Honeywell BDR91 newbie question

[Adam Braunton]

Hello!

In the spirit of adventure I am trying to understand my existing Honeywell wireless base and transmitter setup and have come across a real head-scratcher with the wiring, I wonder if anyone can shed some light.

I understand N and L, I understand that A, B and C are essentially a fancy switch.
What I don't understand is why C is shorted to A?
Indeed, if I remove the wire from A to C, the system still works as expected.

Any clues appreciated! This system was installed by a professional by the way so I assume they knew what they were doing...

 

[picasso]

Take the link out of A-C , A to B is normally open so it takes a call for heat to close them and fire boiler, A to C is normally closed meaning the contact is closed when unenergized.

 

[muggles]

What I don't understand is why C is shorted to A?

Because the installer was an idiot

 

[Adam Braunton]

Thanks @picasso, @muggles. Thought I was going mad