Smoke detectors low volt signal wire

[kwired]

..if you can get a thhn to it you can fish in the 3-wire....

That is what I think.

The voltage on this conductor may be low voltage but it is in same enclosures with power conductors.

If you want to call it a 725 class 2 circuit it needs supplied by a listed class 2 source, and will need separation from power conductors.

 

[Jim W in Tampa]

Once it is out of the junction box is it not class 2 ?

 

[LarryFine]

... this 9volts is + on the red - on the neutral, ...

Doesn't the requirement to group conductors prohibit the separate-single-wire interconnect method?

 

[LarryFine]

The voltage on this conductor may be low voltage but it is in same enclosures with power conductors.

As well as likewise insulated.

 

[eprice]

Doesn't the requirement to group conductors prohibit the separate-single-wire interconnect method?

If this signaling circuit is an article 725 circuit, then 300.3 does not apply. Even if 300.3 does apply, 300.3(3) can probably be used to get around the grouping requirement.

 

[Mr 3phase]

If you are trying to interconnect smoke detectors where a three wire cannot be installed (unless it's all concrete I don't know why it can't be done), BRK makes a smoke detector that is UL listed that allows you to wire one as 'hardwired' and the rest function off a radio signal that they all transmit. I spoke at length with the NFPA regarding this matter as I am not only and electrician, but also a retired professional fire fighter, and I wanted a definitive answer on this subject as I too had to deal with interconnecting detectors in a tough situation. Bottom line, the NFPA would allow them but the AHJ would not allow them. So, check with the local AHJ before trying any fancy options.

 

[kwired]

Once it is out of the junction box is it not class 2 ?

If there were class 2 wiring connected to the device it would not exit into the power wiring area (the outlet box). Look at HVAC equipment with class 2 controls. The place you connect field wiring of the class 2 circuits is in a separate compartment from power wiring. Where they do come together with power wiring like at a contactor or other control device the class 2 wiring usually is separated from the power wiring. The internal wiring is part of the listed unit. Although sometimes you see things that make you wonder how some piece of equipment ever was listed.

 

[hurk27]

If you are trying to interconnect smoke detectors where a three wire cannot be installed (unless it's all concrete I don't know why it can't be done), BRK makes a smoke detector that is UL listed that allows you to wire one as 'hardwired' and the rest function off a radio signal that they all transmit. I spoke at length with the NFPA regarding this matter as I am not only and electrician, but also a retired professional fire fighter, and I wanted a definitive answer on this subject as I too had to deal with interconnecting detectors in a tough situation. Bottom line, the NFPA would allow them but the AHJ would not allow them. So, check with the local AHJ before trying any fancy options.

Above in red;

It was listed in post 19

With these units you can have wire linked smokes in one area and a separate set of wire linked smokes in another area, and by using two of these units replacing two of the wire linked smokes, this will interlink both areas together as if they were wired.

 

[hurk27]

thanks Wayne,. hey the thing I don't get is this, from the "one link " alarm instructions:

The same fuse or circuit breaker must power all interconnected units

not sure it would help all that much in a retro fit or did I miss something ?

Because they want you to keep them all on the same neutral, as a few do tell you this, but why this one says same breaker is kind of deceptive to the real reason.

 

[M. D.]

Above in red;

It was listed in post 19

With these units you can have wire linked smokes in one area and a separate set of wire linked smokes in another area, and by using two of these units replacing two of the wire linked smokes, this will interlink both areas together as if they were wired.

and keep in mind:

The same fuse or circuit breaker must power all interconnected units

thats from the instructions of the "one link".

Still not sure how this helps much with retro as alarms are required( when bedroom added in Ma.) in just about every room... it would be much better if you could just grab a feed from any ol'e where.

 

[kwired]

Do the wireless interconnected units communicate via RF or through the power line?

With either method how do they keep from giving false alarms at a neighbors house?

I can see where the typical three wire devices on one circuit would be more reliable and probably cost less.

 

[hurk27]

and keep in mind:

thats from the instructions of the "one link".

Still not sure how this helps much with retro as alarms are required( when bedroom added in Ma.) in just about every room... it would be much better if you could just grab a feed from any ol'e where.

The same circuit is only required for each section of wire interconnected units, not for the wireless part, remember these units are both wire interconnected and wireless.
heres the instructions:
http://www.brkelectronics.com/pdfs/2008/10/13/a9724c3c.pdf

Lets say you have a two story house, floor one has a string of wired smokes from one circuit, and floor 2 has another from a different breaker, you could put one of these in each system and they would be both interlinked. they also have straight battery ones that are wireless that work off these same smokes, and they have no wires or circuit run to them, so that tels me the same circuit requirement is just for the wired portion.

Do the wireless interconnected units communicate via RF or through the power line?

With either method how do they keep from giving false alarms at a neighbors house?

I can see where the typical three wire devices on one circuit would be more reliable and probably cost less.

This is from the link I posted in post 19:

? Hardwired interconnect and RF Interconnect: reliable and secure radio frequency communication between alarms. 915 MHz frequency with 65,000 security codes and 3 channel frequency hopping.

 

[TobyD]

A few years ago we would power up smokes from multiple circuits and pull a floating low volt conductor between them.A problem occurred when the ARC Faults sensed the different neutral conductors.When we tested the smokes at any given time a different arc fault breaker would open.So ,now we keep all them on the same circuit.

 

[M. D.]

The same circuit is only required for each section of wire interconnected units, not for the wireless part, remember these units are both wire interconnected and wireless.
heres the instructions:
http://www.brkelectronics.com/pdfs/2008/10/13/a9724c3c.pdf

Lets say you have a two story house, floor one has a string of wired smokes from one circuit, and floor 2 has another from a different breaker, you could put one of these in each system and they would be both interlinked. they also have straight battery ones that are wireless that work off these same smokes, and they have no wires or circuit run to them, so that tels me the same circuit requirement is just for the wired portion.



This is from the link I posted in post 19:

Thanks Wayne , I was just wondering if it could help here in Mass on a reno job,.. here in Ma. if a bedroom is added the smokes\ co2\heats, have to be brought up to current requirements... I thought these might offer an option , they don't really. here are the rules regarding smoke alarms in Ma. if any are interested.
www.mass.gov/Eeops/docs/dfs/osfm/pubed/flyers/consumers_guide_w_sell_1_and_2_fam.pdf