fire alarm slc Class A style 7

[markpaul]

What does it take to change a class A style 6 system to a class A style 7?

 

[ron]

Per NFPA 72-2007 Table 6.6.1, the only difference is that a Style 7 needs to be able to receive alarms during a wire to wire short on that circuit. It entails adding isolation modules between each field device on the circuit. It is an expensive proposition depending on the # of field devices you have.

 

[markpaul]

thanks..that is what I was thinking. I was hoping the answer would come back that I would just need them (isolation modules) at the panel for the loop that goes out and not every device. I see where it states "wire to wire short" in the table, but not where that is interpreted to be every device.

 

[mistabass]

you need one at panel for begining of loop then one at 25 devices and one more at panel for return of the loop. ALSO you need one if you go between floors

 

[ron]

Unfortunately, the code does not indicates how often the modules are needed, just that it needs to perform during a wire to wire fault. If you only put the modules every 25 devices, then during a fault the 25 devices in between the modules will not function.

 

[nhfire77]

Unfortunately, the code does not indicates how often the modules are needed, just that it needs to perform during a wire to wire fault. If you only put the modules every 25 devices, then during a fault the 25 devices in between the modules will not function.

I use isolation modules for every device with bases for smoke/heat heads. Then proper modules for the others.


I believe this meets the intent.

 

[smo]

The only way to truly achieve style 7 is with isolation modules between each and every device. Any other way still leaves "n" devices vulnerable to a direct short.

Adding two or three isolation modules is a good thing to do, but does not really give direct short protection.

Of course, your AHJ can interpret the intent to be anything that he wants...so if your AHJ will let you get away with only a few isolation modules, great!

Please see this diagram for details on proper style 7 wiring:

 

[peter d]

you need one at panel for begining of loop then one at 25 devices and one more at panel for return of the loop. ALSO you need one if you go between floors

That is a Rhode Island local fire alarm code. It is not a national code that I am aware of. Beware that when citing code rules for fire alarms there is no uniformity from state to state or area to area. We do our best not to add confusion to the matter when someone asks a question like that on a national forum, particularly with fire alarms requirements.

 

[mistabass]

yes peter d you are correct sorry for giving bad info.

 

[peter d]

yes peter d you are correct sorry for giving bad info.

No problem. I used to be under the impression that the RI fire alarm codes were typical of national practice, but after spend some time here on the forum I learned they are not (thankfully!).

 

[RJohnsonMasterElectrician]

I beleive the only thing that changes between class 6 nad 7 are isolation modules added in a class7