Bonding Methods, Code-Compliant Drawings and More

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Shutterstock / Macrovector
Published On
May 14, 2021

Jim Dollard has an extensive background in codes and standards. Send questions about the National Electrical Code (NEC) to Jim at codefaqs@gmail.com. Answers are based on the 2020 NEC.

Any, all or two bonding methods

An inspector told us it is an NEC requirement to always bond the gas piping on the load side of the gas meter with a 6 AWG copper conductor, and two means of bonding are needed. However, in other areas, I have been told that the equipment grounding conductor (EGC) with the branch circuit to the gas heater, range and dryer does the bonding. The inspector tells me that the 6 AWG to the gas piping is necessary in addition to the EGC to protect from a lightning strike.

Requirements for bonding are found in Part V of Article 250. Section 250.104, Bonding of Piping Systems and Exposed Structural Metal, contains the requirement you are referencing in 250.104(B), Other Metal Piping. This requires a metal piping system, including gas piping, to be bonded where the piping is likely to become energized. A metal piping system is likely to become energized only where the piping supplies an appliance or equipment that is also supplied with a branch circuit or feeder that could possibly energize the piping.

As you stated, the gas piping is supplying appliances that are also served by branch circuits, so 250.104(B) applies. The requirement to bond can be achieved through any of the five options provided. The first option to achieve the bonding is through the EGC for the circuit that is likely to energize the piping system. That is all that is required. The NEC does not require installers to bond to two or more, or all of the five options in 250.104(B). The options are (1) the EGC with the branch circuit, (2) the service equipment enclosure, (3) the grounded conductor at the service, (4) the grounding electrode conductor and (5) one or more grounding electrodes. Additionally, it is extremely important to note that conductors and equipment installed to protect buildings or structures from lightning are under the scope of NFPA 780, the Standard for the Installation of Lightning Protection Systems, and not the NEC.

Code-compliant drawings?

Why doesn’t the Code require all drawings to be NEC-compliant? Once again, we are involved in a runaround with an inspector. If a plan review is done, shouldn’t the installer do exactly what the drawings tell them to do? What is the engineer responsible for?

The scope of the NEC is outlined in Section 90.2. The Code covers the installation and removal of electrical conductors, equipment and raceways; signaling and communications conductors, equipment and raceways; and optical fiber cables for all of the types of installations listed.

Electrical drawings play an important role in the installation process, but are not prescriptively covered by the NEC . Installers must meet the minimum NEC requirements, not the drawings. It is not possible to list all of the pertinent installation requirements on a set of drawings. Additionally, the individuals doing a plan review may not have the time to review every little detail. In some areas, the plan review may only spot-check for significant omissions or errors. Where the drawings are not Code -compliant, the installer must work with the engineer and the owner toward a Code -complaint solution.

Panelboard mounting

On a recent trouble call, I encountered panelboards mounted on their back, facing up, on top of partitions between washers and dryers in a laundromat. This is a serious safety hazard and certainly must be a Code violation. The owner told me that the entire installation was purchased as a package, was prewired and installed. He also told me that it was listed, which I find hard to believe. Is this permitted?

No, the NEC does not permit an installation of a panelboard in the face-up position. There are many significant concerns here including, but not limited to, working space, electrically safe work practices, ready access and things falling into an energized panelboard. Clarity is provided in the new Section 408.43, which prohibits a panelboard from being installed in a face-up position. Substantiation for this and other actions in the 2020 NEC included installations similar to the one in your question.

It is important to note that Section 240.33 was modified for the same reasons. This section now requires that enclosures for overcurrent devices be mounted in a vertical position. The previous text had permission to do otherwise where mounting in a vertical position was deemed impractical. The permission to mount circuit breaker enclosures horizontally where the circuit breaker is installed in accordance with 240.81 still exists, along with permissions for listed busway plug-in units mounted in orientations corresponding to the busway mounting position.

Ampacity?

An inspector red-flagged us for the number of current-carrying conductors in a metal wireway. It was less than 10 feet (not even 8 feet) inside of the wireway where there were 46 current-carrying conductors. Doesn’t the exception that allows a higher ampacity where the lower ampacity of the conductors is less than 10 feet apply in this case?

No, the inspector is correct. There are multiple requirements in play here and we need to start in 310.14, Ampacities for Conductors Rated 0 Volts–2,000 Volts. Section 310.14(A)(2), Selection of Ampacity, requires that where more than one ampacity applies for a given circuit length, the lowest value must be used. The exception that follows this general rule is what you are referencing in your question. It applies only to the ampacity chosen (tables or through engineering supervision) and the impact of ambient temperature on a small portion of the circuit.

This exception permits the higher ampacity to be used where the lower ampacity (as adjusted due to ambient temperature) does not exceed the lesser of 10 feet or 10% of the total circuit. This adjustment cannot be applied to correction factors on rooftops or for adjustment factors for more than three current-carrying conductors.

The general rule for adjustment factors where more than three current-carrying conductors are installed is modified for metal wireways in 376.22(B), which allows up to 30 current-carrying conductors at any cross-section of the metal wireway without an ampacity adjustment.

When an installation has more than 30 current-carrying conductors at any cross-section, the adjustment factors are significant. For example, your question notes 46 current-carrying conductors, which would reduce the conductor ampacity to 35%. This is why planning is critical where wireways are used to consolidate conductors above panelboards, for example. A little bit of planning to arrange conductor placement to stay at or below 30 current-carrying conductors will eliminate rework when this type of violation is identified during an inspection.

Omit the laundry outlet?

New townhouses with a washer and dryer included in the laundry room are being built in our area. The drawings do not include a 20A, 120V laundry branch circuit for a receptacle. We were informed that the 240V dryer has a 120V receptacle for the washing machine, which meets the intent of the Code and there is no need for another branch circuit. Is that correct?

No, Section 210.11 lists the required branch circuits and 210.11(C)(2) requires at least one additional 20A branch circuit to supply the laundry receptacle outlet(s) as required by 210.52(F). This branch circuit can only serve receptacle outlets in the laundry area. The parent text of 210.52 provides requirements for 125V, 15A and 20A receptacle outlets. 210.52(F) requires that any area in dwelling units intended for the installation of laundry equipment be provided with at least one receptacle outlet supplied from the branch circuit required by 210.11(C)(2). Receptacle outlets in the laundry area must also be GFCI-protected as required by 210.8(A)(10). The required 2A, 125V circuit supplying a receptacle outlet in the laundry area is intended to supply the washing machine, a gas-supplied dryer and other laundry appliances such as irons. Installing a 240V dryer that includes a 125V receptacle does not negate these requirements.

About the Author

Jim Dollard

Code Columnist

Jim Dollard is the safety coordinator for IBEW Local 98 in Philadelphia. He is a member of the NEC Correlating Committee, NEC CMP-10, NEC CMP-13, NFPA 70E, NFPA 90A/B and the UL Electrical Council. He can be reached at codefaqs@gmail.com.

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