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Clarification on two distinct groups of synchronized strobes

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BigAbacus

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NFPA 18.5.5.4.2 states “ Visible notification appliances shall be installed in accordance with Table 18.5.5.4.1(a) or Table 18.5.5.4.1(b) using one of the following: (2) Two groups of visible notification appliances, where visual appliances of each group are synchronize, in the same room or adjacent space within the field of view. This shall include synchronization of strobes operated by separate systems.”

I believe this to be interpreted as the two groups of strobe being out of sync would be the same as two individual strobes being out of sync. As of 1996 the strobe rate was adjusted so that two strobe could not exceed the 5 flashes per second that would potentially cause epileptic seizures. This would hold true for the two distinct groups just as it would for two strobes being out of sync with a max combined flash rate of 4 per second.

My dilema is in a larger building with two physical addresses. Each address is protected by a dedicated fire alarm system and all notification devices within that address are synchronized. The two systems are networked together for shared function but the two systems are not synchronized together due to differing strobe protocols. When one address is in alarm it only causes a supervisory in the adjacent address and vice versa. The issue arises in common corridors when both systems are in an alarm condition. Each group/ system of notification appliances is synchronized but the two are creating different two strobe patterns.

Am I wrong to feel that we are compliant in this situation of two groups not synchronized in common corridors ? I understand the AHJ has the final determination but I believe my interpretation is defendable
 
I would say NO


My thought is any visible strobes are required to synchronize.

Not near the book, will look when I am.
 
Some others agree if seen they shall synch

NFPA 72 - rules regarding synchronization of strobes

We're doing work in an office building (happens to be a medical office building) and we're re-doing a single suite). Our strobes in that suite will be synchronized but the strobes outside the suite are on an older system and will not be synchronized. We're being told that we need to replace...
www.thebuildingcodeforum.com


www.ecmag.com

Strobe Code Compliance 101: Visible Appliance Requirements

Most contractors install strobe lights to comply with the National Fire Alarm and Signaling Code by simply using a combination audible-visible appliance everywhere one or the other is shown on the plans. It should be obvious that if you follow this method of “compliance,” you will either have an...
www.ecmag.com www.ecmag.com



If two strobes are in any field of view they must flash in synchronization, and any interruption in the clear viewing path will require additional strobes.
 
cda said:
Some others agree if seen they shall synch

NFPA 72 - rules regarding synchronization of strobes

We're doing work in an office building (happens to be a medical office building) and we're re-doing a single suite). Our strobes in that suite will be synchronized but the strobes outside the suite are on an older system and will not be synchronized. We're being told that we need to replace...
www.thebuildingcodeforum.com


www.ecmag.com

Strobe Code Compliance 101: Visible Appliance Requirements

Most contractors install strobe lights to comply with the National Fire Alarm and Signaling Code by simply using a combination audible-visible appliance everywhere one or the other is shown on the plans. It should be obvious that if you follow this method of “compliance,” you will either have an...
www.ecmag.com www.ecmag.com



If two strobes are in any field of view they must flash in synchronization, and any interruption in the clear viewing path will require additional strobes.
Click to expand...
Code is “when more than two are in field of view”
 
BigAbacus said:
Code is “when more than two are in field of view”
Click to expand...


ok am I lost on the question

In a corridor

Strobes in it

From two different systems

You can see both system strobes, in the corridor

The two systems do not synch?

Your question is do they have to???

If these are the facts submitted,

My answer is yes they do.
 
cda said:
So other question new or existing????
Click to expand...
One system is new and one system is existing. Two distinct systems protecting different parts of the building. My question references the code reference noting “two groups” do not need to sync. The code allows two strobes to be out of sync but not more than two. The code section I referenced applies that same logic to two “ groups” of strobes. The flash rate of the two groups can not flash at a rate (5-30) that could induce seizures. Strobe are set up to not flash more than 2 times a second.
 
BigAbacus said:
One system is new and one system is existing. Two distinct systems protecting different parts of the building. My question references the code reference noting “two groups” do not need to sync. The code allows two strobes to be out of sync but not more than two. The code section I referenced applies that same logic to two “ groups” of strobes. The flash rate of the two groups can not flash at a rate (5-30) that could induce seizures. Strobe are set up to not flash more than 2 times a second.
Click to expand...



Code reference out of 72, and year edition, so I can see how it reads::::::: The code allows two strobes to be out of sync but not more than two"""

I have not heard it stated that way, and have not been challenged, when I see strobes out of sync, to include only twp.


How many strobes are you talking about in the corridor????????
 
cda said:
Code reference out of 72, and year edition, so I can see how it reads::::::: The code allows two strobes to be out of sync but not more than two"""

I have not heard it stated that way, and have not been challenged, when I see strobes out of sync, to include only twp.


How many strobes are you talking about in the corridor????????
Click to expand...
Multiple strobes in multiple common corridors. Don’t have my code book handy but 2013 NFPA72 and the section is in my original post
 
May not be an easy fix since more than one corridor, but put all the strobes in the corridor on the new system, till you hit a location where you do not see the old strobe???

Or do you need all the strobes ???

Or similar, up the candela and remove some??
 
cda said:
May not be an easy fix since more than one corridor, but put all the strobes in the corridor on the new system, till you hit a location where you do not see the old strobe???

Or do you need all the strobes ???

Or similar, up the candela and remove some??
Click to expand...
Definitely not any easy fix hence why I reached out to the hive mind of the internet. Looking for validation and additional code interpretations that would solidify the case of “ two distinct groups” being acceptable. Thanks for your input
 
Commentary ....
 

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cda said:
Commentary ....
Click to expand...
The handbook description is my reasoning that backs up the argument that two groups can not flash at a rate that would cause any seizure issues. The handbook explanations are not enforceable the same that appendix notes are not but add the hows and whys of a code section.
 
Still do not agree.

Are you going to calculate the flash rate, and put it in writing that it meets NFPA 82?
 
NFPA 72, 2013
18.5.5.4.2
Handbook indicates the purpose of the synchronized requirements are guided by the human eye and its ability to view a flash of light at a 120/135 degree field of vision. The code’s revision in 07 clarified the intent of the multiple detectors two/ groups.

Handbook (18.5.5.4.2) “The flash rate was adjusted so that two appliances (or groups of synchronized appliances) not flashing in unison cannot produce a flash rate that is considered dangerous. If more than two appliances or groups of synchronized appliances can be viewed at the same time, they must be synchronized”.

It has always been my understanding the the code meant that if there are two visible and not synchronized its not compliant OR if there are two groups within the same field of view and both groups of appliances are not synchronized, they are not compliant.

Example - would be your common corridors shared by two separate groups of strobes. One end or half the length by lets say the existing system and the other half length by the new system. Those groups therefore need synchronization.

So my opinion would be the common corridors are non-compliant. I’ve seen this many times in large industrial, storage and healthcare expansions connecting corridors to buildings etc.

I would recommend having your electrical engineer and or fire alarm service provider check availability of ones system expansion of the notification alarm circuit(s) to cover the corridors and possibly separate the common corridor with detection alarm activated self closing doors keeping the corridors synchronized by the applicable system expanded circuits.
 
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