# Wiring for residential smoke alarms under 2008 NEC



## jeffers (May 13, 2010)

I am doing the electrical work in connection with an addition. The town inspector told me that under the 2008 NEC the interconnected smoke alarms must be wired with MC not NM cable (I already installed it with NM cable as per my approved permit application) and do not need AFCI protection. I think he is confusing this with the "fire alarm system" requirements which are different than residential smoke alarms put in hallways, bedrooms, etc. Does the 2008 NEC require these smoke alarms to be installed with MC cable and not use AFCI?


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## Scuba_Dave (Jan 16, 2009)

Where are you located ?
Only NM needed here


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## jeffers (May 13, 2010)

In New Jersey. The town uses the 2008 NEC and told me that this is required under the 2008 NEC.


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## Scuba_Dave (Jan 16, 2009)

Did he cite a specific code reference ?


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## sparks1up (May 5, 2010)

NM is ok here in Miami too! But they are now requiring some of the detectors be combination smoke/carbon monoxide detectors.

I would simply ask him where you can find that in the code! And if he is wrong...and I am pretty sure he is I would then ask him how he comes to that interpretation!


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## HouseHelper (Mar 20, 2007)

I don't have the 2008 handy, but there are 2 exceptions in the section concerning AFCI protection in dwellings that allow for no AFCI protection to be necessary if the wiring in in AC conduit (or other metal conduit). Sorry I don't have to full text available.


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## HooKooDooKu (Jan 7, 2008)

I did a little searching in the code, and while some of it is a bit conflicting, I can see where your inspector is making the argument that MC cable is required.

First of all, I'm going to argue that a "Residential Smoke Detector" and a "Fire Alarm System" are the same thing. 

[UPDATE: Based on the definision of a "Smoke Detector" as supplied by the IFC, I no longer make this argument. The rest of this post is now irrelevant, other than to indicate AFCI protection is required for smoke detectors]. 

The reason is because R313.1 of 2006 IRC says that a smoke alarm must be installed per NFPA 72, and 760.1 of 2008 NEC says that a "Fire Alarm System" must be installed per NFPA 72. Additionally, the NEC makes no reference to "smoke alarm" (I did a word search, and you won't find those words in the NEC), and 760.1 FPN No. 1 of 2008 NEC states that "Fire alarm systems include fire detection and alarm notification...", which sounds like a smoke detector to me. So unless there is something that NFPA 72 says otherwise, I think an AHJ can claim a "Residential Smoke Detector" is a sub-set of a "Fire Alarm System".

Now here's where the wording gets a bit aquard, but I think it's where the AHJ gets the requirement for MC...

760.41(B) and 760.121(B) specify that a fire alarm system must be powered from its own branch circuit, and that circuit shall not be protected by AFCI or GFCI. However, 210.12(B)Ex.2 (poorly worded) seems to say AFCI isn't required for a fire alarm system IF the power source is installed in RMC, IMC, EMT, or steel armored cable.

In general it seems that 210.12(B) is saying AFCI protection isn't required IF the cable is protected by MC or conduit (i.g. if you run conduit from the circuit breaker to the 1st outlet, you can place an AFCI in the outlet to protect the circuit rather than an AFCI breaker). However, 760 is basically saying you can't use an AFCI... therefore taken together, since the smoke detectors can't be protected by AFCI, then the wiring must be protected by MC or conduit.


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## Jim Port (Sep 21, 2007)

The is no prohibition in the NEC from using NM in a dwelling to wire a smoke alarms.

A smoke alarm in a house is not a fire alarm system.


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## HooKooDooKu (Jan 7, 2008)

Jim Port said:


> The is no prohibition in the NEC from using NM in a dwelling to wire a smoke alarms.


Can't argue with that from the stand point of NEC never uses the words "smoke alarm".



Jim Port said:


> A smoke alarm in a house is not a fire alarm system.


But if you don't include a smoke alarm under the umbrella of a "fire alarm system", then there isn't anything in the NEC that grants an exception to smoke alarms from being protected by an AFCI. 

210.12(B) specifies that ALL 15 and 20 amp branch circuits that supply outlets to family rooms, living rooms, bedrooms, hallways, et.al. (i.e. all the places you install a smoke detector) must be protected by an AFCI. The only exception that completely eliminates any sort of AFCI protection from these rooms is for branch circuits to a "fire alarm system".

So unless there is something in NFPA 72 saying otherwise, it would seem to me that you either classify a smoke detector as a sub-set of a "fire alarm system" and wire it with MC not protected by an AFCI, or declare it simple utilization equipment and protect it with an AFCI. 

And since smoke alarms are supposed to be battery backed-up, there shouldn't be an issue with protecting the circuit with an AFCI since the detectors should still function even if the breaker trips.


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## HooKooDooKu (Jan 7, 2008)

Jim Port said:


> A smoke alarm in a house is not a fire alarm system.


The best argument I can find to support this claim is the 2006 IFC where section 902 defines a Smoke Alarm as "A single- or multiple-station alarm
responsive to smoke and not connected to a system."

But the IFC doesn't provide an exemption from AFCI protection because it only states "Wiring shall be permanent and without a disconnecting switch other than as required for overcurrent protection."


So unless NFPA 72 says otherwise, it sounds like to me that NM cable is fine for smoke detectors, but the power for the smoke detectors has to be protected by an AFCI breaker.


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## jeffers (May 13, 2010)

Thanks for all of your responses. I am new to this and it is great to see some real thoughtful responses. I think that the inspector is definitely considering the system as an alarm system. I found some information from a another location from Mike Holt, an NEC consultant and he states that smoke alarms must be AFCI protected and that _The exemption from AFCI protection for the “fire alarm circuit” contained in 760.41 and 760.121 doesn't apply to the single and multiple station smoke alarm circuit typically installed in dwelling unit bedroom areas. This is because a smoke alarm circuit isn't a fire alarm circuit as defined in NFPA 72, National Fire Alarm Code. Unlike single and multiple station smoke alarms, fire alarm systems are managed by a fire alarm control panel. _


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## sparks1up (May 5, 2010)

> First of all, I'm going to argue that a "Residential Smoke Detector" and a "Fire Alarm System" are the same thing.


The reason you don't need AFCI for a fire alarm system is because it is a low voltage system run from a remote panel. So the panel doesn't need to be protected by AFCI. 

A 120-volt powered smoke detector needs to be fed via AFCI and it is NOT a fire alarm system!


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## Jim Port (Sep 21, 2007)

jeffers said:


> Thanks for all of your responses. I am new to this and it is great to see some real thoughtful responses. I think that the inspector is definitely considering the system as an alarm system. I found some information from a another location from Mike Holt, an NEC consultant and he states that smoke alarms must be AFCI protected and that _The exemption from AFCI protection for the “fire alarm circuit” contained in 760.41 and 760.121 doesn't apply to the single and multiple station smoke alarm circuit typically installed in dwelling unit bedroom areas. This is because a smoke alarm circuit isn't a fire alarm circuit as defined in NFPA 72, National Fire Alarm Code. Unlike single and multiple station smoke alarms, fire alarm systems are managed by a fire alarm control panel. _


Now you have the best answer and why your inspector is incorrect. In the beginning of the NEC Article is a defintion of what that article applies to. Article 760 would be like an alarm panel in a commercial building with tamper switches, flow switches, pull stations etc.


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## jbfan (Jul 1, 2004)

Smoke detectors have had to be afci protected since the 05 code cycle(if I remember correctly)

Like was stated, your inspector must be confusing a SD for a fire alarm system.


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