No, a single #12 AWG grounding conductor from the wireway ground bar to the panel would NOT be code-compliant in the situation you've described. Here's a breakdown of why:1. Individual Circuit Grounding (Equipment Grounding Conductors - EGCs)

Each MC cable contains a circuit. Each circuit must have its own dedicated Equipment Grounding Conductor (EGC) that runs back to the panel's grounding bus. The EGC's purpose is to provide a low-impedance path for fault current back to the source (the panel). This is critical for the overcurrent device (circuit breaker or fuse) to trip quickly and clear the fault.

NEC 250.134(B) generally requires that the EGC (in this case, within the MC cable) terminate at the equipment enclosure and then connect back to the panel's ground bus.2. Wireway Grounding Requirements

Wireways themselves must be grounded. The ground bar in the wireway is intended to provide a convenient connection point for: Bonding the wireway itself to the grounding system. This is commonly done with a larger conductor connected to the panel's grounding bus. Terminating the EGCs from the MC cables within the wireway before extending them to equipment, and connecting them to the local wireway equipment grounding buss. While you do need to ground the wireway, this grounding is separate from the required EGCs for each individual circuit. A single #12 AWG conductor may not be adequate to properly bond the wireway and provide a low-impedance path to the grounding electrode system, depending on the size of the conductors and overcurrent protection in the circuits served.3.

Sizing the Equipment Grounding Conductor

The size of the EGC within the MC cable (or any other wiring method) is determined by the size of the overcurrent protective device (breaker or fuse) protecting the circuit, not by the number of circuits in the wireway.

NEC 250.122 specifies the minimum size of EGCs based on the overcurrent device.4. Why sharing isn't allowed

The purpose of the EGC is to quickly trip the breaker and sharing equipment grounding conductors could overload and possibly fail, and defeat the purpose.

In summary

Each MC cable needs its own EGC running all the way back to the panel's grounding bus, sized according to the circuit's overcurrent protection. This EGC is typically within the MC cable itself (the aluminum armor or a separate grounding conductor). The wireway also needs to be bonded to the grounding system. A single conductor from the wireway ground bar to the panel's grounding bus is for the wireway itself. The size of this conductor is determined by

NEC 250.28 and 250.66, 250.102.

What to do (General Guidance - Consult a Qualified Electrician)


Terminate each MC cable's EGC at the wireway's ground bar. This means bonding the metal armor of the MC cable, or the insulated grounding conductor within the MC cable, to the ground bar.2. Run a separate equipment grounding conductor from the wireway's ground bar to the panel's grounding bus. The size of this conductor is determined by NEC 250.28, 250.66 and 250.102, and depends on the size of the largest ungrounded conductor feeding circuits through the wireway.3. Ensure all connections are made using approved connectors and methods. Use appropriate lugs and bonding jumpers.

Important Note: This is a general explanation. Electrical codes can be complex, and the specific requirements depend on the details of the installation. Always consult a qualified and licensed electrician for any electrical work. They can assess the specific situation and ensure compliance with all applicable codes. Improper grounding can create serious safety hazards, including shock and fire risks. Flag for review