0-10v dimming again

[david]

So, in our instance, can the luminaire operate without the LV dimmer? Yes it could. So dollars to donuts the NEC shot down allowing the 0-10V LV to be reclassified and be run with the power conductors because they didn't consider it functionally associated with the luminaires operation.
-Hal

I do not think that is the threshold at all, it isn’t that the fixture can operate without a dimming function.

The threshold would be when you are using a dimming function are the power cables and low voltage circuit functionally associated.

Lets say you have multible 0-10 volt dimmers ganged in one location. Three on the left and three on the right same switch box.

There is one 20 amp branch circuit for the fixtures. There is a pull box in the ceiling that you intend to go left and right in the building to control lighting fixtures.
You run one conduit from the pull box to the switch box in the conduit you have the 0-10 volt class 2 circuits and the 20 amp branch circuit you need to reclassify the class 2 circuits ,

the 20 amp branch circuit and the original class 2 circuits are functionally associated with dimming the lighting fixtures.

However same exact circumstance as sated except you feed the switch box with two 20 amp branch circuits one for half the fixtures being dimmed and one 20 amp branch circuit for the other three dimmers being used to control dimming of the fixtures.

If you use one pull box in the ceiling and one conduit to the switch box it could be stated that one of the 20 amp branch circuits is not functionally associated with three of the 0-10 volt dimmers controlling half of the fixtures being dimmed.

 

[wwhitney]

We know that there is a luminary cable available with power and LV under one sheath. The manufacturer (AFC) spent a lot of money having this cable listed. Why would they do that if it were permissible to follow the Articles above and just use an off the shelf 4 conductor cable?

Because reclassifying to Class 1 isn't always an option? Some equipment can only be fed by a Class 2 circuit? I'm guessing.

Cheers, Wayne

 

[hbiss]

I would think that's a good part of the reason. A device that is designed to operate with 12v certainly wouldn't do well if there was a cross between the reclassified wiring and a 277v line.

@David- As a reference we are talking about the requirements relating to the basic installation of a single 0-10v dimmer and a single fixture. Multiple dimmers, fixtures and boxes with different devices doesn't change anything except to make it more confusing.

-Hal

 

[hbiss]

All of this being said, my problem is where is it written that you can't reclassify? If you follow the NEC Articles I copied above, you are free to pull a pair of THHNs in the raceway with the power and use that for the LV dimming- barring any instructions to the contrary from the manufacturer of the luminaire.

If you are prohibited from doing that for some reason then you have to use one of the following methods:

1) Luminary MC cable.
2) Running the LV separately.
3) Pulling a listed 600v cable assembly for the LV into a raceway with the power conductors.

Until the NEC clarifies their intent for reclassifying, this is probably going to be the AHJs call.

-Hal

 

[wwhitney]

3) Pulling a listed 600v cable assembly for the LV into a raceway with the power conductors.

I'm sorry, I still don't see anything that would require the LV cable assembly to be 600v rated, just rated at least as high as the voltage applied to the power conductors. And there's also

4) Pulling a cable assembly for the power conductors into a raceway with individual LV conductors.

For example, Southwire 12/3 NM has a nominal OD of 347 mils. One of those and two 18 awg TFN conductors fit (40% fill) in most 1/2" raceways (except ENT and Sch 80 PVC).

Cheers, Wayne

 

[david]

@David- As a reference we are talking about the requirements relating to the basic installation of a single 0-10v dimmer and a single fixture. Multiple dimmers, fixtures and boxes with different devices doesn't change anything except to make it more confusing.

-Hal

the post was was only to illustrate an application of a power circuit and a class two 0-10 dimming circuit being functionally associated, in contrast to your statement if the fixture could operate without a dimming circuit than the power circuit was disqualified as functionally associated with the dimming circuit.

 

[hbiss]

I'm sorry, I still don't see anything that would require the LV cable assembly to be 600v rated, just rated at least as high as the voltage applied to the power conductors. And there's also

4) Pulling a cable assembly for the power conductors into a raceway with individual LV conductors.

For example, Southwire 12/3 NM has a nominal OD of 347 mils. One of those and two 18 awg TFN conductors fit (40% fill) in most 1/2" raceways (except ENT and Sch 80 PVC).

Cheers, Wayne

The 600V comes from the 600V insulation of the THHN. What other cable do you propose? CL2 cables are rated at 150V and CL3 cables are rated at 300V BUT you aren't supposed to know that and that's why it's not stamped on the jacket. They don't want anybody to do what you propose to do. You are supposed to use it strictly by the CL2 and CL3 power supply requirements. You cannot pull a CL2 or CL3 cable with line voltage conductors.

Yes, you could do it the other way around and run the power with a listed cable such as what you suggest. But then you run into the problem of what kind of connector do you terminate it with at the fixture and wall box- unless you are only using the raceway as a sleeve. When you use that cable for line voltage you have to use the proper connectors. Use it for CL3 or CL2 LV you don't even need connectors.

-Hal

 

[wwhitney]

The 600V comes from the 600V insulation of the THHN.

I agree, but I don't see anything that says that if Class 2 conductors and power conductors are within the same raceway via the separation of an additional sheath and the allowance of 725.136(I)(1), then the Class 2 conductors need to have an insulation rating of 600V. 300.3(C)(1) tells you the insulation rating of the Class 2 conductors would have to be sufficient for the voltage applied to the power conductors. So what would be wrong with running 600V THHN power conductors and 300V FPLR 16/2 for dimming conductors inside a raceway on a 208/120Y system?

But then you run into the problem of what kind of connector do you terminate it with at the fixture and wall box

While I can't find it, surely there is wording in the NEC that cables installed in complete raceway systems don't need to be secured to enclosures.

Cheers, Wayne

 

[david]

I'm sorry, I still don't see anything that would require the LV cable assembly to be 600v rated, just rated at least as high as the voltage applied to the power conductors. And there's also

4) Pulling a cable assembly for the power conductors into a raceway with individual LV conductors.

For example, Southwire 12/3 NM has a nominal OD of 347 mils. One of those and two 18 awg TFN conductors fit (40% fill) in most 1/2" raceways (except ENT and Sch 80 PVC).

Cheers, Wayne

If the class 2 circuit is mixed with power conductors you would reclassified all to class 1 wouldn't 725.49 apply

Handbook 2008 NEC
Section 725.49 requires all Class 1 circuit conductors to be rated at 600 volts. This effectively requires Class 1 circuits to be wired using the wiring methods found in Chapter 3 or the use of conductors specifically listed for Class 1 circuit use.

 

[hbiss]

Around and around we go...:? Please re-read post #17.

-Hal

 

[wwhitney]

If the class 2 circuit is mixed with power conductors you would reclassified all to class 1 wouldn't 725.49 apply

725.136(I)(1) lets you run the class 2 circuit together with the power conductors without reclassifying, that's how luminary MC cable works. So you have two different options for getting everything in one conduit:

1) Use 725.136(I)(1) with an appropriate cable method for either the power conductors or the class 2 conductors.
2) Reclassify the class 2 conductors to class 1, then under the "functionally associated" rule you can just run individual conductors for both circuits.

The question I have is whether FPLR is an appropriate cable method for 725.136(I)(1) compliance: when that section talks about "non-metallic sheathed cable" is it referring specifically to one of the Chapter 3 wiring methods (NM or TC), or more generically to any cable with a non-metallic sheath? I think FPLR has a thinner outer jacket than NM, so there is a functional difference. I've sort of convinced myself that FPLR isn't sufficient, it would need to be NM or TC.

Cheers, Wayne

 

[david]

I am going to post a section from a commentary of part I for your comment, i was under the impression this section addressed cables through bored holes and such in framing and things like that.

I did not think there was an application for this section for running both class 1 and class 2 in a common race way

McGraw-Hill’s National Electrical Code 2011 Handbook, Twenty-Seventh Edition

In part (I), Class 2 or 3 circuit conductors must be separated not less than 2 in.
(50 mm) from conductors for light, power, Class 1, or non-power-limited fireprotective
signaling circuits.

The present wording of 725.136(I) clarifies many
past misunderstandings about the intent of the rule. Previous Code editions
only mentioned raceways, porcelain tubes, or “loom” as a means of separating
Class 2 circuits, such as “bell wiring,” from conductors of light and power systems
where such systems were closer together than 2 in. (50 mm).

And on that
basis, some inspectors required such bell wiring or similar Class 2 wires to have
a 2-in. (50-mm) clearance from any type of cable (NM, UF, AC, etc.) that contained
conductors for power or lighting circuits. The old rule was also commonly
applied to prohibit bell wires and NM cables in the same bored holes
through studs, and so on.

With the present wording, the 2-in. (50-mm) clearance
from Class 2 wiring applies only to “open” light, power, and Class 1 circuit
conductors. Power and light circuits or Class 1 circuits that are in raceway or
cable do not require 2-in. (50-mm) separation from Class 2 and/or 3 circuits


Note, however, that there is no express permission to include Class 2 or
Class 3 conductors within a common cable assembly with power conductors.
Paragraph (2) here comes the closest, because it recognizes a “continuous and
firmly fixed nonconductor.”

This is crucial to the production of hybrid cables,
where additional separation beyond the conductor insulation is applied to the
power-limited conductors in accordance with the spirit of these principles. For
example, 334.116(C) expressly recognizes this type of construction for Type
NMS cable, and UL has been listing such constructions for many years

 

[david]

Around and around we go...:? Please re-read post #17.

-Hal

What specifically do you want me to re-read in post 17

 

[david]

I give up. Read 725.136. There is NOTHING about being able to reclassify CL2 to class 1.

Like I said above, this is an subject needing immediate clarification from the Code making panel.

-Hal

725.130(A) Exception 2

725.136 (D) Associated Systems Within Enclosures.
(2) The circuit conductors operate at 150 volts or less to ground and also comply with one of the following:
b. The Class 2 and Class 3 circuit conductors are installed as a Class 1 circuit in accordance with 725.41.

 

[Michael Scully]

LED Highbay has 2 cords coming out of the housing with a hook mount.

This speaks to the core question that has lead me to this thread and the migrane that goes with it. Being a new poster to the forum, I am not sure if my subtly different question warrants it's own thread......

When it comes strictly to the point of termination in the lighting fixture at the ballast, there must be some point where a properly separated CL2, open air pair of conductors with it's 0-10v signal enters the fixture and eventually shares interior space with the source voltage for the ballast. Under any other circumstances, such in a raceway without seperation, if the two were to intermingle, CL2 installation wouldn't be allowed, and entire the length of the installation would be constrained to CL1 standards. [725.55 etc.]. I get that. (I've paid close attention to post #17, so don't hate me Hal.)

In https://www.mikeholt.com/mojonewsarchive/NEC-HTML/HTML/Article725CodeBasics~20021217.htm it states:
"You can mix Class 2 and Class 3 conductors with power conductors in boxes or enclosures, if the power circuit conductors are introduced solely to connect to the equipment connected to Class 2 and 3 circuits and you meet certain spacing and voltage requirements."

From the sound of this Mike Holt article, https://cdn.shopify.com/s/files/1/0..._for_a_Manufacturer_2.pdf?7534444860945924288 they could share the space if it's a 120Vac lighting circuit, and proper spacing is observed, but not, for example, a 277 lighting circuit.

I'd dare speculate from these correlated items that CL2 dimming is only an option for 120V lighting and any 277 application would be strictly in the realm of CL1 dimming.
Additionally I would submit that the Lighting Circuit and CL2 wiring would (to avoid co-mingling in raceway) be required to enter the lighting fixture through a separate penetration.

As Hal has asserted, this is in need of clarification, but I'm hoping someone out there has a solid answer, or can at least tell me I haven't missed something fundamental.

 

[Dennis Alwon]

Good luck getting a solid answer. I have been looking for one for years.

 

[lordofthisworld]

LED Highbay has 2 cords coming out of the housing with a hook mount.

One 3c 14ga cord is for the 120v Power, One 2c 16ga cord is for the 0-10v dimming.

All will be in a warehouse, all surface mount exposed conduit installation.

The plan is to hang the fixtures on an eyebolt and piping to each fixture and setting a box next to each and bringing both cords into a common 4sq box from the switch location.

Here's the delima.

Can the 120v and 0-10v wiring be installed together in one conduit from the switch location to the fixtures if all Thhn wiring is used ?

or

Do (2) separate conduits need to be installed from the switch location to (2) separate boxes next to the fixture to keep the 120v and 0-10v cords and wiring completely separate?

JAP>

I would say yes to the 120V and dimming wire be in the same raceway as long the insulations of the wire are rated the same, I would use THHN 600v.

 

[Mongomania]

All of this being said, my problem is where is it written that you can't reclassify? If you follow the NEC Articles I copied above, you are free to pull a pair of THHNs in the raceway with the power and use that for the LV dimming- barring any instructions to the contrary from the manufacturer of the luminaire.

If you are prohibited from doing that for some reason then you have to use one of the following methods:

1) Luminary MC cable.
2) Running the LV separately.
3) Pulling a listed 600v cable assembly for the LV into a raceway with the power conductors.

Until the NEC clarifies their intent for reclassifying, this is probably going to be the AHJs call.

-Hal

In NYC the only approved listed method for installing the 0-10 v wiring in the same conduit as the line voltage is in a luminaire mc cable . No other install is approved . Once in your J box the blue jacket must remain on the purple and grey pair and only skin enough to accommodate the splice . A 1/4 inch separation must maintain in the box from line voltage wires . In other words do a nice job on the splice box and do not remove the jacket at the connector . You can not install 600v rated thhn in the same conduit as 0-10. You can not use thhn for the 0-10 and say " as long as the wire is rated " .in NYC this is a violation .
If you are installing an emt or pipe job you must install 2 conduit systems right down to the switch box or conduit to the switch for the line voltage and free air if allowed for your 0-10 cable from light fixture or ceiling splice box right to the switch box . This all sounds silly since you will have a LV jacketed cable entering a knockout in a switch then entering the ceiling box or fixture all while a pipe or bx is doing the exact same thing . I get it but that's the code . Let's talk why.
In the wall box or light fixture or ceiling box you MUST maintain 1/4" separation by code when making splices . It is impossible to maintain 1/4" separation in a conduit or greenfield or regular 4 wire bx . The only approved method is again the luminaire cable . Sounds so ridiculous to run a LV cable from box to fixture or switch to fixture as a separate raceway or conduit system or free air system if allowed but that's the rule in NYC . I am currently on a job where the wall switches are 277v with 0-10 dimming . The job is a 100 percent emt job with no flex tails allowed at all anywhere except a light fixture tail or motor tail. We installed 2 - 3/4 emt to every switch box . One will be hard piped to the ceiling 277v box that will also have the tails to the lights . The second pipe will be just a sleeve to bring the plenum rated 0-10 cable from the sw to the ceiling above finished tiles . Then free air with tie wraps to the same ceiling box as the pipe with the 277 went to. Add a squeeze connector and splice as specified maintaining a 1/4" separation . The fixtures are pre tailed with the 277 and 0-10 in the tail . The manufacturer has a UL rating for that tail which means they received approval for that tail to be in the light . This relieves me of any responsibility if there is failure of the 0-10 due to interference from the 277v.

The biggest issue is how do you keep the apprentices from pulling out their phones every 7 seconds