Boiler keeps firing up and also loses water and pressure..

1 Dec 2015
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United Kingdom
Hi all..
I need help with a problem.
I have a vokera linear 28 boiler and lately (about 4 wks) it's been firing up every hr for about 30 secs.
Also we lose all the pressure pretty quick when using heating or running hot water and I have had to fill the pressure at least 3 times a day.we replaced the expansion vessel and 2 thermistors but the problem still exists although I only have to refill the pressure maybe once a day..we get a lot of water dripping out of outside pipe from the pressure relief valve.(relief valve is a spring loaded one that seems to be working fine as we have tested it to relieve pressure on boiler).we have checked for leaks and there are no leaks anywhere.any help would be greatly appreciated.
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Who was the "we" who replaced the expansion vessel?

I don't think that it was done properly! Where did the replacement come from?

I suspect there may be a comfort setting which you have activated and the boiler is just warming itself up to ensure you get faster hot water.

Hi tony..
Thanks for your reply.
I purchased the expansion vessel from a plumbing company on eBay and replaced like for already had an external vessel on it done by previous plumber (about 4 yrs ago,before I met my partner), as he said it was too much messing about to change the one on the back of the boiler.
As for the boiler 'warming itself up'..should this be happening every hour day and night,and also lose all pressure at least once a day..
Is it dripping outside all the time or just when the heatings on ? How much (from cold) does the pressure rise when the heatings on ? You don't say which boiler you have (He/se) but have you tried seitching to summer mode as this switches pre heat off.
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Hi gigz
Thanks for your reply.
I can't see anything to state wether it's he/se but it's about 10 yrs I right in thinking (he) means high doesn't state this anywhere in the manual..
It does drip outside all the time.heating is on at the thermostat is on20 degrees and boiler on about 70c ..I've just been outside and watched it trickle out of the pipe 3 times for about 10 secs every 2 mins..pressure goes up at least 1-1.5 bar when heating is on.
When having a look behind the pump,I took the automatic air release valve cap off and noticed a tiny amount of water weeping out with a little a bubble and then it would pop and drip.(very small amount of water)..
It should'nt be leaking outside unless the pressure rises to over 3.5 bar. So the good news is, you've found your leak. Re the aav on the pump, just close it.
I closed the aav a few days ago becUse of the water bubble and minute water leakage..
Another thing I noticed (which may be normal) is that from the cold water inlet, through the lever/tap.the copper pipe( leading to the domestic heat exchanger) is freezing(obviously) and the pipe is full of condensation for about 8 inches.the rest of the pipe before it enters the heat exchanger(about 4 inches) is red hot..
Do you think there may be a problem with the heat exchanger..?

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