BACKGROUND

UL has received requests from industry, both swimming pool and fountain luminaire manufacturers, to remove the requirement for an equipment grounding conductor (EGC) in a low-voltage luminaire. Manufacturers felt the EGC had no value and sometimes caused problems with newer LED luminaire circuits. They also pointed out that the requirements in UL 676 conflicted with the requirements for certification of the same luminaries in Europe.

BACKGROUND AND RATIONALE OF PRESENT REQUIREMENTS

Beginning with the 1972 first edition, UL 676 included the Electric Shock Test to evaluate the risk of electric shock posed by the electric current that escapes a swimming pool or spa luminaire that has a leaking gasket or a cracked or broken lens. Specifically, this test determines if the average density of electric current that conducts out of the cracks, gaps, or openings in the face of the water-filled luminaire and into a pool occupant poses a risk of ventricular fibrillation or immobilization of the muscles of the pool occupant’s arms, legs, or diaphragm (used for breathing).

Electric current will conduct out of a pool or spa luminaire only if there is a conductive path back out of the pool water to metal (current-carrying or non-current-carrying) that is part of, or connected to, the same circuit and that exhibits a voltage potential difference with respect to the water-contacting current-carrying parts of the flooded luminaire. The current path from the pool water back to the metal that is part of, or connected to, the same circuit can be through metal, pool water, earth, or any combination of these. Items (a) – (c) below identify examples of current paths for electric current that has exited the face of a flooded luminaire and, therefore, poses a risk of electric shock to a pool occupant. These examples do not cover all possibilities. The design of the Escape Current Density Test, however, addresses these and all other possible current paths.

a) Current-carrying parts within the flooded luminaire are supplied by a grounded branch circuit (120 volts) and the current conducts out of the luminaire to return to the circuit by conducting into grounded metal of the same flooded luminaire, grounded metal of other underwater luminaires, or to the grounding electrode of the premises electric system through a ladder, reinforcing steel, or other metal object of the pool that contacts both the pool water and earth.

b) Current-carrying parts within the flooded luminaire are supplied by a normally ungrounded line voltage branch circuit (240 volts) that has experienced an insulation failure, allowing a current-carrying part of the circuit to fault to metal that, in turn, is connected to the pool water. This insulation failure can be within the same flooded luminaire, within another underwater luminaire or other (non-immersed) equipment connected to the circuit, or within the circuit wiring.

c) Current-carrying parts within the flooded luminaire are supplied by a normally ungrounded low voltage, isolated source and a conductive through-water path has formed between current-carrying metal of the circuit and either earth or metal that, in turn, has a conductive path to the water in the pool. This situation can develop, for example, as described in items (i) and (ii) below.

i) The gasket of another luminaire connected to the same ungrounded circuit leaks, allowing water to form a conductive water path from the current-carrying parts within the second luminaire to the pool water in front of the that luminaire or to metal of the luminaire that, in turn, has a conductive path to the pool water.

ii) A flexible cord connected to the same ungrounded circuit becomes damaged or deteriorates as a result of continual immersion in the chemical-treated pool water. The flexible cord may be of a wet-niche or removed-for-service no-niche luminaire and located within the water-filled forming shell, water-filled space behind the luminaire, or inside the pool-water-filled conduit supplying the luminaire. Where cracking or water permeation of the cord jacket and conductor insulation occurs, water will pass into the cord and form a through-water conductive path between the current-carrying conductor and the water around the cord. This conductive water path will extend, for example, through water within the conduit to pool water behind the wet-niche or removed-for-service no-niche luminaire, which is contiguous with the water in front of the luminaire through water passage openings in the luminaire design. A path from the water around the flexible cord to the earth around the conduit (and then to the pool water) will exist if the conduit is nonmetallic and has cracked to allow water from within it to pass out of the conduit into the earth or if the conduit is metal.

FIELD HISTORY OF LOW-VOLTAGE WET-NICHE AND NO-NICHE LUMINAIRES

After researching the issue, UL believes the scenarios detailed in items c(i) and c(ii) above have not manifested in the field. An equipment-grounding conductor was believed to be necessary in the low voltage luminaire and forming shell in order to collect stray currents. If these scenarios need not be addressed, then UL believes the requirement for an equipment-grounding conductor in a low-voltage luminaire and its forming shell could be deleted. UL requests industry input on this possible revision to UL 676.

MARKINGS AND BACKWARD COMPATIBILITY WITH EXISTING FORMING SHELLS

To prevent confusion with inspection authorities, UL believes a marking on low-voltage luminaires not requiring grounding might be needed. UL suggests a simple marking such as “Low-Voltage Luminaire Not Requiring Grounding.” This would reflect the text in Sections 680.23(B)(2) of the National Electrical Code, NFPA-70-2008. Before UL attempts to develop any revisions to the marking requirements for low-voltage luminaires, UL needs industry input concerning issues involved with ungrounded low-voltage luminaires and the existing installed base of forming shells.