Low voltage(24volts) and high voltage(277volts) in same pipe?

[Danny89]

Can 277volts and 24volts be ran in the same emt raceway?

Situation is a dimmer switch to control led lights.

Is it legal to run 277volts and 24 volts in the same raceway?

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[infinity]

The 24 volts would have to be run as Class 1 wiring. If it's Class 2 only then no they cannot be in the same raceway.

 

[Danny89]

The 24 volts would have to be run as Class 1 wiring. If it's Class 2 only then no they cannot be in the same raceway.

Where is this explained in the code book?

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[don_resqcapt19]

See 725.136 and 725.130(A) Exception #2

 

[paulengr]

If it is general wiring as long as nothing is under 18 gauge and they are all insulated to the maximum voltage in the raceway you are good to go. For instance if it is all THHN (600 V rated) that is OK.

A common industrial problem that this solved is induced voltage. So a common situation is locating start and stop buttons by the motor, some distance from the MCC. The control circuit is usually 120 VAC. If the motor and the three wires for the push button are in the same conduit and the buttons go to say a miniature relay or PLC, when the start button is pushed the motor starts. But now the motor leads induce enough voltage into the start push button wiring that hitting the stop button does nothing! Same scenario with DC control signals AC induction doesn’t matter so it shuts off as expected. Another solution is use a big industrial machine tool relay which requires enough current that phantom induced voltages can’t hold it in.

 

[infinity]

If it is general wiring as long as nothing is under 18 gauge and they are all insulated to the maximum voltage in the raceway you are good to go. For instance if it is all THHN (600 V rated) that is OK.

Regardless of the insulation value Class 2 only wiring cannot be in the same raceway. Take a look at Don's code sections.

 

[tom baker]

If it is general wiring as long as nothing is under 18 gauge and they are all insulated to the maximum voltage in the raceway you are good to go. For instance if it is all THHN (600 V rated) that is OK.

Please reply with the code section that allows 277 volts and 24 volts in the same raceway.

 

[hbiss]

Can 277volts and 24volts be ran in the same emt raceway?

Situation is a dimmer switch to control led lights.

Ummm, 24 volts? Are you sure this isn't 0-10V dimming? No matter though. Use 18/2 tray cable (type TC) for the low voltage. You can pull that along with the 277 conductors in the conduit.

-Hal

 

[don_resqcapt19]

Why do so many code users fail to read Informational Note #1 to 300.3(C)(1)???

 

[don_resqcapt19]

Ummm, 24 volts? Are you sure this isn't 0-10V dimming? No matter though. Use 18/2 tray cable (type TC) for the low voltage. You can pull that along with the 277 conductors in the conduit.

-Hal

If you are not on the 2020 code, your local inspection authority may not permit you to use Type TC for the application as I believe that was a 2020 code change to put TC into 725.136(I)(1).

 

[hbiss]

If you are not on the 2020 code, your local inspection authority may not permit you to use Type TC for the application as I believe that was a 2020 code change to put TC into 725.136(I)(1).

It's always been permitted, but before 2020 you had to put together several articles and sections and do some thinking to see it. 2020 just made it clear.

-Hal

 

[don_resqcapt19]

It's always been permitted, but before 2020 you had to put together several articles and sections and do some thinking to see it. 2020 just made it clear.

-Hal

Not really as TC is not listed as having a non-metallic sheath as defined in the listing standards. I see no reason to prohibit it, but the old code language does.

 

[tom baker]

Why do so many code users fail to read Informational Note #1 to 300.3(C)(1)???

Ditto. Everyone knows 300.3 C 1. On the job, we don't say "as long as all conductors have insulation, but look at the IN first."

 

[hbiss]

Not really as TC is not listed as having a non-metallic sheath as defined in the listing standards.

From the 2011:

336.2 Definition
Power and Control Tray Cable, Type TC. A factory assembly
of two or more insulated conductors, with or without
associated bare or covered grounding conductors, under
a nonmetallic jacket.

-Hal

 

[don_resqcapt19]

From the 2011:

336.2 Definition
Power and Control Tray Cable, Type TC. A factory assembly
of two or more insulated conductors, with or without
associated bare or covered grounding conductors, under
a nonmetallic jacket.

-Hal

That would be fine if the rule in 725.136 said nonmetallic jacket, but it doesn't. It says non-metallic sheath. Those are not the same things in the listing standards and is why the 2020 code specifically added TC cable to the rule. The panel statement on the change read:

Type TC cable is added since it has a jacket thickness at least as thick as the presently permitted wiring method.

It is apparent that CMP did not believe that TC met the requirements found in the 2017 code.

 

[don_resqcapt19]

Ditto. Everyone knows 300.3 C 1. On the job, we don't say "as long as all conductors have insulation, but look at the IN first."

I was going to submit a PI to expand that Informational Note to included the other Chapter 7 and 8 articles where the same thing applies, but did not get it done before the deadline.