Multiwire Branch Circuits, AFCIs and More

By George W. Flach | Sep 15, 2006
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Article 210                Branch Circuits
Article 250                Grounding and Bonding
Article 406                Receptacles, Cord Connectors and Attachment Plugs (Caps)
Article 430                Motors, Motor Circuits and Controllers
Article 702                Optional Standby Systems
The General Information for Electrical Equipment Directory published by Underwriters Laboratories Inc. is also mentioned.

Multiwire branch circuits

Q:  Under what conditions can single-pole circuit breakers with handle ties be used on 120/240-volt single-phase multiwire branch circuits? Are multipole common-trip circuit breakers ever required on these branch circuits?

A: Where the circuit breakers supply 120-volt lighting or receptacle loads, single-pole circuit breakers without handle ties are permitted by 210.4, even though multiwire branch circuits are used. Where a 120/240 volt, three-wire branch circuit supplies devices or equipment on the same yoke a two-pole or two single-pole circuit breakers with a handle tie are required.

This revision in the 2005 National Electrical Code (NEC) appears in 210.7(B): “Multiple Branch Circuits. Where two or more branch circuits supply devices or equipment on the same yoke, a means to simultaneously disconnect the ungrounded conductors supplying those devices shall be provided at the point at which the branch circuits originate.”

To confirm that this requirement applies to multiwire branch circuits, this sentence is taken from 210.4(A): “A multiwire circuit shall be permitted to be considered as multiple circuits.”

An Exception to 210.4(C) allows multiwire branch circuits to supply line-to-line loads where the branch-circuit overcurrent device opens all ungrounded conductors of the circuit simultaneously. This requires a multipole common trip circuit breaker.

AFCI requirements

Q: Is an arc-fault circuit interrupter (AFCI) circuit breaker required on a branch circuit that supplies outdoor floodlights from a three-way wall switch in a bedroom in a residence? The other three-way switch is in the living room.

A: No. The requirement in 210.12(B) applies to 120-volt, single-phase, 15- and 20-ampere outlets installed in dwelling unit bedrooms. The word “outlet” is used in 210.12(B), and a switch does not meet the definition of an “outlet” that is defined in Article 100 as: “A point on the wiring system at which current is taken to supply utilization equipment.”

Some changes that were made to 210.12(B) in the 2005 NEC include a requirement for a combination-type AFCI on and after Jan. 1, 2008. This type of AFCI provides protection from arcing faults in branch-circuit wiring or feeder wiring or both and cord sets and power supply cords connected to receptacles. This device provides protection from series faults in flexible cords, whereas, the branch/feeder- type AFCI may not protect the wiring from series arcs in flexible cords (for more information on AFCIs, see page 240).

Laundry room receptacles

Q: I have installed a 120-volt, 20-ampere branch circuit with a 15-ampere duplex receptacle in the laundry room of a one-family dwelling unit. Does the NEC permit 15-ampere branch circuits to supply other receptacles in this room?

A: At least one 20-ampere, 120-volt branch circuit is required to supply receptacle outlet(s) in the laundry. This branch circuit is not permitted to supply any other outlets [see 210.11(C)(2)].
There is nothing in 210.11 or 210.52(F) that prevents the installation of additional branch circuits to supply other receptacles in the laundry room. These additional receptacle branch circuits may be 15 amperes. Also, the 15-ampere duplex receptacle is permitted on a 20-ampere branch circuit by 210.21(B)(2) and Table 210.21(B)(2).

Air conditioning service-receptacle location

Q: Does the NEC permit or require a 15-ampere, 120-volt receptacle to be located adjacent to an air conditioning unit installed above a suspended (drop) ceiling in a commercial occupancy?
A: Yes, a 15- or 20-ampere, 125-volt receptacle is required by 210.63. The receptacle must be installed at an accessible location for servicing the air conditioning equipment. The second sentence of 210.63 reads: “The receptacle shall be located on the same level and within 7.5m (25 ft.) of the heating, air conditioning and refrigeration equipment.”

“On the same level” means that the receptacle for servicing the equipment cannot be located 25 feet above or below the air conditioning equipment.

It has been said that a receptacle cannot be located above a suspended ceiling, but this is not true. There is no restriction on the location of the receptacle. However, there is a restriction on the use of flexible cords that limits this receptacle to use by a mechanic or repairman working on the air conditioning equipment.

Here is the restriction on the use of this receptacle, which appears in 400.8(5) under Article 400—Flexible Cords and Cables: Uses Not Permitted. (5) Flexible cords shall not be used where concealed by walls, floors or ceilings or located above suspended ceilings.

If the electrical inspector is concerned about locating this receptacle above the suspended ceiling, it may be located a foot or two below the ceiling tile and still be accessible to the person servicing the equipment.

Wiring an electric range

Q: I wired a surface-mounted cooktop with five burners and a wall-mounted electric oven with three 6 AWG copper conductors. The total range top and oven load is 15.6 kW. This branch circuit is protected by a 50-ampere, two-pole circuit breaker. The 6 AWG copper conductors terminate in a junction box behind and below the cooktop.

From there, three 10 AWG copper conductors extend to the oven. These tap conductors are 9 feet long. A 3-foot whip provided with the oven is connected to the 10 AWG tap conductors. This installation has received a red tag with this comment: “Tap conductors are too long.” Are the tap conductors for an electric oven limited to 10 feet?

A: Not necessarily. The length of the tap conductors is limited to the length required for servicing. This is a judgment call by the electrical inspector, but 12 feet of tap conductors appears to be excessive. I do not believe this length of tap conductors is necessary for servicing the oven.

This is what Exception No. 1 to 210.19(A)(3) says about tap conductors that supply electric ranges, wall-mounted ovens and counter-mounted cooking units from a 50-ampere branch circuit: The tap conductors must have an ampacity of not less than 20 and must be adequate for the load, the tap conductors include any conductors that are part of the leads supplied with the appliance that are smaller than the branch-circuit conductors, and the tap is no longer than necessary for servicing the oven without having to disconnect any wiring.

Grounding meter-socket enclosures

Q: A homeowner has asked me to install a meter-socket enclosure on the load side of the utility meter and service-disconnecting means. The only meter enclosures available have the neutral lug riveted to the metal housing. There is no way to isolate the grounded conductor (neutral) from the equipment-grounding conductor. Is this permitted by the Code?

A: Yes, under specific conditions. First, check with the serving electric utility to make sure there is no objection to the installation of a customer-owned meter on the load side of their meter. If the electric utility does not object, install the owner’s meter to comply with Exception No. 2 to 250.142(B).

This exception applies where a meter enclosure is grounded by connection to the grounded-circuit conductor on the load side of the service-disconnecting means, provided that these three requirements are satisfied: 1. ground-fault protection is not installed, 2. the meter socket enclosure is located immediately adjacent to the service-disconnecting means, 3. the size of the grounded-circuit conductor is not smaller than the size specified in Table 250.122 for equipment-grounding conductors.

Receptacle for HVAC equipment

Q: I have a job to install the wiring for a new outdoor air conditioning unit within a fenced area of a multioccupancy office building. A 15-ampere, 125-volt receptacle is required within 25 feet of the unit for service personnel. Since this receptacle will not be accessible to the public, is GFCI protection required? Is an in-use receptacle cover required for this receptacle that is provided for portable power tools?

A: GFCI protection is required for this receptacle by 210.8(B)(5), which refers to 210.63. The requirement for the receptacle is in 210.63 and the requirement for GFCI protection is in 210.8(B)(5).
The requirement for a weatherproof cover while the receptacle is in use is located in 406.8(B)(1). It applies for all 15- and 20-ampere, 125- and 250-volt receptacles installed outdoors in wet locations. Other receptacles (not 15 and 20 ampere, 125 and 250 volt) installed in wet locations where the tool or appliance will be plugged in only while attended are permitted to have covers that are weatherproof when the attachment plug is removed.

Locking device for motor-disconnecting means

Q: Does a lock-off device that is secured by the cover plate screws of a snap switch meet the requirement for a motor-disconnecting means that is not within sight of the motor?

A: Where the disconnecting means for a motor is not within sight of the motor, but is within sight of the controller, the disconnecting means must be capable of being locked in the open position. The exception to 430.102(B) provides this information: “The provision for locking or adding a lock to the disconnecting means shall be installed on or at the switch or circuit breaker used as the disconnecting means and shall remain in place with or without the lock installed.” Similar language appears in 422.31(B) for motor-driven appliances with motors over one-eighth horsepower.

According to the 2005 edition of the General Information for Electrical Equipment Directory published by Underwriters Laboratories Inc., Alternating current (AC) general-use snap switches are tested and listed for control of a motor load that does not exceed 80 percent of the ampere rating of the switch and the motor does not exceed 2-horsepower. For example, a 30-ampere, 120-volt, single-pole AC general use snap switch could be used as the required disconnecting means for a 120-volt, single-phase 2-horsepower motor.    EC

FLACH, a regular contributing Code editor, is a former chief electrical inspector for New Orleans. He can be reached at 504.734.1720.


About The Author

George W. Flach was a regular contributing Code editor for Electrical Contractor magazine, serving for more than 40 years. His long-running column, Code Q&A, is one of the most widely read in the magazine's history. He is a former chief electrical inspector for New Orleans and held many other prestigious positions in the electrical industry, including IAEI board of directors and executive committee. He passed away in August 2009.





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