BEST OF CODE TIME 4: Grounding and Bonding, Junction Box Covers and Securing and Supporting MC Cable

Let’s face it. The NEC code book is BIG and has tons of articles in it! And we need to have a good understanding of those codes and articles to be able to perform our jobs. In the latest episode of Electrician U, Dustin dives back into the NEC code book to discuss a few of these with us.

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For our first topic, we will be discussing grounding and bonding. Are we allowed to use the conduit as the ground path? Say we had some air handlers that used the EMT conduit as the ground path and did not pull a specific grounding wire. On the same project, GRC was used for the outdoor units. What does the NEC code say about this. Article 250 of the NEC governs grounding and bonding and part 6 discusses types of grounding conductors allowed. Article 250.118 states “The equipment grounding conductor run WITH or ENCLOSING the circuit conductors shall be one or more or a combination of the following”. In that article, it goes on to list all the items we are allowed to use, which include copper/aluminum/copper-clad aluminum conductors, Rigid Metal Conduit, and Electrical Metallic Tubing. So, the NEC does in fact allow some types of conduits to be used as the equipment grounding conductors provided your couplings are tight and that a good continuous electrical pathway is achieved. Having said that, make sure and check your project specifications as many projects require you to install a separate equipment grounding conductor be installed with the other conductors to a piece of equipment. There are issues that can arise from using just the conduit as the equipment grounding conductor. Over time, couplings can become loose if not installed properly, pathways/wiring methods can change if places are remodeled, etc. and you can sometimes lose that continuous electrical pathway, hence the reason that most jobs these days require a separate equipment grounding conductor.
Next, are we required to close the cover of a junction box after working in it? Article 314.25 states in part “In completed installations, each box shall HAVE a cover, faceplate, lamp holder, or luminaire canopy”. This tells us that the box shall be PROVIDED with some type of cover but doesn’t specifically say it has to be INSTALLED or the box itself CLOSED with the cover. Where your voltage gets over 1000 volts, the language of the NEC code DOES change to include closing the boxes up. Always make sure and check with your local AHJ (inspector usually) and project specifications as there may be local codes or project specific requirements that may specifically state that the lower voltage range of electrical boxes be CLOSED in finished installations.
Are we allowed to use STAPLES to support MC Cable? While many electricians would argue that you cannot use staples but rather one-hole straps, some type of Caddy strap, etc. Article 330.30 covers securing and supporting of MC Cable. In 330.30(A) it states “Type MC cable shall be supported and secured by staples: cable ties listed and identified for securement and support; straps, hangers, or similar fittings; or other approved means designed and installed so as not to damage the cable”. So, staples ARE in fact allowed to be used to support MC Cable if you do not damage the cable and follow the supporting and securing code references. Zip ties may even be used if they are listed and identified to be used as such. Once again, check with your local AHJ to make sure they will accept that in your local jurisdiction.
We hope this has been helpful in understanding a few of the many code articles in the NEC. Is there a topic you would like to see a video on? Leave a comment in the comment section and let us know. Please continue to follow Dustin and Electrician U as we are constantly updating our content to help our followers become the best electricians they can be!