Mike Dolt Enterprises
Mike Dolt Enterprises
User: joesmoeblue, Location: Hawthorne, New York NEC: 2014
Asked on: Wednesday, January 8, 2025 at 4:13 pm EST
Answered on: Thursday, March 6, 2025 at 7:04 am EST
Question: Quick question and can't seem to find the answer because I'm 60 miles from my code book. I'm upgrading a service for a duplex and have an issue with the branch circuit from one unit being fed through the other units panel. Is this a problem. Not sure if it's in 230 but thought I'd ask quick I'm not near my book. There's only maybe a dozen wires in a 1 inch emt but just not certain if they view this as a problem in terms of concerns with one unit paying another one's electrical bill with some minor or accidental adjustments. And yes this place is a code nightmare all around. Thanks
Yes, this is a problem.While not specifically spelled out in Article 230, the NEC requires that each dwelling unit have its own service disconnecting means and distribution equipment. The situation you described clearly violates the intent, if not the exact wording, of these rules.Here's why it's a problem and what articles are relevant: Article 210.25, Branch Circuits in Dwelling Units
Generally requires each dwelling unit to have its own branch circuits supplying only that dwelling unit. While not explicitly prohibiting circuits from passing through another unit's panel, it strongly implies separation.
Article 225.30 - Number of Supplies
(If it's considered a building with two "buildings") requires that there be no more than one supply to a building. (In this case your house). However there are other options in 225.30 that may allow this but this would be rare in a standard house.
230.2(B), One Building or Other Structure Not to Be Supplied Through Another is the rule that you need to follow. It states, "Service conductors shall not pass through the interior of another building or other structure." This is in reference to a second building of property and might not be the case if you are just dealing with a standard duplex unit.
Why it's bad
Billing Issues
The biggest issue is the potential for one tenant to be paying for the electricity of the other. Even if the circuits involved are minimal, the arrangement is fundamentally unfair.
Safety
If a fault occurs on the circuit fed through the other unit's panel, it could affect the other unit's electrical system.
Confusion/Maintenance
It makes troubleshooting and maintenance incredibly difficult. Each tenant needs access to their circuits, and having to go through the other unit's panel complicates this.
Potential for Abuse
It opens the door to tenants tampering with the other unit's electrical system.
How to Fix It
The correct solution is to separate the electrical systems completely. This likely involves:1.
Running a dedicated branch circuit(s) from the appropriate unit's panel.2. Removing the existing branch circuit wiring from the incorrect panel.
In short, you need to re-wire it so that each unit's circuits are fed only* from its own panel.Good luck with the nightmare wiring! Flag for review