Fitting honeywell CM901 to Combi... help please!

[neilo1977]

Hi

I have a MAIN Combi 30 HE, without a timer on it, and have gone about replacing a Honeywell 6360B with a CM901. Following advice on here, I changed over putting 1 (on T6360B) as common to A (on the CM901), and 3 as call to B.

Put the electrics back on, and now have the boiler constantly heating up even if the CM901 is switched to OFF or Manual settings (Room temp is 22C, and put the setting to 18C).

Can anyone point out something I might be missing? Otherwise will just switch back to previous and call on professional help!

 

[doitall]

What have you got the boiler end. Assuming it worked before, you could have a faulty stat.

 

[neilo1977]

To be honest, I couldn’t tell you anything other than the boiler make and model. Not sure what I’m looking for.

I just presumed that it would be a simple task of replacing one thermostat for another... shows what little I know!

 

[doitall]

AS above, if it worked before then you have changed them correctly.

So one has to assume the stat is faulty.

or you haven't programmed it correctly.

 

[neilo1977]

Thanks.

Yes, fitted as I stated so absolutely sure that is correct. As far as programming, I think the fact that the boiler is still firing on the off setting must indicate a faulty stat.

Many thanks

 

[neilo1977]

Further to the previous info...

The colour wire going to common is Red
The colour going to call is blue
The Yellow/green wire is not used

Is this correct?

 

[doitall]

Further to the previous info...

The colour wire going to common is Red
The colour going to call is blue
The Yellow/green wire is not used

Is this correct?

Depends how it's connected in the boiler, but shouldn't make any difference, the stat is only a switch.

Remove one of the wires, does the boiler still work.

 

[neilo1977]

I guess I was thinking the 2 wires might be the wrong way around... Any I have British Gas coming over for the annual service next week, so will see if they can sort it while here... Rather than me blowing it up!!!