Replacing Drayton RTS1 with Honeywell CM907

[Gavster]

Hi,

I am trying to replace my Drayton RTS1 thermostat with a Honeywell CM907, my boiler is a Baxi Combi 133HE Plus.

The Drayton RTS1 had three wires connected, Neutrel, Live & 3 (Call), the backbox also had a earth cable connected.

The Honeywell CM907 only has two connections to use, A & B. I have connected the Live to A & the Call to B, blocking off Neutral When I turns on, I hear the click to say it's turning on the heating & I see the flame symbol on the LCD display.

The boiler has a summer/winter mode enabled, summer = Hot Water only, where as Winter = Heating & Hot Water, so I have the Winter mode enabled, I've also set the dial on the boiler to constant, so that the thermostat will turn on the heating when desired.

However, the boiler doesn't turn on when the therm wants it too, the boiler pretty much is on constantly. I've search around the net to see if anyone else has the same issue/configuration, but can't seem to find anything.

Any suggestions?

 

[doitall]

Have you programmed it correctly

 

[Gavster]

Yes, I had the same Honeywell CM907 stat at a previous house.

Currently the stat is in the off position, however it still turns the heating on.

 

[doitall]

my 921 did that yesterday, I turned it on to auto and then off again and it was fine.

 

[Gavster]

I tried that too. It's currently off, however the boiler seems to be overriding it & the heating is coming on all the time

 

[doitall]

Check the timer and frost stat if there's one.

Where is A_B wired into the boiler connections.

Did the old Drayton work.

 

[McCombi]

Unlikely if prev stat worked but ia the a and b wired into 1 and 2 terminals on boiler next to incoming mains on boiler beside pcb? Is there a link wire between 1 and 2? If so remove link.

 

[Gavster]

The old stat worked fine before I changed to the Honeywell.

Where will the PCB be on the boiler? All I see are the controls for setting the timer etc.

 

[Gavster]

I've put my old Drayton stat back on, however I no longer hear the click anymore & it doesn't appear to be firing up the boiler. The boiler does it on its own accord.

 

[Gavster]

Any suggestions, I've reset the boiler, checked the wiring again, putting the Honeywell back on, but still it doesn't turn the boiler on. The boiler is on all the time, no matter what setting the stat is set to.