Schmoleskin
Member
- Location
- Denver, CO, USA
I have recently learned (again) that I have an awful lot to learn. Please find attached, the instructions for a lighting system that uses 0-10 V dimming ballasts, and ethernet cabling for communication to the dimmers. Note on page 1 right above Important Safeguards where it says, "For Class 2 DLM devices and device wiring: To be connected to a Class 2 power source only. Do not reclassify and install as Class 1, or Power and Lighting Wiring."
Note also on the right side of that page that it says the 0-10 V dimming output is Class 2 also, but without the note that prohibits reclassifying it as Class 1. Article 725.130 (A) exception 2 appears to be where this is allowed, and says, "Class 2 and Class 3 circuits shall be permitted to be reclassified and installed as Class 1 circuits if the Class 2 and Class 3 markings required in 725.124 are eliminated and the entire circuit is installed using the wiring methods and materials in accordance with Part II, Class 1 circuits."
A friend is a large lighting system designer, and says they always pull the Class 2, 0-10 V dimming leads in with the power wiring, and do not get dinged by inspectors for doing so and violating 725.136 (A), "Cables and conductors of Class 2 and Class 3 circuits shall not be placed in any cable, cable tray, compartment, enclosure, manhole, outlet box, device box, raceway, or similar fitting with conductors of electric light, power, Class 1, non–power-limited fire alarm circuits, and medium-power network-powered broadband communications circuits unless permitted by 725.136(B) through (I)." I don't see a way around this in raceways, except to be "(B) Separated by Barriers."
So it seems they must be reclassifying The Class 2 dimming wires as Class 1 so they can occupy the same raceway without a barrier. I know that 300.3 (C) (1) allows wiring from different systems to occupy the same raceway, as long as everything is insulated for the highest voltage present. Article 725.49 Class 1 Circuit Conductors is more specific, and allows for wire size down to #18, but requires all insulation to be 600 V, and gives the list of permitted insulation types. Am I missing anything? Is all that's required to reclassify this circuit to remove the Class 2 markings from the power source and follow 725.49? And you have to follow the entire rest of Chapter 3, but that's kind of a given.
I had little experience with Class 1, 2, 3 wiring rules until now, and had always been told that as long as you're following 300.3 (C) (1), it was good. I now understand the error of that thinking, on to the next item. Even though I asked our crew to run a separate conduit system for the Class 2 DLM signaling wiring (CAT6), which is not permitted to be reclassified per the manufacturer's instructions, we got dinged because they pulled that cable in the power conduits. We are going to install the dedicated raceway for it, but the dimmers are going to be in boxes that have a receptacle circuit passing through them. I think we are allowed to have those Class 2 cables in that box with power wiring as long as we follow the rules in 725.136 (D) (1),
(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 installed 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:
(1) The electric light, power, Class 1, non–power-limited fire alarm, and medium-power network-powered broadband communications circuit conductors are routed to maintain a minimum of 6 mm (0.25 in.) separation from the conductors and cables of Class 2 and Class 3 circuits.
As long as we can keep them separated by 1/4" I think it's ok, would you agree or disagree?
Last item, we have always (maybe incorrectly) used the 300.3 (C) (1) section to allow us to run 300 V rated CL2P, 18 ga thermostat wire for HVAC control in a wire way with 240 VAC power wiring. I can't find anywhere in the HVAC units' documentation that says it is Class 1 or 2 or anything. Does anyone know if 24 VAC HVAC control wiring falls in any of those classes? Is it considered "Class 1 Remote-Control and Signaling Circuits?" If it is Class 1 wiring, it would be subject as above to 725.49, and so be required to be 600 V insulated. But HVAC control wiring is run all the time in 150 V thermostat cable, Is there another type of circuit that this could be? Or does it go like this: 24 VAC wiring is either Class 2 or Class 3, but if you want to run it in the same raceway with power wiring, you have to reclassify it as Class 1, which invokes the 600 V insulation rule of 725.49. I'm hoping there is some other classification of this type of circuit that won't require 600 V insulation, and just falls under 300.3 (C) (1).
Sorry for my long windedness, but I wanted to have enough detail for you all to work with. Thanks in advance.
Note also on the right side of that page that it says the 0-10 V dimming output is Class 2 also, but without the note that prohibits reclassifying it as Class 1. Article 725.130 (A) exception 2 appears to be where this is allowed, and says, "Class 2 and Class 3 circuits shall be permitted to be reclassified and installed as Class 1 circuits if the Class 2 and Class 3 markings required in 725.124 are eliminated and the entire circuit is installed using the wiring methods and materials in accordance with Part II, Class 1 circuits."
A friend is a large lighting system designer, and says they always pull the Class 2, 0-10 V dimming leads in with the power wiring, and do not get dinged by inspectors for doing so and violating 725.136 (A), "Cables and conductors of Class 2 and Class 3 circuits shall not be placed in any cable, cable tray, compartment, enclosure, manhole, outlet box, device box, raceway, or similar fitting with conductors of electric light, power, Class 1, non–power-limited fire alarm circuits, and medium-power network-powered broadband communications circuits unless permitted by 725.136(B) through (I)." I don't see a way around this in raceways, except to be "(B) Separated by Barriers."
So it seems they must be reclassifying The Class 2 dimming wires as Class 1 so they can occupy the same raceway without a barrier. I know that 300.3 (C) (1) allows wiring from different systems to occupy the same raceway, as long as everything is insulated for the highest voltage present. Article 725.49 Class 1 Circuit Conductors is more specific, and allows for wire size down to #18, but requires all insulation to be 600 V, and gives the list of permitted insulation types. Am I missing anything? Is all that's required to reclassify this circuit to remove the Class 2 markings from the power source and follow 725.49? And you have to follow the entire rest of Chapter 3, but that's kind of a given.
I had little experience with Class 1, 2, 3 wiring rules until now, and had always been told that as long as you're following 300.3 (C) (1), it was good. I now understand the error of that thinking, on to the next item. Even though I asked our crew to run a separate conduit system for the Class 2 DLM signaling wiring (CAT6), which is not permitted to be reclassified per the manufacturer's instructions, we got dinged because they pulled that cable in the power conduits. We are going to install the dedicated raceway for it, but the dimmers are going to be in boxes that have a receptacle circuit passing through them. I think we are allowed to have those Class 2 cables in that box with power wiring as long as we follow the rules in 725.136 (D) (1),
(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 installed 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:
(1) The electric light, power, Class 1, non–power-limited fire alarm, and medium-power network-powered broadband communications circuit conductors are routed to maintain a minimum of 6 mm (0.25 in.) separation from the conductors and cables of Class 2 and Class 3 circuits.
As long as we can keep them separated by 1/4" I think it's ok, would you agree or disagree?
Last item, we have always (maybe incorrectly) used the 300.3 (C) (1) section to allow us to run 300 V rated CL2P, 18 ga thermostat wire for HVAC control in a wire way with 240 VAC power wiring. I can't find anywhere in the HVAC units' documentation that says it is Class 1 or 2 or anything. Does anyone know if 24 VAC HVAC control wiring falls in any of those classes? Is it considered "Class 1 Remote-Control and Signaling Circuits?" If it is Class 1 wiring, it would be subject as above to 725.49, and so be required to be 600 V insulated. But HVAC control wiring is run all the time in 150 V thermostat cable, Is there another type of circuit that this could be? Or does it go like this: 24 VAC wiring is either Class 2 or Class 3, but if you want to run it in the same raceway with power wiring, you have to reclassify it as Class 1, which invokes the 600 V insulation rule of 725.49. I'm hoping there is some other classification of this type of circuit that won't require 600 V insulation, and just falls under 300.3 (C) (1).
Sorry for my long windedness, but I wanted to have enough detail for you all to work with. Thanks in advance.
