Rewiring a Hardwired Smoke Detector WITH THE POWER ON

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I have a hardwired smoke detector that is old and outdated, that I'd like to switch with a new unit. The only problem is that I can't shut off the power to the alarm before I disconnect it and reconnect the new one. I'm going to have to do the take-down and installation while the power is LIVE.
I live in a high-rise apartment building and the smoke detector is powered not by my unit's individual power, but off of a line brought in from a common hallway. There is no way to cut power to the smoke detector without cutting power to all the lights in the common hallway, which is impossible.
So, how can I safely (or as safely as possible) change this detector with a new one? If I don't touch certain wires together, will I be OK? What are the chances I would get shocked?
I know your first inclination will be to tell me to get the circuit turned off or call an electrician, but please (at least hypothetically) assume that neither of those options are possible.
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On Apr 1, 5:32 pm, snipped-for-privacy@gmail.com wrote:

When I wire with power on I carefully remove wire nuts or screws with a rubber insulated screwdriver and carefully rewire it, but if its a building unit why bother it probably works, test it, I cant believe it will set off others, but maybe call the manager. Gee, Free electric is what I see from the building, or maybe you know that, but you will get caught eventualy.
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On Apr 1, 6:32 pm, snipped-for-privacy@gmail.com wrote:

Most of those 110V smoke detectors have a quick-disconnect plastic connector that you should be able to work with while the power is live. You would have to open up the detector and see if it does have one of those connectors. And plus you would have to make sure the new detector has a similiar connector. Usually they are interchangeable. If the old unit is hardwired with no connector, I would try to cut the power before working on it.
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I answer the questions without making judgments.
Hypothetically speaking, there is no way to get shocked or damage anything if you work with one wire at a time and do not ground yourself while touching the bare part of the hot (usually black or red) wire.
If I were to do something like this I would do the bare or green wire first, the white wire second and the hot wire last. Once I had all the wires connected to the new modular plug, I would plug it in and test it before attached it to the box.
Note there may be an inter-connection wire (usually yellow that must also be connected. This has no juice and can be done at any time.
Also the base plate may need to be changed even if it is the same brand.
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Colbyt
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Hot comes off first goes on the last
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If you pop the breaker how will you restore power? If you get shocked will you fall?
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No problem working 120V live if you know what you are doing. Sounds like you don't, than you must ask yourself what would be the upside vs. the downside when the building maintenance staff take care of this at no cost to you. Shouldn't liability and ventricular fibrillation should be a major factor to you?
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snipped-for-privacy@gmail.com wrote:

Do you know if your smoke detector is "powered" by a 120 volt AC line or by a low voltage line?
Do you know if the smoke detector sends a signal back to an alarm panel to notify an alarm company that it's been tripped, or does it just sound off in your place?
Do you know whether your "new" detector will be electrically and operationally compatible with the existing system(s) in all respects?
If you aren't certain about all the above, stay away from that job.
Further, I'd suggest you'd be much better off taking the matter up with the apartment building's management (if you haven't already) before you do anything to the existing detector. I'd hazard a guess that they have the right to be in control of things like that.
Play it safe, guy.
Jeff
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Jeff Wisnia wrote:

have no clue whether that is possible, but you have no right to mess with it. Let the building management replace it or embroider a pretty doily to cover it up.
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Yes if it is a building supplied system you should not mess with it, its not yours, its under the owners controll and you could trigger an event you dont want. So it old looking , so what.
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You could conceivable damager every detector on the system depending on the design and where you sent 110.
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The unit is a line voltage unit, not low voltage. The smoke detector is stand-alone and does not signal back to a building-wide alarm system. And the new detector is compatible with the old one.
Someone mentioned that I should use a special screwdriver. Where can I find something like this and what does it look like?
So as long as I don't touch two of the same wires at the same time, I'll be OK? How can I not ground myself? If I'm on a ladder wearing rubber-soled sneakers, would that take care of it?

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Someone mentioned that I should use a special screwdriver. Where can I find something like this and what does it look like?
So as long as I don't touch two of the same wires at the same time, I'll be OK? How can I not ground myself? If I'm on a ladder wearing rubber-soled sneakers, would that take care of it?
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Looks like you have to do this anyway so here are some advice.
1 Work with a buddy so he/she could call 911 and get help.
2 Use non conducting ladder. Ware electrical insulating gloves and shoes.
3 Don't need special screwdriver, wrap conducting part with electrical tape.
4 Work with one hand only, put the other hand in your back pocket.
Remember it doesn't take much, as little as 6 milliamps, to go into ventricular fibrillation or cardiac arrest.
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On Tue, 1 Apr 2008 17:22:31 -0700, Frank wrote:

The key is to not let the current go across the heart. I just did some wiring and forgot the outlet next to the switch was live and on another circuit. I touched it and held for about a second before I realized what was happening. Work with 120 enough and it barely fazes you. I don't worry too much about 120 and occasionally work with live wires. You bigger concerns are compatibility with the existing system, likely interwired so that when one goes off they all go off, and also with not destroying the rest of the system. I seriously doubt it is connected to the lighting system as the smoke alarms are supposed to be on their own breaker.
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Mike Dobony wrote:

I've heard it both ways; makes more sense to me to go ahead and put it on the lighting circuit, reason being that the homeowner will notice if the lights aren't working but if the breaker dedicated to a run of detectors trips he may not notice that and be unprotected.
Of course, the local AHJ has the final word on what's cool and what isn't.
nate
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Nate Nagel wrote:

Only touch one wire at a time. Don'r make your body a current path. I often work on live 120 or 220V lines. As long as this is kept in mind, it is OK. More is needed? Wear a pair of thin rubber gloves. Or use a tool with insulated grip.
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On Tue, 01 Apr 2008 23:00:58 -0400, Nate Nagel wrote:

That is assuming that they don't have a battery backup (never seen such an animal) and that you are dealing with a homeowner, not a commercial apartment complex, as in the OP's case.
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If by "barely fazes you", you mean it's less likely to hurt you, well, yer nuts. You've just been lucky so far.
The OP probably shouldn't be doing this. The setup doesn't make sense, and he doesn't know enough to be playing with live wires.
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wooden ladder, rubber tennis shoes, AND only work one wire at a time and don't touch the metal box it's mounted in.
s
Back when i was 13, i landed about 4 dozen duplex outlets and 8 or nine switches all with the power on. Just have to take your time and handle one wire at a time.

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Pat makes a good point. What if the breaker pops? What if you reach up there and cut all the wires at once? (use an old cutter, it will be hard on the edge of it) The breaker will be popped, and you can continue with your changing out of the unit. Then at some point, the breaker will get reset by someone eh????
s

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