Inspectors, manufacturers, contractors and electricians have debated the installation orientation of panelboards and circuit breakers for many years. Should a panelboard be installed only in a vertical position, or can it be installed horizontally? Can the panelboard be installed on its back, or would that be a violation of the National Electrical Code (NEC)? Can the panelboard be installed upside down, and if not, why not? Does proper circuit breaker operation enter into the discussion, and is there a safety issue in determining whether the breaker handle is on when up or off when in the down position? Researching through the permutations and changes in the various editions of the NEC should provide the answers to these questions.

In the 1975 NEC, Section 240.33 provided text dealing with the orientation of panelboard and switchboard enclosures. One of the determining factors of enclosure mounting was the orientation of the circuit breaker. In 1975, the text in this section read, “Vertical Position. Enclosures for overcurrent devices shall be mounted in a vertical position unless in individual instances this is shown to be impracticable.” One of the determining factors of how the panelboard was mounted was the orientation of the circuit breaker. In the same edition of the NEC, Section 240.81 indicated, “circuit breakers shall clearly indicate whether they are in the open (off) or closed (on) position.” It also stated, “where circuit breaker handles on switchboards are operated vertically rather than rotationally or horizontally, the ‘up’ position of the handle shall be the ‘on’ position.” This last issue applied only to switchboards, not panelboards. These two sections of the NEC remained unchanged until the 1984 NEC.

The change that occurred for the 1984 NEC involved making an exception of the phrase “unless in individual instances this is shown to be impracticable.” Section 240.33 read, “Enclosures for overcurrent devices shall be mounted in a vertical position. Exception: Where this is shown to be impracticable and complies with Section 240-81.” While 240.81 applied to these installations previously, this new exception now made it crystal clear that compliance with 240.81 was necessary. There was also a change in 240.81 relating to the circuit breaker orientation, requiring both switchboards and panelboard circuit breakers operating vertically to have the up position of the handle be the on position. The purpose of this change was to enhance safety, since the position of the blades cannot be seen within the circuit breaker, and someone having to operate the circuit breaker in an emergency situation may not take the time to read the marking indicating “off” and “on.” The new text in the second paragraph of 240.81 in the 1984 NEC read, “Where circuit breaker handles on switchboards or in panelboards are operated vertically, rather than rotationally or horizontally, the ‘up’ position of the handle shall be the ‘on’ position.” With the addition of panelboards to 240.81, this rule now applied to both switchboards and panelboards. The text in these two sections of the NEC stayed relatively unchanged until the 1990 NEC.

In the 1990 NEC, any reference to switchboards or panelboards was deleted from the second paragraph of 240.81, since any circuit breaker mounted in the vertical position in any enclosure must have the up position of the handle as the on position. Section 240.33 did not change. In the 1999 NEC, all exceptions in Article 240 were removed and made into positive text, so Section 240.33 returned to the pre-1984 Style. Also, text was added dealing with listed busway plug-in units that read, “Enclosures for overcurrent devices shall be mounted in a vertical position. Circuit breaker enclosures shall be permitted to be installed horizontally where the circuit breaker is installed in accordance with Section 240.81. Listed busway plug-in units shall be permitted to be mounted in orientations corresponding to the busway mounting position.” In the 2002 NEC, the phrase “unless that is shown to be impracticable” was added back into the first sentence, so the text reads, “Enclosures for overcurrent devices shall be mounted in a vertical position, unless that is shown to be impracticable. Circuit breaker enclosures shall be permitted to be installed horizontally where the circuit breaker is installed in accordance with Section 240.81. Listed busway plug-in units shall be permitted to be mounted in orientations corresponding to the busway mounting position.”

The text, as written in the 2002 and 2005 NEC would permit the circuit breaker enclosure to be mounted horizontally in compliance with 240.81, but not upside down, since the circuit breakers would not comply with 240.81.

Next month’s column will deal with circuit breaker enclosures lying on their back on a horizontal surface, work space issues and a major change in the 2008 NEC for placement of panelboards in stairwells.