How would buildings go after supervising AC signals on modern FACPs?

This isn’t really a ‘help’ topic, but I’ve seen youtube videos where some panels have both AC and DC devices on the same NAC/Gong circuit, or straight out AC horns/bells in every corner with no modern devices. Some AC devices made in the early 2000s by Faraday even have UL listings for “general fire alarm” instead of non-fire signaling purposes, so I suppose maybe certain NAC boosters can have a “sprinkler” output for something like a Wheelock FARR-LARM to go off at?

There is one building we do, that used to have an Edwards 1523 panel. They had 120V Edwards bells all around the place. When the system was upgraded to a Simplex, they kept the 120V bells. What they did, was take the signal circuit output from the Simplex panel, and hooked it up to a relay, which triggered the 120V bells in alarm.

As far as supervision, I don’t think it really worked for that system. The other issue was when the power failed in the building, the bells wouldn’t work, as they were 120V. They did do an upgrade and added 24VDC horns and took out the bells finally.

The only way you could see an AC and DC device working on the same NAC is if the DC device is getting power from an AC/DC converter (like the SpectrAlert Advance 120V from System Sensor - which is just a regular 24VDC SpectrAlert Advance with a 120VAC-24VDC power adapter built into the backplate!)

AC N/As have been obsoleted for years, but on the old school AC panels, the AC horns were series wired for supervision. The only way you’ll drive an AC horn from a DC based panel is through a relay. If you do that, make sure you know for sure what the AC signals need for voltage (in the series-wired NACs you multiply the signal’s rated voltage by the total number of signals) and supply that to the relay. You won’t have any supervision in this case, and as has also been said, the AC signals would not work in a power failure.

In modern installations you will occasionally see a 120VAC sprinkler bell and it’s normally connected directly to the auxiliary contacts of the waterflow switch.

In modern installations you will occasionally see a 120VAC sprinkler bell and it’s normally connected directly to the auxiliary contacts of the waterflow switch.

In Minnesota, you see a lot of Wheelock FARR LARMs used instead of sprinkler bells. Thanks for your answer btw. Do NAC signals HAVE to be supervised for it to be up to code, or is it a building management decision?

The NFPA fire alarm code technically isn’t law, just guidelines on industry-accepted best practices to design and install fire alarm systems. And NFPA code absolutely requires every NAC to be supervised.

Now let me make an important distinction: what the rules are depend on where you live. The local “authority having jurisdiction” (could be college campus board of directors, could be city electrical inspector, could be the fire chief… it all depends on where you live) gets the final say on how fire alarm systems under their jurisdiction must be wired. Now, 90% of them simply adopt the NFPA’s code and say “that’s our laws.” But some of them make changes or have different requirements. I have never heard of a single AHJ not requiring supervised NACs.

Additionally, many AHJs require that if you make a significant change to a severely outdated fire alarm system, you’ll be required to bring the entire system up to code. I.e. if you have an AC fire alarm system from 1967, replacing a failed pull station is fine, but if you build a whole new wing requiring new signals and pull stations, the AHJ is likely going to tell you that your entire fire alarm system must be upgraded to meet current standards. To know for sure, find out who your local AHJ is and review their code.

As to substituting sprinkler bells for other signals, again, the local AHJ will have the final say on what does and doesn’t fly, i.e. bells are preferable since they create a separate sound from the fire alarm system. But in most cases, they just want to see some signal that the sprinkler system is activated.