Dear Experts,
I have convinced myself that recent problems with my central heating are due to a failed expansion vessel. I think I can resolve this by fitting an external one, but before I do that it would be great to know if others agree with my diagnosis.
I've lived here for a couple of years. The boiler is I think about 15 years old -it's a Volkera Linea 28, and is the first combi boiler i've lived with. I have always had to top up the pressure periodically. Since turning on the heating in the autumn, and especially more recently as it has got colder, the pressure have reached 0 overnight and i've got up to a cold house. Something must be done!
My first guess was of course a leak, but there is nothing obvious above floor level. Googling revealed how a failed expansion vessel would cause the pressure to rise as the system heats up and vent through the pressure relief valve, resulting in zero pressure when next cold and failing to start. So i looked for the pressure relief valve and found that it is plumbed into a pipe that just dangles behind the kitchen units and empties into the space under the floorboards! I removed that and put a bucket under the value. Now, if i provoke it by pressurising to 1 bar when cold and turning up the boiler thermostat, i see the pressure reaching 3 bar and water in my bucket.
As an experiment, i drained a small radiator and left it with its main valve off and lockshield valve slightly open. The idea is that the air in this radiator acts as an improvised expansion vessel. This actually seems to work, up to a point; having pressurised to 1 bar cold and turned the boiler thermometer to max, the pressure now rises to about 1.3 bar and there is nothing in my bucket.
BUT, having run for 24 hours the pressure is below 1 bar. There is nothing in the bucket, so maybe there is a leak somewhere...
I attempted to pump up the in-boiler expansion vessel, but it seems that the pressure is already high enough (or even a bit over pressure - it's hard to read on a cheapo tyre pressure gauge that goes up to 10 bar). There does not seem to be water leaking from the expansion vessel valve.
So, am i right that the pressure vessel is the problem?
Should i do more to "fix" the present one before i resort to fitting an externl one?
Will fitting an external one be as straightforward as i hope?
If i do go ahead, can anyone comment on:
- does the orientation matter?
- does the position (above, below) the boiler matter?
- would it be OK to use a flexible hose to connect it?
- should there be a valve in series with it?
Many thanks for any feedback.
Phil.
I have convinced myself that recent problems with my central heating are due to a failed expansion vessel. I think I can resolve this by fitting an external one, but before I do that it would be great to know if others agree with my diagnosis.
I've lived here for a couple of years. The boiler is I think about 15 years old -it's a Volkera Linea 28, and is the first combi boiler i've lived with. I have always had to top up the pressure periodically. Since turning on the heating in the autumn, and especially more recently as it has got colder, the pressure have reached 0 overnight and i've got up to a cold house. Something must be done!
My first guess was of course a leak, but there is nothing obvious above floor level. Googling revealed how a failed expansion vessel would cause the pressure to rise as the system heats up and vent through the pressure relief valve, resulting in zero pressure when next cold and failing to start. So i looked for the pressure relief valve and found that it is plumbed into a pipe that just dangles behind the kitchen units and empties into the space under the floorboards! I removed that and put a bucket under the value. Now, if i provoke it by pressurising to 1 bar when cold and turning up the boiler thermostat, i see the pressure reaching 3 bar and water in my bucket.
As an experiment, i drained a small radiator and left it with its main valve off and lockshield valve slightly open. The idea is that the air in this radiator acts as an improvised expansion vessel. This actually seems to work, up to a point; having pressurised to 1 bar cold and turned the boiler thermometer to max, the pressure now rises to about 1.3 bar and there is nothing in my bucket.
BUT, having run for 24 hours the pressure is below 1 bar. There is nothing in the bucket, so maybe there is a leak somewhere...
I attempted to pump up the in-boiler expansion vessel, but it seems that the pressure is already high enough (or even a bit over pressure - it's hard to read on a cheapo tyre pressure gauge that goes up to 10 bar). There does not seem to be water leaking from the expansion vessel valve.
So, am i right that the pressure vessel is the problem?
Should i do more to "fix" the present one before i resort to fitting an externl one?
Will fitting an external one be as straightforward as i hope?
If i do go ahead, can anyone comment on:
- does the orientation matter?
- does the position (above, below) the boiler matter?
- would it be OK to use a flexible hose to connect it?
- should there be a valve in series with it?
Many thanks for any feedback.
Phil.