Hardwired smoke detectors, interconnect...

16 years ago

... grrr... sometimes I hate doing work for friends.

I've inherited a project involving... umm... six? yeah, six hardwired smoke detectors.

Wouldn't you know it - only four can be found. We have no idea where the other two went. All the hardware exists - brackets, connectors, etc., but the detectors themselves? GONE. Vanished. Got sucked into a spontaneously-generated wormhole and transported to an alternate dimension.

I told him to go buy six new, matching units.

He came back several days later with two completely different ones. It is his belief that I should be able to use them.

Y'know what? Whatever. I don't care, there's hot and neutral there, I can just leave the interconnect wire disconnected and forget it. His alternate plan is to just use 9V battery powered ones anyway.

and yet I wonder to myself (but don't dare try it without someone else's input), is the 'interconnect' standard? Do different brands/models use the same signalling? Can I mix brands? Will it work? Will the world end? Will it create another wormhole and teleport more matter? I mean, the latter wouldn't necessarily be a bad thing if I could coordinate it with the presence of his very irritating ten-year-old son...

Featured Answer

pharkus
Original Author

16 years ago

There is a standard. A number of them actually, they just don't apply to proprietary residential smoke detectors.

There's a 4-wire standard, for 24V-powered smoke detectors with a set of contacts to report to a central controller that smoke is detected.

There is a 3-wire variant, which shares one of the contact terminals with one of the power terminals.

There are newer digital serial standards.

If I want to turn this guy's house into an office building, school, or factory, then there are definitely standards available. Unfortunately, they require him to buy stuff, something he seems very... uhh... well, did I mention I told him to buy a set of matching smoke detectors and he came back with only two, which don't match either the existing units or themselves???

It appears from my searching the internet that Firex (existing) simply connects the 9VDC supply to the interconnect wire to signal, and both of the new ones are Kidde, which is apparently the same company - whose website seems to indicate they are compatible... At this point, I'll believe it when I see it.

Work resumes Monday.

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Comments (7)

azlighting
16 years ago
The manufacturer's don't want you to mix an match, as they say they can't "guarantee" the units will operate correctly or to their maximum operating efficiency, but if you install all their units you can!

Shouldn't be a big deal unless manufacturer's have completely different connection guidelines, or wattages, voltages, etc.

Def. verify before.
pharkus
Original Author
16 years ago
Well, I'm TRYING to verify before. That's why I asked. :)

The other method I have to verify is to simply clip my meter on to the interconnect wire and press the test button. Frankly if the signal voltages are the same I'm going to wire them up and see if they work. I'm just not at the project house for the weekend (taking a much-needed break) and won't be able to do this until Monday.
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joed
16 years ago
Hook it up. When it starts going off or the smokes blow up then you can tell him I told to buy six new matching units. I sure there is probably some code either electrical or fire that requires them to be interconnected and the same.
ontariojer
16 years ago
You're asking for trouble in my experience. I have found that sometimes different models from the SAME manuf. That are supposed to work together have troubles. I wouldn't even bother interconnecting them if they aren't the same brand.Tell your buddy why though.

The funny thing is that the prblems never seem to show up until you have been gone from that job for a month or so!
brickeyee
16 years ago
"is the 'interconnect' standard?"

No, and that is the problem.

There is no standard.
smithy123
16 years ago
well, tell the dummies who made the dangerous tr recs REQUIRED to make a STANDARD.