Smoke detectors false trips

Alec_t

Joined Sep 17, 2013
14,280
Is anyone in your household a smoker? Over time a thin layer of smoke particles can build up on ceilings, and ceiling-level alarms, and perhaps cause drift of some circuit parameter.
 

Thread Starter

MikeML

Joined Oct 2, 2009
5,444
It is possible that "new house" off-gassing (even after 2 years) is tripping the ionization type smoke detectors. You could switch to the photo-detector type and see if that helps. The gas builds up at the ceiling at night when the air is still.
This is the most plausible explanation... The house is conventional stucco exterior, frame construction, non-Chinese sheetrock, latex paint, some carpeting. It is very energy efficient and tight. 9ft ceilings throughout on one floor (slab, no crawl-space or basement)

What type do you have? Use ionization type near kitchens to reduce the likely hood of false alarms do to burned toast etc. Use the photo-detector type near the bedrooms where smouldering type fires are more likely. Either will work in either situation regardless. It more about reducing false alarms and preventing the homeowner from riping the unit from the ceiling and throwing it out the window.:eek:

No kind of power supply problem should ever put a smoke detector into full alarm mode. It could, however, sound a short chirp to signal that the power has glitched, gone off, or come back on.
The first batch were FireX Ionization Smoke Alarms, model i4618A. The second batch are similar, just a different manufacturer. Some of the alarms are a single loud chirp, which do not trigger the other alarms. Others are full-on alarms that last for several minutes (but do eventually time-out) but do trigger all the alarms at once. AFAICR, one of the early units failed in a mode where the only thing that shut-it up was disconnecting it from the AC and removing the 9V battery.

Thanks for the insightful post...
 

Thread Starter

MikeML

Joined Oct 2, 2009
5,444
Is anyone in your household a smoker? Over time a thin layer of smoke particles can build up on ceilings, and ceiling-level alarms, and perhaps cause drift of some circuit parameter.
If you are smoking in our house, you'd better be on fire. (Just ask my wife).
 

Thread Starter

MikeML

Joined Oct 2, 2009
5,444
Still an ongoing problem. I am about to replace all of the #$#@$#$%$ ionization detectors with photoelectric.

I still think that the power company is doing something funky with the power feed at about 2am. I got so mad that I tore one off the ceiling last night, threw it on the floor so hard that it broke open.

It has a rudimentary off-line AC to DC power supply(no transformer) with a series capacitor to drop the voltage, a series resistor to reduce in-rush current, a MOV for transient suppression, a couple of diodes (1n400x) and an electrolytic filter capacitor. The 9V battery is diode-ored into the mix.

Since all of the detectors in the house are fed with a separate electrical-panel breaker (that branch circuit powers nothing else), I'm still leaning toward a line filter.

Anybody else have anything new on this problem?
 

Thread Starter

MikeML

Joined Oct 2, 2009
5,444
Still an ongoing problem. ...
I just noticed something else. The branch circuit that powers the smoke detectors has a 15A Arc-Fault type of circuit breaker (likely because some of the smoke detectors are in bedrooms, and code requires all branch circuit going to bedrooms to be Arc-Fault). The current draw in that branch is likely to be only a couple of mA. Is there something about very-lightly-loaded Arc-Fault C.B.s that could cause the false alarms in the smoke detectors?
 

gerty

Joined Aug 30, 2007
1,305
I just noticed something else. The branch circuit that powers the smoke detectors has a 15A Arc-Fault type of circuit breaker (likely because some of the smoke detectors are in bedrooms, and code requires all branch circuit going to bedrooms to be Arc-Fault). The current draw in that branch is likely to be only a couple of mA. Is there something about very-lightly-loaded Arc-Fault C.B.s that could cause the false alarms in the smoke detectors?
I think you'll find that only applies to receptacle circuits..

edit:
210.12 Arc-Fault Circuit-Interrupter Protection.
(A) Dwelling Units. All 120-volt, single phase, 15- and
20-ampere branch circuits supplying outlets installed in
dwelling unit family rooms, dining rooms, living rooms,
parlors, libraries, dens, bedrooms, sunrooms, recreation
rooms, closets, hallways, or similar rooms or areas shall
be protected by a listed arc-fault circuit interrupter,
combination-type.
 

Thread Starter

MikeML

Joined Oct 2, 2009
5,444
I think you'll find that only applies to receptacle circuits..
...
Maybe, but the commercial electrician that wired the house ran a unique circuit that goes only to the smoke detectors, and nowhere else. That circuit is protected by an Arc-Fault type of breaker.

Are you suggesting that I exchange the Arc-Fault with a standard breaker?
 

DerStrom8

Joined Feb 20, 2011
2,390
My house was built in the '70s and it has hardwired 120V smoke detectors as well. I tended to set them off by accident while running my small (4" tall) Tesla coil in the basement. Electro-magnetic interference tends to trigger them. It could be caused by a fan motor or other appliance (furnace ignitor? Air conditioner? Refrigerator cooling system?) turning on or off. Mine were on a separate breaker but I would still set them off with my TC.
 

gerty

Joined Aug 30, 2007
1,305
Maybe, but the commercial electrician that wired the house ran a unique circuit that goes only to the smoke detectors, and nowhere else. That circuit is protected by an Arc-Fault type of breaker.

Are you suggesting that I exchange the Arc-Fault with a standard breaker?
That's what I would do. And it's always recommended (but not code required) to put your smoke detectors on a dedicated circuit.
 

BR-549

Joined Sep 22, 2013
4,928
I would dis-connect the common alarm signal, run all units on DC, to find out, which unit, or which house area , is setting it off.
 

MrAl

Joined Jun 17, 2014
11,389
Hi,

We had a similar problem until all the units were updated to a newer type detector.

You could also try a small fan if you can get the air to circulate in the various areas. Might need more than one, but any small one would probably keep the air circulating.

Also, any insects around? The crawlies can get in and block the mechanism too.

A low voltage might trigger it too. You could get the modern equivalent of a chart recorder and record the voltage over time then compare to when the alarm is ok and when it goes off by accident.
 

GopherT

Joined Nov 23, 2012
8,009
My house was built in the '70s and it has hardwired 120V smoke detectors as well. I tended to set them off by accident while running my small (4" tall) Tesla coil in the basement. Electro-magnetic interference tends to trigger them. It could be caused by a fan motor or other appliance (furnace ignitor? Air conditioner? Refrigerator cooling system?) turning on or off. Mine were on a separate breaker but I would still set them off with my TC.
@MikeML
Do you have staticelectricity issues all year in Arizona or just in winter? Could it be a static issue?
 

Thread Starter

MikeML

Joined Oct 2, 2009
5,444
@MikeML
Do you have staticelectricity issues all year in Arizona or just in winter? Could it be a static issue?
In the three years we have been in the house, the highest incidence of alarms seems to be in the summer months (now). We are in the monsoon season, where moisture streams up from the gulf of Mexico, raising the relative humidity to about 35% (from our normal of 5 to 10%), so this is the time when static electricity is the least... Even at its highest, our relative humidity is a fraction of what it would be in Texas or Florida...
 
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