Class A/B FA Wiring

[designer82]

I have two questions regarding Class A/B Fire Alarm wiring.

1) Is Class A for addressable systems and Class B for conventional systems or can they be either way?
2) When are Class A required and when are Class B required?


Thanks!

 

[don_resqcapt19]

That is a design issue, but Class A will require the conductors to return to the fire alarm control panel and not end at a field installed end of line resistor like for Class B.
When you have a single open in the Class A circuit all of the initiation devices will still be able to trigger an alarm condition. With Class B, only the devices between the panel and the open can trigger an alarm condition.