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    Article 424 Disconnect Rating

    1. 424.19

    2. New Text

    3. 424.19 Disconnecting Means Means shall be provided to disconnect the heater. motor controller(s), and supplementary overcurrent protective device(s) of all fixed electric space-heating equipment from all ungrounded conductors. Where heating equipment is supplied by more than one source, the disconnecting means shall be grouped and marked. The disconnecting means specified in 429.19(A) and 424.19(B) shall have an ampere rating not less than 115 percent of the total load of the motors and the heaters.

    4. There is no specification in Article 424.19 on the rating of the disconnecting means. Based on this, one could install a 30-ampere rated disconnect on a 60-ampere branch circuit and still be in compliance with the code. This new requirement would be consistant with disconnect ratings in other articles such as motors and air conditioning and refrigeration equipment.
    Bryan P. Holland, MCP
    NEMA - Codes & Standards

    #2
    Re: Article 424 Disconnect Rating

    But such an installation would be in violation of the listing of the disconnecting means.
    Bob

    Comment


      #3
      Re: Article 424 Disconnect Rating

      :confused: What do you mean? :confused:

      How does this proposal effect listing of a disconnect?
      Bryan P. Holland, MCP
      NEMA - Codes & Standards

      Comment


        #4
        Re: Article 424 Disconnect Rating

        If a disco is only rated for 30 amps, it would violate listing to install it on a circuit where it would interrupt more than 30.

        Right?

        Comment


          #5
          Re: Article 424 Disconnect Rating

          This is true, however, why do motor and A/C equipment disconnects need to be sized at 115% of the load and yet other similiar appliances like heating equipment do not?
          Bryan P. Holland, MCP
          NEMA - Codes & Standards

          Comment


            #6
            Re: Article 424 Disconnect Rating

            Specificity is generally a good thing and motor sustained inrush (especially for fans) make this an appropriate Proposal at least "in principal."

            For Manual of Style purposes you may want to propose the requirements to be in the specific appropriate sub-sections rather than the "basic" rule. Otherwise, it gives the CMP a basis to reject if they feel it's too general or if accepted may cause unintended consequences, such as requiring it for heaters that have no motors at all.

            Another possible option is to refer back to Art 430.

            You may want to correct your reference to 429.19(A).

            Nevertheless, IMO this is an appropriate Proposal on its face. Right now, technical merit is not the primary goal of this forum. We want to help folks make Proposals that will not be rejected outright without due review. Technical merit is the goal of the Comment stage.

            [ March 08, 2005, 10:32 AM: Message edited by: rbalex ]
            [COLOR=black]"Bob"[/COLOR]
            Robert B. Alexander, P.E.
            Answers based on 2017 NEC unless otherwise noted.

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