Panelboard neutral and grounding conductor terminations.

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REPORT ON DISCUSSIONS DURING UL MEETINGS
WITH ELECTRICAL INSPECTORS AT THE 2006 IAEI SECTION MEETINGS

Question: Panelboard neutral and grounding conductor terminations. For panelboards, how many grounding and neutral bar conductors can you use under each terminal screw?

Answer: UL Lists Panelboards under the product category “Panelboards (QEUY).” Guide Information can be found in UL’s Online Certification Directory at www.ul.com/database, and on page 196 in the 2006 UL White Book.

Panelboards are required to be marked with the number and size of conductors for each terminal on the grounding or neutral bus.

For panelboards, UL requires that an individual terminal be provided for the connection of each branch-circuit neutral conductor and, with one exception, that the number of individual terminals be not less than 75 percent of the total number of individual fuseholder or circuit-breaker poles capable of being installed in the panelboard. Under the exception, the number of terminals may be reduced to 50 percent if the panelboard is marked to indicate the maximum number of circuits and the need to use mulitpole branch-circuit units to limit the number of terminals to a specified number.

As indicated in the UL Guide Information for “Electrical Equipment for Use in Ordinary Locations (AALZ)” product terminals are acceptable for connection of only one conductor, unless there is a marking or wiring diagram indicating the number of conductors, which may be connected.

Always comply with any markings located on the panelboard; these markings will identify the number and size of conductors permitted for each terminal.