480V circuit in EMT

[NEC User]

I've been informed that a coworker of mine overheard someone say that you can't put 480V circuits in EMT conduit. I couldn't find any justification for this comment in Article 358 Electrical Metallic Tubing. Can someone please clarify?

 

[peter d]

It's false.

He might be talking about a job spec, but if so, it's a very unreasonable one.

 

[infinity]

You can put 480 in MC cable so why would EMT be prohibited?

 

[480sparky]

I've been informed that a coworker of mine overheard someone say that you can't put 480V circuits in EMT conduit. .........

If that's true, I've installed miles of Code violations. I suspect you'll find it on page 37 of the Urban Legend Electrical Code.

 

[kwired]

NM cable is rated for 600 volts. You may very rarely see it used on 277/480 volts, but it can be used as long as there is no restriction on NM for other reasons.

 

[Jraef]

I see that on a lot of industrial project specs, especially Water / Wastewater plants. But it's not a code thing, it's an engineer's preference thing.

 

[iwire]

NM cable is rated for 600 volts. You may very rarely see it used on 277/480 volts, but it can be used as long as there is no restriction on NM for other reasons.

We used to run a lot of 480 & 277 in NM. That pretty much stopped when the NEC restricted NM above dropped ceilings.

Don't snip that 12/3 going by thinking 'no big deal its 120 volt travelers', its really a 3 phase 480 circuit to a fan. POW!

 

[Carultch]

If that's true, I've installed miles of Code violations. I suspect you'll find it on page 37 of the Urban Legend Electrical Code.

I'd like to see Mike Holt publish that book, explaining common NEC myths, how they came to be, and what the reality is on that subject matter.

 

[peter d]

We used to run a lot of 480 & 277 in NM. That pretty much stopped when the NEC restricted NM above dropped ceilings.

Don't snip that 12/3 going by thinking 'no big deal its 120 volt travelers', its really a 3 phase 480 circuit to a fan. POW!

And 90% of the electricians hearing this died from heart attacks just pondering 480 volts on NM cable.

 

[jap]

We used to run a lot of 480 & 277 in NM. That pretty much stopped when the NEC restricted NM above dropped ceilings.

Don't snip that 12/3 going by thinking 'no big deal its 120 volt travelers', its really a 3 phase 480 circuit to a fan. POW!

More like KAAAABOOOOMMMM>.....


JAP>

 

[480sparky]

I'd like to see Mike Holt publish that book, explaining common NEC myths, how they came to be, and what the reality is on that subject matter.

I'll bet 90% of the myths come from job specs.

Some greenhorn is hired by Fly-By-Night Electric and gets sent to a big commercial job. His foreman tells him to do something, say, "Run ¾" rigid from here to here for this 480-volt circuit." The poor cubby, not wanting to do all that work, says, "Why can't we just use EMT? I know how to bend that, and it doesn't need threaded." To which the foreman just says, "You can't run 480-volt in EMT."

What the foreman doesn't expound on is that the job specs prohibit EMT on the site due to it being a classified location, it's a vibration issue or any number of reasons why on that particular job, or in that particular portion of the job, the specs say to use rigid. So from then on, the newbie thinks the NEC prohibits 480-volt circuits in EMT.

 

[Nuber]

What's the big deal about cutting into 480 volt NM?

The electrician school I went to hooked us up to 480 volts on day 1! If it killed you, you weren't allowed to be an electrician...:blink:

Of course I used to have to walk to school in 4 ft of snow, uphill both ways also...

 

[Fnewman]

EMT is generally banned in large industrial settings because it is simply not rugged enough to hold up for years of corrosive and physically abusive environments. Then, the cost of installing GRS generally results in a switch to cable in tray.

 

[jap]

What's the big deal about cutting into 480 volt NM?

The electrician school I went to hooked us up to 480 volts on day 1! If it killed you, you weren't allowed to be an electrician...:blink:

Of course I used to have to walk to school in 4 ft of snow, uphill both ways also...

That must have been a very long time ago, seeing as how it's actually 600v NM.

JAP>

 

[wrobotronic]

I'd like to see Mike Holt publish that book, explaining common NEC myths, how they came to be, and what the reality is on that subject matter.

I'm positive I have used several of the code sections in this book....

Sent from my SM-G930V using Tapatalk

 

[Little Bill]

NM cable is rated for 600 volts. You may very rarely see it used on 277/480 volts, but it can be used as long as there is no restriction on NM for other reasons.

We used to run a lot of 480 & 277 in NM. That pretty much stopped when the NEC restricted NM above dropped ceilings.

Don't snip that 12/3 going by thinking 'no big deal its 120 volt travelers', its really a 3 phase 480 circuit to a fan. POW!

And 90% of the electricians hearing this died from heart attacks just pondering 480 volts on NM cable.

What's the big deal about cutting into 480 volt NM?

The electrician school I went to hooked us up to 480 volts on day 1! If it killed you, you weren't allowed to be an electrician...:blink:

Of course I used to have to walk to school in 4 ft of snow, uphill both ways also...

That must have been a very long time ago, seeing as how it's actually 600v NM.

JAP>

How did we go from the OPs question about EMT to NM?

 

[iwire]

How did we go from the OPs question about EMT to NM?

The OP got the correct answer for their question about EMT right away, after that we moved on.

 

[kwired]

How did we go from the OPs question about EMT to NM?

From my post. I was trying to rhetorically ask if NM can be used for 600 volts, why can't one use EMT for 600 volts?

To go further yet, I imagine you could put medium voltage cable in EMT if you wanted.

 

[480sparky]

From my post. I was trying to rhetorically ask if NM can be used for 600 volts, why can't one use EMT for 600 volts?

To go further yet, I imagine you could put medium voltage cable in EMT if you wanted.

I don't see any voltage limitations in 358.

 

[kwired]

I don't see any voltage limitations in 358.

And I doubt you see any limitations in any of the raceway articles, you don't apply voltage to the raceway you apply it to the contained conductors.