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Fire Alarm -- Installation

I have a question on how something works.
Douglas Krantz -- Fire Alarm Engineering Technician, Electronic Designer, Electronic Technician, Writer







I have a Question

I have a question concerning the homeruns on a Class A install.

Can two (2) separate homeruns (NAC 1 + NAC 2) be in the same conduit running back to the panel? I know that each individual circuit homerun can't be in any of the conduit for that circuit but can two separate homeruns from two different NAC circuits be in the same conduit run back to the FACP?

Signed J N

Reply

Keep in mind that the purpose of Class A isn't so any problem with the wiring can be repaired in a timely manner; the purpose of Class A is to keep the system working once the fire hits and starts to degrade the system - or at least before wiring problems can be repaired.

The feed part of the circuit gets the signal to all the devices in a daisy chain, and the return should be run as a redundant Class B wiring path so that cutting one conduit doesn't prevent devices from being activated by the panel.

As far as running more than one NAC (Notification Appliance Circuit) in a conduit, whether it's a homerun conduit to the panel or conduit somewhere out in another part of the building, as long as the feed and return of the Class A are separated to prevent both from being destroyed at the same time, as many feed NACs or return NACs as needed can be run in the same conduit. (Of course, keep within National Electrical Code [NEC] conduit fill guidelines.)

The biggest concern is survivability of the NAC. Keep the feed and return separate, and the rest can be just standard wiring practices.

Douglas Krantz





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Douglas Krantz

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Electrical Flow


On this website, most references to electrical flow are to the movement of electrons.

Here, electron movement is generally used because it is the electrons that are actually moving. To explain the effects of magnetic forces, the movement of electrons is best.

Conventional current flow, positive charges that appear to be moving in the circuit, will be specified when it is used. The positive electrical forces are not actually moving -- as the electrons are coming and going on an atom, the electrical forces are just loosing or gaining strength. The forces appear to be moving from one atom to the next, but the percieved movement is actually just a result of electron movement. This perceived movement is traveling at a consistent speed, usually around two-thirds the speed of light. To explain the effects of electrostatic forces, the movement of positive charges (conventional current) is best.

See the explanation on which way electricity flows at www.douglaskrantz.com/
ElecElectricalFlow.html
.