Code Question - Low Voltage Cable(300V Rated) in Same Conduit as 277V Circuit Wires (600V Rated)

[TaylorSchod]

OK - my question is regarding wire of different voltage ratings in the same conduit. Currently, I have dimming vacancy sensor switches supplied with 277V. My electrician ran the LV (300V Rated) plenum rated cable down the wall and into the box to connect to the dimming leads. The local inspector came out and called her senior inspector, and was told that I cannot have wire of differing voltages in the same conduit/wiring enclosure. After doing some research I came across 300.3-C-(1), which states that as long as the voltage rating of the wire AT LEAST meets the voltage running in the raceway, I am ok to run it in the same raceway, or have it enter the same box. Since this is for lighting circuit and dimming purposes, I don't see there being any issue. Can anyone confirm or provide me with more details as to why cannot have this LV cable enter the same box as wire that has 600V rating?

 

[tom baker]

Please read the IN at the end of 300 3 C 1
What class circuit are the dimming controls (per article 725)?

 

[TaylorSchod]

Please read the IN at the end of 300 3 C 1
What class circuit are the dimming controls (per article 725)?

Not sure how to go about classifying the dimming wires. That part is unclear to me. I just know that the 18/2 is for the purpose of 0-10V line dimming the lighting fixtures. Not sure what classification they would fall under. If you could help me with the classification as well, this would help too.

 

[tom baker]

I don’t have a code book, but it is allowed to have low volt and 277 in the same box for interconnection as long as separation is maintained. There are others here with more experience, so watch for more answers

 

[don_resqcapt19]

Not sure how to go about classifying the dimming wires. That part is unclear to me. I just know that the 18/2 is for the purpose of 0-10V line dimming the lighting fixtures. Not sure what classification they would fall under. If you could help me with the classification as well, this would help too.

That information comes from the dimming equipment itself.

 

[infinity]

If the dimmer has both 0-10 volt leads and 277 volts leads how can you possibly connect both of those to the dimmer if the conductors do not enter the same box?

 

[jap]

Not sure how to go about classifying the dimming wires. That part is unclear to me. I just know that the 18/2 is for the purpose of 0-10V line dimming the lighting fixtures. Not sure what classification they would fall under. If you could help me with the classification as well, this would help too.

There is something that states the cable with the sheath on it is rated at 300 volts as long as the cable sheath is still covering the conductors inside of it.

Meaning when you make the connection at the dimmer or at the fixture you don't take the complete sheath off the cable to expose much of the conductors inside, you should only strip enough of the outside cable back to make the connection so that the individual conductors aren't exposed any more than they have to be.

Don't tell anyone but I strip em back and terminate as see fit.

I figure until someone puts the effort forth to make the separation from the factory at the fixtures or the dimmers, why should I have to worry about how I terminate to them on my end.

JAP>

 

[tom baker]

To clarify even if the dimming wire was 600 volt rated, if I was a class 2 circuit, it could not be in the same raceway or box. Class 1 (edit was class 2) wiring could be in the same raceway or box if functionally associated
Note there is a MC cable that is listed and has the power and dimming circuit in the cable

 

[kwired]

I think a majority of the time this 0-10V dimming circuit is permitted to be class 1.

 

[kwired]

Please read the IN at the end of 300 3 C 1
What class circuit are the dimming controls (per article 725)?

Speaking of 300.3(C)(1), what is the difference in having three 277 volt circuits (all three phases) in a raceway vs having a 480 volt three phase load in the raceway? Applied circuit voltage is technically 277 for the one and 480 for the other, but both are still 277 to ground and 480 ungrounded to ungrounded.

 

[TaylorSchod]

To all: hopefully this helps you all in the future - please refer to code 725.49(B) - " insulation on conductors shall be rated for the system voltage and not less than 600V." Class 1 wires must be rated at 600V... i can't find any 18/2 or 16/2 rated at 600V that is also plenum rated... the only stuff is with luminaire mc cable... but they charge you an arm and a leg for that stuff.

it seems 300.3(C)(1) is pretty useless then. I'm very upset. lol

 

[jap]

So what do you do?

JAP>

 

[kwired]

To all: hopefully this helps you all in the future - please refer to code 725.49(B) - " insulation on conductors shall be rated for the system voltage and not less than 600V." Class 1 wires must be rated at 600V... i can't find any 18/2 or 16/2 rated at 600V that is also plenum rated... the only stuff is with luminaire mc cable... but they charge you an arm and a leg for that stuff.

it seems 300.3(C)(1) is pretty useless then. I'm very upset. lol

Most the conductors you would run will be 600 volt conductors. You mentioned a 300 volt cable in OP. What kind of cable do you have?

T310.4(A) is all 600 volt cables.

T400.4 has flexible cords with 300 volt rating.

Some fixture wire is limited to 300 volts.