Buzz from GCH boiler

My gas boiler has started making what I can only describe as a
mechanical buzzer sound. It appears to happen randomly when the
boiler thermostat kicks it back into life. Time the boiler has been
on for doesn't seem to make a difference, sometimes it takes hours of
use before it does it, sometimes it's barely been on.
Anyone got any ideas? Listening to the boiler when it is running, it
does have a faint hum that sounds to be at the same frequency as the
louder buzzer sound. It's a sealed system, with 'Classic' on the
casing (no idea on the 'brand'), with a fanned flue
I'd rather have some idea what it could be before I get bamboozled by
a plumber.
Reply to
In message , Alan writes
Ideal (Stelrad) Classic
The items inside which can buzz are the fan, the pcb (Stelrad 25b) and the gas valve
fans tend to buzz when the bearings have failed and it is no longer turning
The gas valve tends to buzz because the relay on the pcb is buzzing because the drive circuit is faulty - not the most common problem with this pcb
... or you have an internal timer which has a faulty clutch - if so, is it losing time
You will have to look a bit closer
Reply to
Thanks Geoff - it only happens for about 5 seconds, and it's a really loud rattling buzz, probably either the valve or whatever mechanism lights the boiler up. I'll call a plumber!
Reply to
In message , Alan writes
Then I would hazard a guess that it's a zener diode/capacitor fault in the drive circuit on the pcb causing the relay and hence the gas valve solenoid to suffer from the DTs
If it is, you can prolly fix it yourself
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