Alpha CB50 - Loss of pressure every 24-36 hours

[sprocket2012]

Hi all, I'm hoping for some assistance with a small issue we have!
Our Alpha CB50 boiler loses pressure down to flatline every 24-36 hours... We've had British Gas out 5 times now, a pressure release valve replaced, an expansion Vessel replaced yesterday morning... Yet when my wife came home at 5pm yesterday is was down again..
annoyingly you can pressure it up and there no problem, sometimes longer periods than others, then it goes again!

I haven't tried bleeding the radiators yet since they changed everything, should I? in the evening you can sometimes hear one or two of the radiators making a random "plinking" noise and I wondered if that was a sign of Air in the system. If it does go off we normally find water residue out of the pressure relief overflow, hard to say how much as it's on the floor outside.

I was just wondering reaklly if there is a trick to these things and potentially something missed by our now friendly British Gas Boiler man!
Any help/advice would be great!

 

[pt-1]

Hello sprocket,

did you ever find the root cause for this as I have a similar issue.

Originally our fan had stopped working and would not allow the boiler to light the flame as Air Pressure sensor would prevent it.

After an Engineer came out and gave the Fan a good old clean and filled up the system all looked ok for a while.

The system then kept pressuring itself over the next few hours until water leaked out of the cylinder.

We carefully lowered the pressure and the system is working ok if it powered up the whole time.

If it is set to Auto and once the water/heating is hot enough and the boiler shuts down the pressure get's to low and cannot start again.

The only way to get it back is to fill it up slightly, run it on constant on and bleed some of the radiator water / pressure.

Any Ideas?

THX