Changing Honeywell T6360B thermostat for CM907 - PLEASE HELP

[drketanga]

Hi, I have had a Worcester Bosch 42 CDi boiler fitted in the garage. I have currently only got a Honeywell T6360B manual thermostat in the lounge which means I can't control the boiler from inside the house.

I was hoping to exchange to a thermostat that allowed me more control from in the house. I was thinking about the Honeywell CM907. Would this be an easy exchange?

I have opened the casing of my current thermostat (T6360B) and there is an earth connection and connections in terminal 2, 3 and 1. Where would I plug these wires in to the CM907?

Many thanks

 

[D_Hailsham]

I have opened the casing of my current thermostat (T6360B) and there is an earth connection and connections in terminal 2, 3 and 1. Where would I plug these wires in to the CM907?

Old Terminal 1 goes to New Terminal A
Old Terminal 2 is not used - make it safe, e.g. a terminal block
Old Terminal 3 to New Terminal B
Old Terminal Earth is not used - make it safe, e.g. a terminal block

NB The wire to Old Terminal 1 comes from the timer/programmer CH ON terminal, so you must do one of two things:

1. Set the Programmer CH to permanently ON; or

2. Disconnect the wire from Programmer CH ON terminal and connect to Programmer L terminal.

 

[drketanga]

NB The wire to Old Terminal 1 comes from the timer/programmer CH ON terminal, so you must do one of two things:

1. Set the Programmer CH to permanently ON; or

2. Disconnect the wire from Programmer CH ON terminal and connect to Programmer L terminal.

Thanks so much. At the moment I have an MT10 mechanical timer which plugs on to the fascia of the boiler. I use it to set the time I would like the central heating to come on. If I put this on the "on" position, is that what you mean by your point 1 above?

 

[D_Hailsham]

At the moment I have an MT10 mechanical timer which plugs on to the fascia of the boiler. I use it to set the time I would like the central heating to come on. If I put this on the "on" position, is that what you mean by your point 1 above?

Yes.

Set the slider switch, located about 4-5 o'clock relative to the rotary dial, to the ON position. The settings on the MT10 are then ignored and all time/temperature settings are controlled by the CM907.

When setting the CM907, the first time you set is when you want the house to have reached the set temperature, say 0700hrs. It is not the time you want the boiler to come on. The CM907 works that out automatically from the overnight temperature drop. I've been running some tests on my CM927 (wireless version) and the actual ON times do vary, despite what some cynics say.

Also, the "OFF" setting is not an OFF in the traditional sense; it's a very low temperature, usually 5C. So the boiler will stay off unless the temperature drops that low. If you want the boiler to be off, say when at work or on bed, you have to set a temperature below what you expect it to drop to when you are out/asleep. So at night you would set the last time/temperature to say 2300hrs/5C.

 

[drketanga]

Thats great. You've been awsome!

 

[mrnotfixit]

Hello I wonder if someone knowledgeable could help me. I did the exact same thing as drketanga, all the same 4 pieces of kit and the same situation, so the posts above were most helpful in terms of confirming the wiring.

When I switched the heating on it all seemed to work OK. The only thing was the display on the CD42i boiler started flashing, alternating between the digital numeric display and a weird looking symbol like this -| |-

I think this is to do with the interruption to the power supply to the boiler, while I did the wiring. Or siphoning. Or something... It stopped doing it after a while so I hope I am OK but can anyone offer some reassurance please?!