Class and Style

[desnov74]

I'm very confused about class and style in classifying SLC and IDC circuits, and mux circuits. Even the code is a little confusing. I know the basics about what class A and B circuits, but can someone classify what constitutes the different styles? Occasionally, Ill see a style Z or something.

I’m asking because I’m reviewing a shop drawing. The main fire alarm as an addressable loop with DGP's on various floors. (High rise building) I noticed that the SLC's though are on a class B circuit with end of line resistors from the transponder. We specify a class-A style7 system, is this permitted.

Thanks to everyone in advance,
JT

 

[cdafd]

if you specify class A than that is what should be submitted and installed.

Not sure where you are in the loop if you are an ahj or designer, etc.

AS an AHJ we require by code admendment class A notification and iniaiting circuits. We do not specify style.

 

[sfallows]

class a is a loop
class b is with a resistor at the end (it varies by mfg)

a more descriptive style is in the appendix of nfpa 72

 

[cdafd]

http://www.pottersignal.com/fire/tools/Manuals/8700055-D Adv Fire Train.pdf

http://findarticles.com/p/articles/mi_qa3737/is_/ai_n8906938

NFPA 72 contains a table for each type of circuit that defines the performance of various circuit styles. Table 3-5 covers initiating device circuits, Table 3-6 covers signaling line circuits, and Table 3-7 covers notification appliance circuits.

http://articles.directorym.net/We_H..._Style_Milwaukee_WI-r879541-Milwaukee_WI.html

But few have style
In the 2007 edition, you are no longer given a choice of Styles for Initiating Device Circuits, Notification Appliance Circuits and the Class B Signaling Line Circuit. Now, the IDCs and NACs are simply designated as either Class A or Class B. Period. This alone dropped 16 Style designations from the three tables. The only choice of Styles remaining is for the Class A Signaling Line Circuit which will be designated as either Style 6 or Style 7. The difference being, if a Class A SLC has Alarm Receipt
Capability (ARC) with a wire-to-wire short, then it's a Style 7. If not, it's a Style 6. Simple. Finally.



The three tables have not been removed because they still define how the Class A or B circuits will operate under various "abnormal conditions." However, even this list has been shortened. IDCs now only list two "abnormal conditions" where there used to be four (IDCs are no longer graded for wire-to-wire shorts or loss of carrier channel interface). There you have it, SLCs, NACs and IDCs are either Class A or Class B and when the SLC is a Class A circuit, it is designated as either a Style 6 or Style 7.