Vokera Boiler Starting without when turned off

[spiro]

I have a Vokera 12/48 Mynute R.S.E Boiler which has been intermittently starting even though the timer/programmer is turned Off for both Heating and Hot Water. I noticed it heats a little water which sits in the outlet pipe from the boiler up to the control valves ( which remain shut since everthing is switched off) Thereafter all pipework is cold.

I originally thought this was a faulty timer/programmer, so I bought a new one, but it still has the same issue, so this indicates there is some other issue? The Timer/programmer was an ACL Lifestyle LP522 and the replacement a LP247 ( these are duel channel controllers and are a straight swap)

I also noted that there is also a small humming noise coming from the boiler even when it is off now - I think this is coming from the behind the expansion chamber ( big red doughnut-shaped vessel - think thats what its called -oops: ) as if it is constantly running now. The only way to stop this and the random running of the boiler is to totally isolate all power to the boiler.

Would be very grateful for any advice
Thanks

 

[ChrisR]

Is there a frost stat?

See if the humming noise is the pump - listen with a stick.

If a switch in one of the motorised valves has stuck shut and you have no bypass pipe, the boiler will just heat itself up, with the pump running.

You'll have to disconnect wires and test, to diagnose.

 

[spiro]

Thx. !

Will investigate further, when I get home