Wiring 480v and 120v same conduit

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Abe5gt

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I am wiring a actuator valve that has 480Vac power and 120vac control wiring. I was wondering if I could wire them through the same conduit.
 
Smart $ said:
Yes, as long as you use 600V rated wire.

Welcome to the forum :thumbsup:
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Maybe not. It depends on what type of circuit the solenoid valve is. We often see 300.3(C)(1) quoted, as above, But what is missed is the informational note.
1000 Volts, Nominal, or Less. Conductors of ac and dc
circuits, rated 1000 volts, nominal, or less, shall be permitted
to occupy the same equipment wiring enclosure, cable,
or raceway. All conductors shall have an insulation rating
equal to at least the maximum circuit voltage applied to any
conductor within the enclosure, cable, or raceway.
Informational Note No. 1: See 725.136(A) for Class 2 and
Class 3 circuit conductors.

If you review Art 725, there are Class 1, 2 and 3 circuits. A class 1 circuit is wired with a chapter 3 wiring method and if functionally related (725.48)

If the solenoid circuit is class 2 or 3, then the answer is no. PLC circuits are typically a class 2 circuit. Motor control circuits can be art 430 or 725.
 
And just to chime in one more detail: If you choose to redesignate a class 2 or 3 circuit as class one and use Chapter 3 wiring methods to make use of this allowance, you are not permitted to continue to treat any other portion of the same circuit as class 2 or 3 and use those lesser methods there. It is an all or nothing decision.
 
GoldDigger said:
And just to chime in one more detail: If you choose to redesignate a class 2 or 3 circuit as class one and use Chapter 3 wiring methods to make use of this allowance, you are not permitted to continue to treat any other portion of the same circuit as class 2 or 3 and use those lesser methods there. It is an all or nothing decision.
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It seems not just the same circuit, but the entire load side of the power source... because you have to eliminate the Class 2 or 3 marking on the supply equipment.

However, I wonder :blink:...

Under Article 210, Branch Circuits, the branch circuit starts at the branch circuit OCPD and ends at the branch circuit OCPD if L-L or at the grounded conductor bus terminal. If we use this as a model, can we install a fuse(s) after the power source and keep the line side as Class 2 or 3, while the load side is reclassified as Class 1...???
 
Smart $ said:
Yes.

A easily recognized example is a 480V motor starter with a 480V-120V Class 2 control transformer.
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How could a Class 2 or Class 3-120 volt circuit provide acceptable protection from electric shock as required by 725.2?
 
GoldDigger said:
I will have to think about for awhile....
Done, I will tentatively agree with you on that.
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FWIW, the definition of a Class 1 circuit says the portion of the wiring system from OCD or power-limited source and note thereto refers to 725.41.
 
Smart $ said:
Yes.

A easily recognized example is a 480V motor starter with a 480V-120V Class 2 control transformer.
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infinity said:
How could a Class 2 or Class 3-120 volt circuit provide acceptable protection from electric shock as required by 725.2?
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Smart $ said:
IDK... perhaps limited energy. Definition doesn't say it won't shock.
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I agree it doesn't say it won't shock, but have a hard time believing that at 120 volts, it won't have dangerous shock hazards if it has enough capacity to operate just about any NEMA design motor starter contactor.
 
Smart $ said:
Yes.

A easily recognized example is a 480V motor starter with a 480V-120V Class 2 control transformer.
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It would have to be a very very small starter coil...the current on a Class 2 circuit at 120 volts is limited to a maximum of 0.005 amps. See Chapter 9, Tables 10 and 11.
I have never seen a 120 volt secondary CPT in a motor starter that was marked Class 2.
 
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don_resqcapt19 said:
It would have to be a very very small starter coil...the current on a Class 2 circuit at 120 volts is limited to a maximum of 0.005 amps. See Chapter 9, Tables 10 and 11.
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And the source would still need to deliver necessary inrush current for the contactor coil, so that means inrush would have to be no more than 5 mA.
 
kwired said:
I agree it doesn't say it won't shock, but have a hard time believing that at 120 volts, it won't have dangerous shock hazards if it has enough capacity to operate just about any NEMA design motor starter contactor.
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don_resqcapt19 said:
It would have to be a very very small starter coil...the current on a Class 2 circuit at 120 volts is limited to a maximum of 0.005 amps. See Chapter 9, Tables 10 and 11.
I have never seen a 120 volt secondary CPT in a motor starter that was marked Class 2.
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kwired said:
And the source would still need to deliver necessary inrush current for the contactor coil, so that means inrush would have to be no more than 5 mA.
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I will just go on record as maybe I inserted foot in mouth... :p

However, I may have been thinking of an occasion where there was an interposing 120V relay for the control and the actual motor contactor had a 480V coil. As I recall, it was not a NEMA motor starter.

Anyway... getting back to the OP, can we agree that the 120V control likely has a Class 1 source, making the installation in same conduit compliant, dependent on this condition existing?
 
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Changing things up a bit, can I install feeders from a generator to a transfer switch and the generator control wiring in the same raceway if the insulation is properly rated?
 
Yes, under the NEC. However the fact that the conductors are functionally and operationally related is a judgment call for an inspector.

Tapatalk!
 
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