading over 3.2 bar and when heating is on is going up to around 4.0 (sometimes just over the red line)
I can't get anyone to service it until 29th Dec.
What I need to know is - is it OK to run the central heating (for short periods) or will it do serious damage to the boiler ?
(I know you can take the cover off and there's a pressure release button but to be honest the cover is a real pain to get back on - even the engineers sometimes have problems) TIA

[buildersmate]

You don't say how the pressure got to rise up to around 3. Alternatives could be either someone inadvertently overfilled it, or there is a fault meaning mains pressure water is somehow leaking across the heat exchanger to gradually increase the pressure of the sealed boiler water system.
At around 4 bar, a pressure relief valve comes into play and releases water out, usually via a vent pipe to the outside.
You could more easily release pressure by bleeding a little water via a radiator. Get one person to watch the gauge whilst another bleeds the water. Only a couple of eggcup fulls will need to come out. You could do this until your service call on 29th, assuming water is continuing to seep into the system, as per my suggestion 2 above.
Operating it at 3 to 4 bars is OK as well, these systems are designed to cope with that.

[BRIGHT SPARK]

How old is the boiler paddy? bm may be right as the heat exchanger could be 'pin holed'...or maybe the expansion vessel is faulty.

[paddyk]

Both answers helpful - thank you. Boiler has a Magnatec filter on it and I opened bleed valve on that (wrapped an old sheet around) and pressure went down, it took more than 2 eggcups full though. When i put the heating on, pressure starts to go up again which suggests something else is going on. Hope it's not expansion vessel or heat exchanger because that'S going to be pricey no doubt. Boiler is 12 years old.

[buildersmate]

My guess is that the heat exchanger is pin-holed, as identified by BS earlier.

I fear that this is going to be pricey, and it's a bad time to be trying to get boiler work done at minimum price (in that heating technicians of repute are undoubtedly busy). Depending the rate at which this is happening, you could live with the a manual intervention for a while, though bear in mind that gradual dilution is occurring of the inhibitor.

[paddyk]

FAO Builders Mate.
Thanks for the advice. One last question - can I add inhibitor via the magnaclean filter to top it up ? system has plastic pipe and a british gas engineer told me that's why the water is black as it has so much ferrous oxide in it. he said plastic pipe is no good - especially the cheap type (which I suspect it is). Is this right or is there better plastic pipe which is as good as copper ? it would be easier to replace with better plastic than all copper. I think the plastic pipe may be the cause of several problems I have had with the boiler

[buildersmate]

Yes you can feed inhibitor via the Magnaclean.

I dislike plastic pipe as well. It does have to be 'barrier' pipe for heating applications. This has a layer that protects against oxygen ingress through the pipe wall. Yes, such a thing is possible. Well-known brands (JGuest, Polypipe) will be, but I suppose it is possible unscrupulous heating technicians may use non-barrier pipe - BG technicians would probably know.

[ivor4781]

it should read 1 to 1.5 when heating is not working.when its is on it will rise up to around 4 bar this is normal it should go back to the lower level after a while when the heating is off, i it rises way up to 6/7 when off you have a hole in the expansion tank. we have the same model as you, and we had this problem.,still a lot of life in the old boiler yet,

[paddyk]

Ivor - hope you're right about the Vokera. The thing is the pressure stays constantly up at 4.0 bars even when heating has been off for 12 hours. It doesn't come down at all. This makes me think that BM is right and there's a fault.
Thanks to all for their input.

[buildersmate]

4 bar is the point at which a conventionally installed system ceases to increase in pressure because the relief valve comes into play. You should see a constant drip of water from the outlet pipe if leakage into the sealed system is still occurring. No system should rise to six bars as it stresses the components and could cause other leaks.
Don't doubt that's what maybe happens to ivors system, but quoting his experience as common practice is just plain wrong.