Class 1 Circuits

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Thanks in Advance for your Help.

[The Following is reprinted from Mike Holt's Newsletter:]

Dear Mike I need your help.

A proposal (16-43) was submitted and approved by Code Panel 16 (which I am a nonvoting member) to delete Class 1 power limited circuits from the Code (Article 725).

Mike Holt’s Comment: A power-limited Class 1 circuit is defined by the NEC as that portion of the wiring system between the load side of the power-limited supply and the connected equipment. Power-limited Class 1 circuits can be either ac or dc and must be supplied from a power source that limits the output to 30 volts and 1,000 VA [725-21(a)]. Power-limited Class 1 circuits are necessary when the energy demands of the system exceed the energy limitations of Class 2 or Class 3 circuits (100 VA) [Chapter 9 Table 11(a)]. All wiring for power-limited Class 1 circuits must be installed in accordance with Chapters 1 through 4 of the NEC. This means that 600 volt conductors [725-27] must be installed in a Chapter 3 wiring method [725-25], splices must be in outlet boxes in accordance with Section 300-15 [725-25], and overcurrent protection must be as specified in Article 240 [725-24].

(back to the newsletter) The submitter of this Proposal makes no claim that Class 1 Power-limited Circuits are unsafe or present any type of hazard. His only reason for recommending these circuits be deleted is because he states that no one uses them.

In my opinion, deleting Class 1 power-limited circuits from the Code will unnecessarily deny installers the option of using a Class 1 circuit.

Irving Mande, Edwards Systems Tech, CT

Irv.Mande@gsbsc.gensig.com

Question to Mike Holt: “I work for a control contractor and install 120 to 24vac X-formers for HVAC low voltage controls. The X-former VA is usually 250 or 500VA. Fed from a 20amp breaker. What is the proper way to protect this X-former?"

Mike Holt’s Comment: I guess some people are installing Class 1 circuits. I need your help. Do you know of any installations that utilize a 24 volt power supply that is rated more than 100 VA, but less than 1000 VA? Could you let me know what the installation is for? Do you think if the Code deleted this rule it would be a good idea?

Please respond to Mike@MikeHolt.com

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