Thermostat wiring?

[BUDFORCE]

Hi not me, a mate.

Says the boiler is a "potterton"

This is how the old thermostat is wired:

This is the wiring diagram for the new one:

He's taken a meter to it, there is 24v AC coming from the yellow wire, nothing from the blue or red.

Any ideas?

And yes 24 not 240 he double checked against a mains socket.

 

[Richie]

From the diagrams:

Red (Live) to Port 1
Blue (Neutral) to Port 2
Yellow (To Boiler for Heat) - Port 3
Jumper wire (Brown in old one) needs connected between 1 and 4

Essentially, you have power going to thermostat via Port 1 (Live). The jumper then allows a live feed from port 1 to port 4. When the thermostat clicks on, it internally connects the switched live (port 4) to Port 3 which allows power to flow to the boiler turning it on. When the thermostat clicks of, it disconnects power from Port 3 and the boiler turns off.

 

[rodders]

Jumper cable 1 to 4 not needed.
Internal switch goes 1 to 3 (heating) or 1 to 4 (something else, in your case, nothing)

 

[BUDFORCE]

Perfect cheers guys