Y-Plan with a CM927 wireless stat

[falkirkbairn11]

My basic question is - Is a CM927 wireless room thermostat suitable for a Y-plan central heating system.
I have modified my central heating system to a Y-Plan. The idea was to be able to controll the HW and CH independantly.
The components used are Honeywell.
V4073 3-way valve, L641 cylinder stat, CM927 wireless room stat.
I can't have the CH on without the HW being on.
The wiring diagrams available all show a T6360 wired room stat and also 3 wires from the boiler, I have 4 wires from my boiler.
If the CM927 is suitable, I need a wiring diagram of a complete Y-plan system.
PS - My boiler is a Glow-Warm 30hxi

 

[45yearsagasman]

Go to the Honeywell site to download the wiring diagram. Wired correctly Y plans allow independent control. Your CM927 is compatible. Programmer should be 2 channel.
http://www.honeywelluk.com/

 

[D_Hailsham]

The CM927 only controls the heating. You need a second programmer to control the HW times - a single channel one will do, e.g Honeywell ST9100A (24hr) or ST9100C (7 day). (Make sure it has a boost button so you can easily heat the water up out of the normal times.)

I don't have a wiring diagram available but I will list the changes to the 'standard' Y plan diagram shown below. (Click to enlarge)

View media item 31288
The Time Controller is the HW timer, so you wire as shown, ignoring the red HTG wire.

Note that there are connections to HW ON and HW OFF

The T6360B thermostat is replaced by the CM927 relay box and wired as follows:

L to terminal 1
N to terminal 2
A is linked to L
B to terminal 5 (this will go to the Valve white wire)

The fourth wire to the boiler will be the pump connection as it has pump overrun.

 

[45yearsagasman]

My apologies, for not realising the cm927 is programmable room stat

 

[twgas]

I think you should have 5 wires, permanant live, switched live, pump live, neutral and earth.

 

[falkirkbairn11]

I think you should have 5 wires, permanant live, switched live, pump live, neutral and earth.

Thanks TWGAS.
I have 5 wires if the pump live is included. It was the switched live that confused me.

 

[falkirkbairn11]

The CM927 only controls the heating. You need a second programmer to control the HW times - a single channel one will do, e.g Honeywell ST9100A (24hr) or ST9100C (7 day). (Make sure it has a boost button so you can easily heat the water up out of the normal times.)

I don't have a wiring diagram available but I will list the changes to the 'standard' Y plan diagram shown below. (Click to enlarge)

View media item 31288
The Time Controller is the HW timer, so you wire as shown, ignoring the red HTG wire.

Note that there are connections to HW ON and HW OFF

The T6360B thermostat is replaced by the CM927 relay box and wired as follows:

L to terminal 1
N to terminal 2
A is linked to L
B to terminal 5 (this will go to the Valve white wire)

The fourth wire to the boiler will be the pump connection as it has pump overrun.

Thanks DH
That's how I wired it, but my query was
"Can I have CH without the HW being on" and the above configuration doesn't do it. Perhaps it can't be done.

 

[D_Hailsham]

That's how I wired it, but my query was: "Can I have CH without the HW being on" and the above configuration doesn't do it. Perhaps it can't be done.

It should do it - it's how my system is wired!

There is either a wiring error of one of the components is faulty.

Your boiler has pump overrun, so you need to follow the small diagram on the left in the wiring diagram.

We assumed that you did not have a timer for the HW, but you obviously do have one. Which model is it?

 

[falkirkbairn11]

That's how I wired it, but my query was: "Can I have CH without the HW being on" and the above configuration doesn't do it. Perhaps it can't be done.

It should do it - it's how my system is wired!

There is either a wiring error of one of the components is faulty.

Your boiler has pump overrun, so you need to follow the small diagram on the left in the wiring diagram.

We assumed that you did not have a timer for the HW, but you obviously do have one. Which model is it?

HORSTMANN C27

 

[D_Hailsham]

We assumed that you did not have a timer for the HW, but you obviously do have one. Which model is it?

HORSTMANN C27

Thanks.

Is the Horstmann wired as follows (H=Horstmann, WC = wiring centre)?

H - WC
L - 1
N - 2
1 - 7
2 - NOT connected
3 - 6
4 - NOT connected

Has the system always been Y plan, or has it been recently converted from gravity HW to fully pumped?

 

[falkirkbairn11]

HORSTMANN C27[/quote]
Thanks.

Is the Horstmann wired as follows (H=Horstmann, WC = wiring centre)?

H - WC
L - 1
N - 2
1 - 7
2 - NOT connected
3 - 6
4 - NOT connected

Has the system always been Y plan, or has it been recently converted from gravity HW to fully pumped?[/quote]

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 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.?

 

[falkirkbairn11]

Is the Horstmann wired as follows (H=Horstmann, WC = wiring centre)?

H - WC
L - 1
N - 2
1 - 7
2 - NOT connected
3 - 6
4 - NOT connected

Has the system always been Y plan, or has it been recently converted from gravity HW to fully pumped?[/quote]

Sorry DH, I forgot to confirm that thr Horstmann is wired as above

 

[D_Hailsham]

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 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.?

Your boiler has 'pump overrun', which the standard Y-plan wiring diagram does not cover. I posted the correct diagram earlier but here it is again for ease of reference. You must follow the wiring in the small diagram on the left for terminals 8, 9 and 10. Click diagram to enlarge, then right click to Save Image.

View media item 31288
To make it perfectly clear:

1. The two 'short' wires shown connected to T8 are the orange and brown, as shown in the main diagram;
2. L, N and E from the boiler connect directly to terminals 1, 2 and 3;
3. Boiler switched live connects to T10;
4. Pump L connects to boiler Pump Live via T9;
5. Pump N and E connect directly to terminals 2 and 3.

 

[falkirkbairn11]

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 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.?

Your boiler has 'pump overrun', which the standard Y-plan wiring diagram does not cover. I posted the correct diagram earlier but here it is again for ease of reference. You must follow the wiring in the small diagram on the left for terminals 8, 9 and 10. Click diagram to enlarge, then right click to Save Image.

View media item 31288
To make it perfectly clear:

1. The two 'short' wires shown connected to T8 are the orange and brown, as shown in the main diagram;
2. L, N and E from the boiler connect directly to terminals 1, 2 and 3;
3. Boiler switched live connects to T10;
4. Pump L connects to boiler Pump Live via T9;
5. Pump N and E connect directly to terminals 2 and 3.

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.

 

[D_Hailsham]

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 )