Let’s take a look at a couple of questions workers in the field asked about the requirements that affect their fire alarm system installations.

How do I use 177-candela (cd) visible notification appliances on a 24V DC fire alarm system when 177-cd appliances require 120V AC? How would one monitor the integrity of the circuit connected to this appliance?

First of all, contact the manufacturer of the fire alarm system control unit you intend to use to determine how they recommend you connect 177-cd visible notification appliances to the unit. This information may be in the installation manual for the fire alarm system control unit. Very few people realize that the nationally recognized testing laboratories review the contents of the installation manual for a particular piece of fire alarm equipment and include that manual in the equipment listing.

Of course, you normally use 177-cd visible notification appliances only in sleeping areas where the distance from the ceiling to the top of the lens of a wall-mounted visible notification appliance is less than 24 inches. This distance describes the anticipated depth of a smoke layer during the initial stages of a fire in the room. 

Listed 177-cd visible notification appliances that operate on 120V AC include a means within the appliance to monitor the availability of power and operate a set of contacts should the power fail. NFPA 72-2022, National Fire Alarm and Signaling Code, provides for operating interfaced equipment in Chapter 21. This chapter includes a requirement to monitor the integrity of the interconnecting means. 

An installation contractor could use a fire alarm output from the fire alarm system control unit to connect to the 120V AC powered 177-cd visible notification appliance. This same circuit could monitor the contacts of the appliance that indicate the loss of AC power.

It’s been a repeating battle with salespeople who insist we move forward with what they sold, only to be told by an AHJ that something else needs to be done. We end up looking dumb in front of the owner. Where does it state that a panel replacement does or doesn’t require you to bring the whole protected premises up to code? My understanding was if it was a defective fire alarm control panel (not working for any number of reasons) that a panel-for-panel replacement was allowed without any other code updates required. But if the panel is just being upgraded, when does the whole system need to follow suit?

I am pretty sure there is no exact code requirement that answers your question. In my opinion, when the fire alarm control unit (FACU) is replaced, the system will need to be upgraded when it is not compatible with the existing devices, or the new devices you might be installing will potentially require a new FACU. Or if the FACU is obsolete and is replaced, then it’s a good chance the system will need a total upgrade.

That said, here is what my research turned up:

NFPA 1, 13.7.1.5.7: The system owner shall replace required fire alarm systems that cannot be serviced or repaired to eliminate system impairments or chronic nuisance alarms [AHJ opinion].

NFPA 101, 29.3.4.3.6: Where the existing fire alarm system does not provide for automatic emergency forces notification in accordance with 9.6.4, provisions shall be made for the immediate notification of the public fire department by telephone or other means in case of fire, and, where there is no public fire department, notification shall be made to the private fire brigade.

NFPA 101, 29.3.4.3.7: Where a new fire alarm system is installed or the existing fire alarm system is replaced, emergency forces notification shall be provided in accordance with 9.6.4.

International Fire Code (IFC-2018), 907.5.2.3 Visible alarms: Visible alarm notification appliances shall be provided in accordance with Sections 907.5.2.3.1 through 907.5.2.3.3. Exceptions: 1. Visible alarm notification appliances are not required in alterations, except where an existing fire alarm system is upgraded or replaced, or a new fire alarm system is installed.

Nothing in the above requires FACU replacement when you replace or add smoke detectors to an existing system. However, if the AHJ has experienced a large number of false alarms from the facility, they may require a new FACU when the smoke detectors are replaced.

As stated earlier, the FACU replacement may generate a whole system upgrade, especially if the new one is not compatible with the existing smoke detectors. 

Ultimately it may be the AHJ’s call, but you are responsible for checking with them before attempting to install what the salesperson sold.

I also recommend that when bidding on a device replacement, you look at the FACU, call the manufacturer and find out how long the FACU will be supported with replacement parts. Then it may be your responsibility to advise the owner before the AHJ steps in and requires it.

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