Residential Smoke Alarms

tom baker said:
I wired my 120v smokes with 14-3 as they are interconnected on a separate ckt. Building dept required them to be interconnected. They are battery backed up. Now thankfully smokes have a ten year battery which is the life of a smoke det
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That’s the most common practice when wiring 120 volt interconnected smoke alarms , they are fed by a branch circuit described by art 210 !
 
Jaybone812 said:
No I wouldn’t I disagree .and 760.41(b) says as much, and if it was 120 volt interconnected smoke alarms would need to be supplied by a individual branch with a disconnecting means that has a red identification .
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Yeah thats what he failed me on no red identification, I thought for sure he'd want a AFCI, I had intended to wirenut it onto a AFCI bedroom lighting circuit in the panel.
If the following conditions were met it could be a NPLFA circuit;
Had to be
  • on a circuit with no loads other than somke / heat or combo CO detectors ,
  • battery backed,
  • inter connected and have a hush button (thus forming a system)
to qualify as a NPLFA circuit then 760.41(b) and 760.3 applies so I guess they had a meeting about it, I just checked the state code and there is no amendments so its an interpretation of a non-NEC defined term a 'fire alarm system'. In the definition in NFPA 72 of 'fire alarm system' pretty general in scope;

Fire Alarm System. A system or portion of a
combination system that consists of components and
circuits arranged to monitor and annunciate the status
of fire alarm or supervisory signal-initiating devices and
to initiate the appropriate response to those signals.
[2019 NFPA 72 section 3.3.111]
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They look at the risks pros/cons I guess they think its more important smoke / heat / CO alarms have reliable 120V power than any benefits AFCI protecting such a circuit would offer.
 
Jaybone812 said:
A fire alarm system is monitored as well
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I don't know a lot the lesser details about fire alarms, but this is one aspect that typically makes a network of general use smoke alarms not a fire alarm system. They would need to tie into some control panel where monitoring can be incorporated. How much monitoring is required? IDK. Typical fire alarm systems you see in public access buildings have supervised circuits, so it can tell if there is a trouble condition in those circuits. How does one do that with the typical residential smoke alarm network that all run parallel to one another?
 
kwired said:
I don't know a lot the lesser details about fire alarms, but this is one aspect that typically makes a network of general use smoke alarms not a fire alarm system. They would need to tie into some control panel where monitoring can be incorporated. How much monitoring is required? IDK. Typical fire alarm systems you see in public access buildings have supervised circuits, so it can tell if there is a trouble condition in those circuits. How does one do that with the typical residential smoke alarm network that all run parallel to one another?
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If you go by the definition of a fire alarm system in NFPA 72 none of those are criteria to meet the definition of a fire alarm system, but since fire alarm system is not a NEC defined term its entirely up to the AHJ.
The AHJ here considers it when it meets these criteria:
fire_alarm_circuit.png
 
Jimmy7 said:
When wiring a new home do you put the smoke detectors on their own circuit, or do you put them on with a lighting circuit? I know some people put them on with a lighting circuit so the homeowners won’t turn the circuit breaker off and keep it off. Is there a code anywhere on this?
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Here's something that might help, the NFPA 72, 10.6.5.2 The branch circuit supplying the equipment shall have no other loads. IMO if there is a fire alarm system then you would need to put it on its own circuit.
 
Simple said:
Here's something that might help, the NFPA 72, 10.6.5.2 The branch circuit supplying the equipment shall have no other loads. IMO if there is a fire alarm system then you would need to put it on its own circuit.
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Its not a 'system' unless you put them all on their own circuit.
 
tortuga said:
Yeah thats what he failed me on no red identification, I thought for sure he'd want a AFCI, I had intended to wirenut it onto a AFCI bedroom lighting circuit in the panel.
If the following conditions were met it could be a NPLFA circuit;
Had to be
  • on a circuit with no loads other than somke / heat or combo CO detectors ,
  • battery backed,
  • inter connected and have a hush button (thus forming a system)
to qualify as a NPLFA circuit then 760.41(b) and 760.3 applies so I guess they had a meeting about it, I just checked the state code and there is no amendments so its an interpretation of a non-NEC defined term a 'fire alarm system'. In the definition in NFPA 72 of 'fire alarm system' pretty general in scope;


They look at the risks pros/cons I guess they think its more important smoke / heat / CO alarms have reliable 120V power than any benefits AFCI protecting such a circuit would offer.
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And that’s not a code correct interpretation at all IMO because 760.41 isn’t applicable at all based on the fact the feed is not supplying a fire alarm system , it supplies 120 volt interconnected life safety devices that are not part of a monitored system, and the NFPA says that this is a 210 branch circuit so 210.12 is applicable to outlet locations in areas /rooms listed in 210.12(B) , which is why the battery backup is required
 

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tortuga said:
It’s not a 'system' unless you put them all on their own circuit.
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Which is why its not considered a fire alarm system, there’s no requirement to put the 120 volt interconnected smoke alarms on a individual branch circuit , the nec makes no mention of the type of 210 branch circuit, and it can’t be a 210 branch circuit if the life safety devices share their circuit , but then a 760.41 circuit if you choose to supply the devices with a individual branch circuit, that’s not how our code works
 
tortuga said:
If you go by the definition of a fire alarm system in NFPA 72 none of those are criteria to meet the definition of a fire alarm system, but since fire alarm system is not a NEC defined term its entirely up to the AHJ.
The AHJ here considers it when it meets these criteria:
View attachment 2575999
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Where do you put that circuit disconnecting means that is required to be accessible only to qualified personnel? Especially in a dwelling?
 
tortuga said:
The guy is a smart inspector and more knowledgeable in fire alarm code / terms than me
Would you agree a NPLFA Circuit in a residential occupancy is not subject to 210.12?
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You can't have a NPFLA circuit unless you have a fire alarm control panel. Household smoke alarms are not connected to a fire alarm control panel.
 
Jaybone812 said:
If a actual fire alarm system was installed in a residential dwelling which does happen, then the circuit supplying the power for the fire alarm system would be considered NPLFA and 760.41(b) prohibits afci/gfci protection of that circuit
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I don't agree. The power supply to the fire alarm control panel is never a NPLFA circuit. NPLFA and PLFA circuits are always supplied by a fire alarm control panel.
 
3.3.120.2 Household Fire Alarm System.
A system of devices that uses a fire alarm control unit to produce an alarm signal in the household for the purpose of notifying the occupants of the presence of a fire so that they will evacuate the premises. (SIG-HOU)

3.3.117* Fire Alarm Control Unit (FACU).
A component of the fire alarm system that receives signals from initiating devices or other fire alarm control units and processes these signals to determine part or all of the required fire alarm system output function(s). (SIG-PRO)
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Interconnected household smoke alarms do not have a fire alarm control unit.
 
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don_resqcapt19 said:
I don't agree. The power supply to the fire alarm control panel is never a NPLFA circuit. NPLFA and PLFA circuits are always supplied by a fire alarm control panel.
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While thats typically the case its not mandated by the definition in article 100.
kwired said:
Where do you put that circuit disconnecting means that is required to be accessible only to qualified personnel? Especially in a dwelling?
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Its a breaker in the loadcenter, if your qualified to push the hush button ....
don_resqcapt19 said:
Interconnected household smoke alarms do not have a fire alarm control unit.
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I dont see how that applies to a NPLFA circuit or the lack of a NEC definition of a Fire Alarm System.
 
don_resqcapt19 said:
I don't agree. The power supply to the fire alarm control panel is never a NPLFA circuit. NPLFA and PLFA circuits are always supplied by a fire alarm control panel.
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After reading your comment I went back to 760.41 and I feel I was wrong and you are def correct . The power supply couldn’t be considered a NPFLA circuit because it would be the power supply for the fire alarm system , not supplied by the fire alarm panel .Thank for the correction Don!!
 
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tortuga said:
While thats typically the case its not mandated by the definition in article 100.

Its a breaker in the loadcenter, if your qualified to push the hush button ....

I dont see how that applies to a NPLFA circuit or the lack of a NEC definition of a Fire Alarm System.
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NFPA 72 and not NFPA 70 has purview on this. There are multiple places in 72 where circuits for fire alarms are mentioned, and other that the power supply circuit, they all originate at the fire alarm control panel.
 
don_resqcapt19 said:
NFPA 72 and not NFPA 70 has purview on this. There are multiple places in 72 where circuits for fire alarms are mentioned, and other that the power supply circuit, they all originate at the fire alarm control panel.
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NFPA 72 is not enforcable here on a dwelling, and 760 does not pull in anything from NFPA 72 by reference.
 
tortuga said:
NFPA 72 is not enforcable here on a dwelling, and 760 does not pull in anything from NFPA 72 by reference.
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Correct me if I’m wrong but didn’t the inspector reference 760.41 when explaining his interpretation? 760.41 references the power supply for NPFLA circuits , which isn’t in itself a NPFLA circuit .
 
Jaybone812 said:
Correct me if I’m wrong but didn’t the inspector reference 760.41 when explaining his interpretation? 760.41 references the power supply for NPFLA circuits , which isn’t in itself a NPFLA circuit .
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I was going off the diagram in post #44 and the definition of 'fire alarm circuit' in the NEC.
Gadfly corrected me that the NFPA 72 does apply by refrence in our residential code:
R314.7.1 General
Fire alarm systems shall comply with the provisions of this code and the household fire warning equipment provisions of NFPA 72
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