Switches

Single-throw knife switches must be placed so that gravity will not tend to close them. Single-throw knife switches approved for use in the inverted position must be provided with a locking device that will ensure that the blades remain in the open position when so set.

Double-throw knife switches may be mounted so that the throw will be either vertical or horizontal. If the throw is vertical, a locking device must be provided to ensure that the blades remain in the open position when so set.

Connection of Switches

Single-throw knife switches and switches with butt contacts must be connected so that the blades are de-energized when the switch is in the open position.

Single-throw knife switches, molded-case switches, switches with butt contacts, and circuit breakers used as switches must be connected so that the terminals supplying the load are de-energized when the switch is in the open position.

Snap switches, including dimmer switches, must be effectively grounded and must provide a means to ground metal faceplates, whether or not a metal faceplate is installed.

Regulations pertaining to switchboards and panelboards are set out in 29 CFR 1910.305.

Switchboards that have any exposed live parts must be permanently located in dry locations and accessible only to qualified persons.

Panelboards

Panelboards must be mounted in cabinets, cutout boxes, or enclosures designed for the purpose and must be dead front. Blades of knife switches mounted in switchboards or panelboards must be dead when open.

Enclosures for Wet or Damp Locations

Enclosures in damp or wet locations must be installed such that moisture cannot enter and accumulate. There must be at least one-fourth inch of airspace between the enclosure and the supporting surface. The enclosures must be weatherproof in wet locations. A receptacle installed in a wet or damp location must be suitable for the location. A receptacle is considered to be in a location protected from the weather when it is located under roofed open porches, canopies, marquees, or the like and where it will not be subjected to a beating rain or water runoff.

A receptacle installed in a wet location where the product intended to be plugged into it is not attended while in use, such as sprinkler system controllers, landscape lighting, and holiday lights, must have an enclosure that is weatherproof with the attachment plug cap inserted or removed. A receptacle installed in a wet location where the product intended to be plugged into it will be attended while in use, such as portable tools, must have an enclosure that is weatherproof when the attachment plug cap is removed.

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