Until recently, almost all current transformers (CTs) used with electric submeters were certified by Underwriters Laboratories (UL) as UL Recognized Components under the XODW standard, using a subset of the requirements from IEEE C57.13 and CSA 60044-1. The key phrase is “UL Recognized Component”. The UL Recognized status meant the CTs were not approved for standalone field installation. UL did approve the use of UL Recognized Component CTs with UL Listed submeters (like the WattNode meter) for field installation.
In the past, the meter approval was generally accepted by the building inspector or authority having jurisdiction (AHJ). But in some cases, inspectors would request a copy of the conditions of acceptability for the current transformers and find that the CTs were not approved for field installation, and so would not approve the job.
UL 2808 CT safety standard
The UL 2808 CT safety standard was released by UL in 2012 under category code XOBA. The 2017 Edition of the National Electrical Code (NEC) requires that field installed CTs used to measure current on the service entrance or branch circuit conductors within panelboards, switchboards, industrial control equipment, and energy-monitoring/management equipment, must be listed (UL Listed).
The 2017 NEC updates section 312.8 (B) Power Monitoring Equipment as follows: The wiring space of enclosures for switches or overcurrent devices shall be permitted to contain power monitoring equipment where all of the following conditions are met:
- (1) The power monitoring equipment is identified as a field installable accessory as part of the listed equipment, or is a listed kit evaluated for field installation in switch or overcurrent device enclosures.
- (2) The total area of all conductors, splices, taps, and equipment at any cross section of the wiring space does not exceed 75 percent of the cross-sectional area of that space. with language allowing UL Listed power monitoring equipment
Relevant UL 2808 Language (from UL 2808, June 10, 2016)
- 1.1 These requirements cover open-type current transformers and their associated signal level combiner and/or multiplexer board accessories thereto 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.
National Electrical Code state by state adoption map: Nation Electrical Code Adoption Map As the 2017 Edition of the code is adopted by states and other authorities, only UL Listed CTs will be permitted in circuit breaker panels or related electrical enclosures.
The following CT Series sold by CCS are all UL 2808 Listed