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Pressure increasing in oil central heating?


Nick
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Hi,

Our oil burning boiler pressure keeps rising.

from cold we charge the system with about 2 bar pressure and after about 2 or 3 hours of working, the pressure on the manometer guage has risen to 3 bar before the valve releases the pressure. (manually or automatically)

can anyone identify why this is happening? One suggestion was that the copper coil exchanger has a hole in it which takes water from the hot tank increasing the pressure in the central heating sealed system.

nick.
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Thanks Gluestick, RicandJo.

So the exchanger problem of a leak internally is not the cause?

I've looked at the picture and my expansion vessel is 'slimmer' than this picture. Would I need the precise replacement for my boiler, or are they all universal?

Also, my current vessel, sits in a holder on the back of the boiler casing. The bricodepot one would just hang off the flexible braided pipe!
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[quote user="Nick"]Thanks Gluestick, RicandJo. So the exchanger problem of a leak internally is not the cause? I've looked at the picture and my expansion vessel is 'slimmer' than this picture. Would I need the precise replacement for my boiler, or are they all universal? Also, my current vessel, sits in a holder on the back of the boiler casing. The bricodepot one would just hang off the flexible braided pipe![/quote]

The way to work it out, is to take the tank out of circuit and test the calorifier (Heating Coil) with a pressure gauge: if the pressure drops then voila !

Edit now as more time!

What I did some time back, was to solder a gash Schrader valve (From a car tyre) into a piece of spare copper pipe: then a T Junction with a suitable manchon and a spare pressure gauge. Isolate the suspected bit, screw in the pressure gauge: and pump up to 5 Bar.

If the pressure drops as you watch, then you have a leak.

The Vase d'Expansion I found quickly is but one example: if yours is the smaller type inside the boiler casing itself, then you will either have to pattern this (Leroy Merlin: or one of the dedicated plumbing wholesalers): or re-plumb to have the vase external.

The internal integrated Vases are normally much smaller.

 

 

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I recenly made exactly the same thing for pressure testing my pipework, aside from the elevated risk when pneumatic rather than hydraulic testing it should be born in mind that subject to the volume in the pipework a small leak may take a long time to show on the pressure guage, when pressure testing with water one drip and the guage drops immediately to zero.

I have recently pressure tested some hot water ballons and I had to leave them ovenight to be sure that there were no seams weeping.

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  • 2 weeks later...
[quote user="Nick"]Hi,

Our oil burning boiler pressure keeps rising.

from cold we charge the system with about 2 bar pressure and after about 2 or 3 hours of working, the pressure on the manometer guage has risen to 3 bar before the valve releases the pressure. (manually or automatically)

can anyone identify why this is happening? One suggestion was that the copper coil exchanger has a hole in it which takes water from the hot tank increasing the pressure in the central heating sealed system.

nick.[/quote]

if you charge the system to 2bar (cold) and then switch the heating on the water in the system will try to expand thus creating an increase in pressure, it should drop back when it cools down. I presume that when your system is up to temperature the pressure rises above the pressure release valve limit and so releases some of that pressure to protect the system, so when your system cools down after that the pressure will drop below the original 2 bar as it has exhausted some of the water in the system.logically if you leave the pressure alone it should settle into a working norm, my pressure gauge has a red area that if the pressure drops back too far the heating will not restart, is that happening in your case? I had a similar problem and the result was to change the pressure ballon but it still does pretty much the same just that when it cools down the gauge reading doesn't fall below the low level limit

does that help make sense??

Tim

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