Fire Alarms Conduit size

[dave evans]

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?

TIA

Dave

[nick markowitz]

You can use 1/2 " conduit for fire as long as you do not exceed the
amount of conductors allowed.

The codes and tables can be found in the NFPA-70- National
Electrical Code. and on some internet sites. Theres also couple apps
for sizing boxes and conduit available.

A code book can be purchased on line or at most electrical supply
houses. You should not be installing or touching fire alarms with out
a copy of it and NFPA 72 fire alarm signalling code . Or you will find
your self in a big world of shit when things go very wrong.

Most electricians spec 3/4" because its standardizes the run and
allows for expansion in future. But there is no such code which
requires 3/4" unless it is a specific local code which I do not know
of any.

[doug]

"dave evans" <daveev...@gmail.com> wrote in message
news:4b2a4dad-178f-4098...@h6g2000yqk.googlegroups.com...

I've heard that many times too, mostly from electricians that have lost the
bid and complained when they see me running 1/2". I believe it falls into
the same category as the "requirement" that all fire alarm conduit must be
red in colour.

The practice of specifying a minimum 3/4" conduit size probably started
before addressable SLC circuits drastically reduced the number of conductors
in fire alarm raceways.

I have seen numerous job specs that call for a minimum of 3/4" conduit and a
few that specify red conduit but I don't believe you will find either
anywhere in the NEC.


Doug

[Bill]

"dave evans" <daveev...@gmail.com> wrote in message

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?

[yodeler123]

On Jan 29, 9:40 pm, "Bill" <billnomailnosp...@yahoo.com> wrote:
> "dave evans" <daveevans...@gmail.com> 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?

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