Appeal 34784

NFPA 70 Article 500

NFPA 70 (NEC) Article 500

The NEC outlines requirements for electrical installations/equipment in hazardous (classified) locations. In order to determine appropriate area classifications at a wastewater facility, NEC 500.4 offers (via an informational note) reference to NFPA 820.

NFPA 820 Standard for Fire Prevention in Wastewater Treatment and Collection Facilities

FPA 70 (National Electrical Code) Article 500 specifies requirements for electrical installations and equipment in hazardous (classified) locations. To determine appropriate area classifications for wastewater facilities, the NEC refers to NFPA 820 via an informational note.

NFPA 820, Table 6.2.2(a) Row 9, provides guidance to classify the wet-weather clarifier pipe gallery and its connecting interior spaces as Class I, Division 2, Group D. The existing wet-weather clarifier pipe gallery is a separate structure, but is connected to four (4) existing sludge Transfer Buildings via stairs. The main electrical and control equipment is housed in each of the four Transfer Buildings.

NFPA 820 1.3.1 Application defines the scope of coverage of the standard as applicable to "…new installations or changes in use of space, electrical hazard classification, or process capacity." Additionally, 1.3.1.1 states that "Replacement-in-kind of components or devices are not considered modifications."

NFPA 820 1.4.1 states that "Unless otherwise specified, the provisions of this standard shall not apply to facilities, equipment, structures, or installations that existed or were approved for construction or installation prior to the effective date of the standard."

The proposed design considers the pipe gallery and sludge Transfer Buildings as unclassified areas. This approach would facilitate the replacement of outdated electrical equipment (dating from the 1950s and 1970s) without the additional considerations required for NEC Class I, Division 2 installations.
The design aims to replace unreliable, antiquated electrical equipment in the existing structures, specifically:
• Motor control centers
• Panelboards
• Dry-type transformers
• Control panel interior components
This project does not involve process improvements or other facility changes, and there will be no change to the current intermittent operation of the facility. The replacements are essentially "in-kind," with minor location adjustments to meet current clearance and working space requirements.
The new equipment would adhere to current standards (including UL listing), significantly reducing the risk of failure and improving maintenance. Additionally, the replacement motor control centers would feature arc-flash resistant construction, further enhancing safety.

Work is not covered under the NFPA 820 standard per 1.3.1.1 as the project is a replacement-in-kind and there is not change in use of space or process capacity. Additionally, per 1.4 retroactively, the facility was approved for construction prior to the effective date of NFPA 820.
Facility History and Current Status:
The existing facility was constructed in phases between the 1950s and 1970s, predating the establishment of NFPA 820. Consequently, it was not originally built to meet the NEC requirements for a Class I, Division 2, Group D space.
Electrical and control systems have undergone upgrades over time. Circa 2002, new motor control centers and upgraded controls were installed during a plant expansion/upgrade. Although NFPA 820 existed during the 2002 upgrades, the facility was neither classified nor constructed to meet that standard at that time.
Safety Record and Ventilation:
The primary sludge that might trigger the classification of the facility is contained in watertight piping and pumping systems. The facility has operated for over 70 years without any known incidents of gas detection or ignition. While the space is continuously ventilated, it does not meet the NFPA 820 requirement of 6 air changes per hour necessary for an unclassified rating.
Proposed Project Scope:
The project aims to enhance safety and reduce the likelihood of equipment failure through the proposed replacements. However, it does not attempt to address the extensive scope and cost of reclassifying the entire facility to meet NFPA 820 standards and associated NEC requirements.