I have a Worcester Combi which I set at 1 Bar when cold. The pressure is however dropping about 0.1 bar every 24hr period. I am consequently topping it up every day. The pressure stayed at 1 bar over the winter when the central heating was not used. I have checked for leaks but can not find any. Does anyone have any sugesstions on likely cause ?
Worcester Combi Pressure Drop
- Thread starter aka123
- Start date
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The fact that the pressure doesn't drop when the heating isn't on (which is what I think you mean) suggests that it is not a leak.
I would think that if the system depressurises every 24hrs and the leak was in the combustion chamber there would be water dripping out by now assuming this has happened several times. The chambers are not completely water tight.
Fill the boiler to 1 bar cold. Switch on the heating and monitor the pressure gauge. Does the pressure slowly increase towards the 3 bar mark? If so could be the expansion vessel has gone.
I would think that if the system depressurises every 24hrs and the leak was in the combustion chamber there would be water dripping out by now assuming this has happened several times. The chambers are not completely water tight.
Fill the boiler to 1 bar cold. Switch on the heating and monitor the pressure gauge. Does the pressure slowly increase towards the 3 bar mark? If so could be the expansion vessel has gone.
I agree with Geoff... There is a diaphram in the expansion vessel that has air on one side so that there is room for the water to expand into when the system heats up (hence the name).... If the diaphram in faulty (or if the air pressure is too low) there is no room for this expansion so the pressure rises until it opens up the boilers pressure release valve...the water then escapes and when it cools again you have a lower pressure.
Another way you can check if the vessel is gone is to remove the pressure fill cap (looks like a tyre valve on a car) and quickly press the valve needle down for a fraction of a second... if water comes out you have a problem.... if air comes out try checking the pressure with a good tyre pressure guage and pump up if necessary to the required pressure as stated by the manufacturer. You do need to release the system pressure before doing this.....
If in any doubt call an expert.
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Thanks for the reply Grib,
I have water dripping out of the pipe that goes from the boiler to outside the house, I have pressed the valve needle and only air comes out so I will check the pressure. If it needs increasing can I use a standard tyre pump and how do I release the system pressure ?
I have water dripping out of the pipe that goes from the boiler to outside the house, I have pressed the valve needle and only air comes out so I will check the pressure. If it needs increasing can I use a standard tyre pump and how do I release the system pressure ?
K
keego
That pipe that's dripping is what is causing your pressure loss.
Follow that pipe back to the boiler & it will go to a valve that has a red cover on it that has 3MB on it, that is the bit you need to change.
Follow that pipe back to the boiler & it will go to a valve that has a red cover on it that has 3MB on it, that is the bit you need to change.
Keego wrote:
It's important that the system pressure is released before checking the expansion vessel ... Easiest way to do this is via the boiler drain point.
DO NOT release the pressure using the PRV or it may not reseal properly due to crud and you'll have more problems than you've got already
If it proves to be the expansion vessel they are not too difficult to change but the boiler will need to be drained down.
One small point aka123, its always useful to know what type of boiler you have ... It helps with the advice
MW
Highly unlikely Keego as it would have leaked without the CH on also, it's far more likely to be the expansion vessel and I would follow GeoffGas1 and Grib's advice if I were you aka123.
It's important that the system pressure is released before checking the expansion vessel ... Easiest way to do this is via the boiler drain point.
DO NOT release the pressure using the PRV or it may not reseal properly due to crud and you'll have more problems than you've got already
If it proves to be the expansion vessel they are not too difficult to change but the boiler will need to be drained down.
One small point aka123, its always useful to know what type of boiler you have ... It helps with the advice
MW
Thanks MW. The boiler is a Worcester 28CDi installed in 1998. I will check the expansion vessel presure before I do anything else, but if it needs increasing, where do I find the boiler drain point and how much water do I need to drain ? Can I use a tyre pump to increase the pressure and I assume that I refill the system via the filling loop ?
The installation instructions state that the initial system pressure = expansion vessel charge pressure + 0.3 bar. The system pressure is set at 1 bar when cold so I assume that I set the expansion vessel pressure to 0.7 bar ?
If the expansion tank needs changing I will call Worcester Bosch but at £170 odd pounds a visit I do not want to call them if its only the expansion vessel pressure that needs topping-up.
The installation instructions state that the initial system pressure = expansion vessel charge pressure + 0.3 bar. The system pressure is set at 1 bar when cold so I assume that I set the expansion vessel pressure to 0.7 bar ?
If the expansion tank needs changing I will call Worcester Bosch but at £170 odd pounds a visit I do not want to call them if its only the expansion vessel pressure that needs topping-up.
On your boiler there are drain points on both the feed and return pipes. Rather than me go into detail I've attached the link to the WB site ... On the installer area there is all the documentation and, if you download the Installation and Servicing instructions, it tells you how to drain the boiler and how to charge the EV (0.5bar).
http://www.worcesterbosch.co.uk/index.php?fuseaction=literature.detail&con_id=5058&from_id=5029
Good idea to get someone in on this boiler though as the EV isn't a straightforward change.
An easy option which you could do yourself though (much less than £170) would be to fit an additional EV somewhere else in the return circuit (at least 10litre, as close to the boiler as possible and accessible).
Treat it in the same way as the in-built one in terms of setup and then simply ignore the boiler's integral vessel.
MW
http://www.worcesterbosch.co.uk/index.php?fuseaction=literature.detail&con_id=5058&from_id=5029
Good idea to get someone in on this boiler though as the EV isn't a straightforward change.
An easy option which you could do yourself though (much less than £170) would be to fit an additional EV somewhere else in the return circuit (at least 10litre, as close to the boiler as possible and accessible).
Treat it in the same way as the in-built one in terms of setup and then simply ignore the boiler's integral vessel.
MW
You tell him Softus
I am surprised he hasn't mentioned how much he charges and all that [fully guaranteed etc]
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