Ensuring UL-Compliant Jobsite Power

By Brian Earl, Contributor

Critical to safe jobsite power, UL announced two new standards affecting Jobsite Temporary Power – UL 943 affecting GFCI’s and UL 1640 affecting Open Neutral Protection, effective May 5, 2021.

These two mandates are particularly impactful as they both involve life safety measures to prevent electrical shock.

UL 943

Throughout GFCI evolution, UL 943 provides specific requirements for ground-fault circuit-interrupters that adhere to the electrical installation codes of Canada, Mexico, and the United States. As of May 5, 2021, UL 943 requires that products used in portable applications (in-line GFCI cordsets and Portable Distribution Units, for example) incorporate auto testing technology to further elevate worker and worksite safety.

UL 1640

UL 1640 applies to portable power distribution units (PDUs) which regulate and provide power to locations without adequate, existing distribution systems. To attain UL 1640 compliance in a construction site, a product must provide open neutral protection, along with standard GFCI protection.

Understanding The Basics of How UL 943 and UL 1640 Work Together

UL 943 ensures that GFCI’s work as intended by automatically and continuously testing their circuitry. Jobsites are harsh environments where GFCI typically fail through moisture and dust intrusion, or electrical power surges. GFCI’s by nature are mechanically held devices. Meaning once you latch the device, unless it trips, power is being delivered to the receptacles. In their operation, GFCI circuity monitors the hot, neutral, and ground conductors, measuring the amount of power that goes out and is returned. If there is a difference, the circuit immediately releases and prevents shock to the user. On jobsites with portable cords supplying power to portable distribution units (PDU)’s (often called spider boxes or sleds either because of the cords that exit at all angles or because they are often dragged along by their cords, like a sled), there is a potential for the cord be damaged, perhaps the neutral severed, leaving the hot conductor intact and rendering the GFCI module in operative to sense a fault.

Since the GFCI is a mechanically held device, power from the hot conductor would still flow through the GFCI receptacles. Without the neutral conductor to sense a fault, the remaining hot conductor and power could cause electrical harm to a worker.

Enter UL 1640. Among several requirements for safe electrical design, construction. and wiring practices, is the requirement for open neutral protection for electrical receptacles. In the situation described above, if the neutral conductor was damaged or severed the open neutral relay, protecting the electrical outlet would release.

Together, these two UL Standards ensure safe electrical power is continually delivered to electrical receptacles in portable electrical devices including GFCI in-line cord sets used in portable applications. ESW

Brian Earl is VP of Marketing, Product Management and Sales at Ericson Manufacturing (www.ericson.com).

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