Buzz from GCH boiler

[Alan]

Hi,

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.

[geoff]

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

[Alan]

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!

[geoff]

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