NEC Class 2 Issue

[Mark Lyons]

Over the past few years I've designed several small-to-medium commercial LED light strip projects using NEC Class 2 components and wiring. The project I am working on now, though, appears to be a less-than-optimal application of the NEC Class 2 code requirements.

Project Scope: This commercial project requires lighting an outdoor structure with twelve (12) LED RGBW strips that are each 24 feet in length. All twelve (12) LED strips are intended to operate in sync. All power supplies, controller, and related components will be enclosed in single electrical enclosure attached to the structure. As a side note, these twelve (12) LED strips will be attached to the twelve (12) inner rafters noted in this drawing:

https://drive.google.com/file/d/1-hJghofR1VeyTZIk5jPGHjNxF_rqmlvF/view

Present Design: Each of the twelve (12) LED strips require approx. 72 watts to operate at full power (3 watts/foot). I selected these strips to keep the LED strips under NEC Class 2 maximum wattage (96 watts x 80% = 76.8 watts). Apparently, I'll need to use twelve (12) 120VAC to 24VDC power supplies/drivers AND twelve (12) RGBW controller/receivers to keep within the NEC Class 2 requirements.

Preferred Design: I'd like to use higher wattage LED strips (5-7 watts per foot) AND fewer higher wattage 120VAC to 24VDC power supplies AND fewer RGBW controllers/receivers.

Bottom line, how can I circumvent the NEC Class 2 requirements to accomplish this preferred design and still conform to the NEC code?

I suspect I am overlooking a simple solution ... please advise.

Thank you!
Mark

 

[don_resqcapt19]

Over the past few years I've designed several small-to-medium commercial LED light strip projects using NEC Class 2 components and wiring. The project I am working on now, though, appears to be a less-than-optimal application of the NEC Class 2 code requirements.

Project Scope: This commercial project requires lighting an outdoor structure with twelve (12) LED RGBW strips that are each 24 feet in length. All twelve (12) LED strips are intended to operate in sync. All power supplies, controller, and related components will be enclosed in single electrical enclosure attached to the structure. As a side note, these twelve (12) LED strips will be attached to the twelve (12) inner rafters noted in this drawing:
https://drive.google.com/file/d/1-hJghofR1VeyTZIk5jPGHjNxF_rqmlvF/view

Present Design: Each of the twelve (12) LED strips require approx. 72 watts to operate at full power (3 watts/foot). I selected these strips to keep the LED strips under NEC Class 2 maximum wattage (96 watts x 80% = 76.8 watts). Apparently, I'll need to use twelve (12) 120VAC to 24VDC power supplies/drivers AND twelve (12) RGBW controller/receivers to keep within the NEC Class 2 requirements.

Preferred Design: I'd like to use higher wattage LED strips (5-7 watts per foot) AND fewer higher wattage 120VAC to 24VDC power supplies AND fewer RGBW controllers/receivers.

Bottom line, how can I circumvent the NEC Class 2 requirements to accomplish this preferred design and still conform to the NEC code?

I suspect I am overlooking a simple solution ... please advise.

Thank you!
Mark

Those are mutually exclusive ideas,

 

[ramsy]

(12) LED RGBW strips that are each 24 feet in length.

Why not LED rope light, listed for outdoor use?

If each rope had a cord & plug, 12 duplex outlets could be on same circuit.

If 100ft of LED rope was allowed to wrap around to make 4 strips each, 2 duplex outlets could handle 3 ropes.

 

[petersonra]

I don't see how that you can increase the circuit VA any and still remain nec class 2.

However, if you don't care about staying in class 2, you have more options, but you're wiring methods are a little more expensive.

 

[hbiss]

However, if you don't care about staying in class 2, you have more options, but you're wiring methods are a little more expensive.

Exactly. Is there any reason the light strips couldn't be powered by a higher wattage source using a chapter 3 wiring method? Extra wiring cost would be minimal due to the size of the shed.

It's the power source that determines the class of the circuit, not the loads.

-Hal

 

[darekelec]

may I ask why one cannot run 96 watts of light strips on 96 watt power supply?

I selected these strips to keep the LED strips under NEC Class 2 maximum wattage (96 watts x 80% = 76.8 watts)

 

[don_resqcapt19]

may I ask why one cannot run 96 watts of light strips on 96 watt power supply?

I selected these strips to keep the LED strips under NEC Class 2 maximum wattage (96 watts x 80% = 76.8 watts)

I don't believe anyone said you could not do that.

 

[darekelec]

probably OP uses 80% of rated power of transformer to lower operating temperature and extend lifespan. not a requirement thou

 

[tortuga]

I will be following the evolution of Fault managed Power supplies. The new "Class 4" in the 2023 code.

Right now it appears you can get 2000 Watts out of a class4 system.
Its patented and riddled with vendor lock in, so you have to use all one vendors stuff.
I imagine there will emerge some agreed upon open standard where one can make a class4 power supply that will work with another manufacturers class4 light.

 

[Tip DS]

Looks like OP lost interest.

 

[ggunn]

Educate me; what is the difference between the Class X power supplies?

 

[Tip DS]

Educate me; what is the difference between the Class X power supplies?

From NFPA 70:
Class 1 Power-Limited Circuits. These circuits shall be supplied from a source that has a rated output of not more than 30 volts and 1000 volt-amperes.
Class 2 & 3 Power-Limited Circuits:


The Class 1 circuit has defined wiring methods, where Class 2 & 3 are not as well defined. IOW, the designer has much more flexibility in wire and overcurrent protection selection for Classes 2 & 3.

 

[don_resqcapt19]

Prior to the 2023 code, the Class 1 circuit ratings shown above were Class 1 power limited circuits. There were also Class 1 circuits that were not power limited.

725.41(B) Class 1 Remote-Control and Signaling Circuits.
These circuits shall not exceed 600 volts. The power output of the source shall not be required to be limited.

Often 120 volt control circuits were installed as non-power limited Class 1 circuits.
They have been working to fix the mess that was created when the non-power limited Class 1 circuits were removed from the code in the 2023 cycle as there were unintended consequences. There was a TIA issue for 300.26 to fix some of the issues, and I expect there will be additional fixes in the 2026 code. Note that the TIA took effect 4/10/23, and you have the first edition print copy, you will not see these changes. If you are using Link, they show up with the letter "T" in a highlighted circle. If you click on the T it will show you the original text along with the effective date of the TIA.