Smoke detectors gone wild!!!

[markheiks]

I have a tech scratching his head (me too) and thought I might see if anyone here has had a similar problem and what is the fix.

We took a service call saying smoke detectors keep chirping. (system is BRK, 120 volt AC with 9 volt Backup) The tech assumed it was batteries, so he replaced them all. Problem didn't go away. So tech advises a detector is bad, replace all detectors. Did so and problem still exists. Tech calls me. I asked him to check voltages on red (signal) and neutral wires...50 volts!!! I told him to isolate the circuit to find where he was picking up the voltage. As he took apart the 9 detectors the voltage kept dropping by about an average 9 volts each opening, some openings didn't make a difference. So when he got them all apart, he has no voltage at any opening, once he starts putting the junctions (no detectors) back together, the voltage starts to climb again. Any ideas?

 

[charlie b]

Re: Smoke detectors gone wild!!!

The chirp appears to be a "low voltage" warning, meaning that the AC has dropped below minimum and the device is running on battery power. I can't guess what is causing the strange voltage behavior, without first asking what is meant by "took apart the 9 detectors." What was going on with the internal wiring? Are you saying that he just disconnected the detector, or that he remade a connection to bypass the detector?

 

[physis]

Re: Smoke detectors gone wild!!!

Is the 50 volts being picked up with a digital meter? If so use an analog meter or put a 100k resister across the leads. If it's not there anymore it's just a little induced voltage.

 

[markheiks]

Re: Smoke detectors gone wild!!!

(charlie) Yes sir, I understand the low voltage chirp...but there is 120 there at each detector, including the last one on the circuit. "took apart the 9 detectors" means we removed them, left the junction there, measured between red (signal) and neutral, and read 50 VAC. Then he took each junction apart and the voltage disappears. He did both, disconnected detectors and opened the circuit.

(physis) It is a digital meter. According to the manufacturer of the Detectors, any voltage, induced or otherwise across the signal wires will cause the chirp. Their fix is to get the 50 volts off the circuit. My question is, where is it coming from? Smashed romex in the line? Shared neutral picking something up? And why all of a sudden? It has been installed for 9 years.

 

[hurk27]

Re: Smoke detectors gone wild!!!

I just went on a service call yesterday and had the very same thing. I had about 40 volts between the signal wire and the neutral at all the smokes after I reconnected the neutral all was well except this smoke lost the ability to communicate to the other smokes so I changed it out and it's fine. Maybe there is a hidden smoke somewhere?

 

[physis]

Re: Smoke detectors gone wild!!!

By markheiks:

(physis) It is a digital meter. According to the manufacturer of the Detectors, any voltage, induced or otherwise across the signal wires will cause the chirp. Their fix is to get the 50 volts off the circuit. My question is, where is it coming from? Smashed romex in the line? Shared neutral picking something up? And why all of a sudden? It has been installed for 9 years.

That's a very poor response from the manufacturer.

If their product can't withstand a few microamps on the interconnect terminal they ought to find a different field to get into. Maybe toys for instance.

If there is in fact any significant amount of current there it's a whole different problem.

I think you need to do two things.

1) Find out how much current there is on those terminals.

2) Find somebody with the manufacturer who's more helpful. Because the guy you talked to is either late for lunch, doesn't care, or doesn't know.

 

[physis]

Re: Smoke detectors gone wild!!!

My question is, where is it coming from?

If it's induced it's likley just coming from the adjacent conductors in the cable.

It would be pretty embarrasing if their representive is right and the detectors wouldn't work using a three conductor cable for a wiring method.

 

[physis]

Re: Smoke detectors gone wild!!!

One more thing.

Then he took each junction apart and the voltage disappears. He did both, disconnected detectors and opened the circuit.

I'm not sure what this means.

[ July 19, 2005, 09:14 PM: Message edited by: physis ]

 

[George Stolz]

Re: Smoke detectors gone wild!!!

Originally posted by physis:
It would be pretty embarrasing if their representive is right and the detectors wouldn't work using a three conductor cable for a wiring method.

C'mon, Sam! Do they have to plan for every conceivable scenario?

 

[physis]

Re: Smoke detectors gone wild!!!

That's why I don't fit in well with corperate America, I'm just too damn demanding!

[ July 20, 2005, 03:57 PM: Message edited by: physis ]

 

[hurk27]

Re: Smoke detectors gone wild!!!

I have never had a smoke detector not work on a 3-wire cable. We use all 4 major brands, and they all work unless there is some other problem with the wiring. Like having the wrong three conductor ran to the smokes. (a multiwire home run) I have had even the 3 conductor for 3-ways ran to a smoke before but most of the time I find a loose wire at one of the smokes or a forgotten feed between two smokes. Loosing the neutral at one smoke, can back feed the interconnect wire as the interconnect use just the neutral and the red wire. but it sound more like you have some kind of load between the hot and interconnect wire that is allowing the voltage?

 

[physis]

Re: Smoke detectors gone wild!!!

I wouldn't blame the smokes right away either.

I just think that the manufacturer's response was about as useful as asking two six year olds "who broke the lamp". :roll:

Edit: In fact, all my money is on it ain't the smoke alarms. I wouldn't have thought it was before they were replaced.

[ July 20, 2005, 02:46 AM: Message edited by: physis ]

 

[markheiks]

Re: Smoke detectors gone wild!!!

Okay, after further review...the manufacturer (BRK) had an engineer reply that said the voltage is induced, throw in the 100 k resistance and it will go away. This model alarm has a silent feature, when activated does anything but silence the detector, in fact once "silenced", it will chirp on the minute for the next 15 mins. when it resets itself back into normal mode...great plan. BRK admits it wasn't the smartest move and has since changed the design to flash a red LED instead of the annoying chirp.

It appears that there were bad batteries, both when the batteries were replaced and when the smokes were replaced and/or the silent feature was activated on one or more of the detectors. So I will send a tech back out, and let you know if in fact this is fixed.

Please wait by your computer(s) with breath held! :roll: