# Duct Smoke Detector not Tripping



## Hoons (Jun 23, 2014)

Hello all,

Did not see any topic on this by seaching so thought I'd start a new thread...

We have an issue where we can't get the minimum distance downstream from a tee to install the duct detector.

We verfied it's getting the correct pressure differential and velocity and we're using smoke bomb to test the photoelectric sensor.

Still not tripping... any advice on how to test the sensor?

Thanks

Hoons


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## cda (Jun 23, 2014)

I take it holes are oriented correctly

Correct tube is installed

Plug is installed , if required

Have you taken the housing off and smoked it to make sure it works???

Does the panel/ detector have  verification ??? May be the problem

Air movement to fast???


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## Hoons (Jun 23, 2014)

we verfied the head and board functions by taking the cover off.

I spoke with manufacturer's rep about the orientation of the sampling and exhaust tubes and he said it doesn't matter...


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## cda (Jun 23, 2014)

Hoons said:
			
		

> we verfied the head and board functions by taking the cover off. I spoke with manufacturer's rep about the orientation of the sampling and exhaust tubes and he said it doesn't matter...


Interesting and strange

Download the instructions and see what they say

Air movement to fast??

Do you have the model and number

Is it set for verification??

Correct tube length ?


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## cda (Jun 23, 2014)

Sorry should have asked if these are tied into a building fire alarm system


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## cda (Jun 23, 2014)

Does the duct smoke go into alarm/ latch??  But not shut the unit down?


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## Hoons (Jun 24, 2014)

cda said:
			
		

> Interesting and strangeDownload the instructions and see what they say
> 
> Air movement to fast??
> 
> ...


It's Simplex 4098-9755, their TruAlarm photoelectric sensor. It has correct tube length. What do you mean by is it set for verification? We've already verfied the head and board works by spraying directly if that's what you're asking...


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## Hoons (Jun 24, 2014)

Yes, it won't go into alarm


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## cda (Jun 24, 2014)

http://xtra.simplexnet.com/a_e/FA/4098-0030.PDF

check page three for tube orientation requirement


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## cda (Jun 24, 2014)

Hoons said:
			
		

> It's Simplex 4098-9755, their TruAlarm photoelectric sensor. It has correct tube length. What do you mean by is it set for verification? We've already verfied the head and board works by spraying directly if that's what you're asking...


What do you mean by is it set for verification?

in the old days and maybe still today, to avoid false alarms,

the detector  would sense something, but would not go into alarm, it would cycle and if it sees something the second time, it would go into alarm

kind of a delay

3.3.16 Alarm Verification Feature.   A feature of automatic fire detection and alarm systems to reduce unwanted alarms wherein smoke detectors report alarm conditions for a minimum period of time, or confirm alarm conditions within a given time period after being reset, in order to be accepted as a valid alarm initiation signal. (SIG-PRO)

problem is when you are testing a system with verification you basically have to continually smoke the device, while it cycles, to get the thing to actually go into alarm.

what is the alarm company saying????  If they know what they are doing they should be able to solve this.


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## cda (Jun 24, 2014)

and the tubes are the correct length, check the bottom of page two, for the ducts in place

http://xtra.simplexnet.com/a_e/FA/4098-0030.PDF


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## Ronald Bets (Jun 26, 2014)

"we can't get the minimum distance downstream from a tee to install the duct detector. " There is a reason for that  minimum distance.


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## Francis Vineyard (Jun 26, 2014)




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## Ronald Bets (Jun 26, 2014)

Congratulations! You have learned the laws of air dynamics.


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## Francis Vineyard (Jun 26, 2014)

Ronald Bets said:
			
		

> Congratulations! You have learned the laws of air dynamics.


From working on automobiles and heavy-duty trucks for 22 yrs. no less.


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## cda (Jun 26, 2014)

http://www.usfa.fema.gov/downloads/pdf/coffee-break/cb_fp_2012_31.pdf


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## Dr. J (Jun 27, 2014)

NFPA 72 Table 10.4.4.2

Smoke detector test method:

"_The detectors shall be tested in place to ensure smoke entry into the sensing chamber and an alarm response. Testing with smoke or listed aerosol approved by the manufacturer shall be permitted as acceptable test methods. Other methods listed in the manufacturer’s published instructions that ensure smoke entry into the sensing chamber shall be permitted."_

Duct detector test method:

_"Air duct detectors shall be tested or inspected to ensure that the device will sample the airstream. The test shall be made in accordance with the manufacturer’s published instructions."_

Translation: you squirt canned smoke into the housing to confirm the detector will actually sense smoke, and you measure DP in the tubes to confirm the airstream is being sampled.

If these two methods are successful, you pass.

NEVER USE SMOKE BOMBS FOR ANY SORT OF FIRE/LIFE SAFETY TESTING!!!!  WRONG WRONG WRONG!!!


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## cda (Jun 27, 2014)

Dr. J said:
			
		

> NFPA 72 Table 10.4.4.2Smoke detector test method:
> 
> "_The detectors shall be tested in place to ensure smoke entry into the sensing chamber and an alarm response. Testing with smoke or listed aerosol approved by the manufacturer shall be permitted as acceptable test methods. Other methods listed in the manufacturer’s published instructions that ensure smoke entry into the sensing chamber shall be permitted."_
> 
> ...


I was wondering about that

Never seen it done , heard of it

But still the question why didn't the detector alarm


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