It seemed like a simple run-of-the-mill question when first presented. So, let's run it again.
QUESTION: "If I split-wire a receptacle by breaking off the tab provided on the receptacle, do I have to use a two-pole breaker to feed this receptacle?" The answer is a qualified yes. If you use a multiwire branch circuit to feed this receptacle and the installation is in a dwelling unit, the branch circuit must be provided with a means to disconnect simultaneously all ungrounded conductors at the panelboard where the branch circuit originated. The 1999 National Electrical Code (NEC) reference is Section 210-4(b).
ANSWER: 210-4 Multiwire Branch Circuits (b) Dwelling Units. In dwelling units, a multiwire branch circuit supplying more than one device or equipment on the same yoke shall be provided with a means to disconnect simultaneously all ungrounded conductors at the panelboard where the branch circuit originated.
The intent of that requirement is obvious. If a multiwire branch circuit consisting of two ungrounded conductors with a common neutral is used to feed the two receptacles, and the tab on the ungrounded side of the duplex receptacle is broken off, it becomes necessary to ensure that both circuits are simultaneously de-energized. This is meant to protect someone working on that receptacle outlet after the person turns off one circuit, with the assumption that the entire outlet was de-energized. The requirement of Section 210-4(b) for simultaneous disconnection of all ungrounded conductors would eliminate that possibility.
But why only in dwelling units and only where multiwire circuits are used? This type of installation is common at dwelling unit kitchen countertops where electric appliances are more commonly used. But aren't many kitchens located in schools, factories, nursing homes, hospitals, office buildings and, of course, restaurants? Is equal protection merited in these locations? Perhaps in other than dwelling units, "qualified" persons would be engaged in doing the maintenance work rather than the homeowner doing his own maintenance.
Receptacles on Separate Circuits
QUESTION: "Your answer about split-wired receptacles on a multiwire circuit is okay, but what if the split-wired receptacles were fed by two circuits, each with its own neutral?"
ANSWER: Since this would not be a multiwire circuit, there is no requirement for the desired protection either in a dwelling unit or other than a dwelling unit. But I made the following observation. Although it was clearly pointed out that tabs are present on both the ungrounded and the grounded terminals of the receptacle, is it permissible to break off the tabs on the grounded terminal? Can these receptacles be used in this manner by breaking off the tabs on both sides of the receptacle, eliminating their use on a multiwire circuit? The manufacturer provides the tabs on the grounded terminal side and does not provide any instructions that they cannot be used.
Now we must go to the UL White Book (General Information for Electrical Equipment Directory, 1999) and see how these receptacles are listed. This interesting paragraph appears under the heading of Receptacles for Attachment Plugs and Caps: "Duplex receptacles rated 15 amp or 20 amp that are provided with break-off tabs may have those tabs removed so that the two receptacles may be wired in a multiwire branch circuit." Is this an indication that the tabs may not be removed so that the two receptacles can be used in other than a multiwire circuit? Then why do we have tabs on the grounded terminal of the duplex receptacle? Their only purpose is to split the neutral and that would eliminate multiwire circuit possibilities.
In summary, if you run two circuits to two receptacles on the same yoke, there is the distinct possibility that only one circuit could be de-energized, leaving the other energized. Some unwary person working on this receptacle outlet could grasp the unit and come into contact with both the energized ungrounded circuit conductor and the grounded circuit conductor or some grounded surface simultaneously. For this reason, Section 210-4(b) requires simultaneous disconnection of both circuits in the panelboard where they originate. But this protection is only required for installations in dwelling units and only for multiwire circuits.
If a hazard exists here, can we logically say it only exists in dwelling units? Can we also say it only exists in multiwire circuits? We can probably say whenever there is more than one device on a single yoke, in any occupancy, in multiwire circuits or otherwise, if we do not require simultaneous disconnection of all circuits, to all devices, on the same yoke we are allowing a potentially dangerous condition.
Frequently, the break-off tab on the ungrounded side of a duplex receptacle is removed for a switched receptacle. In this installation, the same circuit is presumably used to feed the switch and the unswitched receptacle on the yoke. Then, the switch leg is connected to the other receptacle on the yoke. This is not a multiwire circuit, so our original problem does not exist, but does the listing permit this? Can we use break-off tabs in other than multiwire circuit installations?
If the wording in the UL White Book means that tabs provided on duplex receptacles may only be removed for use in a multiwire circuit, then some action should be taken to prevent tabs being provided on the grounded (neutral) terminal of the duplex receptacle.
TROUT is a technical consultant for Maron Electric Company of Chicago, and he is Chairman of the National Electrical Code-Making Panel 12, representing NECA. He is also the principal author of Electrical Contractor magazine's online feature "Code Question of the Day."