Boiler losing pressure
Discussion
Worcester Bosch 35 CDi 2.
Since the cold spell, has been gradually losing pressure overnight or when left off. Doesn't drop below 0.75 bar when cold, and runs up to about 2 bar when heating on.
I've topped up the system using the charge key, but problem remains. Annoying thing is we are supposed to have boiler cover with our energy supplier, but they still haven't been out to check the boiler is in ok condition and therefore start the cover! As I'll be away for a few days this week, I don't want the family left freezing if the boiler won't run due to low pressure.
A colleague suggested he had the same problem, and the engineer simply re-pressurised the expansion vessel. Looks like a simple tyre valve, but is this likely to be the issue?
No signs of pipes / rads leaking btw.
Since the cold spell, has been gradually losing pressure overnight or when left off. Doesn't drop below 0.75 bar when cold, and runs up to about 2 bar when heating on.
I've topped up the system using the charge key, but problem remains. Annoying thing is we are supposed to have boiler cover with our energy supplier, but they still haven't been out to check the boiler is in ok condition and therefore start the cover! As I'll be away for a few days this week, I don't want the family left freezing if the boiler won't run due to low pressure.
A colleague suggested he had the same problem, and the engineer simply re-pressurised the expansion vessel. Looks like a simple tyre valve, but is this likely to be the issue?
No signs of pipes / rads leaking btw.
We had the same trouble with our old boiler and it was the expansion vessel. Boiler would lose pressure over 24hrs then fail to run til it was topped up, usually with the filling tap. A vessel recharge worked for a week or two but then the problem would occur again. We decided to fit a new boiler as it had to come off the wall to have the vessel replaced and the cost of doing it to a 10 year old boiler seemed mad as other bits were starting to go on it as well. As for doing it, it was quite simple but did require a drain down of the system to do it. I'm sure a proper plumbery person will help more soon though.
I'm no 'plumbery' type person, but agree with potential diagnosis, mine did something similar a while back. Expansion vessel needed pumping up, problem solved although I think it might need another pump up.
Slight hijack - can I just put a foot pump on and pump it up or does the tank need emptying first?
Slight hijack - can I just put a foot pump on and pump it up or does the tank need emptying first?
Sounds like a loss of pressure in the expansion vessel. Drop the system pressure to Zero, preferably by using a drain-off cock. Re-instate pressure in vessel to around 1Bar (make sure gauge stays on Zero) with a bike pump or similar. Refill system to 1Bar COLD.
Edited to add:
If you have to KEEP pumping the vessel up then the valve may be suspect or worse. If water comes out of the valve when you push the pin in it's new vessel time.
Edited to add:
If you have to KEEP pumping the vessel up then the valve may be suspect or worse. If water comes out of the valve when you push the pin in it's new vessel time.
Edited by Ferg on Saturday 15th January 15:36
it is the expansion vessel you can try pumping it but i would change it for new one and maybe flush system and add ihibitor as there could be crappy water in system causing corrosion also if the vessel has a storage part for hot water your mains pressure could be too high you should have a small exp vessel on your cold main to the boiler worcester installs call for them and maybe a pressure reducer had same problem on a job with a baxi too much pressure nackerd up vessel as it had a heat store built in aswell
also the pressure relief valve could be passing but if its creeping up when running sounds like vessel
try a bike pump let the pressure off connect pump and pump till you fell some resistance re pressurise and try
also the pressure relief valve could be passing but if its creeping up when running sounds like vessel
try a bike pump let the pressure off connect pump and pump till you fell some resistance re pressurise and try
Edited by eskidavies73 on Saturday 15th January 20:49
Funnily enough I have exactly the same problem with my boiler at the moment (Ideal Classic FF250). Like the OP, it doesn't drop below 0.75 bar when cold, and runs up to about 2 bar when heating on full blast.
It has been like this since the beginning of December, and given the time of year and that it seemed to be heating OK, I have not got around to doing anything about it. I am tempted to leave it for another few weeks until the weather is likely to be better, before taking the suggested action of pumping up the expansion vessel, just in case that is the final straw and it stops working altogether.
I presume, other than the boiler not firing up due to low pressure, that delaying taking any action is not likely to make it worse?
It has been like this since the beginning of December, and given the time of year and that it seemed to be heating OK, I have not got around to doing anything about it. I am tempted to leave it for another few weeks until the weather is likely to be better, before taking the suggested action of pumping up the expansion vessel, just in case that is the final straw and it stops working altogether.
I presume, other than the boiler not firing up due to low pressure, that delaying taking any action is not likely to make it worse?
PF62 said:
Funnily enough I have exactly the same problem with my boiler at the moment (Ideal Classic FF250). Like the OP, it doesn't drop below 0.75 bar when cold, and runs up to about 2 bar when heating on full blast.
It has been like this since the beginning of December, and given the time of year and that it seemed to be heating OK, I have not got around to doing anything about it. I am tempted to leave it for another few weeks until the weather is likely to be better, before taking the suggested action of pumping up the expansion vessel, just in case that is the final straw and it stops working altogether.
I presume, other than the boiler not firing up due to low pressure, that delaying taking any action is not likely to make it worse?
Probably not. It sounds like your heating system is quite small so it can fluctuate between 'enough' pressure to run and 'not over 3 Bar (safety valve blow-off)'. It may be that you are running it at a low temperature, that will make a difference. Ultimately, if the vessel is FUBAR-ed then it may rot through the steel eventually. It has been like this since the beginning of December, and given the time of year and that it seemed to be heating OK, I have not got around to doing anything about it. I am tempted to leave it for another few weeks until the weather is likely to be better, before taking the suggested action of pumping up the expansion vessel, just in case that is the final straw and it stops working altogether.
I presume, other than the boiler not firing up due to low pressure, that delaying taking any action is not likely to make it worse?
mrsxllifts said:
Don't leave it too long before you do anything, we tried this to get us through to spring and the vessel split on Boxing Day! I am now having a nice new shiney kitchen fitted!
Unless I get a f
king bacon sandwich your not!Can you tell I'm pissed off this morning and what's worse there playing s
t rugby again!!!! Why do I waste my money sponsoring them?Thanks for all the advice. Think I'll leave it for the timebeing and wait for the boiler cover to start before I put a call in! 
Anyway, day 1 of the wood burner installation and now the old fireplace is out we've been told they can't create the inglenook we were expecting - so today we have a new priority! Anyone have a victorian house with a woodburner? With 3m high ceilings, I thing we need a high mantlepiece, but the original one can't apparently go back on the wall because the lintel is lower than expected. More expense I could do without.
Can't find any pictures on net of similar room setup with a woodburner installed for inspiration!
Anyway, day 1 of the wood burner installation and now the old fireplace is out we've been told they can't create the inglenook we were expecting - so today we have a new priority! Anyone have a victorian house with a woodburner? With 3m high ceilings, I thing we need a high mantlepiece, but the original one can't apparently go back on the wall because the lintel is lower than expected. More expense I could do without.
Can't find any pictures on net of similar room setup with a woodburner installed for inspiration!
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