Re: Fire Alarms Conduit size

["Bill" <billnomailnospamx@xxxxxxxxx>]

"dave evans" <daveevans350@xxxxxxxxx> wrote in message
> Many electricians tell me that the minimum EMT conduit size for fire
> alarms is 3/4"
> I can't find any reference in any code book that supports this.
> Can someone point me to a reference or is the 3/4" not required by
> national codes?
>

The NEC calls conduit a "raceway" and uses a "raceway fill"
calculation as to how many wires of a given size can be run in a
particular size conduit. Here is a calculator...
http://www.electrician2.com/calculators/rf_calculator.html

Then there are "Box Fill" calculations for how many wires are
"crammed" in to a particular electrical box and this is based on the
cubic inches of the box. Each electrical box is usually marked with a
Cu. In. number.
http://ecmweb.com/nec/code-basics/electric_box_fill_calculations/

And with electrical wires there is heat, so the above allows air
around the wires so the wires stay cool. Tightly packed wires might
overheat.

BUT with a fire alarm, it is low voltage and very little amperage
draw, so very little heat in the wiring!

So anyway if you follow the NEC raceway and box fill calculations,
then I should think that would be quite acceptable as it would be
"over engineering" it. (So far as the NEC is concerned?)

As for pulling wires, it is a LOT easier with 3/4 conduit! So if the
electricians are the ones doing the wire pulling, they may be saying
that just because it will make their jobs less frustrating?