Smoke alarms

[Len Couey]

Inspected a home today, had just checked the alarms by manuel test and worked ok. Turned on the heat at air handler and the wiring shorted out and burned in two. Smoke alarm did not respond, checked with smoke test later (after scare from heater wiring buring up) they did not work these are all wired togeather one goes all go. Just checking to see what could be the problem. The same guy that did the splicing on the Heating unit also installed the smoke alarms. I checked four of the units using smoke test and none of them worked. If you manuely tested all seemed to be ok.

Any thought or Ideas.
P.S The Heat power cords were Dryer type plug in ??? is this ok

Thanks
Len Couey

[Rick Cantrell]

"Inspected a home today, had just checked the alarms by manuel test and worked ok. Turned on the heat at air handler and the wiring shorted out and burned in two. Smoke alarm did not respond, checked with smoke test later (after scare from heater wiring buring up) they did not work these are all wired togeather one goes all go. Just checking to see what could be the problem. The same guy that did the splicing on the Heating unit also installed the smoke alarms. I checked four of the units using smoke test and none of them worked. If you manuely tested all seemed to be ok."


There are two main types of smoke detectors, Ionization and Photo electric.
A simple description of how they work is as follows:
Photo electric detectors "see" smoke when particles of smoke enter the sensing chamber.
Ionization detectors "detect" the products of combustion, NOT smoke itself.
Your everyday, garden variety smoke detectors are most often ionization.
With ionization detectors you could have a considerable amount of smoke, but very little "products of combustion" .
So with ionization detectors the "smoke test" you performed may not cause an alarm. Even with photo detectors it takes a lot of smoke to set them off.
If they worked when you pressed the test button, most likely they work fine.

[Len Couey]

Rick, I had a house full of smoke from electrical arc and fire and the units did not work.???? I checked four of them with smoke cans and they did not work????

Len C

[Jerry Peck]

Rick, I had a house full of smoke from electrical arc and fire and the units did not work.????

How old is the house, or more importantly, how old are the smoke detectors? The smoke detectors should be replaced every 10 years.


I checked four of them with smoke cans and they did not work????

That's what Rick said would likely happen - smoke testing them may not cause them to go off.

[James Duffin]

Inspected a home today, had just checked the alarms by manuel test and worked ok. Turned on the heat at air handler and the wiring shorted out and burned in two. Smoke alarm did not respond, checked with smoke test later (after scare from heater wiring buring up) they did not work these are all wired togeather one goes all go. Just checking to see what could be the problem. The same guy that did the splicing on the Heating unit also installed the smoke alarms. I checked four of the units using smoke test and none of them worked. If you manuely tested all seemed to be ok.

Any thought or Ideas.
P.S The Heat power cords were Dryer type plug in ??? is this ok

Thanks
Len Couey

Is it possible that the smoke detectors are on the same power circuit as the AHU? Also is it possible that the smoke detectors have a set of contacts that can be used to shut off the HVAC system in the event of a fire?

[Len Couey]

Jerry, they are new old home with hard wired units when you manual test they all go off. I had a home full of smoke and nothing happened.????

Len c

[Jerry Peck]

I had a home full of smoke and nothing happened.????

I've heard it takes A LOT of smoke to set them off, and during a real fire there is A LOT of smoke, as well as a lot of products of combustion.

Based on what Rick said (Rick is the smoke alarm guy here), I would say that the "home full of smoke" was not sufficient in and of itself as the products of combustion Rick referred to would be minimal, and it would be those products of combustion which would trigger most residential smoke alarms.

Once triggered, any one of them of set all others off, yes, but it is triggering that first one.

[Rick Cantrell]

Sometimes work at a house will create dust.
May just need to be cleaned.
Also
The cheep detectors that are sold just about everywhere are not very reliable.
I bought a few cases to install in my rental properties.
I think the cost was about $40 for a case of 6.
It seemed like all of them worked, but after about 6 months some would go into alarm for no apparent reason. This went on for about a year before I replaced them all.

Anyhow, if you are in doubt, just recommend that they be replaced.

(Why the heck does "Doubt" have a "B" in it?)

[Rick Cantrell]

Len said they worked when he pressed the test button, but did not when he use canned smoke or when there was real smoke.
This got me to thinking,
On the detectors I use (fire alarm systems, not the home type detectors) the test button actually does test the smoke detectors capability to detect smoke (or products of combustion). I wonder if the test button on everyday detectors do that or just sound the sounder? I'll see if I can find out more about this.

[Rick Cantrell]

Len said he " had just checked the alarms by manuel test and worked ok. Turned on the heat".

This is from BRK they make First Alert smoke detectors.
To me it sounds like that if you test them by using the test button they are inactive for 10 minutes.

(bold added)

A Quick Homeowner's Guide to Understanding Your Smoke Alarms (http://www.brkelectronics.com/diy/quick-homeowners-guide-to-understanding-your-smoke-alarms)
Test/Silence Button: This is an easy way to make sure your smoke alarm is functioning properly. Just push and hold the test/silence button until the alarm sounds. It is important to test your smoke alarms every week to make sure they are working properly. The test button is the only recommended way to test them. If any smoke alarm does not alarm during testing, make sure it is receiving power and test it again. If it still does not alarm, replace it immediately. During testing, you will hear a loud, repeating horn pattern: 3 beeps, pause, 3 beeps, pause. When testing a series of interconnected units you must test each unit individually. Make sure all units alarm when each one is tested. This button is also used to silence unwanted or nuisance alarms and reset the Latching feature. The alarm will be silenced for about 10 minutes. The alarm can be re-tested while in silence mode by pushing the test/silence button.



And it does look like the test button actually does test the detectors capability to detect smoke.

[Matt Fellman]

On many detectors "testing" also activates the "hush" feature which would likely prevent them from going off for 10/15 minutes after testing. Any chance your fire was within that time frame?