Dimming Wires

mstrlucky74

Senior Member
Location
NJ
I know we’ve spoke about class 2(0-10v) wires not being combined in the same conduit as 120v. But two questions one that my engineer mentioned.


  • As long as the 0-10v wire has same insulation it can be combined. This is what he said.
  • Curious as to why they make an MC cable that has the power and dimming under one jacket. Isn’t that the same as combining them in the same raceway?
 

Attachments

Sierrasparky

Senior Member
Location
USA
Occupation
Electrician ,contractor
Yes the insulation has to have the same minimum rating.
A cable is not a raceway.
 

rlundsrud

Senior Member
Location
chicago, il, USA
You can't mix them. You can mix class 2 if you change it to class 1 and mark it as such. It can only be combined with power wires that are for that application.
 

mstrlucky74

Senior Member
Location
NJ
You can't mix them. You can mix class 2 if you change it to class 1 and mark it as such. It can only be combined with power wires that are for that application.
Yes I got the reclassifying part. I was told they could be mixed if the insulation was the same.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Yes I got the reclassifying part. I was told they could be mixed if the insulation was the same.
If they are not reclassified they cannot be mixed no matter what the voltage rating of the insulation is. The MC with the power and control conductors in the same cable is designed so that the control conductors comply with one of the provisions of 725.136(I) and is listed for the application.
 

mstrlucky74

Senior Member
Location
NJ
If they are not reclassified they cannot be mixed no matter what the voltage rating of the insulation is. The MC with the power and control conductors in the same cable is designed so that the control conductors comply with one of the provisions of 725.136(I) and is listed for the application.
Thanks. Which code section does it not allow to mix these even is same insulation?
 

mstrlucky74

Senior Member
Location
NJ
So what's crazy to me is if you have a job that's full conduit you have to run two separate conduits to each fixture one for dimming wires and one for power. On a big job that can be a huge cost. Thanks

Sent from my SM-N960U using Tapatalk
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
So what's crazy to me is if you have a job that's full conduit you have to run two separate conduits to each fixture one for dimming wires and one for power. On a big job that can be a huge cost. Thanks

Sent from my SM-N960U using Tapatalk
Buy the luminaries with dimming systems that can be wired as either a Class 1 system or a Class 2 system. The ones that are suitable for Class 1 control circuits can have their control conductors in the same raceway with the power conductors as long as the insulation is rated for the highest voltage in the conduit.
 

ActionDave

Moderator
Staff member
Location
Durango, CO, 10 h 20 min without traffic from wing
Occupation
wire pulling grunt
Buy the luminaries with dimming systems that can be wired as either a Class 1 system or a Class 2 system. The ones that are suitable for Class 1 control circuits can have their control conductors in the same raceway with the power conductors as long as the insulation is rated for the highest voltage in the conduit.
All the 0-10V controlled lights I have wired up have the power conductors and dimming conductors going to the same make up box on the fixture and the dimmers have no way to separate the power and dimming wires in the junction box for the switch, so are they by default "re-classifiable"?

What does it even mean to re-classify a class 2 power supply or system?
 

mstrlucky74

Senior Member
Location
NJ
Buy the luminaries with dimming systems that can be wired as either a Class 1 system or a Class 2 system. The ones that are suitable for Class 1 control circuits can have their control conductors in the same raceway with the power conductors as long as the insulation is rated for the highest voltage in the conduit.
But the Lutron equipment that's feeding the fixtures are rated class 2
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
All the 0-10V controlled lights I have wired up have the power conductors and dimming conductors going to the same make up box on the fixture and the dimmers have no way to separate the power and dimming wires in the junction box for the switch, so are they by default "re-classifiable"?

What does it even mean to re-classify a class 2 power supply or system?
The code permits them to be in the same box for the connections to the equipment. The code does not permit them to be in the same raceway or cable.
Reclassification just means you remove or cover all the Class 2 markings and wire the controls using a Chapter 3 wiring method. In that case, the control wiring must follow the same rules as the power wiring.
 

ActionDave

Moderator
Staff member
Location
Durango, CO, 10 h 20 min without traffic from wing
Occupation
wire pulling grunt
The code permits them to be in the same box for the connections to the equipment. The code does not permit them to be in the same raceway or cable.
Reclassification just means you remove or cover all the Class 2 markings and wire the controls using a Chapter 3 wiring method. In that case, the control wiring must follow the same rules as the power wiring.
That makes sense. Thank you.
 

mstrlucky74

Senior Member
Location
NJ
All the 0-10V controlled lights I have wired up have the power conductors and dimming conductors going to the same make up box on the fixture and the dimmers have no way to separate the power and dimming wires in the junction box for the switch, so are they by default "re-classifiable"?

What does it even mean to re-classify a class 2 power supply or system?
Not sure what you mean. You can have two separate conduits(power & 0-10v) going to same box.
 

kwired

Electron manager
Location
NE Nebraska
Thanks. Which code section does it not allow to mix these even is same insulation?
Basically the general requirements for a class 2 circuit.

The rule isn't so much "same insulation" as it is "rated for the maximum voltage applied to any of the conductors". You can have 300 and 600 volt insulation in same raceway if none of those conductors is used for more than 300 volts.


I am not all up to speed on what is all out there for low volt lighting control/dimming, but similar situations have been around for a long time with HVAC controls.

If you want to run the 24 volt control conductors in same raceway with power wiring - it usually needed to be the raceway containing the power wiring to that HVAC equipment and not just any raceway with power wiring in it. You then needed to use conductors rated for maximum voltage present in the raceway. Then you must make it so the class 2 source is no longer identified as a class 2 source. Along with that goes making all of the control circuit comply with rules for a class 1 circuit - meaning you will use a line voltage thermostat instead of one intended for use only on class 2 circuits. You can not run half the circuit within power raceway because it is convenient then transition to CL 2 cable and run the other half the circuit to a typical CL2 thermostat, or other CL2 only system devices.
 

mstrlucky74

Senior Member
Location
NJ
Basically the general requirements for a class 2 circuit.

The rule isn't so much "same insulation" as it is "rated for the maximum voltage applied to any of the conductors". You can have 300 and 600 volt insulation in same raceway if none of those conductors is used for more than 300 volts.


I am not all up to speed on what is all out there for low volt lighting control/dimming, but similar situations have been around for a long time with HVAC controls.

If you want to run the 24 volt control conductors in same raceway with power wiring - it usually needed to be the raceway containing the power wiring to that HVAC equipment and not just any raceway with power wiring in it. You then needed to use conductors rated for maximum voltage present in the raceway. Then you must make it so the class 2 source is no longer identified as a class 2 source. Along with that goes making all of the control circuit comply with rules for a class 1 circuit - meaning you will use a line voltage thermostat instead of one intended for use only on class 2 circuits. You can not run half the circuit within power raceway because it is convenient then transition to CL 2 cable and run the other half the circuit to a typical CL2 thermostat, or other CL2 only system devices.
So can't run the 0-10v dimming wires with 120v power if the dimming wires are 600v insulation?
 
Top