Honeywell to Drayton Wiser Kit 2

[SingingDwarf]

I currently have a Honeywell ST9400 programmer with a CM900 wireless room stat.

I want to change this to a Drayton Wiser two channel system.

I also have a three port valve to divert the heating circuit to the hot water cylinder.

The image below shows the existing backplate, the two white cables on the left come from the CM900 receiver and the white cable on the right goes to the wiring centre.

I am assuming that 1 and 2 are the HW as per the Drayton wiring diagram :

The wiring centre looks like this:

Top left (white) : Programmer
2nd left (white) : Mains
3rd left (white) : Cylinder stat
Bottom left (black) : Three-port valve
Bottomg right : Boiler

I'm looking for a bit of help please.

I'm assuming I'll need to remove the wireless receiver (blue and two browns), but not sure how to wire up #2 and #4 for the CH.
Or is it simply a case of moving the earth wire with red sheath to #4 and removing the three wire for the wireless receiver?

 

[RandomGrinch]

It appears as if the ST9400 is only timing the hot water.
The C/H timing has been completely taken over by the CM900.
To confirm, I expect the blue and brown wires in the second white cable go to N and L in the BDR91, a link between L and A, and the brown wire in the first white cable would go to terminal B.

In which case, you are correct...

Is it simply a case of moving the earth wire with red sheath to #4 and removing the three wires for the wireless receiver?

There will be no wire in terminal 2 of the ST9400/Wiser receiver. The green/yellow wire is not an earth wire, but the switched live for the C/H (rather poor practice, and against current regs, but at least it's marked in red!).
You won't need to touch the wiring centre.

 

[SingingDwarf]

It appears as if the ST9400 is only timing the hot water.

Sorry, I omitted to mention that the ST9400 is only used for the hot water.

The CM900 does the central heating as you say.

I haven't opened the BDR91 to check the wiring there, but will do so tomorrow.

Yes, I had thought the earth wire re-use was a no-no - the wiring centre is withing 30 cm of the backplate, but agree.

Thanks for the help.

 

[RandomGrinch]

Yes, I had thought the earth wire re-use was a no-no - the wiring centre is withing 30 cm of the backplate, but agree.

It wasn't against regs when it was installed, so I wouldn't worry too much about it!