Class 2 wiring vs Class 3

[gadfly56]

I wasn't very clear.

Exception No. 2: 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.
Informational Note: Class 2 and Class 3 circuits reclassified
and installed as Class 1 circuits are no longer Class 2
or Class 3 circuits, regardless of the continued connection
to a Class 2 or Class 3 power source.

(A) Sizes and Use. Conductors of sizes 18 AWG and 16
AWG shall be permitted to be used, provided they supply
loads that do not exceed the ampacities given in 402.5 and
are installed in a raceway, an approved enclosure, or a
listed cable. Conductors larger than 16 AWG shall not supply
loads greater than the ampacities given in 310.15. Flexible
cords shall comply with Article 400.

(B) Insulation. Insulation on conductors shall be rated for
600 volts. Conductors larger than 16 AWG shall comply
with Article 310.

So if we start with a Class 2 or 3 circuit and call it a Class 1, can we then use Art. 310 to select the wire?

Reclassifying a Class 2 or 3 circuit requires more that simply using Class 1 wiring methods. You also have to add addtional overcurrent protection to each leg of the circuit, usually with a 4 or 5 amp fuse. This then allows you to run the cable in a raceway with power and lighting circuits, for example. If, however, you don't do any of the things that are prohibited for Class 2 and 3 circuits, then Article 300 requirements don't apply, except as noted. So if you wire a Class 2 circuit with NM, and the NM otherwise meets the requirements (plenum/riser, etc), then you can have open junctions and flying splices galore. Convincing the AHJ that the open splice is compliant may afford you the opportunity to fully engage the skills learned from "How to Win Friends and Influence People" by Dale Carnegie, but some people thrive on that sort of challenge .

 

[Dennis Alwon]

Somehow I cannot read the last thread so I am going to post and see what happens. It worked.

 

[DARUSA]

Reclassified class 2 as a class one circuit is more to not have expose live parts. As other people says before class 2 circuits can have free air splices and live parts expose like the class 2 transformers if you mix it with class one circuits and for any reazon you have a fault betwen the systems probably you can end up with a regular class 2 transformer having 120 volt at the terminals .
In order to prevent this hazard situation the code require you to reclassified the circuit using the wiring methods described on chapter 3 and no live parts or free air spliced are allowed after this.
Class 3 circuit require a minimun of 300 volts inssulation wire!!!