My house has four smoke detectors, all of them hard-wired with back up batteries. I needed to replace one and the replacement seemed very easy. I had turned off the AC power, installed the new smoke detector, but when I turned the power off, all four detectors went off and wouldn't shut off at all. The only way I could silence them was switching the circuit breaker off. Any thing I am doing wrong?
JohnBo

but when I turned the power off, all four detectors went off and wouldn't shut off at all. The only way I could silence them was switching the circuit breaker off. Any thing I am doing wrong?
JohnBo

What are the two ways you shut off the power? One the breaker, the other?

Guessing, I would think power and interconnect are reversed, verify the black to detector has power, and orange does not.

My mistake. I meant to say when I turn the power back ON, the smoke alarms all go off. I've been turning power off by switching the circuit breaker off.

We thought you meant that, Did you check that hot and interconnect wires were not reversed??
And when you say the detectors went off, do you mean they all "go off"(create noise).

Sorry for being so unclear. When I mean the alarms "go off" I meant that all three of the smoke detectors start sounding. I can only get it to stop by flipping the circuit breaker off.

Try pushing the test/reset button on each detector to see if that stops the alarm. If not, most likely a wiring problem as start noted.

I thought you meant that too. Still check that the black and orange at the detector you replaced. Probably need to swap connections.