Boiler ignoring timer settings

[W1tchseason]

Hi
We have an old free standing boiler that provides hot water and central heating. A few weeks ago I noticed that the hot water was going on at odd times, even when (according to the timer/programmer) it was supposed to be off. If I turned the programmer off at the mains switch then the boiler cut out, but when I turned the mains switch back on the water fired up again - even if the programmer 'water' switch was turned to 'off'.
So I figured the programmer was faulty and replaced it - but the same thing is happening again.
I would have thought that if both the 'heating' and 'hot water' switches on the programmer were set to 'off' then presumably no power would be getting to the boiler, but that isn't the case - even with both off the hot water sometimes fires up - but then shuts down if I turn off the mains supply at the wall socket.
Any ideas what could be happening? I'm reluctant to call in a heating engineer since I suspect I could probably fix it myself - if I knew what was wrong!
Cheers
Jerry

 

[45yearsagasman]

Got anything like this? View media item 30391 View media item 38425

 

[W1tchseason]

Thanks Pete.

...couldn't see exactly that, where would it be? We have this (boiler.jpg) inside the boiler casing and these three (tank.jpg) in the cupboard where the tank is.

Cheers

Jerry

Boiler

• W1tchseason
• 17 Oct 2012
• 1

Tank

• W1tchseason
• 17 Oct 2012
• 1

 

[D_Hailsham]

We have ... these three (tank.jpg) in the cupboard where the tank is.

Tank

• W1tchseason
• 17 Oct 2012
• 1

The thing on the left, attached to the cylinder, is the cylinder stat. Other two boxes attached to the pipes are zone valves - like the left pic in Pete's post.
Your symptoms sound like the valve on the HW circuit (top left one) is either sticking or the internal switch is permanently closed.

Turn the power off.

There is a lever on the end of the valve; it should be at the Auto end of the slot.

Move the lever to the Man end - you should feel some resistance and the lever should move back to the Auto end when released.

If the lever is loose in the slot, the valve is stuck permanently open.

If the lever opens and closes the valve correctly the internal switch is permanently closed.

Stuck valve
Remove the actuator (that's the box on the top).
This exposes the valve spindle, which should rotate easily by hand (about a quarter turn). If stiff, try a little silicon lubricant.

Faulty switch
Replace the actuator.

 

[45yearsagasman]

Good advice above. That looks like an old Thorm M series boiler. Looks a bit tatty and could probably do with a service before Winter.

 

[W1tchseason]

...spent a couple of hours fiddling around with it over the weekend - amanged to break the lever so it no longer does anything but since it's broken in the 'auto' position I guess that's OK? It behaved as you said before that (bit of resistance & then returned to its original position).

The actuator *seems* to be working OK - responds to the water being switched on & off - so I'm guessing that it's a stuck valve as you suggest.

Dismantled the actuator but couldn't get it off the pipe because one of the brass screws is knackered & has no head. Planning to try to extract it this week & then see if I can grease the valve to loosen it up.

Thanks again for your help - reluctant to call in a plumber if I can fix it myself but might have to end up doing so (esp. if it involves the piping in any way).