Short answer: under NFPA 70B-2023, low-voltage and medium-voltage circuit breakers are inspected, serviced and electrically tested at least every 60 months in good condition, every 36 months in average condition, and every 12 months in poor condition, where a failure would endanger people, or in a harsh environment. Infrared thermography of the same equipment is every 12 months, or every 6 months in the worst condition.
What NFPA 70B-2023 changed
The 2023 edition turned NFPA 70B from a recommended practice into a standard. Its maintenance interval table (Table 9.2.2) sets a maximum interval for each kind of equipment and each kind of work: visual inspection, cleaning, lubrication, mechanical servicing and electrical testing. The interval depends on the equipment's condition.
The three equipment conditions
NFPA 70B rates each piece of equipment on three things, and the worst of the three sets its condition:
- Physical condition. Condition 1 is like new, clean, dry and maintained on schedule. Condition 2 applies when results have drifted from past tests, the last cycle needed major repairs, or there are open findings from monitoring or predictive work such as an infrared scan. Condition 3 applies when the equipment missed its last two maintenance cycles, needed major repairs in the last two cycles, or has urgent findings.
- Criticality. If a failure would endanger people, the equipment is Condition 3.
- Operating environment. Equipment in harsh chemicals, contamination or extreme conditions it was not rated for is Condition 3.
Maximum intervals for circuit breakers
For molded-case, insulated-case and low-voltage power circuit breakers, and for medium-voltage power circuit breakers, NFPA 70B-2023 uses the same intervals for inspection, cleaning, lubrication, mechanical servicing and electrical testing:
- Condition 1: 60 months
- Condition 2: 36 months
- Condition 3: 12 months
Protective relays have their own rows: electromechanical relays are on a shorter cycle than solid-state and microprocessor relays. Infrared thermography applies to all equipment at 12 months for Conditions 1 and 2, and 6 months for Condition 3.
How NETA sets its intervals
The NETA maintenance testing standard (ANSI/NETA MTS-2023, Appendix B) takes a different route to a similar answer. It gives a base frequency for each kind of equipment: for air, vacuum, oil and SF6 circuit breakers, a full visual, mechanical and electrical test every 36 months.
It then multiplies that by a factor from 0.25 to 2.5, depending on the equipment's condition (poor, average or good) and how reliable it has to be (low, medium or high). A breaker in poor condition with a high reliability requirement ends up on a much shorter cycle than a lightly used breaker in good condition. NETA presents its matrix as a guide, to be applied with the site's own test history and trends.
Can the intervals be changed?
Yes, within limits. NFPA 70B allows an interval to change based on the risk to people or operations if the equipment fails to work, and any extension past the table has to be justified and written into the electrical maintenance program (EMP). In practice, intervals get shorter after bad results and can lengthen once a breaker has a clean record.
Putting it into a Canadian program
- Build an equipment list and give each breaker a condition rating. Start with the critical ones: mains, feeders to life-safety and process loads, and anything that missed its last service.
- Set the interval from NFPA 70B or the NETA matrix, check it against the manufacturer's instructions, and record it in the maintenance program. In Canada, CSA Z463 is the guideline for organizing that program.
- Scan the energized equipment with infrared every year in between; a hot breaker connection moves that breaker up the list.
- Re-rate the condition after each test. A breaker that drifts, or needs a repair, moves to a shorter cycle.
How we can help
We test low- and medium-voltage breakers across Canada during planned shutdowns, with primary and secondary injection, contact and insulation resistance, and field test sheets for every breaker. See our circuit breaker testing service, primary vs secondary injection and what a breaker test report should include.