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	Subject - 208 3 phase supply code questions donnfse I have a customer who is using a piece of test equipment that uses 208 three phase wye power. This equipment has 3 hots, a neutral and ground. The equipment uses the power as 3 branches of 120VAC within the system. The system has a 5 wire pigtail. The customer brought 5 wires from a subpanel to a 3 pole switchbox near the system. The three hots of the pigtail and customer's supply go to the terminal lugs of the switch. no problem. The ground wires of the pigtail and customer's supply go to a separate terminal lug installed in the switchbox by the customer. It is screwed into the case of the switchbox. Other than 2 wires to a single lug, it is probably OK. Here's the concern. The neutral wires of the pigtail and customer's supply also go to another separate terminal lug installed in the switchbox by the customer. It is screwed into the case of the switchbox. This effectivly ties neutral and ground together in the switchbox. My questions are: 1)Is this to code?( I suspect not. I believe subpanels shouldn't have neutral & ground bonded together.) 2)What code section is this called out? 3)I suspect that this somewhat negates the safety aspect of the safety ground. What other aspects does it effect? Could this adversly effect the test equipment? Thanks. Scott Vickrey Look again because the neutral bar may still be isolated from the enclosure even though it's mounted on it. This is normally accomplished insulating bushings. If it's making direct contact, Then you are correct this is not up to code. After the main disconnecting means for the building the neutral and the ground should be kept separate. The reason for this is that connecting them in parallel causes objectionable current to flow through the grounding system. If the neutral becomes opened then all the current that would normally flow through the neutral will now be going through the ground system which may not be capable of handling the current. This is actually in the 2002 NEC code section 250.6. The code that prevents the neutral from being connected to the ground on the load side of the main disconnecting means is section 250.24(A)(5)Load-Side Grounding Connections.