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Honeywell DT90 replace with Smart thermostat BHT-006GCW wiring help please
- Thread starter iamjeffers
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Your smart thermostat requires a permanent live and permanent neutral for it to work, your existing has live and switched live. There are additional wires, but would need to be tested to confirm if they can be used.
The existing thermostat is battery powered, the new one is mains powered so it needs an additional 230V supply to provide it with operating power.
So, as @Stuckinarut above, it needs a mains supply connecting to terminals 3&4 [N&L] which should come from the same 3A fused spur that supplies the boiler.
The heating control wires currently in A&B would then go to the new thermostat terminals 1&2.
This is a bit odd though.....
The terminal marked A is clearly a Live as per the square I've highlighted, yet the red wire in it has blue insulation tape on it, which is normally done to identify a wire that is being used as a neutral.
However, terminals 1&2 have exactly the same function as A&B as can be seen from the diagrams on both thermostats. They are both 'normally open' switches. So, if it works now, it will work with the new thermostat once the 230V supply is provided as well.
The Honeywell DT90 is purely a thermostat, so I guess there will be a timeswitch/programmer somewhere that controls the on/off times for the heating. If the new thermostat is a 'programmable thermostat' [ie one that incorporates both time and temperature control] then any existing time control for the central heating would need to be set to permanently 'on' 24/7. You can ignore this if it is only a room thermostat the same as the DT90.
So, as @Stuckinarut above, it needs a mains supply connecting to terminals 3&4 [N&L] which should come from the same 3A fused spur that supplies the boiler.
The heating control wires currently in A&B would then go to the new thermostat terminals 1&2.
This is a bit odd though.....
The terminal marked A is clearly a Live as per the square I've highlighted, yet the red wire in it has blue insulation tape on it, which is normally done to identify a wire that is being used as a neutral.
However, terminals 1&2 have exactly the same function as A&B as can be seen from the diagrams on both thermostats. They are both 'normally open' switches. So, if it works now, it will work with the new thermostat once the 230V supply is provided as well.
The Honeywell DT90 is purely a thermostat, so I guess there will be a timeswitch/programmer somewhere that controls the on/off times for the heating. If the new thermostat is a 'programmable thermostat' [ie one that incorporates both time and temperature control] then any existing time control for the central heating would need to be set to permanently 'on' 24/7. You can ignore this if it is only a room thermostat the same as the DT90.
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Agreed, that and the daisy-chaining of the cables in the back box suggests that there should be a neutral available there.
@iamjeffers could we have a photo of the wiring behind the programmer, so we can confirm?
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