W-C-375E
4.6.2.1 Group C inspection. Group C inspection shall consist of the tests specified in table VIII in the order shown and shall be made on sample units selected from lots which have passed the groups A and B inspections, unless the Government considers it more practical to select a sample from current production. A manufacturer's normal quality control and production tests may be used to fulfill group C inspection. The applicability of a test listed for a particular design of circuit breaker shall be as specified in table IV.
4.6.2.1.1 Sampling plan. Samples shall be selected at random. The sample size shall be as for qualification (see
4.5.1) for each specification sheet, 12 months after the date of notification of qualification and after each subsequent
12-month period.
4.6.2.1.2 Failures. If one or more sample units fail to pass group C inspection, the sample shall be considered to have failed.
4.6.2.1.3 Disposition of sample units. Sample units which have been subjected to group C inspection shall not be delivered on the contract or order.
4.6.2.1.4 Noncompliance. If a sample fails to pass group C inspection, the supplier shall take corrective action on the materials or processes, or both, as warranted, and on all units of product which can be corrected and which were manufactured under essentially the same conditions with essentially the same materials, processes, etc., and which are considered subject to the same failure. Acceptance of the product shall be discontinued until corrective action, acceptable to the Government, has been taken. After the corrective action has been taken, group C inspection shall be repeated on additional sample units (all inspection, or the inspection which the original sample failed at the option of the Government). Group A and B inspections may be reinstituted however, final acceptance shall be withheld until group C reinspection has shown that the corrective action was successful. In the event of failure after reinspection, information concerning the failure and the corrective action taken shall be furnished to the cognizant inspection activity and the qualifying activity.
4.7 Methods of examination and test. For the purpose of testing multi-pole circuit breakers having independent trip, the operation of each pole shall be tested as individual circuit breakers. Unless otherwise specified, no conditioning of the circuit breakers shall take place during or between tests. Unless otherwise specified, the test frequency shall be 60 Hz (see 3.1).
4.7.1 Visual and mechanical examination. Circuit breakers shall be examined to verify that the material, design, and construction, physical dimensions, marking, and workmanship are in accordance with applicable requirements (see 3.1, 3.4, 3.21, and 3.22).
4.7.2 Calibration (see 3.5). Circuit breakers shall be mounted in a vertical position without an enclosure, other than the molded case and wired in accordance with the requirements of UL 489. Devices shall be stabilized (see
6.6.3) at the applicable ambient temperature (see 6.6.4), and subjected to the percent of rated current specified in table Ix for the particular design of circuit breaker under test. The 200 percent test shall be conducted separately on each pole of multi-pole circuit breakers and the 125 -135 percent test shall be conducted with each pole of multi-pole
breakers simultaneously carrying the applicable current. Tests shall be conducted in the order shown reading the x's from left to right.
TABLE Ix. Calibration tests sequence.
Circuit breaker design |
Percent of rated current and ambient temperature ±3° |
||||
200 percent at 25°C |
125 percent at 25°C |
135 percent at 25°C |
200 percent at 40°C |
125 percent at 40°C |
|
Fully magnetic breakers - - - - - - - - - - - - - - - - Uncompensated thermal breakers calibrated at 25°C - - - - - - - - - - - - - - - - - - - Uncompensated thermal and fused breakers calibrated at 40°C - - - - - - - - - - - - - - - - - - - Compensated thermal breakers - - - - - - - - - - |
x x x x |
x x --- --- |
--- --- x x |
--- --- --- x |
--- --- --- x 1/ |
1/ This 125 percent test shall be conducted immediately after the breaker has carried its rated current until constant temperatures have been reached (see 4.7.6).
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