Digital Room Thermostat Wiring

[johndm1957]

Hi,

I want to replace my existing dial room thermostat with a Heatmiser PRT programmable model. I have checked existing connections, and I have 3 plus earth.

Checking with a multimeter, I find I have live (red) neutral (blue)and yellow, plus an earth. When I connect my meter to red and blue, I have 240v.
When I connect red and yellow, I also have 240v when heating is off, but this drops to zero as I turn up the dial to fire up the heating.

I'd expected the red/yellow circuit to have been 'made' to fire the boiler/heating rather than 'broken'. Anyone know why?

Its a combi boiler, currently set to 'constant', but there is another smaller boiler in the kitchen which is the one that fires when the room thermostat is turned up. There is a wiring box in the cuboard with the combi with 'ACL Lifestyle Wiring' written on it.

Help appreciated

Regards,

John

regards

 

[ricicle]

The red and yellow are being made when the stat calls for heat ie the yellow is made live so will not read 240V to the red (permanant live) but should read 240V to blue (neutral).This is how the stat should work so your new stat should follow the same idea (permanant live,switched live and neutral)

 

[johndm1957]

Many thanks for the info.....