The Electrical Contractor Network

ECN Electrical Forum
Discussion Forums for Electricians, Inspectors and Related Professionals

Books, Tools and Test Equipment for Electrical and Construction Trades

Register Now!

Register Now!

We want your input!

Featured:
   

2017 NEC and Related
2017 NEC
Now Available!

   
Recent Posts
Sprinklered equipment 26-008
by twh
Today at 06:28 AM
On Delay Relay with Auto Reset
by Potseal
Yesterday at 09:59 AM
Wow, that was close!
by jraef
11/28/16 07:06 PM
Earthquake in New Zeeland
by RODALCO
11/27/16 11:25 PM
Calling all Non-US members!! (Non-US only)
by Tjia1981
11/27/16 06:33 AM
New in the Gallery:
12.5A through 0.75mm˛ flex (just out of curiosity)
Shout Box

Top Posters (30 Days)
gfretwell 15
HotLine1 10
Texas_Ranger 9
Trumpy 8
sparkyinak 7
Who's Online
0 registered (), 203 Guests and 4 Spiders online.
Key: Admin, Global Mod, Mod
Topic Options
Rate This Topic
#97490 - 02/23/06 12:45 PM Fire Alarm System
George Little Offline
Member

Registered: 01/18/04
Posts: 1492
Loc: Michigan USA
Is there anything in NFPA72 that would require an installer or a design professional to install or design an installation of a fire alarm system to meet the requirements of a Class A circuit?

Secondly- what percent of the systems being installed are Class A?
_________________________
George Little

Top
2014 / 2011 NEC & Related Books and Study Guides
#97491 - 02/23/06 02:47 PM Re: Fire Alarm System
earlydean Offline
Member

Registered: 12/22/03
Posts: 749
Loc: Griswold, CT, USA
I see class 1, 2 & 3 circuits in the NEC, but no class A circuits. What are they?
_________________________
Earl

Top
#97492 - 02/23/06 03:49 PM Re: Fire Alarm System
trekkie76 Offline
Member

Registered: 06/19/04
Posts: 219
Loc: baileyville, maine, usa
A class A FA system uses return conductors for supervision. A class B uses EOLs for the supervision of the circuits.

I have seen more Class B lately. Last Class A I put in was at the Maine State Prison.

Top
#97493 - 02/23/06 06:33 PM Re: Fire Alarm System
Yoopersup Offline
Member

Registered: 03/04/03
Posts: 826
Loc: Michigan
George
Your answers on Page 72-41 Chaper 3 (3-4)
1999 NFPA 72.
Most nowadays are Class B Class A requires the outgoing and return conductors to be routed separately and shall Not be run in the same cable assembly. Page 72-41 (3-4.2.2.2*(Note exceptions) on page 74-42

Top
#97494 - 02/25/06 07:26 PM Re: Fire Alarm System
Ron Offline
Member

Registered: 03/13/02
Posts: 577
Loc: White Plains, NY
Depends on the type of buildings you work in. More than 50% of the building I work in are Class A due to reliability requirements and occasional slow repair cycles.
Many are not familiar with Class A circuits and they are not specified due to "that's the way I always did it, and it worked that time"
_________________________
Ron

Top
#97495 - 02/25/06 10:26 PM Re: Fire Alarm System
JoeTestingEngr Offline
Member

Registered: 11/04/05
Posts: 786
Loc: Chicago, Il.
Most of our systems use class B, where you see 2 jumpers in the panel per zone and 2 wires going out. Class A is safer because it can be cut in the middle of the loop and still cause an alarm on either end. A class B intelligent system may not use EOLs because each device is polled so you don't need a resistor, capacitor, or diode at the end to know that you're getting to the last device.

Top



ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals