Hi,

I am just fitting a new Danfoss ATC Cylinder Thermostat to replace the Honeywell L641A1005

The reason being the temperature knob on the old one was stuck.

This is the question: I have two wires. brown & blue.

I have three terminals:

1 (COM)
2 (N.C.)
3 (N.O.)

Which wire goes where? I guess brown will go to 1 (COM)

Thanks for your help

John

Depends on your system. Pretty sure NC is normally closed and NO normally open.
ie. if the rest of your heating system needs open circuit to switch the water heating on use NC and if it requires closed circuit (most are like this) use NO along with COM as you say.
You can easily confirm this by using a simple meter on the new stat and twidling the temperature knob to see when a connection is made between each of the terminals. If your old stat was working apart from the temperature knob being stuck you can meter that up at room temperature to confirm if you have a system expecting NC or NO. (If NO you will have closed circuit between the terminals that were in use at room temperature.)

_________________
Mike