Douglas Krantz - Technical Writer - Describing How It Works

How Long can the Wire be to the Input Module?

The NFPA doesn't say anything about wire length in their code. The manufacturer has had it tested, and the testing laboratory has put it on their List as working. The NFPA then says an equivalent of "If it is Listed for use there, it's fine with the NFPA".

How Long can the Wire be to the Input Module?

Greetings Douglas,

I have a situation where I have to prove to a government FPE (Fire Protection Engineer) that my IDC (Initiating Device Circuit) 9 coming off an addressable intelligent module can be longer than 10 feet [3 meters]. I am looking for chapter and section from NFPA 72 or another code to list my answer back to him.

I have called my manufacturers (Notifier and System Sensor) but they only state 'a long ways' to me, or System Sensor told me 760 meters at 18awg. But neither could give me a fact from code or from their data sheets other than 'IDC wiring resistance of 1500 ohms'. This just isn't going to cut it.

The government FPE is just being really difficult. He is listing NFPA 72 code on SLC requirements at the same time he is rejecting my submittal on IDC.

If you can give me any help, as quickly as you can, it would be greatly appreciated.

Thank you, TC

This is a multi-level, NFPA Code/Authority Having Jurisdiction (AHJ)/Manufacturer Listing problem. You are required to educate yourself, and then educate the government on the actual relationship of all parties involved.

No. The National Fire Protection Association, Inc. Code (NFPA Code) does not approve the exact wiring of the Initiating Device Circuit (IDC). They also don't forbid any exact wiring of the IDC.

They write legal code that can be used by governments; they don't design anything, including wiring for the IDC.


I'd give you actual code numbers, but the numbers themselves keep changing; the actual rules themselves don't change much. You can look up the numbers yourself when you show this to the government.

In the front of the Code book are definitions. The first definition shown is for the word "Approved". The Code Listing says:

"Approved. Acceptable to the Authority Having Jurisdiction."

In the annex or appendix at the back of the NFPA Code is a further explanation of the Code as it relates to the actual rule. The official annex starts out with:

"Approved. The National Fire Protection Association does not approve, inspect, or certify any installation, procedures, equipment, or materials; nor does it approve or evaluate testing laboratories. In determining acceptability of installations, procedures, equipment, or materials, the authority having jurisdiction may base acceptance on compliance with NFPA or other standards. In absence of such standards, the authority may require evidence of proper installation, or use. The authority having jurisdiction may also refer to listings or labeling practices of an organization that is concerned with product evaluations and is thus in a position to determine compliance with appropriate standards for the current production of listed items."


All fire alarm systems are required by the NFPA to be listed for use by a Nationally Known Testing Laboratory like UL, FM, ULC, CE, CCC, etc.

To be listed, the system has to be fully tested and found to work for use in a fire alarm system. This includes the wire size and length. If the wire itself is FPL, FPLR, or FPLP, the wire is listed to be used for fire alarm systems.

The manufacturer doesn't do this testing. The manufacturer pays the laboratory (UL or FM) to test the fire alarm system, and then if it works, place the design of the fire alarm system on the testing laboratory's list of items found to work. If the system is listed for use in a fire alarm system, the NFPA says that as far as they are concerned, it's suitable for use.

The technical support people for System Sensor know this. If an installation, procedure, particular material, exact equipment isn't listed, they won't tell you that it can be used.

Also, the installation sheets that come with the equipment, and the input modules, have a UL or FM stamp. Even the installation sheets have been tested and listed by UL or FM. On any piece of paper, if the testing laboratory's stamp is on there, it is listed for use.

Authority Having Jurisdiction (AHJ)

To see what role the AHJ has in all this, see:

Just Who Is the Authority Having Jurisdiction (AHJ)?

Yes. The AHJ can require more stringent installations than are shown in the NFPA (like shorter wires), but it's the AHJ's decision; not the NFPA's decision nor the manufacturer's decision.

Douglas Krantz
Life Safety
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