Industrial GFCI FAQ

What is UL 943C and how does it differ from UL 943?

UL 943 Standard applies to Class A, single- and three-phase, Ground-Fault Circuit- Interrupters (GFCI) intended for protection of personnel, for use only in grounded neutral systems in accordance with the National Electrical Code (NEC), ANSI/NFPA 70, the Canadian Electrical Code, C22.1 (CEC), and Electrical Installations (Use), NOM-001-SEDE. These devices are intended for use on alternating current (AC) circuits of 120 V, 208Y/120 V, 120/240 V, 127 V, or 220Y/127 V, 60 Hz circuits. UL 943C requirements cover ground-fault circuit-interrupters intended for use in one of the following applications:

  1. On grounded-neutral systems where voltage to ground is above 150 Vac and equipment grounding or double insulation is required by the NEC®, ANSI and NFPA 70
  2. On grounded-neutral systems where voltage to ground is 150 Vac or less and equipment grounding or double insulation is provided, but the use of a Class A ground-fault circuit interrupter is not practical

Why did UL introduce UL 943C?

UL 943C, Special Purpose Ground-Fault Circuit-Interrupters (SPGFCIs), was introduced to address the two limitations of Class A GFCIs (defined by UL 943) that prohibited their use in many industrial applications. Namely, the system voltage limitation to a maximum of 240 V and a maximum allowed leakage current of 6 mA. UL 943C defines three GFCI Classes: Classes C, D, and E. These new Classes are rated up to 600 V, with a trip level of 20 mA. In addition, UL 943C requires the device to monitor the continuity of the ground wire and interrupt power to the load if ground integrity is lost.

What are the different UL GFCI Classes?

Class A – A GFCI that will interrupt the circuit to the load when the ground-fault current is 6 mA or more but not when the ground-fault current is 4 mA or less and is intended to be used in circuits where the line-to-line voltage is 240 V or less. Class B – A GFCI that will interrupt the circuit to the load when the ground-fault current exceeds 20 mA. Only used with swimming pool underwater lighting fixtures that were installed prior to local adoption of the 1965 edition of the NEC. Class B GFCI is obsolete. Class C – A GFCI that will interrupt the circuit to the load when the ground-fault current is 20 mA or more and is intended to be used in circuits with no conductor over 300 V to ground (i.e. systems where line-to-line voltage is 480 V or less) where reliable equipment grounding or double insulation is provided. Class D – A GFCI that will interrupt the circuit to the load when the ground-fault current is 20 mA or more and is intended to be used in circuits with one or more conductors over 300 V to ground (i.e. 600 V systems), and with specially sized, reliable grounding, to provide a low impedance path so that the voltage across the body during a fault does not exceed 150 V. Class E – A GFCI that will interrupt the circuit to the load when the ground-fault current is 20 mA or more and is intended to be used in circuits with one or more conductors over 300 volts to ground (i.e. 600 V systems) but with conventional equipment grounding provided for the protected equipment in the system or double insulation. These GFCIs respond rapidly to open the circuit before the magnitude and duration of the current flowing through the person’s body exceeds the limits for ventricular fibrillation.

What is the SB6100 Industrial Shock-Block?

SB6100 is available in two models: Special-Purpose Ground-Fault Circuit-Interrupter (SPGFCI) and Equipment Ground-Fault Protection Device (EGFPD). SB6100 – SPGFCI is a UL 943C listed device for personnel protection, while SB6100 – EGFPD is an equipment protection device that is tested to both UL 943 and UL 1053. Both devices implement additional safety features for superior protection.

What does the SB6100 Industrial Shock-Block do?

SB6100 detects leakage current and interrupts the circuit significantly reducing or eliminating the shock potential. One key part of the additional safety features mentioned earlier, is that the SB6100 also monitors the ground wire from the SB6100 to the load for continuity. If the wire is broken or becomes loose, the SB6100 will signal an alarm and interrupt power.

What are the differences between SB6100 – GFCI and SB6100 – EGFPD models?

SB6100 - EGFPD is exactly the same as SB6100 – SPGFCI except that it has variable setpoints (6, 10-100 mA in increments of 10 mA) to provide flexibility and to reduce nuisance tripping in systems with leakage current higher than the fixed 20 mA (SB6100 - SPGFCI setpoint is fixed at 20mA), and the load-ground monitoring is optional (the use of a termination device is not required).

What are the enclosure options available for the SB6100 Industrial Shock-Block?

Two options for enclosures are available: UL-recognized open-chassis models for installation in an existing electrical enclosure (for example, MCCs or switchgears) and UL-listed NEMA-4X enclosed models for stand-alone installations. A mobile version is also available.

What are the typical applications for the SB6100 Industrial Shock-Block?

Any application that involves a wet environment including:

  • Submersible pumps
  • High pressure washers and paint booths
  • Water and waste water treatment plants
  • Dewatering applications
  • Portable equipment (stud guns, heaters, fans, lighting, etc.)
  • Temporary wiring (including welding receptacles) used for construction and maintenance
  • Tile/concrete cutters
  • Power plants
  • Food processing plants
  • Aquariums, fountains, and swimming pools
  • Amusement parks, water slides, golf courses, and arenas