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Smoke Detectors, 2-wire vs. 4-wire


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#16 chrisexv6

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Posted 17 April 2012 - 05:49 AM

Pull a four and use two and you can't go wrong. After all nobody looks at a wire coming out of the ceiling and says "damn, it has to many conductors"

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This.

I pulled 18/4 for my 2 wire detectors. Worked out very well when I found out that you cant have 2 wire heat and smoke on the same zone. I used 2 conductors of the 18/4 for the fire loop, and the other 2 for the heat loop. Everything is still open so I could technically run another wire if I had to (code reasons maybe?) but it was nice to be able to quickly fix the "goof up" and at least have the smoke and heats running again.

Edited by chrisexv6, 17 April 2012 - 05:49 AM.


#17 soccerob

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Posted 17 April 2012 - 11:19 AM

my house is already built and i didn't have any wires pulled from the panel to any smoke detectors. i am able to run wire into the attic and access the rear of one of the smoke detectors. i believe all the smoke detectors are latched to one another, so am i correct in assuming that i can run a 4-wire from my panel to the one smoke detector that i can easily access, and be able to monitor all of them (as a whole, not individually) from the panel?

#18 Lou Apo

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Posted 17 April 2012 - 03:30 PM

my house is already built and i didn't have any wires pulled from the panel to any smoke detectors. i am able to run wire into the attic and access the rear of one of the smoke detectors. i believe all the smoke detectors are latched to one another, so am i correct in assuming that i can run a 4-wire from my panel to the one smoke detector that i can easily access, and be able to monitor all of them (as a whole, not individually) from the panel?


Need to know exactly what smoke detectors you have to answer this. Some detectors have an auxillarly relay which you could wire to the Elk. Odds are, you don't have a relay on yours. But it is possible that you could replace that one detector with a compatible unit that does have the relay. Also, code sometimes the building inspectors give you crap for doing that, sometimes they don't.

#19 gizzmo

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Posted 17 April 2012 - 04:31 PM

I have seen 110volt smoke wiring "T" tapped (ok for high voltage but bad for low) and I have seen in the middle a bedroom light wired in the circuit. Assume nothing!

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#20 gizzmo

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Posted 17 April 2012 - 08:05 PM

Well, I witnessed it today. I don't wire it this way but I did a takeover for a friend. House full of ESL 2-wire smokes with sounders. Started testing and the first one goes temporal and the rest kick in steady. Then I test the heat detector in the kitchen, which is on the same circuit, dead short so no sounders and all it does is place the zone in trouble. Even better the trouble report is not enabled. So here it goes, if the fire starts in the kitchen, nobody gets woke up and the smokes and sounders don't work any more. Congratulations, your all dead. Now I have to explain to the home owner how screwed up his wiring, that I can't get back to, is. This is best example I can give to show why we don't mix heats and smokes on a two wire powered smoke loop.

#21 chrisexv6

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Posted 17 April 2012 - 08:31 PM

Well, I witnessed it today. I don't wire it this way but I did a takeover for a friend. House full of ESL 2-wire smokes with sounders. Started testing and the first one goes temporal and the rest kick in steady. Then I test the heat detector in the kitchen, which is on the same circuit, dead short so no sounders and all it does is place the zone in trouble. Even better the trouble report is not enabled. So here it goes, if the fire starts in the kitchen, nobody gets woke up and the smokes and sounders don't work any more. Congratulations, your all dead. Now I have to explain to the home owner how screwed up his wiring, that I can't get back to, is. This is best example I can give to show why we don't mix heats and smokes on a two wire powered smoke loop.


Im actually surprised I didnt toast my Elk main board.....I had the mechanical heat detectors on the same loop as electronic smokes. I didnt realize exactly what the RRSMOD (reversing relay) would actually do once it kicked in, reversing power across everything. The heat detectors could create a short and blow up power supplies, fuses, or maybe just trip a PTC. Looks like Elk builds their stuff for newbies like me, because its still all up and running.

I have the heat-only detectors on the other 2 conductors of the 18/4 now, running to a separate zone on the board but defined as a 4 fire wire so my "if any fire zone goes into alarm, then turn on output 3" rule fires to get the RRSMOD to sound the sounders in the smokes. I need to test this all of course, but with a mechanical heat detector not sure I have an easy way of making sure all I do is trip the rate of rise and not the heat portion (since only the RoR portion is resettable)

#22 DELInstallations

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Posted 20 April 2012 - 02:48 PM

Well, I witnessed it today. I don't wire it this way but I did a takeover for a friend. House full of ESL 2-wire smokes with sounders. Started testing and the first one goes temporal and the rest kick in steady. Then I test the heat detector in the kitchen, which is on the same circuit, dead short so no sounders and all it does is place the zone in trouble. Even better the trouble report is not enabled. So here it goes, if the fire starts in the kitchen, nobody gets woke up and the smokes and sounders don't work any more. Congratulations, your all dead. Now I have to explain to the home owner how screwed up his wiring, that I can't get back to, is. This is best example I can give to show why we don't mix heats and smokes on a two wire powered smoke loop.


Not to make light of the situation, but it's only an issue on a system where tandem ring is desired.

#23 gizzmo

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Posted 20 April 2012 - 03:47 PM


Not to make light of the situation, but it's only an issue on a system where tandem ring is desired.

Tandem was supposed to be working, it didn't. Panel was supposed to go into alarm, it didn't. Fire signal was supposed to be transmitted, it wasn't. It was supposed to be installed correctly, it wasn't. Yeah, I think it meets my criteria of an issue.

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#24 DELInstallations

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Posted 27 April 2012 - 01:18 PM

As I said, not making light of an inproper install, I would want to know more details as far as the install goes, such as panel, hardware installed, where reversed power was being drawn from, etc. Sounds like the old GE reversing relay issue they had with their unit combined with a steady voltage trigger or no way to get a proper temp-3 pulse from the relay.

I have run across installs where an analog heat was installed in a continous loop where tandem was needed and it brought down the loop on a reversed power short circuit condition.

#25 gizzmo

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Posted 27 April 2012 - 07:46 PM

I said it didn't work. Now for more details, there is no reversing relay. And yes I failed to mention that in the list of things done improperly but it is a moot point. No two wire smoke zone can drive a single sounder or multiple sounders over a dead short. The panel by the way is a GE NX8 and can list this amongst its other known issues.

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#26 gizzmo

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Posted 27 April 2012 - 07:53 PM

I forgot to mention that a worker drove a rebar into the main underground power wire feeding this house and shorted one leg to the neutral. Every motor got smoked, light bulbs blew, and outlets smoked. Who would have thought that this could happen.
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#27 Submatey

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Posted 14 February 2013 - 11:29 PM

I have read on this forum that a 4 wire smoke det. "requires" a supv. relay.   I am presently installing a 4 wire smoke det. and my understanding (according to the installation manual) is that it is a "code" requirement.   In other words, it is optional.   Isn't that correct?



#28 newalarm

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Posted 15 February 2013 - 08:13 AM

I have read on this forum that a 4 wire smoke det. "requires" a supv. relay.   I am presently installing a 4 wire smoke det. and my understanding (according to the installation manual) is that it is a "code" requirement.   In other words, it is optional.   Isn't that correct?

 

You may want to give more background info (what system you have, what smokes brand and model number, etc...). But you should follow manufacturer's instructions. The System sensors I used required a relay ($20 extra). I should have gone with a 2 wire. My idea was to have separate zones, but it was not recommended by the experts as it could cause problems in system, so i did not.

 

BTW, you may want to start new thread.



#29 Lou Apo

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Posted 15 February 2013 - 11:13 AM

I have read on this forum that a 4 wire smoke det. "requires" a supv. relay.   I am presently installing a 4 wire smoke det. and my understanding (according to the installation manual) is that it is a "code" requirement.   In other words, it is optional.   Isn't that correct?

 

 

A 4-wire smoke detectors needs two relays to serve their purpose.

 

1) EOL relay.  You can buy 4 wire detectors with it built in for convenience sake.  This is not electrically required to operate properly.  In other words, if your wires are all intact and properly connected, an eol relay will not be necessary.  But, that is why it is necessary, to alert you in the event of a failure.

2) A reversing relay.  You must have a reversing relay or your smokes will not sound in unison.  Only the one that detects the smoke will sound, all the others will just sit there quiet.

 

It would be foolish to not install these relays.



#30 newalarm

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Posted 15 February 2013 - 12:47 PM

I did not install sounders on my smokes. I did not see the purpose, when the alarm will notify of the emergency already. Am I missing something?






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