Replacing Honeywell T6360b with CM901 - problem

[amars]

Hi All,

I searched the forum to find an answer to the problem i am having but couldnt find an answer.

//www.diynot.com/forums/viewtopic.php?t=245061

I removed the old thermostat and fitted the new one, only connect the live wire to terminal A on the new stat and the switched live wire to terminal B. I isolated the neutral wire and the earth wire and left these unconnected.

My system is:
Valiant Ecotec conderser bolier. and there is a junction box which the honeywell ST699 programer, boiler, room stat, cylinder stat and two motorised valves (one for CH before the manifold and one for HW) all connect to.

I'm not an expert on heating systems by any means though, but i think this is a sundial s plan???

I have left the CH on constant on the programmer, however although the CM901 room stat shows the burner on symbol on screen, the boiler does not fire up, i dont think the valve for the CH moves either. There is a flashing radiator symbol on the boiler which i think means that it is not getting a heating call.

The boiler does work for HW however.

i would be very grateful if someone could let me know if i have connected it incorrectly. do I need to change the wiring in the junction box? If so i think i will call out an electrician.

Many thanks
amar

 

[D_Hailsham]

I removed the old thermostat and fitted the new one, only connect the live wire to terminal A on the new stat and the switched live wire to terminal B. I isolated the neutral wire and the earth wire and left these unconnected.

If you have identified the wire correctly, that's correct.

two motorised valves (one for CH before the manifold and one for HW).

I assume you mean a manifold for a microbore or underfloor system.

i think this is a sundial s plan?

Correct

I have left the CH on constant on the programmer

That's OK until some misguided person fiddles with the Programmer! Better to move the wire from the CH ON terminal to the L terminal.

although the CM901 room stat shows the burner on symbol on screen, the boiler does not fire up, i dont think the valve for the CH moves either.

You can check if the valve moves by feeling the lever in the slot. If the lever is stiff to move, the valve is still closed. But if the lever is loose in the slot, the valve has opened, which proves the CM901 is sending a signal to the valve. This means there is a problem with the switch in the valve.

You will see a grey wire and an orange wire. One of them will be live all the time; the other is only live when the valve is open. You can test this with a meter or a neon test screwdriver.

Make sure that the HW is OFF when you do this or you will get a false result.

 

[amars]

hi thanks for getting back to me so quickly

i've checked my boiler and it has an error code s.30 which as i understand it there is an issue with the external heating controls

i checked the wiring in the cm901 and it is definately correct and the wires are securely in.

the motor valve is loose to move as well

do you think it could be a problem with the actual cm901 unit? or is it that the wiring in the junction box needs to be changed? or would it means that there is a problem with the heating valve?

once again many thanks for your help

 

[amars]

the thermostat itself was broken,

I took it back and the new one worked fine.

Thanks for helping all.

 

[darenfriday]

Hi, I hope you are still listening to this thread...

I am using the same stat CM901 and have tried others and get exactly the same fault.

When the timer turns on the heating it fires up regardless of the stat setting.

I thought I'd wired the stat wrong so I rewired and now I think I've blown the motorised valve upstairs. I've ordered a replacement.

Do you think the Potterton programmer may be faulty?

Thanks

Daren

 

[45yearsagasman]

Start a new thread and describe your system and all its controls. Describe the symptoms and you may get some help.