240.89 Replacement Trip Units.
Code Change Summary: New code section on replacement trip units.
Interchangeable trip units are removable electronic devices installed in some circuit breakers that monitor voltage and current and function to trip the circuit breaker in the event of an abnormal voltage related condition or an overcurrent condition. They can also provide power quality metering capabilities, protective relay functions, diagnostic abilities, and other communications.
Trip units are engineered to work within the capabilities of the specific circuit breaker they are intended for. There are many replaceable trip units on the market that are designed to be installed in a wide age range of circuit breakers and can effectively modernize older legacy circuit breakers. When a manufacturer characterizes their replacement trip unit as “universal”, they typically mean as applied to a specific brand and product line within a specific date range of manufacture.
Just because a replacement trip unit may physically fit into the circuit breaker frame doesn’t necessarily mean that it is intended for that specific circuit breaker application. Mismatching a replacement trip unit with a circuit breaker that it was not specifically designed for can result in the circuit breaker operating outside of its intended design.
In the 2023 NEC®, new Section 240.89 requires replacement trip units to be listed for use with the circuit breaker type in which they are installed. They can be a listed trip unit that is identical to the original trip unit, or a different trip unit that has been listed for use with the specific circuit breaker.
Check the product listing, documentation, and installation instructions to be sure that the replacement trip unit is compatible with the specific low voltage power circuit breaker and be prepared for the electrical inspector who will ask for proof that the combination is compatible.
Below is a preview of the NEC®. See the actual NEC® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2023 NEC® edition of NFPA 70.
2020 Code Language:
This code section did not exist.
2023 Code Language:
N 240.89 Replacement Trip Units. Replacement trip units shall be listed for use with the circuit breaker type in which it is installed.
Informational Note: The replacement trip unit can be a listed unit identical to the original or a different trip unit listed for use with the specific circuit breaker.