Pump/boiler running on

[JezzerH99]

I have a Horstmann Channel Plus XL timer hooked up to a Potterton Suprima 120L. I'm having a problem that the system seems to run on (pump and boiler) even when the timer is off or all of the thermostats have reached their temperature setting.

I've tried to reset the timer but still it seems to play up... any ideas?

 

[gas4you]

Check your external zone valve. It could be the microswitch stuck on.

Could possibly be the pcb faulty on the over run bit.

 

[JezzerH99]

Zone valves (3 of them - hot, upstairs and downstairs) all look okay - there's an indicator light on them to show when they're open/closed and they all appear ok.

Could it be the boiler PCB? And if so which one?

 

[Gas2Air]

So on your diagnosis the valves appear ok? Little light say valve good.

 

[JezzerH99]

Okay so perhaps my diagnostics are a little bit simple but I am just trying to figure out whether there's anything I can check before calling in a heating engineer.

So, I'll check each of the zone valves but I guess the question is - could they be causing the problem even when the timer is "off" on all 3 circuits?

What I see is the pump is running when the all 3 circuits are "off" on the timer.

Ta.

 

[namsag]

Because the light is going on and off does not mean microswitch inside is not stickin and allowing power to pump and boiler.

The valves will have an orange and grey wire to them . disconnect 1 orange at a time (in wiring centre) from each valve and when boiler and pump stop firing that will tell you which valve head is faulty.
Be careful as even with the wire disconnected it may still be live depending how its been wired or switch is faulty

Also when disconnecting the wire turn power off at fused spur and not just the clock for same reason

 

[JezzerH99]

And would that sticking still allow the pump to run when the timer is in the off position?

Ta.

 

[namsag]

yes

 

[JezzerH99]

Hats off to you namsag - took off the downstairs zone valve, played around with it a bit and suddenly it jumped into life... all is now fine

Thanks all.