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Discussion Starter · #1 · (Edited)
Help, I'm lost in land of fault current path.

Consider this situation:

Separate main disconnect enclosure & separate MLO panel enclosure.

I am seeking information as to the code compliant method(s) for the path of the fault current from EGC bus in MLO panel enclosure to the neutral bar in the separate main disconnect enclosure.

Where is such a scenario addressed in the NEC Code ?

Does the Code permit metal raceway between the MLO enclosure and the main disconnect enclosure to provide the path for the fault current?

Does the Code require a conductor be run from the EGC bus in the MLO enclosure to the neutral bus in the main disconnect enclosure ?

Is it ok to have both fault current paths, (1) the metal raceway between the enclosures, and (2) the conductor from EGC bus in MLO enclosure to the neutral bus in the main disconnect enclosure ?

Anyhow, this question boils down to...
what is the Code compliant fault current path between
EGC bus in MLO panel and the neutral bus in separate, main disconnect enclosure. ???

Does my question make sense ?

Thanks. --Zapped

Senior Member
13,020 Posts
You need to bond the neutral in your main disconnect (assuming it's the service disconnect). Bond it to your EGC system with a main bonding jumper, and that is where your EGC system will begin. Everything downstream from there will have a separate neutral and EGC. Check 250.24

Your MLO panel should be supplied with both a neutral and an EGC. Yes, it is permissible to use the metal raceway as the EGC provided that it meets a few criteria. Check 250.118
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