Change Summary

• The Code language at 312.8(B) expands allowances for wiring space of enclosures for switches or overcurrent devices to contain “power monitoring equipment” and “energy management equipment” under specific conditions along with smaller conductors used exclusively for control or instrumentation circuits of such equipment.

Expert Analysis

In response to the demand for such equipment being installed in a cabinet containing switches or overcurrent devices, the 2017 NEC adopted new text at 312.8(B) to allow “power monitoring equipment” within the wiring space of enclosures for switches or overcurrent devices with specific conditions including the limit on the amount of space occupied by all conductors, splices, taps, devices, and equipment to the same 75 percent fill requirement that was previously located at 312.8(2) [now 312.8(A)(2)].

For the 2020 NEC, CMP-9 took this requirement one step further by adding the term “energy management equipment” to this wiring space requirement. Both types of equipment present the same concern and is governed by the same product standards (UL Product Spec category XOBA). This category covers open-type current transformers intended for field installation within distribution and control equipment such as panelboards, switchboards, industrial control equipment, and energy-monitoring/ management equipment, to measure current on a branch circuit. Energy Management Equipment is also addressed by UL Product Spec category PAZX.

A new list item was also added at 312.8(B)(3) for conductors used exclusively for control or instrumentation circuits of equipment installed within these cabinet enclosures containing switches or overcurrent devices. Sensors associated with power monitoring and energy management equipment operate at very low current levels and smaller conductors which can introduce concern with the mechanical strength of the wire and its ability to withstand the wiring space environment. The new text provides two options for conductors. The first option references 725.49.

This section provides sizing and insulation requirements for Class 1 circuit conductors. The second option establishes use of smaller AWG conductors, along with specific construction and installation requirements to address suitability within the wiring space normally reserved for nominal power equipment such as overcurrent devices.

Leviton Solution
Equipment typically installed in cabinet enclosures for power monitoring typically include CTs (Current Transformers). The CTs encircle conductors and measure current flow and thus energy usage. The measurements are transmitted to a submeter where it is collected and turned into useful energy consumption data.

Organizations can monitor, control, and manage energy usage through submetering strategies, which track energy usage and power consumption for individual tenants, departments, and pieces of equipment or other loads to account for their actual energy usage.

From tenant billing to energy measurement & verification (M&V), Verifeye™ offers a seamless solution that enables smart metering and simplifies the complexities of monitoring energy usage, allocating energy costs and billing tenants.