Trying to fit central heating thermostat in Italy

[hefner11]

I am presently in Italy and I am trying to install a Honeywell CM907 thermostat to replace an existing thermostat on teh central heating system. I have removed the cover of the old thermostat and there are 3 wires, brown, blue and grey.

Can anyone advise me in what order I connect these to the A,B & C terminals on the CM907. The boiler is a combi Ferroli New Elite boiler if that makes any difference.

I connected the grey wire ( which was live when I tested it) to the A terminal on the CM907 and the blue wire to terminal B. I isolated the brown cable which was not live when I tested it. Nothing happened until I increased the temperature on the on the thermostat. As soon as I did this the fuse tripped.

I then connected the brown to terminal A and left the blue in B ( I isolated the grey wire) but nothing has happened. The fuse did not trip.

Can anyone offer any advice on the correct way to wire the CM907.

Thanks

 

[Sam Gangee]

Determine which wire is A live, B neutral and C switched.

Look at the technical specification for the Honeywell CM907 and Determine which terminals correspond to the above.