Welcome to the final installment of this series on important National Electrical Code requirements related to branch circuits and feeders. Last month we discussed all the nuances involved with feeder grounded/neutral conductors. With that conversation, we have pretty much wrapped up the basics of branch circuits and feeders. This month’s article will take a minute to review those significant points before moving on to the major player of the electrical system in a building: service equipment.

This journey through branch circuits and feeders has covered a lot of ground. We have spent the last 15 months looking at key requirements, and there are still several areas we have not investigated yet. But have no fear—these areas will be discussed as we continue our deep dive into the NEC. Let’s review what we have covered so far. 

Article 90 and the code’s purpose

To really understand all the requirements mentioned in the last 15 articles, one simply needs to go back to the very beginning of the NEC in Article 90 and review the code’s purpose. The purpose behind all the requirements we have looked at so far is the practical safeguarding of people and property from hazards arising from the use of electricity. Applying this to the requirements for branch circuits and feeders, it is easy to see why they are the way they are. 

First, we started our branch circuit conversation talking about what types of branch circuit the NEC allows to be installed and how to identify each one. This is particularly important with the multiwire branch circuit, which uses the same neutral conductor to serve as the return path for multiple ungrounded conductors of different phases or legs. 

Multiwire branch circuits are one of the leading causes of injury among electrical workers when not all ungrounded conductors are disconnected and the neutral conductor is open. Workers often disconnect the circuit they are working on, but, if the other ungrounded conductors are not disconnected, they can still be shocked by what they think is a grounded conductor. 

However, when you disconnect the neutral of a multiwire branch circuit while ungrounded conductors are still energized, part of that splice becomes energized—hence the requirement for disconnecting all ungrounded conductors simultaneously. Following the requirements for identification of conductors, disconnecting means and the grouping of these circuits is imperative. 

Sizing branch circuits

Another important safety concern discussed was sizing branch circuit conductors. This is what I would consider the front line of electrical safety through proper electrical system design. Sure, if the conductors are not properly sized, the system might still work, but for how long? 

We discussed critical steps in making sure the selected conductors can safely carry the current of the load based on the continuous nature of the load or the conditions in which the conductor is installed. Both are critical considerations, as an undersized conductor can quickly overheat and damage the electrical insulation. If these rules are not followed, there is a serious risk of causing a fire in the building or causing someone injury from electric shock or arc flash. 

Along these same lines, articles 210 and 215 also provide for overcurrent protection of the branch circuit and feeder conductors. Like properly sizing the conductors, this conversation was all about making sure the conductors don’t overheat and damage the insulation. For this reason, the general rule for conductor overcurrent protection is that the overcurrent protective device (OCPD) must provide the full range of overcurrent protection for a conductor in alignment with the conductor’s ampacity and must be provided at the point where the conductor is supplied. 

However, sometimes the NEC has a few tricks. We can use a few alternatives to the general rule that still provide the protection needed for conductors. We discussed the allowance in 240.4(B) to use the next highest standard OCPD above the conductor’s ampacity when it doesn’t directly correspond to a standard rating of OCPD. But there are several conditions that come along with this permission aimed at making sure we don’t damage the conductor during normal use.

Feeder tap rules

We also explored the famous feeder tap rules. This is a major deviation from the general rule for overcurrent protection of conductors. This allows the installation of a combination of OCPD devices upstream and downstream to provide the full range of protection. The upstream device provides protection from faults such as short-circuits and ground-faults, while the downstream device limits the load on the conductor to within the conductor’s ampacity. However, scores of conditions must be met here to ensure the installation remains safe.

Branch circuit design features

We spent several months discussing design features of branch circuits. But remember that each of the specific design features is aimed at the NEC’s purpose of practical safeguarding of people and property. 

One of the major branch circuit design sections deals with receptacle placement. This might not seem like a direct safety requirement, but for dwelling units, this is one of best things we can do. I think most people can relate to the frustration of being at home without a receptacle close by. It is one of those annoyances that just really gets under my skin. 

To the untrained homeowner, this is a problem they often choose to fix with extension cords. However, extension cords are not designed to take the place of the building wiring, and when used continuously or hidden under rugs or behind baseboards, they can present a real shock and fire hazard. Therefore, the requirements of 210.52 for receptacle placement are indeed safety requirements.

AFCIs and GFCIs

Of course, no conversation about branch circuits would be complete without a discussion on AFCIs and GFCIs. We covered common myths about these protective devices as well as when and where they are required. Recognizing that both topics have been rather controversial over the years, it is more important than ever to understand that these are safety devices meant to stop dangerous conditions before they become a serious threat to people and property. 

When we look at all that has been covered about branch circuits and feeders, we can see how the NEC protects our modern world. We use electricity in nearly every aspect of our lives, and it all gets delivered through this network of branch circuits and feeders. Safety is a critical consideration when installing the backbone of the electrical system and should be a driving factor in every decision we make. 

As we continue our deep dive into NEC requirements, make no mistake, we will be revisiting many of the requirements discussed during this series of articles. Our time on this topic is not over, but rather is on pause so we can spend time going upstream to look at the service equipment. Next month’s article will start to unpack some of the basic requirements for building services and how that will drive our conversation going forward.

Until next time, stay safe and always remember to test before you touch!

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