On Sat, 25 Mar 2017 16:04:00 -0400, wrote:

Problem is I want to rewire it and I don't know how to cut the power to it since there is no breaker.

Thoughts?
There HAS to be a breaker. It will likely be shared with another
circuit - in USA the code required the smoke detectors to be on AFCI
breakers, I believe.they are GENERALLY connected to a bedroom circuit
- which also requires AFCI protection.. This is NOT a code requirement
but is acceptable best practice..

There HAS to be a breaker by code.... Connect a light or radio to the
wires and turn off every breaker in the house, one at a time. Working on
live wires is stupid, unless you're an electrician. SHUT OFF THE MAIN
BREAKER, if nothing else works. (During the day, so you can see, or use
a flashlight).