Old style boiler with tank, it’s getting on a bit now, but when it has power it switches on (even if time controller set to off off & all temp dials turned to minimum) goes like the clippers for a few minutes then starts to boil over into the filler tank. If thermostat turned up them the pump seems to be going, can hear a lot of water flow & radiators start to warm up. Still boils up to fuller tho, the overheat lockout doesn’t kick in.

Have just replaced the pcb, no difference.

When it’s starting to boil up theres a weird “pinging” noise, sounds like something kinda metallic pings up a water pipe then rattles back down before pinging up again a few seconds later.

Have to kill the power to boiler to stop it. It’s a wickes (halstead) LW60ci

Any ideas?

as a possible thing to rule out… we don’t have a boiler as we’re on a district system….. but we’ve had issues with the heating running away and everything going on full bung. (always in the middle of the night which is a nice way to be woken up)

It turned out it was the programmer / timer which was sort of crashing. To look at it seemed to be fine – the buttons / display all seemed to be doing what they were supposed to so we focused out attention elsewhere – but it wasn’t actually reponding to any inputs or being turned off and was frozen with the valves open and the pump running but the thermostat off.

When it turned all those other elements were working fine we found out that cutting the power to the programmer and turning it back on again would  resolve it until it surprises us again a few months later.

So if it isn’t part of killing power to the boiler try cutting the power to the programmer instead

Kettling is caused by limescale. The thermostat measures the temp of the metal under the limescale rather than the water temp, so it boils a bit each heating cycle. Pretty normal in hard water areas.

You need to descale it, using something like Fernox DS40, which is basically a huge bag of citric acid you put in the header tank, drain into the system and circulate for a few hours. Then drain and refill.

I do our 35 year old boiler every 8 years or so.

NB There is a small risk, with an old system that the mild acid could eat a hole somewhere and cause a leak. We get one in the back of the cast iron heat exchanger. The good news is that after a few days, rust re-seals the hole.

Our combi’s condensate pipe sometimes gets clogged causing a kettling noise.

You say boilers turning on even when programmer/thermostat says off? In which case problem could equally be at the programmer end, or some point in the wiring. Disconnect the call for heat wire at the boiler end and see if it comes on or not. It shouldn’t.

Sorry posted a thread then havent been back to check it.

You need to descale it, using something like Fernox DS40,

Thought about this, but think there’s something going on with the controller/boiler short circuit, but maybe this is also a problem.

Disconnect the call for heat wire at the boiler end and see if it comes on or not. It shouldn’t

Will give this a go….soon as I figure out how to do it 🙂
One thing I hadn’t actually considered is it’s the controller rather than the boiler itself, hmm. Controller was replaced not long ago so assumed that wouldn’t be the problem, worth another look.