Wiring on a Honeywell dt90e Thermostat to Replace old Manual Dial Ask questions and find answers to many subjects relating to electrics and electrical work

[bobthompson1]

I have a manual dial thermostat that I want to change to a Honeywell dt90e the wiring is as follows red to No1 yellow/green to no3 blue to no4 is it possible they have used the earth wire as the switched live as the blue is the neutral

[Mr White]

From your description it does sound like it. Are you sure it is yellow / green not just yellow?
If it is the earth core, it is dangerous and should be corrected.

[bobthompson1]

Definitely green and yellow it does look like it's sleeved. on the dt90e you do not need a neutral if I marked it appropriately could I use the blue wire as the switched live

[Mr White]

So long as the earth is used for its correct purpose, any of the other cores can be used for any purpose so long as they are tagged / marked at both ends.

[bobthompson1]

Thanks will have another look at it