horn strobe requierments

[Angel Electric]

I have an addition at land rover dealership,and ive added a strobe in the middle of a rm on the longest wall rm is rectangular 54' *24' the strobe is nearly center of the longer wall. Im being told per 7.5.4.3 nfpa 72 room spacing i have to add one more strobe.
Im in need of explaning this to my client, can anyone recite this reference so i can understand . Thanx in advance...

 

[nhfire77]

I have an addition at land rover dealership,and ive added a strobe in the middle of a rm on the longest wall rm is rectangular 54' *24' the strobe is nearly center of the longer wall. Im being told per 7.5.4.3 nfpa 72 room spacing i have to add one more strobe.
Im in need of explaning this to my client, can anyone recite this reference so i can understand . Thanx in advance...

Are there other devices in this space? What are there candela ratings? What is the candela rating of the new device?

You may (may) get away with 1 110 cd strobe as their coverage is 54'x54'. It would need to be perfectly centered on the long wall. See 2007 72 tables 7.5.4.3.1(a), 7.5.4.3.1(b)


Don't forget, the horn needs to be 15dB above ambient noise levels throughout the space, including in the far corner.

 

[nhfire77]

Just a thought, if you are adding a 110cd strobe, or any device, the battery/load calcs need to be rerun to ensure you are not overdrawing the individual circuit or the panel as a whole. Voltage drop could be an issue, although unenforcable.

 

[Angel Electric]

candelas are set 110

candelas are set 110

Im not sure how to interpret 54' *54'
I really need the reference if possible verbatim... The plans hv included new battery calc... Thanx... I appreciate the feed back.... The strobe is off center at 20' from one end of wall . This leaves 34' to inside corner.

 

[nhfire77]

Im not sure how to interpret 54' *54'
I really need the reference if possible verbatim... The plans hv included new battery calc... Thanx... I appreciate the feed back.... The strobe is off center at 20' from one end of wall . This leaves 34' to inside corner.

You need to read 72 yourself, you can for free at nfpa.org, you have to register a free account. 54'x54 is the area covered by the strobe, with the strobe in the center of a wall. 26' to one side and 26' to the other side of the wall with the device mounted on it. The other 54' is the depth off that wall.

You need another strobe, they're right. (assuming the new strobe is 110 cd or less, most are)

 

[gadfly56]

Im not sure how to interpret 54' *54'
I really need the reference if possible verbatim... The plans hv included new battery calc... Thanx... I appreciate the feed back.... The strobe is off center at 20' from one end of wall . This leaves 34' to inside corner.

54' *54' means that you can cover an area that is 54 feet wide by 54 feet long with a single strobe. Since the notification appliance is offset, you'll need to add another one.

As for verbatim reference, c'mon. If you are doing alarm work at all, you should have a copy of whatever edition of NFPA 72 your jurisdiction is using. nhfire77 gave you exactly where to look, meet him halfway.

 

[Angel Electric]

i agree i should hv a copy

i agree i should hv a copy

Thanx for the assist ..