# boiler pressure



## maggiew (3 Oct 2013)

I have a worcester bosch boiler that is 12 yrs old. This summer the pressure on the boiler shot up over the 2 mark whilst the weather was very hot. As the weather has cooled down the marker has come down again. I have had the boiler checked by BG but they have never heard of the problem. Again today it was colder this morning and the marker had gone down but later rose to around 1.5.

This is all without having the heating on or using the hot water.


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## TTI (3 Oct 2013)

Is is a sealed pressure system or do you have a small black header tank?


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## bstop (4 Oct 2013)

Temperature and pressure are directly related. If temperature rises pressure also rises. What you are describing could be caused in a pressurised system if the pressure vessel is faulty. The diaphram may be burst of there may be to little air in the vessel. Press the pin on the air valve on the vessel briefly and if water is released then the diaphram is burst. If air is released then the vessel may need to be repressurised with air.


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## Shane007 (10 Oct 2013)

maggiew said:


> I have a worcester bosch boiler that is 12 yrs old. This summer the pressure on the boiler shot up over the 2 mark whilst the weather was very hot. As the weather has cooled down the marker has come down again. I have had the boiler checked by BG but they have never heard of the problem. Again today it was colder this morning and the marker had gone down but later rose to around 1.5.
> 
> This is all without having the heating on or using the hot water.



You most likely have a "semi-sealed" system with a f & e tank in the attic. This will have a non-return valve on the feed pipe to the system. This has most likely failed. Semi sealed systems are not ideal anyhow & it is always best to fully seal a system with a proper filling loop, not an auto fill valve.
I would also check the boiler expansion vessel.


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## sammya (2 Dec 2013)

Shane, my boiler pressure is around 4bar when heating & 1 bar when idle. I tried venting the rads with no joy. Any suggestion before I call for a service/repair. I have closed loop system with auto fill valve. If it needs a service or repair would you suggest someone in Maynooth.


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## Shane007 (2 Dec 2013)

Most likely cause is your boiler expansion vessel requires re-charging with air or the vessel diaphragm is split & would require a replacement vessel.
If the boiler is a gas boiler, all of the above works & checks would need to be carried out by a RGI unless the vessel is external to the boiler.


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## sammya (3 Dec 2013)

Shane, I closed the autofill valve & opened it very slightly & noticed the boiler pressure this morning & was aroung 3bar. Does this indicate something?


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## Shane007 (3 Dec 2013)

When the system is cold, bring the pressure to about 1.3 bar. Close the valve & leave completely closed. Turn on the heating. If the pressure goes beyond 2.5 bar, the vessel is the problem. This can easily be determined if split as a push of the schrader valve will determine if air or water comes out. 
Once fixed, I would remove the auto fill valve & replace it with a filling loop & gauge.


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## sammya (3 Dec 2013)

Shane, Can this be done by me or do I need a RGI to troubleshoot. If yes I would be thankful if you can give me some more details of the valve. Thanks


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## Shane007 (3 Dec 2013)

If the vessel is built into the boiler, by law it must be carried out by a RGI. If the vessel is external to the boiler, you can check it.
The reason for this is so that you do not unknowingly disturb any boiler components that may or may not affect the gas safety or combustion of the appliance.


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## Leo (3 Dec 2013)

Reminder, recommendations are only allowed in[FONT=&quot] the Recommend tradesmen and suppliers forum.[/FONT]


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