Bonding Equipment Grounding Conductors to conduit and cabinet?

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mjc1060

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I just installed one 800A 480V Disconnect Switch fed from the new switch gear for the building ( Iam working in). This switch is to provide temporary power for the building. We pulled a 3-Phase parallel.(multi-wire circuit) with no neutral but we also pulled an equipment ground (ine each conduit). The foreman gave us a neutral assembly kit (this was isolated from the cabinet) and told me to connect the equipment ground to these lugs. I wanted to bond the equipment grounding conductors to the cabinet that contained the disconnect switch (as the lugs were isolated and had no physical connection). When I questioned my foreman and told him I was creating a parallel path (higher resistance) for the equipment grounds (by isolating them from the cabinet and metal conduits) and that I believed the equipment grounding conductors should be bonded to the metal conduit and enclosure to provide a low impedance path back to the source (circuit breaker located in the switch gear). My foreman told me this is only done at the service. My question is I was not bonding a neutral (service conductor) but an equipment grounding conductor? So why isolate equipment grounding conductors from the metal enclosures and metal conduit. My first thought was we were violating 110.3b by using lugs the wrong lugs (neutral assembly kit instead of equipment grounding conductors). My foreman told me this was a commercial job not a residential house. Whats the difference? My point is to install a low impedance path back to the overcurrent device. I am very confused can someone explain what I am missing?:(
 
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