Quick answer on mid position valve fault please

[OffshoreGas]

Yes, there’s something sending voltage to the synchron. I was reading up last night on an intriguing article.

UK DIY FAQ

The synchron is held engaged in mid position in dc and if heating is called ac is sent to the synchron to move it.

The plot thickens! I’ll find the problem, never been defeated yet.

May be wrong but my understanding was they only have a single demand.

Voltage on the demand moves the valve to the CH position. No voltage the spring returns to the HW position. Then there are two switched outputs for the valve limits back to the boiler.

 

[Chuck]

Wiring most likely but if not...

Honeywell 3-ports must be on the flow (not return) pipework. I think that getting this wrong will overload the motor.

Is the motor the correct 230-240V variant as opposed to the 220V one sold in other countries?

Is the mechanism operating smoothly when turned manually?

 

[OffshoreGas]

Ignore that, I’ve just bothered to read the manual.

I’m reading that as
CH only:
White - 240v
Grey - 240v

CH + HW
White - 240v
Grey - 0v

HW only
White - 0v
White - 0v

 

[Sharp Point]

Yes, you’ve confirmed what the coloured wires should read. Now what’s going on inside? I’m intrigued now, totally the tinkerer I am

 

[Sharp Point]

Why I haven’t got into the workings of a mid position valve is by now is embarrassing. One of those haven’t got time moments, I’d rather spend my spare time under the bonnet of my toy

Nitrous

 

[OffshoreGas]

Just found this, would have saved working out the crappy diagram they give you. Explains it quite nicely.

 

[Sharp Point]

Yep, seen that a gazillion times. I think you’re missing my point, what’s going on inside? I think it’s fair to say, going by the article I posted early this morning... that there’s more that goes on inside.

 

[Burger]

This any good to you?

 

[Sharp Point]

View attachment 38347

This any good to you?

Cheers, seen that though

 

[Burger]

Cheers, seen that though

Ok, what is it you want to know?