Earth grounding - No neutral

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IMNTRSD

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I have been working with electricity for a while as a plant technician. We have 3 phase 208v. I have to hook up an autostep harig surface grinder. The schematic shows 3 phase coming in and several places where parts of the machine's intricate parts are grounded. In talking with the manufacturer, I am told that neutral and ground are called common and must be to an earth ground. Is it possible that a transformer within this machine can use the 208 3 ph. and come out with 110 without a neutral - using the ground as a neutral?
 
If the factory bonded one side of the transformers secondary to the frame you now have a 'grounded conductor' to use with the 120 volt circuits. It may not technically be a neutral but it is a 'grounded conductor' which is really what you want.
 
IMNTRSD said:
The schematic shows 3 phase coming in and several places where parts of the machine's intricate parts are grounded. In talking with the manufacturer, I am told that neutral and ground are called common and must be to an earth ground. Is it possible that a transformer within this machine can use the 208 3 ph. and come out with 110 without a neutral - using the ground as a neutral?
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No, the EGC should not be subject to a load. Do not use the equipment ground as a circuit conductor. It's hard to believe they'd recommend it.

There should be a grounded (back at the service) neutral conductor for 120v loads, and a grounding (EGC) conductor for bonding machine parts.

These two conductors should be isolated from each other within the machine, the supply circuit, and all the way back to the service's main disconnect.
 
In the not too distant past, some of the manufacturer's reps were demanding that a 'clean' ground be used to feed their machine. In many cases a hole was drilled in the factor floor and a ground rod driven to 'ground' the machine. All was well until there were some electrocutions and the practice was stopped. The problem was that some of the older reps were of the opinion that they still needed a 'clean' ground. I suspect that is what you are running into here. :-?
 
If the machine is 3 phase then the manufacturer probably just wants an equipment grounding conductor. No neutral required...any 120volt loads should be served from an integral transformer. You only need a 4 wire plug, L1-L2-L3-G. If you must use the 5 wire plug and receptacle I would leave the neutral out of the equation and mark the plug, but check the current on the ground just to be sure. If for some reason the machine is pulling a neutral off the case for a oil pump or something like that then you have a issue of load on you egc.
 
are you trying to add a convenience receptacle? Or is this wiring purely for he equipment? A convenience receptacle at the work station?
 
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