Trip Tolerances for Field Testing of Circuit Breakers

Instantaneous Trip Tolerances for Field Testing of Circuit Breakers

Tolerances of Manufacturer's Published Trip Range
Circuit Breaker Type Tolerance of Settings High Side Low Side
Electronic Trip Unit (1) +30% / -30% ---- ----
Adjustable (1) +40% / -30% ---- ----
Nonadjustable (2) ---- +25% -25%

Notes:

  1. Tolerances are based on variations from the nominal settings.
  2. Tolerances are based on variations from the manufacturer's published trip band (i.e., -25% below the low side of the band; +25% above the high side of the band).

References: NEMA publication AB4, Table 4. ANSI/NETA-ATS 2013 Table 100.8.


Inverse Time Trip Test at 300% of Rated Continuous Current of Circuit Breakers Molded-Case Circuit Breakers

Range of Rated Continuous Current (Amperes) Maximum Trip Time in Seconds For Each Maximum Frame Rating (1)
≤ 250V 251 - 600V
0-30 50 70
31-50 80 100
51-100 140 160
101-150 200 250
151-225 230 275
226-400 300 350
401-600 ---- 450
601-800 ---- 500
801-1000 ---- 600
1001-1200 ---- 700
1201-1600 ---- 775
1601-2000 ---- 800
2001-2500 ---- 850
2501-5000 ---- 900
6000 ---- 1000

Notes

  1. Trip times may be substantially longer for integrally-fused circuit breakers if tested with the fuses replaced by solid links (shorting bars).

References: NEMA Standard AB 4-1996: Guidelines for Inspection and Preventive Maintenance of Molded-Case Circuit Breakers Used in Commercial and Industrial Applications, Table 5-3. ANSI/NETA ATS-2013 Table 100.7