Pros and cons of class A wiring in fire alarm systems
Utah is one of the few places in the country that still requires class A wiring on specific projects like state buildings, public buildings, hotels,schools, daycares and rest homes that are under the jurisdiction of the State Fire Marshal.
What does it matter? What are the PROS and what are the CONS?
What is class A? The wire for the circuits goes out from the panel and out to the devices (smokes, monitor modules etc...) or NAC circuits (Horn/Strobes and strobes ) and then the wire comes back to the panel and it is at least 6 feet apart so it is not class A if 2 conductors go out in the same conduit and 2 come back in the same conduit. (not class A)
Why? The reasoning is that if there is a cut in the cable at any point the system will continue to operate with that cut because the panel feeds the circuits from both ends. This sounds great and is a good thing.
The new addressable panels will let you know when there is a cut in the wire immediately whether it is class B (wire going out and stopping without coming back to the panel) With this feature you can get the repairs made right away. Many panels will also indicate where the cut or break in the wire is. The reasoning that many use is that a hotel may ignore these indications and troubles and they still want you to be able to get an alarm from all the devices or have the appliances still function (Horn/Strobes or Speaker strobes)
Installing wire in a class A configuration costs more in cable and conduit and installation labor so the cost is one reason most States no longer require class A.
Also when you use class A wiring on Horn/Strobe circuits you need to know that you will need double the power supplies in many cases because you can only use 2 of the 4 circuits available. Some panel allow you to use all 4 circuits per panel so it depends on the manufacturer. When you use equipment where you loose half of the NAC panels you need to install say 8 panels instead of 4 on a hotel and each one of these panels is about 700 or 1000 dollars so that is also a factor in the additional cost.
Larry@peakalarm.com (801) 428 1384