Lampholder to Receptacle Adapter (1-12-2K)
Question: Why does Underwriters Laboratories "List" lampholder outlet adapters (lamp-socket-to-receptacle)? I believe theses adapters are also used with track lighting systems. What Code rule prohibits the use of lampholder outlet adapters?
Mike Holt's Comment:
Section 410-47 states that "Lampholders of the screw-shell type shall be installed for use as lampholders only. Where supplied by a circuit having a grounded conductor, the grounded conductor shall be connected to the screw shell."
UL does not "List" track lighting receptacle adapters. You may have seen a device that looks similar to track lighting that is provided with receptacles. This was most likely a Non-Metallic Surface Extension (PZMX) or a Non-Metallic Extension Fitting (PYYZ), see page 66 and 67 of the 1999 White Book. These devices are intended for installation in accordance with NEC Article 342 Nonmetallic Extensions.
Regarding lampholder outlet adapters, as I'm sure you are aware these devices have been around for a long time, at least since the 1930's. The verbiage in the NEC in Section 410-47 has probably been around since the 1940's. We believe the intent of the Code requirement was that in the original installation of an electrical system, that a lampholder should only be installed as a lampholder. A lampholder with an outlet adapter installed "should not" be considered as a required receptacle outlet to comply with Section 210-52.
This is somewhat of a gray area, because an adapter is an after market add-on and not addressed by the NEC. It seems these were originally developed to provide a means to tap electricity from a branch circuit in old occupancies before the NEC required receptacles in basements. There was a need a long time ago for these devices and apparently the need still exists in older occupancies.
The devices still serve a purpose to provide a means to tap a branch circuit in older occupancies where there is an unfinished basement or other unfinished area where receptacles are not provided. This would most likely be more convenient and less of a concern than routing extension cords through doorways, down stairs or all over the place to obtain electricity in those older houses.
In addition, it is a certainty that if UL chose not to List these devices, that manufacturers would continue to produce non-Listed devices, because there remains a use for these devices today. At least with a UL Listed adapter, UL requires that the products meet a level of performance that has shown that there should not be a problem with these devices. An un-listed device has not met any requirements.
To the best of my knowledge, as long as these devices have been around, there have been no field problems.
Tom Lichtenstein, Ext. 42160
Staff Engineer, Regulatory Services
Underwriters Laboratories Inc.