Y-Plan with a CM927 wireless stat

[falkirkbairn11]

I have re-checked my wiring and it is per the diagram (including the pump overrun). My aim was for the room stat to switch the boiler ON and OFF independently of the HW and my system doesn't do that.

If I switch the HW OFF at the timer, the boiler switches OFF and the room stat has no effect. I don't if I am asking my system to do something it is not designed for.

The there is something else wrong as the wiring diagram is designed to do exactly what you are asking!

Have you disconnected the wires from the Horstmann T2 and T4 to the wiring centre?

Do you have a multimeter? (And know how to use it )

Yes, I have a multimeter and can use it

 

[matt1e]

Thanks again DH,
I have re-checked my wiring and it is per the diagram (including the pump overrun). My aim was for the room stat to switch the boiler ON and OFF independantly of the HW and my system doesn't do that.
If I switch the HW OFF at the timer, the boiler switches OFF and the room stat has no effect. I don't if I am asking my system to do something it is not designed for.

If it is behaving as described then either
the horstmann programmer is faulty
the mid position valve is faulty
or the wiring is not as per DH's instructions

The system has just been changed to a Y-Plan.
Previously it was a fully pumped system with the HW controlled by the Horstmann programmer/timer.
The CH was switched ON/OFF by the programmer using a single 2-way zone v/v.
I suspect the system was modified from a gravity HW sometime in the past.

I suspect that your wiring centre does not have a permanent live to it, is the boiler new too?

I may appear thick but can you clarify for me something that I am still not clear about in my mind.
The wiring diagrams all show a live going to terminal 8 on the WC.
Exactly which live are we talking about. Is it the switched live or a wire from the L terminal on the boiler to the WC.?

the live terminal 8 is a system switched live to fire the boiler its coming from the WC to the boiler

Matt

 

[falkirkbairn11]

Thanks again DH,
I have re-checked my wiring and it is per the diagram (including the pump overrun). My aim was for the room stat to switch the boiler ON and OFF independantly of the HW and my system doesn't do that.
If I switch the HW OFF at the timer, the boiler switches OFF and the room stat has no effect. I don't if I am asking my system to do something it is not designed for.

If it is behaving as described then either
the horstmann programmer is faulty
the mid position valve is faulty
or the wiring is not as per DH's instructions

The system has just been changed to a Y-Plan.
Previously it was a fully pumped system with the HW controlled by the Horstmann programmer/timer.
The CH was switched ON/OFF by the programmer using a single 2-way zone v/v.
I suspect the system was modified from a gravity HW sometime in the past.

I suspect that your wiring centre does not have a permanent live to it, is the boiler new too?

Matt[/quote

Thanks for your input Matt.
Id delighted to report that the system is now operating as design.
I completely disconnected the wiring centre and re-instated it wire by wire
I then switched on the system and bingo - it works.
I suspect there was a faulty connection somewhere in the WC.
To all the guys who helped me - especially DH - thank you.
Just one other thing. I obtained a diagram of the 3-way valve internal wiring and how it functions and that helped me to better understand how the system operates

 

[D_Hailsham]

Well done!