I’m doing a commercial kitchen that has exhaust fans. The 120 feed for these exhaust fans is run directly to the fans, and there is a shielded twisted pair (600v rated) to be ran from the exhaust fan to the hood control panel. I was told I could run them together down into the building, land the seal tight to a box, then free air my STP. My inspector nearly failed me on it but I showed him 300.3(c) and he said he’ll pass but he’s going to look into it. I’m struggling to understand the nuances of 300.3, as well as article 725. I understand typically low-voltage communication wires cannot be ran in the same conduit as higher voltages as they are class two and three circuits. But 725.136(d) allows for them to be in the same conduit if they have to do with the load in question. Also dimming mc exists so please help me understand.
Kitchen Exhaust fan remote start 300.3
- Thread starter Pinnie
- Start date
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Did you see the IN to 300.3 C?
The **Informational Note** to **NEC 300.3(C)** explains that separating conductors of the same circuit can cause electromagnetic induction, leading to heating issues. Keeping conductors together minimizes this risk.
Is this how you would interpret the note?
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
I will have to look later as no code book
I believe so. It’s a 24v circuit. 600v rated shielded twisted pair. Unless I’m missing something.
Strathead
Senior Member
- Location
- Ocala, Florida, USA
- Occupation
- Electrician/Estimator/Project Manager/Superintendent
My codebook doesn't say they can be installed in the same raceway just enclosures and fittings: 725.136(D):
(D) Associated Systems Within Enclosures. Class 2 and Class 3
circuit conductors in compartments, enclosures, device boxes,
outlet boxes, or similar fittings shall be permitted to be instal‐
led with electric light, power, Class 1, non–power-limited fire
alarm, and medium-power network-powered broadband
communications circuits where they are introduced solely to
connect the equipment connected to Class 2 and Class 3
circuits, and where (1) or (2) applies:
Once the any of the Class 2 conductors from a class 2 power source violate the class 2 separation rules, all conductors from that power supply are virtually reclassified to not be class 2 conductors.
Okay thank you!
725.136(I) always seemed to me to give you the most options. Either run the power conductors in a cable, like NM, MC, SE, TC type cables, or sleeve the individual power conductors together in its own "firmly fixed" insulated sleeve and route it in the raceway with the CL2 cable. I'm just not sure what passes for firmly fixed.
Do you have room in a raceway to change the power conductors to a cable type instead of individual conductors? Would 14-2 MC work instead of your CL2 cable, or even smaller TC if you don't care about a shield? If not, can you find a sleeve the inspector is happy with to sleeve all the individual power conductors?
Do you have room in a raceway to change the power conductors to a cable type instead of individual conductors? Would 14-2 MC work instead of your CL2 cable, or even smaller TC if you don't care about a shield? If not, can you find a sleeve the inspector is happy with to sleeve all the individual power conductors?
I have a 3/4 seal tight going to the unit. All that’s in it is a red, white, and green (10awg) for the fan and the STP cable. What could I use to sleeve either the THHN or the STP. at this point it’s easier just to run another seal tight for the dang STP but I’m curious how to do that for the future.