Zone valve electrics

[cully]

Htg circuit is UH3 wiring centre for UFH
Had a problem with the pump not running when stat demands heat.
The zone valve opened and I have power on the orange wire firing the boiler, at this point I didn't check the grey wire voltage as I presumed it was permanent live to one side of the aux switch and because the orange had fired the boiler then the operation of the valve was complete.
Concluded that the pump relay was the issue so new wiring centre ordered, but!
went back to the wiring centre and found no volts on the grew wire?
Changed the zone valve and all is well!
Question, if there was no power on the grey where did the orange wire get its power from?
The above raised a second question
I had the honeywell o/heat stat on the hot side manifold pipe that, when operated, would stop the pump.
When I had the above problem (no pump) the boiler pump kept the system running.
I only knew there as a problem because the pump light wasn't on.
What should the o/heat stat shut down?
Thanks

 

[stem]

The grey and orange wires are simply connected to a switch. So, from a functional point of view it doesn't matter which way around the grey and orange wires are connected. Having said that, convention has it that the grey is the permanent live, and orange the switched live. The vast majority of valves are connected this way.

However, there are a few rogue installations that aren't, so if the wires are transposed, and the orange wire was connected to the live, it would show 230V when you measured it. But, when the valve opened if the switch was faulty then the grey wire wouldn't become live and so the boiler won't fire.

It's only a theory of course and your valve maybe wired in the 'right' way around, but as you seem able to use a multimeter, there's an easy way to find out.

 

[cully]

Thanks Stem
The grey and the orange were in the right terminals (UH3 wiring centre has the zone valve terminals marked in their respective colours)
Checked the old zone valve no continuity when zone valve levered open (the linkage isn't depressing the switch when the valve is opened mechanically, in fact it's quite a way off so I presume it wouldn't have made the switch electrically, but back to the problem, the orange wire, in its right terminal showed 240V and gave demand to fire the boiler and at that time I had no volts on the grey and the pump didn't run.
I will disconnect the gray tomorrow to see if the orange has volts thus giving demand to the boiler as previous but not the pump.
the unknown to me is how the UH3 circuit board is configured? I would have thought as you pointed out permanent live grey switched live orange.

 

[ianmcd]

Checked the old zone valve no continuity when zone valve levered open

when you lever the valve open, this is for filling purposes , it will not make the end switch so you wont get continuity , only when the synchron motor opens the valve does it go far enought to make the switch

 

[cully]

Just an update on the Heatmiser wiring centres.
When the room stat demands heat through the board it powers the zone valve and the "orange" (boiler) terminal the zone switch "grey" terminal completes the circuit powering the pump. (I told Heatmiser they were rogues)
Returning to a problem I mentioned earlier that stopping the pump in an overheat situation doesn't work as the boiler pump circulates the water where would you interrupt power to prevent an o/heat situation? (didn't have the luxury of installing floor sensors 20 years ago)
Thanks

 

[ianmcd]

Just an update on the Heatmiser wiring centres.
When the room stat demands heat through the board it powers the zone valve and the "orange" (boiler) terminal the zone switch "grey" terminal completes the circuit powering the pump. (I told Heatmiser they were rogues)
Returning to a problem I mentioned earlier that stopping the pump in an overheat situation doesn't work as the boiler pump circulates the water where would you interrupt power to prevent an o/heat situation? (didn't have the luxury of installing floor sensors 20 years ago)
Thanks

So wrong

 

[cully]

If what you mean being wrong is Heatmisers wiring centre I presume their thoughts are that identifying each of the zone valves five wires to the board means they can configure that board as they want but I ordered a new wiring centre based on orange being live and no pump running.
Sent the board back to uk underfloor heating today (£20 cheaper than Heatmiser store)