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View the thread, titled "Programmer/Thermostat wiring CH problem?" which is posted in UK Plumbers Forums on UK Plumbers Forums.

Hi Guys,

Hoping someone can help me, we have a 2-zone heating system that consists of 3 honeywell 2-port valves on a system/hot water tank gas boiler.

Recently the HW motorised valve broke - so I replaced it (motor/housing only) and problem solved. However when diagnosing this, I also noticed that CH2 ignores the thermostat and is always calling for heat. That is, when the thermostat is on 0 and the CH2 is on at the programmer, it's always firing up the boiler. CH1 is working correctly.

I figured it was probably the valve, so replaced that along with the HW valve while I was at it, however the problem remains exactly the same. So next I figured it must be the thermostat, so I replaced that like-for-like (£20 honeywell) and problem still remains the same! The thermostat is clicking correctly and my current buzzer shows it is certainly 'getting power'.

So now, I believe it must be either the programmer faulty on that single channel, or the wiring is bad, and has been bad since it was first installed? I've only been here 2 years and honestly not sure if this is a new or old problem - so the wiring seems more plausible?

Does anyone have any suggestions for diagnosing? Or should I just get a plumber in at this stage? I could buy a multimeter but can't say I'm confident with using/diagnosing it.

This is the system layout (attached)

This is the wiring box, black wires are the valves and the left hand side white cables are CH2/HW thermostats (attached).


Thanks for any help!
 

Attachments

  • PXL_20210709_175128532.jpg
  • PXL_20210712_201856472.jpg
The CH2 valve should only motor over and connect the endswitch with permanent live to boiler live when theres a call from programmer and through stat. This really needs a multimeter. Even if the programmer was faulty and sending a constant feed the stat should still govern the feed to motor.
 
Ok thanks. Looking at that diagram it looks like that taped wire from the stat should maybe be connected to 2 Neutral. But I'm way out of my depth! Is this something for a plumber or an electrician?
 

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