A Picture Is Worth 1,000 Words

Residential July 2020
It's important to carefully review any wiring inside a home.

An electrical contractor emailed me a photo of a feed-through all-in-one 200A 120/240V, single-phase, eight-circuit panelboard with 200A main circuit breaker. It had an auxiliary 2-pole circuit breaker position where up to a 100A 2-pole circuit breaker could be connected. The EC had questions about potential violations in the panelboard, which he had not installed.

I am painting a verbal picture so readers can understand the National Electrical Code issues I noticed with the installation.

In addition to the 200A main circuit breaker, the 100A two-pole disconnect auxiliary position is located adjacent to the main circuit breaker and is connected in parallel with the 200A main circuit breaker. The 200A main circuit breaker is rated at 25,000A of interrupting current.

The panelboard enclosure is a Type 3R that is designed for outdoor installation and an underground utility company supply. The utility service-entrance conductors enter the bottom left side of the all-in-one in the enclosure’s utility company pull area connect to the top of the meter socket located immediately above the utility pull area. On the right, (distribution side of the all-in-one), the busbar extends down from the 200A circuit breaker to the bottom of the enclosure, terminating in two terminal blocks as the feed-through point of connection. The neutral and grounding terminals are on the bottom right side of the enclosure with the main bonding jumper (connecting behind the insulation barrier sheeting of the vertical power busbar) to the neutral point of connection at the enclosure’s top.

The first issue is the lack of barriers installed over the line-side connection of the main circuit breaker and fusible disconnecting means, which is now required based on 408.3(A)(2) in the 2017 NEC.

This text states: “Barriers shall be placed in all service panelboards such that no uninsulated, ungrounded service busbar or service terminal is exposed to inadvertent contact by persons or maintenance equipment while servicing load terminations.”

This barrier provides a safe separation from unprotected and uninsulated ungrounded conductors. Many times, electricians have had to remove covers from service panels with energized conductors and terminations nearby. One misstep and an arc flash could occur, potentially causing personnel injury and equipment damage. Remember, OSHA and NFPA 70E require protective equipment to be worn and only qualified people are permitted in the restricted approach boundary, especially where the fault current is in excess of 10,000A.

In this case, a single 20A circuit breaker is installed at one of the eight spaces on the busbar, and the circuit breaker looks like it has been exposed to major water damage or was in a flood. The marking on the side of the circuit breaker cannot be read, the rating of the breaker is not discernible on the handle, and the side of the circuit breaker is a dirty brown color. This electrical service is installed in an area where there has been major fire and water intrusion to much of the equipment, so it is very possible someone employed a used circuit breaker.

Four No. 2 AWG black conductors are installed from a raceway at the enclosure’s bottom and connected to the feed-through terminal blocks and the neutral/grounding block. The two ungrounded conductors are identified using red tape, and one black conductor has been reidentified using white tape based on 200.6 as a neutral conductor, although improperly terminated by splitting the individual strands under the small screws on the neutral bus. The last black conductor is reidentified with green electrical tape as an equipment grounding conductor and is improperly terminated on the equipment grounding bus similar to the neutral conductor.

The major problem with using the No. 2 AWG insulated ungrounded conductors connected to the feed-through terminals at the bottom of the busbar is these conductors are not being adequately protected by the 200A main circuit breaker. Even using 310.15(B)(7)(2) for single-phase feeders for dwelling units, the feeder conductors supplying the entire load associated with the dwelling unit are required to have an ampacity of not less than 83% of the feeder rating. Using Example D7 in Annex D (if you don’t want to do the calculation), a No. 2 AWG copper conductor is rated at 125A without any adjustment or correction factors and is not protected using a 200A main circuit breaker.

Based on the number of NEC violations found at the service—such as an improper size of feed-through conductors, lack of barriers over the utility company conductors and possible water damage to circuit breakers—careful review of any wiring inside the home would be necessary. Flood (water) damage at the service is often an indication of similar damage inside the home.

About the Author

Mark C. Ode

Fire/Life Safety, Residential and Code Contributor

Mark C. Ode is a lead engineering associate for Energy & Power Technologies at Underwriters Laboratories Inc. and can be reached at 919.949.2576 and Mark.C.Ode@ul.com.

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