Latest Updates on EPOs for Electrical Energy and Hydrogen Vehicle Fueling

Credit: NIST

OWM is pleased to announce the latest inspection and test procedures for two alternative vehicle fueling applications: Electrical Energy (EVSE for Vehicle Fueling Systems) (EPO 30) and Hydrogen Gas (Vehicle Fueling Dispensers) (EPO 29), as well as the updating of the field examinations of a wider range of device-types covered in NIST Handbook 112. EPOs serve as a step-by-step "shorthand” guide for the specific code requirements within NIST Handbook 44, which weights and measures officials can easily use in field inspections and testing of devices to legal metrology standards.

NIST OWM is actively updating many of the older versions of Examination Procedure Outlines (EPOs), which include detailed inspection and test procedures with references to the applicable code sections in NIST Handbook 44. OWM is also updating NIST Handbook 112, which is a compilation of EPOs for the more frequently regulated commercial weighing and measuring devices. Moving forward, OWM will provide an annual update to the EPOs and publish a version of NIST Handbook 112 annually.

Updated EPO 30 for Electric Vehicle Supply Equipment (EVSE)

NIST OWM Examination Procedure Outline (EPO) 30 for Retail Electric Vehicle Fueling Systems (EVFS; also known as Electric Vehicle Supply Equipment (EVSE)) was first developed in August 2015 through the Test Procedure Subcommittee within NIST’s Electric Vehicle Fueling and Submetering U.S. National Work Group. The inspection and test procedures in EPO 30 are based on the code in NIST Handbook 44 Sections 1.10 General Code, 3.40 Electric Vehicle Fueling Systems, and 5.55 Timing Devices.

In addition to a new, easier-to-follow format, EPO 30 was recently updated to include:

1.  Expanded interference test procedures;
2. Relevant NIST Handbook 44 code modifications adopted since 2021 up through 2023;
3. A new template for an EVSE test report (a single or multiple device’s/system’s official test/inspection history record on the correctness of transaction information and accuracy on the electrical energy delivery and where applicable the assessment of related time-based fees);
4. Electrical energy formula(s); and
5. References to related safety standards.

Updated EPO 29 for Hydrogen Gas Vehicle Fuel Dispensers

NIST OWM Examination Procedure Outline (EPO) 29 for Hydrogen Gas Retail Vehicle Fuel Dispensers was updated in November 2024 and is based on the code requirements in NIST Handbook 44 Sections 1.10 General Code and 3.39 Hydrogen Gas-Measuring Devices. It also includes an Appendix that contains criteria for selecting a reference scale when using the gravimetric test method to verify the accuracy performance of a hydrogen gas dispenser. This methodology is one of three test methods recognized by NIST Handbook 44.

The updated version of NIST EPO 29 includes:

1. Relevant NIST Handbook 44 code modifications adopted since 2021 up through 2024;
2. A rework of standardized text applicable across multiple device codes for clarity;
3. A new test report which can be used as a template for a hardcopy or electronically formatted report form.

Coming in 2025 NIST Handbook 112!

For the highly anticipated complete guide to the field examination of more than 15+ commercial weighing and measures devices, NIST OWM is pleased to announce it will publish an updated NIST Handbook 112 Examination Procedure Outlines (EPOs) For Commercial Weighing and Measuring Devices in the first quarter of 2025. First published in 1973, NIST Handbook 112 covers the legal metrology areas for an inspection of a device’s design, its installation, as well as its use in the marketplace. It also includes the determination of other key factors prior to the test and for stepping through the test to ascertain if the device is in compliance for accuracy and has adequate security for metrological features. EPOs provide a template for a uniform step-by-step examination process to determine a device’s compliance with the minimum legal metrology requirements that apply to the equipment while in commercial operation.

NIST Handbook 112 (and the EPOs within) serve as a step-by-step "shorthand” guide on the application of general and device-specific code within NIST Handbook 44, which weights and measures officials use in device field inspections and testing. It should also be useful to device manufacturers and other organizations involved in the design, installation, and service of commercial weighing and measuring devices. Each individual EPO includes detailed inspection and test procedures, with references to the specific code requirements in NIST Handbook 44. 

Although not a safety standard, NIST Handbook 112 contains: (1) safety notes and reminders to emphasize safety consciousness in and around the inspection and test area; (2) elements to encourage awareness and adherence to the safety policies and regulations in place at the operation site; and (3) a “Glossary of Safety Key Phrases.”

NIST Handbook 112 will continue to compile all NIST Handbook 44-relevant EPOs in an electronic format. Moving forward, NIST OWM plans to update NIST Handbook 112 on an annual basis.

Stay tuned; we will notify everyone as the release date draws closer.