What's wrong with my boiler?
Question:For the second time in about 6 months my boiler pressure has just suddenly dropped to 0 bar for no apparent reason.
I've checked the plumbing around the house and can see no leaks anywhere and no valves are open where they shouldn't be.
The pressure doesn't gradually drop over a long period of time. Instead I go to bed one night, then the next morning jump into the shower to be greeted with ice cold water and a discovery that the boiler pressure is at zero.
I do have a valve next to the boiler to get the pressure back up to 0.7 bar but I'm worried there's something more serious that I can't locate that's causing these pressure losses.
Answers:
I assume from your question that you have a condensing combi boiler - because these do not have a header tank and are sealed there needs to be somewhere for the excess pressure generated as the water heats (and expands) and - this expansion vessel is either inside the boiler or external - looking a bit like a balloon near the boiler - as has be said there MAY be a leak in the membrane between the two halves of this vessel, however, In case of overheating, there is a pressure release valve which dumps hot water and steam to, I hope, an outside point.
If the boiler is on and running hot enough to activate this valve it will dump the pressure and then, as the system cools down it may drop below an operating level.
The dump pipe should be outside near the boiler or the expansion tank and, if installed properly, come out from the wall, bend down and then bend back so that the open end faces the wall - to cool the water fast as it leaves the building - check to see if the wall is wet by this pipe and it it is you MAY need to check the pressure that the relief valve is set to and increase it (get corgi plumber to do this if you are not sure what you are doing).
inside the pressure cylinder there is a bladder (a small balloon) which should be inflated this bladder is what pressurises the water it could have a leak or just needs inflating
First of all tell me which type of boiler do you have is it lancashire or co-charan Boiler so i can explain you more easily.If you cant Then Your Boiler Required A Professional Help...
Thats all i can help..
It can happen quite a often especially if the outside temperature goes up and down, so don't worry if you cannot find a leek,
first of all repressurise, turn on heating, once hot check your prv,,, the pipe from the boiler going to the outside, thats open ende,, if water is coming out get prv replaced, if thats ok,,, have you a white pipe going to outside from boiler? see if water is being discharged from this pipe when boiler is turned off,, if so,, possibly heat exchanger has cracked,,, if these are ok,,, get heating engineer to check your expansion vessel.
hopefully its just your prv,,,, second best, expansion vessel,, worse of all your heat exchanger.
good luck
0.7 is a bit low for system pressure especially if the boiler has a low pressure switch and locks out. Ideally you want between 1 and 2 bar pressure so try to top it up a bit more and bleeding rads will make your pressure drop so refil the system if you need to bleed a rad. Also are you sure it drops suddenly over night? If so that is very unusual do you check your pressure everyday and night as a tiny intermittent drip can make the pressure drop quite quickly?
This problem is similar to my sister new condensing combi boiler.
The fault was traced to a faulty membrane in the flue ( very rare).
New combi have a laptop connection to find the fault.
It is best to contact the manufacture technical helpline and ask for a list of gas boilers engineers in your area.
Sarah is right about the pressure, it needs to be between 1bar and 2 bar, also check the pipe that goes outside, you may see a wet patch on the ground.
Try refilling the pressure to 1 bar, turn on the heating for about 20 minutes and check the pressure again. If it has gone to 2 bar or more, then the expansion vessel has gone.
It could just be that the expansion vessel needs recharging as well, or the pressure relief valve needs replacing.
To be honest you really need someone to look at it to do most of the checks, as it depends on what make it is as well. You can either goto the Corgi website and look for an engineer near you or give Corgi a phone call and they will give you the number of an engineer. If your in the Harrow area you may get little old me =)
Run your boiler at 1.00 - 1.50 bar, as this is the norm. Remember, even though you see no leaks, a lot of pipes are under the floor and are not visible. You may have a pressure display that is not that sensitive and the system may leak for a while and not show much drop until it zero's out. get a plumber to pressure test the system to determine the fault
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