need horns
- Thread starter curti123
- Start date
- Status
ron
Senior Member
- Location
- New York, 40.7514,-73.9925
The horns would likely not need to be on 50' spacing unless the ambient noise level is high. You want to be 15 dB above ambient but not higher then ..... I think it is 110dB (look in NFPA 72 to check). Also in NFPA 72, you will find a nice table for ceiling mounted strobe spacing.
gadfly56
Senior Member
- Location
- New Jersey
- Occupation
- Professional Engineer, Fire & Life Safety
Are the joists 12' on center or is the ceiling height 12'? If the latter, then yes, for visual appliances 115 cd would get you 50' x 50' spacing for up to a 20' ceiling height (NFPA 72-2002 Table 7.5.4.1.1.(b)). You'll want to be in the center of the bay, not at the corners where the poles are. You should do a sound survey to make sure that the audible portion of the appliance will meet the requirements of 7.4.2.1.
ceiling heigth is 12-16 foot, joists are 18" below that. Quiet storage warehouse, good echo, but when full at times would absorb sound better. spoke with ahj, wants the 50' spacing but will allow them 3 years to get to full compliance. good guy. gonna put 1/3 (10ea.) of horns in this year and owner must increase by 1/3 ea. yr and in 2012 be fully compliant. Very hard hit economy as far as jobs lost and does not want to incurr excessive costs at one time. what do you think?
gadfly56
Senior Member
- Location
- New Jersey
- Occupation
- Professional Engineer, Fire & Life Safety
Not a bad plan. I've recently designed this very type of coverage for a client. Make sure you lay out your notification zones very carefully. At 115 cd, your horn/strobes will be power hogs. You probably won't get more than 7-8 devices per notification zone. Also, you need to watch the length of your wire runs to keep voltage drop within limits. Whether there is an existing panel or it's all new equipment, use a power booster with 6, 8, or 9 amps of total output to power the devices in the warehouse; save the panel NAC's for the office area (if any) or sprinkler water flow.
Weaver Road
Member
- Location
- Willington, CT
I agree with this info, however, remember that in most places (codes) the final test of compliance is performance. If you have followed all of the recommended spacing and the visual or audible performance is below those requirements (high ambient noise or dark surfaces absorbing light or bright windows wiping out your visual signal), you are not compliant.
As gadfly56 said, survey what you can before final design is done.
I don't think the AHJ should put the lives of the people that maybe inside this building, for
the next three years, for the sake of 20 devices installed. I understand he is trying to be
easy on the owner, but, imo, life saftey is not the area to do it in. The AHJ is required to
make correct decisions based on the written amendments, in this case I'm not sure if he did.
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