On Wednesday, 3 January 2018 21:28:19 UTC, Fredxx wrote:
On 03/01/2018 08:17, tabbypurr wrote:
On Wednesday, 3 January 2018 07:17:10 UTC, harry wrote:
On Tuesday, 2 January 2018 23:10:04 UTC, wrote:

I need to replace an ancient bell/call box power supply with a modern
wallwart. The original transformer (from the 1930s, with internal fuses
in both L and N) was wired into the lighting circuit. It would be very
difficult to get non-lighting power to this location (near the ceiling,
in the kitchen), I don't have space for a fused spur and I can't find a
13A socket with a built-in fuse. I'm planning on using a standard 13A
socket, fitting an internal 500mA in-line fuse and adding a suitable
label to the socket.
What does the jury think?

Your door bell system with transformer uses a lot of energy.

How many batteries can you buy with say a years worth at a 10W load?

No newish wallwart quiesces at anywhere near 10W. Not even 1W now.
1W is about £1 a year, for which you can get a poundland pack of junk batteries or a few good ones.

The batteries are probably slightly cheaper if using electronic sounders, but you have to buy & replace them every so often, you'l get missed calls and the battery contacts will corrode sooner or later. In short it's a false economy, if it's an economy at all.


Consider getting a (wireless) battery replacement.

unwise

Maybe, you can have wired battery powered door bells.

Yes - the worst of both worlds.


NT