Installing a new junction box - which wire to run it off?

[Space cat]

Site the transformer next to your fuse box -

That's a good place to put it. Think ahead here. You might not always live in that house. Where will a new owner expect to find a bell transformer? Certainly not underneath the floorboards.

- and run a wire from there to your doorbell.

That could be the difficult bit. Another reasonable place to put a transformer would be near to the bell itself.

 

[bernardgreen]

It's a doorbell.

So ? I am aware of a person who put the door bell push in the mains supply to the transformer. Fortunately it was changed before anyone was injured.

The thinking was that transformer would need to be turned on only when the bell was being rung.

There are some un-informed people out there.