Re: Fire Alarms Conduit size

[yodeler123 <keystonesecuritysolutions@xxxxxxxxx>]

On Jan 29, 9:40=A0pm, "Bill" <billnomailnosp...@xxxxxxxxx> wrote:
> "dave evans" <daveevans...@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.c=
om/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_calcul=
ations/
>
> 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?

I think people get confused because many commercial jobs won't allow
anything smaller than 3/4 conduit. Not a code, but it's often spec'd
that way