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Thursday, June 22, 2023

Question:

Hi Code Guru, thanks for all the great code insight. I look forward to your emails every morning. Maybe you can settle a dispute my co-worker and I are having regarding the secondary of a transformer separately derived system. Is an equipment grounding conductor required to be run with secondary supply conductors from the transformer to the disconnect/panelboard it supplies? Thanks in advance, Max Brunner
A

Answer:

Hello Max, glad to hear you are enjoying the CQD. The secondary side of a separately derived system requires a Supply-Side Bonding Jumper per Section 250.30(A)(2). This bonding jumper is often mistaken for an Equipment Grounding Conductor (ECG) and improperly sized. Section 250.30(A)(2) permits the Supply-Side Bonding Jumper to be of nonflexible metal raceway or conductor type. When a conductor type is installed, it must be sized per Table 250.102(C)(1) based on the ungrounded secondary conductor size.

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