A contractor recently installed a MCC in our plant. The equipment consists of VFD,s, motor starters, and a PLC. This panel is fed with 480v. three phase power. In order to obtain 120v. control power, a 15Kva transformer 480v. to 120v. single phase was installed outside of the panel. While troubleshooting a control problem, I discovered that the neutral was not bonded to the grounding conductor for the control circuit. According to NEC Art. 250.20 B,D I feel that this is a code violation. The contractor tells me the neutral does not have to be bonded but cannot cite any code reference. Who is right?
Grounding/Bonding a Control Transformer
- Thread starter kuhala
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- Status
- Location
- Illinois
- Occupation
- retired electrician
Re: Grounding/Bonding a Control Transformer
Look at 250.21(3). If all of the conditions in (a) though (d) are met the control transformer is permitted to be an ungroundec system.
Don
Look at 250.21(3). If all of the conditions in (a) though (d) are met the control transformer is permitted to be an ungroundec system.
Don
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