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Rewiring a Hardwired Smoke Detector WITH THE POWER ON

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Rewiring a Hardwired Smoke Detector WITH THE POWER ON gobofraggle 04-01-2008
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Posted by AZ Nomad on April 1, 2008, 7:25 pm
>Jeff Wisnia wrote:

>> gobofraggle@gmail.com wrote:
>>
>>> I have a hardwired smoke detector that is old and outdated, that I'd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.
>>
>>
>>
>> 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
>>
>Not to mention doing something that might disable the entire system. I
>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.

You could conceivable damager every detector on the system depending on the
design and where you sent 110.

Posted by on April 1, 2008, 7:43 pm
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?

> gobofrag...@gmail.com wrote:
> > I have a hardwired smoke detector that is old and outdated, that I'd
> > like to switch with a new unit. =A0The only problem is that I can't
> > shut
> > off the power to the alarm before I disconnect it and reconnect the
> > new one. =A0I'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. =A0There 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? =A0If I don't touch certain wires together, will I be
> > OK? =A0What 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.
>
> 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
>
> --
> Jeffry Wisnia
> (W1BSV + Brass Rat '57 EE)
> The speed of light is 1.8*10^12 furlongs per fortnight.- Hide quoted text =
-
>
> - Show quoted text -


Posted by Frank on April 1, 2008, 8:22 pm
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?

-----------------------------------------------------------------------


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.





Posted by Mike Dobony on April 1, 2008, 9:29 pm
On Tue, 1 Apr 2008 17:22:31 -0700, Frank wrote:

> 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?
>
> -----------------------------------------------------------------------
>
>
> 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.


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.

Posted by Nate Nagel on April 1, 2008, 11:00 pm
Mike Dobony wrote:
> On Tue, 1 Apr 2008 17:22:31 -0700, Frank wrote:
>
>
>>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?
>>
>>-----------------------------------------------------------------------
>>
>>
>>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.
>
>
>
> 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.

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

--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel

Page 3 of 4       < 1 2 3 > last >>
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