This section applies to
- Portable switchboards
- Portable power distribution equipment
- Commercial appliance outlet centers
There are three first level subdivisions that include the requirements for these items as follows;
- (A) Power Outlets and Commercial Appliance Outlet Centers.
- (B) Portable Switchboards and Portable Power Distribution Equipment.
- (C) Neutral Conductor of Feeders Supplying Solid State Dimmer Systems.
(A) Power Outlets and Commercial Appliance Outlet Centers.
This first level subdivision applies to power outlets and commercial appliance outlet centers that Section 518.5(B) tells us are the only supply equipment permitted to supply portable switchboards and portable power distribution equipment. Section 518.5(B) says too that this equipment can only be supplied from listed “power outlets” or listed “commercial appliance outlet centers”.
Power outlets fall under UL Category code QPYV and the basic standard used to investigate these products is UL 231, ‘‘Power Outlets.’’
Commercial appliance outlet centers fall under UL Category code AUUZ and the basic standard used to investigate these products is ANSI/UL 891, ‘‘Dead-Front Switchboards.’’ The products under this category code AUUZ include appliance outlet centers, which consist of a group of outlets with or without suitable branch circuit overcurrent protective devices, branch-circuit switching and/or timer provisions. Category code AUUZ also covers appliance outlet center enclosures intended for use with specific appliance outlet centers. Keep in mind that these products are not intended for use in residential dwellings.
Power outlets and commercial appliance outlet centers must comply with the following:
(1) Overcurrent Protection. Provide overcurrent protection or be protected by overcurrent devices.
(2) Accessibility. The general public must not have access to overcurrent devices, power outlets, and commercial appliance outlet centers. This aligns nicely with the fact that this equipment falls under category code AUUZ which states that these products are not intended for use in residential dwellings.
(3) Equipment Grounding Conductor Connections. Equipment grounding is important for all equipment in the power distribution system and this equipment is no different. This requirement is such that there must be a connecting means for an equipment grounding conductor.
(4) Markings. Marking requirements are found to again remind us that this equipment is not meant for the general public. The equipment governed by 518.5(A) Power must be marked as follows:
FOR USE BY QUALIFIED PERSONS ONLY. RISK OF ELECTRIC SHOCK.
DISCONNECT ALL POWER BEFORE SERVICING. DISCONNECTING MEANS LOCATION:
(5) Panelboard Orientation. The driver for all of the activity that occurred in this section during the 2023 cycle was driven by the requirement last cycle found in 408.43 which prohibited panelboards from being located in the face up orientation. This was problematic for this equipment and so a lot of activity occurred for the 2023 cycle to rectify. Just as in most examples like this, once people start looking at requirements that just may have been around for years, obvious changes are identified for readability and to address the identified technical detail. This requirement ensures the permission for a panelboard that is installed in a listed commercial appliance outlet center which is designed for in-floor mounting to be orientated in the face-up position. This orientation must be a part of the listing. The icing on the cake is a statement that the requirements found in 408.43 do not apply.
(B) Portable Switchboards and Portable Power Distribution Equipment.
This first level subdivision focuses on the requirements for portable switchboards and portable power distribution equipment. It requires that this equipment is supplied only from listed power outlets or listed commercial appliance outlet centers. Sufficient voltage and ampere ratings are called out as well.
(C) Neutral Conductor of Feeders Supplying Solid State Dimmer Systems.
The neutral conductor of feeders that supply solid state dimmer systems is the focus of this first level subdivision. The neutral conductor for the solid state “phase control” dimming systems must be considered a current-carrying conductor when performing ampacity adjustment. The neutral conductor for solid state “sine wave” dimming systems are not required to be considered as current carrying conductors for the purpose of ampacity adjustment.
The only exception for this section addresses those feeders that supply both phase-control and sine-wave dimmers. These feeders must consider the neutral as a current-carrying conductor for the purposes of ampacity adjustment.