How many Horn Strobes per circuit?

How many Horn Strobes can you put on a circuit:

You can put EIGHT wall mount 75cd horn strobes on a 1.5amp circuit coming off a NAC panel

You can put SIX wall mount 75cd horn strobes on a 1.5amp circuit coming off the FACP NAC Circuits

You can only put FOUR Ceiling mount horn strobes 177cd on a 1.5amp circuit coming off a NAC panel

You can only put SEVEN ceiling mount horn strobes 177cd on a 2.5amp circuit coming off a NAC panel

If you are several hundred feet from your power supply these answers will change..

There are different factors with this question

If the circuit is 1.5amps it has 1500mA and 20% of this is saved for SPARE so you only have 1200mA

If the circuit is 2.5amps it has 2500mA and 20% of this is saved for SPARE so you only have 2000mA

Using a ceiling mount horn strobe that is 95cd the current draw on temporal 3 is 165mA coming off a NAC panel or 198mA FWR coming off the FACP NAC panel.

Using this example take 1200mA divided by 165ma and you can put SEVEN and the coverage is 50x50 feet

If you are coming off the FACP panel NAC then the mA draw is 198mA so only put SIX on the circuit

I like to use the Potter 10amp NAC panels although many companies use the 6amp Honeywell NAC panels so you need to look at how many circuits you have and give yourself 20% spare and figure from there.

Distance from power supply - voltage line drop and wire size will affect this. Normally use 14g4c FPL cable

If you use the FACP NAC circuits use the FWR calculations which have a higher draw.

If you use a NAC panel and the circuits are 1.5amp circuits it limits how many horn strobes per circuit

If you use a NAC panel with 2.5amp circuits obviously you can have more per circuit.

Other factors are the cd and the cd or candela because a wall mount horn strobe that is 75cd has a current draw of 143mA but if you come off the panel the draw is 179 (Using System Sensor appliances as the example)

Here are some examples of coverage on a few ceiling mounted horn strobes using System Sensor

Room size - 30’ Ceiling Height - Candela - mA Draw when tied to NAC panel — How many per circuit

1.5amp / 2.5amp

50’x50’ 95cd 165mA 7 12

55’x55’ 115cd 187mA 6 10

63’x63’ 150cd 217mA 5 9

68’x68’ 177cd 254mA 4 7

Most manufactures have calculation sheets for you to do this work , years ago I was on top of a lift pulling wire and the fire marshal came by and wanted to add some horn strobes to an area and I used a piece of cardboard to do the quick calculations and later I did the official ones but I determined that I needed another NAC panel to add on to what was there doing it properly.

Wire gauge, distance, power supplies and the appliances affect the current draw and you will also need to do battery calculations to pick the proper batteries. Many companies just put standard 7amp hour batteries in the cans and hope it works. Often the calculations will required 12 volt 12amp hour batteries or 12v 18amp hour batteries so do the work before to save time and money later on.

For corrections and comments contact:

Johnson Controls SIMPLEX Fire Alarm currently has the only true ADDRESSABLE Horn Strobes and Speaker Strobes. This makes it possible to do the testing of the audibles and strobes without having to sound them off for long periods of times during your annual testing. This makes a world of difference.

Voltage and line drop and MA draw vary from product to product. Check each datasheet individually.

Larry Love Larry.Love@JCI.com

801 898 6003