0-10 inside the same conduit

P

prattz99

Member
Location
Long Island NY
Occupation
Electrician
Hi, I understand that class 1 and class 2 wiring cannot be installed in the same raceway without a barrier but I'm wondering if I were to use #12 AWG THHN for both the high voltage (120V) and the 0-10 dimming controls if that would be code sufficient? I don't see why not but that's why I'm here
 
Class 2 in general cannot be in the same raceway as power condcutors regardless of the insulation value. 0-10 volt dimming can often be reclassified as Class 1 and you can use #16 TFFN (pink, purple) for the 0-10 wiring within the same raceway.
 
infinity said:
Class 2 in general cannot be in the same raceway as power condcutors regardless of the insulation value. 0-10 volt dimming can often be reclassified as Class 1 and you can use #16 TFFN (pink, purple) for the 0-10 wiring within the same raceway.
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Thank you Roger, I'm missing how to reclassify the wiring and what makes class 1 vs class 2 wiring in general. Would you be willing to point me in the right direction?
 
As far as I know you can't reclassify it. You can get MC cable with 12/2 THWN conductors and a separate 16/2 pink/purple cable all within the MC. It's called luminary cable.

If you are stuck with conduit, you can always pull 18/2 type TC (tray cable) along with the power conductors.

And of course, you can also always run 18/2 CL2 cable outside of the conduit.

-Hal
 
hbiss said:
As far as I know you can't reclassify it. You can get MC cable with 12/2 THWN conductors and a separate 16/2 pink/purple cable all within the MC. It's called luminary cable.

If you are stuck with conduit, you can always pull 18/2 type TC (tray cable) along with the power conductors.

And of course, you can also always run 18/2 CL2 cable outside of the conduit.

-Hal
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In the 2020 and older codes, Exception #1 to 725.130(A) permitted you to change the Class from Class 2 to Class 1 and wire the circuit using Class 1 wiring methods. That is gone in the 2023 as far as I know.
 
don_resqcapt19 said:
In the 2020 and older codes, Exception #1 to 725.130(A) permitted you to change the Class from Class 2 to Class 1 and wire the circuit using Class 1 wiring methods. That is gone in the 2023 as far as I know.
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Not sure "always" is an applicable word to use , for instance I am going to be adding 0-10 volt lighting to a gymnasium. Would tv tray cable be allowed in a place of assembly? How about if it is all contained above the ceiling?
 
macmikeman said:
I am going to be adding 0-10 volt lighting to a gymnasium. Would tv tray cable be allowed in a place of assembly?
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If the TC is run in the conduit, yes.

macmikeman said:
How about if it is all contained above the ceiling?
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Is above the ceiling an air handling space? If the TC is in conduit it wouldn't matter. But if not, and it's run by itself, (if that's what you are getting at) I don't know of any plenum listed TC. Just use a plenum listed 18/2.

-Hal
 
(H) Where Protected.
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Class 2 and Class 3 circuits shall be
permitted to be installed together with the conductors of electric
light, power, Class 1, non-power-limited fire alarm, and
medium-power network-powered broadband communications
circuit, where they are installed using Class 1 wiring methods
in accordance with 724.46 and where they are protected by an
approved raceway.
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So, either the conductors of electric light, power, Class 1, non-power-limited fire alarm, and
medium-power network-powered broadband communications circuit conductors-

OR

The Class 2 or Class 3 circuit conductors-

Must be protected by an approved raceway. Hence the use of type TC tray cable for the CL2 within the conduit carrying the power conductors.

If it were possible to run the power within its own cable or raceway within the conduit, then the CL2 conductors could be run using THWN.


-Hal
 
hbiss said:
So, either the conductors of electric light, power, Class 1, non-power-limited fire alarm, and
medium-power network-powered broadband communications circuit conductors-

OR

The Class 2 or Class 3 circuit conductors-

Must be protected by an approved raceway. Hence the use of type TC tray cable for the CL2 within the conduit carrying the power conductors.

If it were possible to run the power within its own cable or raceway within the conduit, then the CL2 conductors could be run using THWN.


-Hal
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I missed that change, but am reading it much differently.
I see it as saying you can install the Class 2 circuit using Class 1 wiring methods in the same raceway as the power circuit. However 724.46 references 300.2 through 300.26. 300.3 references Table 310.4(1) for single conductors and other than MI or MTW, the smallest single conductor in that table is 14AWG. So I read it as permitting the use of 14 AWG THHN for the Class 2 circuit in the same raceway with the 12 AWG THHN power circuit.
 
I read it as Don does, except in addition I read it as allowing the methods in 724.48 through 724.51, through the exception in 724.46.
6. Which, for example, would allow 16awg or 18awg TFFN where the circuit is functionally associated with the power circuit, which fron what I know I would judge the OP's 0-10 lighting control to qualify for.
 
What about the part that says "where they are protected by an
approved raceway"? They are not talking about everything enclosed in a raceway, they are talking about either the LV or the line voltage conductors being enclosed in a raceway, this raceway is then run with the unprotected conductors in whatever they are enclosed with. This creates a barrier between the line and LV.

Unfortunately, this was probably written by AI because previous versions used "non-conductive sheath" instead of "raceway". This made it clearer what the intent is but it seems all logic is lost with the NEC.

jaggedben said:
Which, for example, would allow 16awg or 18awg TFFN where the circuit is functionally associated with the power circuit, which fron what I know I would judge the OP's 0-10 lighting control to qualify for.
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No. "functionally associated with" has forever come up as an excuse to run LV and line conductors together. Nothing new. Fact is that "functionally associated with" means that the fixture (in this instance) cannot operate without the LV conductors... which is false. It will operate just fine, just not dim.

Rarely does "functionally associated with" ever hold true. An example where it would be true is the 24V coil conductors inside of a 277V contactor enclosure, for instance. The contactor could not operate without the control wiring.

-Hal
 
hbiss said:
What about the part that says "where they are protected by an
approved raceway"? They are not talking about everything enclosed in a raceway,
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The words say they "shall be permitted to be installed together .... where they are installed using Class 1 wiring methods
in accordance with 724.46 and where they are protected by an approved raceway."
Raceway is singular.

Also...
they are talking about either the LV or the line voltage conductors being enclosed in a raceway, this raceway is then run with the unprotected conductors in whatever they are enclosed with. This creates a barrier between the line and LV.
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This option is in the next section, 725.136(I)(1). So you're saying there are two sections that serve the same purpose.

Unfortunately, this was probably written by AI because previous versions used "non-conductive sheath" instead of "raceway".
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Sounds like 725.136(I)(2).

This made it clearer what the intent is but it seems all logic is lost with the NEC.
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I agree that this part of the code has never been clear or logical, and hasn't gotten more so in the 2023. I don't like that the AHJ now has the prerogative to approve or disapprove the raceway, and I don't understand the intent of that.

No. "functionally associated with" has forever come up as an excuse to run LV and line conductors together. Nothing new. Fact is that "functionally associated with" means that the fixture (in this instance) cannot operate without the LV conductors... which is false. It will operate just fine, just not dim.

Rarely does "functionally associated with" ever hold true. An example where it would be true is the 24V coil conductors inside of a 277V contactor enclosure, for instance. The contactor could not operate without the control wiring.

-Hal
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Please cite an NEC definition or another source (such as a product standard) to back up these assertions. Otherwise it strikes me as bizarre to claim that the dimmer switch 'works fine' without performing its full functions, or that the functions aren't associated. I also see no obvious safety reason why a wiring method should be allowed for the contactor and not the dimmer switch.
 
hbiss said:
What about the part that says "where they are protected by an
approved raceway"? They are not talking about everything enclosed in a raceway, they are talking about either the LV or the line voltage conductors being enclosed in a raceway, this raceway is then run with the unprotected conductors in whatever they are enclosed with. This creates a barrier between the line and LV.

Unfortunately, this was probably written by AI because previous versions used "non-conductive sheath" instead of "raceway". This made it clearer what the intent is but it seems all logic is lost with the NEC.



No. "functionally associated with" has forever come up as an excuse to run LV and line conductors together. Nothing new. Fact is that "functionally associated with" means that the fixture (in this instance) cannot operate without the LV conductors... which is false. It will operate just fine, just not dim.

Rarely does "functionally associated with" ever hold true. An example where it would be true is the 24V coil conductors inside of a 277V contactor enclosure, for instance. The contactor could not operate without the control wiring.

-Hal
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That is exactly what they are talking about. You could always make the installation if one or the other was in its own raceway.

There was no previous version of 725.136(H) related to this. The previous (H) was hoistways.

The new 136(H) appears to be in place of the previous Exception #2 to 725.130 which was deleted. The exception would permit the installation of a Class 2 circuit in the same raceway as the power circuit as long as the Class 2 circuit was installed using Class 1 wiring methods and the Class 2 power supply marking was eliminated. The new (H) does the same thing without requiring the removal of the Class 2 markings.

As far as "non-conductive sheath" are you thinking of the language in 725.136(I)(1) that uses "nonmetallic-sheathed"? That is the same section that permits the use of TC for this application.
 
jaggedben said:
Please cite an NEC definition or another source (such as a product standard) to back up these assertions.
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Like I said, that's been debated forever. I believe it was discussed by Mike himself in his material at one time.

If it can be demonstrated that a line voltage device cannot function without low voltage wiring then the low voltage conductors are functionally associated with the operation of the device.

In this case we are talking about lighting fixtures that can be dimmed by low voltage control. In many cases, the fixtures are installed without regard to the dimming function. They function as intended without the LV conductors being connected. So, it's obvious that the LV conductors are not needed for the operation of the fixture. Dimming is just an option.

-Hal
 
hbiss said:
Like I said, that's been debated forever. I believe it was discussed by Mike himself in his material at one time.

If it can be demonstrated that a line voltage device cannot function without low voltage wiring then the low voltage conductors are functionally associated with the operation of the device.

In this case we are talking about lighting fixtures that can be dimmed by low voltage control. In many cases, the fixtures are installed without regard to the dimming function. They function as intended without the LV conductors being connected. So, it's obvious that the LV conductors are not needed for the operation of the fixture. Dimming is just an option.

-Hal
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You said I was wrong. Now you're saying it's been debated forever. Okay, you have an interpretation, probably an informed one, but it's still just your interpretation, that's all.

Again, I don't see any safety reason for the difference.
 
jaggedben said:
Okay, you have an interpretation, probably an informed one, but it's still just your interpretation, that's all.
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Not an interpretation, it came from somewhere, I just can't point to where.

Look up questions about why you can't run thermostat or control conductors with the supply conductors for outdoor condensing units.

Even more interesting, look up running CAT5 or RG59 up inside a light pole along with the supply conductors for a security camera.

jaggedben said:
I don't see any safety reason for the difference.
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Actually I agree. As long as all the conductors have the same voltage rating what difference should it make? But in some cases, like the security camera, that's not possible.

-Hal
 
hbiss said:
Not an interpretation, it came from somewhere, I just can't point to where.

Look up questions about why you can't run thermostat or control conductors with the supply conductors for outdoor condensing units.
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I bet you could if you used a Class 1 wiring method. Probably most HVAC guys don't see a benefit to doing that though.

Even more interesting, look up running CAT5 or RG59 up inside a light pole along with the supply conductors for a security camera.
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Those aren't Class 1 wiring methods. I'm not asserting that anything permitted through 724.46 would allow that.
 
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