Class A & B Style Y & Z Circuits

[PMcCarty]

Where can I find definitions for these circuit types in the NFPA 72 or 70

Class A Style Z is loop circuit. The device will still work with an open in one of the conductors.

Class B Style Y is a Single Parallel Circuit with End of line resistor. Device past the open conductor will not activate the fire alarm panel.

I think I have these correct, Maybe not. I have seen information in the Fire Alarm Manual describing these circuits with diagrams, but not in the code books.

Thanks

 

[peter d]

Where can I find definitions for these circuit types in the NFPA 72 or 70

Look in Annex C of 72.

Class A Style Z is loop circuit. The device will still work with an open in one of the conductors.

Class B Style Y is a Single Parallel Circuit with End of line resistor. Device past the open conductor will not activate the fire alarm panel.

I think I have these correct, Maybe not.

Yes, that's correct.

 

[DUCKMAN]

Chapter 6

Chapter 6

Where can I find definitions for these circuit types in the NFPA 72 or 70

Class A Style Z is loop circuit. The device will still work with an open in one of the conductors.

Class B Style Y is a Single Parallel Circuit with End of line resistor. Device past the open conductor will not activate the fire alarm panel.

I think I have these correct, Maybe not. I have seen information in the Fire Alarm Manual describing these circuits with diagrams, but not in the code books.

Thanks

Most of the styles have been removed from the 2007 NFPA 72. The remaining classes and styles can be found in in Chapter 6 (tables 6.5, 6.6.1 & 6.7). The tables explain how the circuit should function. Annex C has some example diagrams of the various classes and styles.

Hope this helps