Electrical – NEC code regarding grounding and conductor pass through

electricalgroundingjunction-boxnecpermitting

I am adding a mini split system to my house which currently has a smaller air-conditioning condenser in place. In brief, the house is very old so we opted for a ductless mini-split over trying to increase the size of the current unit to avoid needing to add ductwork. We have a 3/4" EMT conduit that leads outside along the back of the house which had only 2 6AWG wires in THHN insulation.

This allowed us to run 2 more 6AWG wires in the same conduit and stay under the NEC fill requirements. Adding a ground wire would have put us over the conduit fill. The original unit was presumably grounded to the panel via the all metal conduit. We also passed the new wire through the original disconnect (going to the original condenser) to a second disconnect (going to the new unit).

To make sure both units were properly grounded an 8' by 5/8" grounding rod was inserted and attached. I may be able to submit for a tax credit on the unit but I'm not sure if the grounding rod meets building codes. The electrician thought possibly not. This route was chosen to avoid running new conduit out of the house (spacing is very difficult). My questions are, does this (grounding to rod and running wire through a disconnect) meet code? Would it pass a permitting inspection?

Best Answer

Don't mix up your EGCs and your GECs!

The EMT, provided it is made up properly and is not excessively exposed to physical damage, is a perfectly fine ground (equipment grounding conductor) by itself in this application -- 440.9 in the 2017 NEC only applies to runs on roofs, which get tread on repeatedly by clueless folks:

440.9 Grounding and Bonding. Where metal raceway is run exposed on a roof for air-conditioning and refrigeration equipment, an equipment grounding conductor of the wire type must be installed within the outdoor portions of metal raceways using non-threaded fittings.

However, the ground rod needs to go, because it inadvertently violates 250.121 by trying to use the EMT as a grounding electrode conductor that ties a remote ground rod back to the main panel bond atop it serving as an equipment grounding conductor:

250.121 Use of Equipment Grounding Conductors. An equipment grounding conductor shall not be used as a grounding electrode conductor.

Exception: A wire-type equipment grounding conductor installed in compliance with 250.6(A) and the applicable requirements for both the equipment grounding conductor and the grounding electrode conductor in Parts II, III, and VI of this article shall be permitted to serve as both an equipment grounding conductor and a grounding electrode conductor.

So, just rip out the errant remote ground rod and whatever wire was hooking it up to the disconnect(s) or just the wire for that matter as the errant rod will do nothing if it isn't connected to anything, and all will be well when the electrical inspector comes around.

Related Topic