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Can a four wire I-Line plug-in unit be used on a three wire I-Line/I-Line II busway system?


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UL 857, CSA C22.2 No. 27-1973, NFPA 70 Art. 368

Occasionally for reasons of availability, a four wire busway plug-in unit may be installed on three wire busway and used to serve a three wire load.  


Yes, but there is one exception, and some clarification is required.  If the load requires a neutral (a 3PH4W load), three wire busway ordinarily cannot be the power source, as the busway would lack the neutral required by the load.  In these instances, an isolation transformer with a four wire secondary is one solution to obtaining the neutral required by the load.  For three wire loads it is possible, with one exception, to install a four wire busway plug-in unit onto three wire busway to power the three wire load.  The one exception is that any plug-in unit with a catalog number beginning with ``PT`` must be used on a busway system with the same number of poles as the plug-in unit.  This is due to the fact that busway plug-in units with catalog number beginning "PT" use a joint pack-like configuration for attachment to the busway, and the number of bars in the joint pack-like connection must match the number of bars in the busway to allow for installation.

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