GEC for Manufacturing Machines

[Noblink]

I work in a small industrial plant, and I have to provide electrical utilities for automated assembly machines. Many of these machines have free standing transformers that are fed by the main control panel of the machine. These transformers provide the various voltages that are required by different parts of the machine. In a typical scenario, the machine is installed on site by the manufacturers technicians. I provide the required 480 volt, 3 phase circuit with equipment grounding conductor to the disconnect on the control panel. All other connections (including those of the transformers) are reassembled by the manufacturer's technicians.

Should I provide a grounding electrode conductor from these transformers to building steel?

 

[ActionDave]

Look at 250.21 and see if that fits your application.

 

[Noblink]

Look at 250.21 and see if that fits your application.

Thank you. 250.21 does not cover my application.

 

[petersonra]

Thank you. 250.21 does not cover my application.

The GEC is required if you have a SDS regardless of whether your system is grounded or not, and 250.21 only tells you when you are allowed to use ungrounded power, which is not relevant to whether you need a GEC or not. There are exceptions for control transformers 1000 VA and less providing power for class 1 and 2 circuits.

 

[tom baker]

You will need to both ground and bond the SDS systems.
Bonding is via the system bonding jumper
Grounding, my preference would be building steel. If you need physical protection for the GEC use PVC conduit.