0-10 inside the same conduit

[don_resqcapt19]

Agreed, and also adding the requirement that the raceway be 'approved'. (I wonder why.)

That word is never needed in any rule as 110.2 requires everything to be approved.

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.

Yes, both the previous "reclassification exception" and the new (H) would permit that.

 

[shortcircuit2]

Agreed, and also adding the requirement that the raceway be 'approved'. (I wonder why.)

In my past research on LV wiring in the same raceway (or cable) as power, 1 concern was that damage to the raceway may cause the power wiring to cross to the LV wiring creating an unexpected hazard at the LV device or equipment.

For example, you have an EMT raceway above a drop ceiling with both power and LV and someone is working up there and damages the EMT enough that the wires are crossed, but not enough damage to trip the breaker.

This may be where the AHJ might elect to "approve" RMC over EMT

 

[shortcircuit2]

My understating of 725.136(I) Other Applications...

This is and was for "open wiring" say in a shaft. "Other Applications" has been in Code for many years.

IMO, 725.136(I) is not for raceway or cable applications with Power and LV installed together within. This is covered in 725.136(A) thru (G). The "Porcelain Tubes" language in I(2) shows us how old the rule is. The "Flexible Tubing" language in I(2) was there so you could run down the hardware store and get a piece of flexible tubing to sleeve your wire where it crossed the other in open wiring applications.

Again my opinion. I don't like LV and Power in the same cable. The language in 725.136(I)(2) was manipulated to create and list luminary cable.

"Other Applications" is also in 760.136(H). Are we going to permit FA Wiring in the same raceway or cable as Power? I hope not.

 

[kwired]

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.


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

I have not looked at the 2023 changes that were mentioned but in past you could always run control wiring with power wiring to a condenser unit or other similar situations, but the thing is you needed to essentially change the class 2 circuit to a class 1 circuit. Not just run 300 or 600 volt insulated conductors but reclassify the entire control circuit. Typical class 2 HVAC thermostats could not be used if you do this, you would have to come up with a thermostat rated for higher voltage which is nearly impossible to get one with all the functions many of the 24 volt ones have. And of course you would need to use different wiring methods rated for class 1 conductors to the thermostat location as well.

With 0-10V dimming there usually is no separate component in the system that doesn't already have power conductors associated with it. No reason to not consider the 0-10V wires as class 1 control circuits and run them in same raceway as power wiring IMO. Strict reading of wording in past NEC editions maybe could be prohibitive of running these conductors in raceways with anything other than conductors associated with the lighting though.

 

[kwired]

In my past research on LV wiring in the same raceway (or cable) as power, 1 concern was that damage to the raceway may cause the power wiring to cross to the LV wiring creating an unexpected hazard at the LV device or equipment.

For example, you have an EMT raceway above a drop ceiling with both power and LV and someone is working up there and damages the EMT enough that the wires are crossed, but not enough damage to trip the breaker.

This may be where the AHJ might elect to "approve" RMC over EMT

EMT above a drop ceiling is normally plenty of physical protection.

Areas where the raceway may be subjected to forklifts, front end loaders, or other similar machinery or abuse - RMC isn't even guaranteed to be enough protection though it will take more abuse than EMT will.

 

[don_resqcapt19]

I have not looked at the 2023 changes that were mentioned but in past you could always run control wiring with power wiring to a condenser unit or other similar situations, but the thing is you needed to essentially change the class 2 circuit to a class 1 circuit. Not just run 300 or 600 volt insulated conductors but reclassify the entire control circuit. Typical class 2 HVAC thermostats could not be used if you do this, you would have to come up with a thermostat rated for higher voltage which is nearly impossible to get one with all the functions many of the 24 volt ones have. And of course you would need to use different wiring methods rated for class 1 conductors to the thermostat location as well.

With 0-10V dimming there usually is no separate component in the system that doesn't already have power conductors associated with it. No reason to not consider the 0-10V wires as class 1 control circuits and run them in same raceway as power wiring IMO. Strict reading of wording in past NEC editions maybe could be prohibitive of running these conductors in raceways with anything other than conductors associated with the lighting though.

Other than some are marked as Class 2, some are marked as Class 1, and some are marked as either,