Douglas Krantz - Technical Writer - Describing How It Works

Is the Fire Alarm Sounder Compatible?

To be compliant, the combination of a particular fire alarm panel and a particular fire alarm sounder have to be tested by a testing laboratory like UL, ULC, CE, CCC, FM, Etc. and put on their list of devices that work together.

Is the Fire Alarm Sounder Compatible?

Is the Fire Alarm Sounder Compatible?

Greetings Douglas,

I have a technical query regarding the installation of "VTG-32E" sounder (approved to EN 54-3) with ELITE (K-1480) UL listed panel. The sounder has a voltage limit of 21.6 - 28Vdc 10%. My question is whether it is a Compatible to the UL listed panel or not? Because the panel is 24V and as per voltage drop calculation method by UL, the terminal voltage starts from 20.4 V (85% of the terminal voltage).

If Compatible, how to do the voltage drop calculation as UL standard (considering 85% of the terminal voltage). I have attached herewith the datasheet of the sounder and panel.

Thank you, RJ

Legal - Compatible

In a fire alarm system, the term "Compatible" is a legal term meaning "It has been tested by a third-party, nationally known testing laboratory like UL, ULC, CE, CCC, FM, etc., and found to work in a particular fire alarm system." The testing laboratory, if they have found it to work as a system (the fire alarm panel and the sounder working together) then they will have "listed" as "Compatible" because they work together.

The people that would have hired the testing laboratory will know if it is "Listed as Compatible". Either the manufacturer that makes the fire panel or the manufacturer that makes the sounder will have this combination tested (this particular panel connected to this particular sounder).

There's a small chance that the fire alarm manufacturer or sounder manufacturer has had it tested and listed. To find out for sure, you have to contact both manufacturer's technical service departments and find out.

Practical - Legal - Compatible

If this is being used for a NAC circuit (Notification Appliance Circuit), all horns, strobes, speakers, etc. have to be listed by the testing laboratory as being Compatible; or not having been tested, you don't know if the combination will work.

I have seen where horns or strobes have been replaced, and the replacements were not listed as being "Compatible". Some of these non-Compatible devices did not work at all, some of these non-Compatible devices worked very intermittently, some of the non-Compatible did work while I was on site, but may not have worked during a power blackout.

Some of the problems involved the synchronization methods used for the various NAC systems. Each manufacturer has a different method of synchronization. It never works to use a device that is not properly synchronized using the method that the panel sends out.

Technical - Works Together

Short of being Compatible, there are technical aspects.

The power supply of the panel uses the word "Regulated". Usually, the words 24 volts regulated means that no matter what happens to the utility voltage, the output will stay at 24 volts. But the specifications aren't complete enough to know for sure if that is what the manufacturer really means.

Both UL and FM have their stamps on the sheet, but there isn't enough information on the sheet to know if the panel will power the sounders properly.

No Diode Inside the Sounder

The power supply does not say that the DC voltage for the sounder is polarized.

All fire alarm horns are polarized so when they are turned off, they will not use any electrical current while the NAC circuit is being wire-supervised. Then, when the voltage on the NAC is reversed to sound the alarm, the sounder will sound off.

If voltage polarity isn't an issue with the sounder, it will not ever work properly on a fire alarm NAC circuit.

Is It Compatible?

Unless the manufacturer of the panel or the manufacturer of the sounder can say, in writing, that this particular combination is listed as being compliant, it is not usable at all.

Douglas Krantz
Life Safety
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