Evenly turn the stops (Figure 5-21) clockwise (viewed from above) to decrease the primary contact gap
and counterclockwise to increase the primary contact gap. Both stops must be turned the same amount to
prevent uneven wear and/or damage. It should be noted that both stops can be turned easily if the locking
nuts are loosened and the breaker is in the CLOSED position. Use caution since the return springs (Figure
5-16) are in the charged position.
After performing the adjustment, tighten the locking nuts against the stops.
Open and close the breaker, then remeasure the primary contact gap.
Repeat steps (1) through (3), above, until the correct primary contact gap is obtained.
d. Return Spring Preloading Setting. The return spring preloading setting is determined by measuring distance B as
shown in Figure 5-22. With the load circuit breaker in the OPEN position, distance B shall be 5.75 O.13 inches (146 i3.2
mm). To adjust distance B, turn the adjustable retainer clockwise (viewed from above) to increase distance B and
counterclockwise to decrease distance B.
e. Contact Compression. Once the above settings and alignments have been performed, cycle load circuit breaker CB1
01 OPEN and CLOSED 25 times to compress the contacts of the new vacuum interrupter(s) which has been installed.
After cycling load circuit breaker CB1 01, remeasure the distances specified in steps b, c, and d, above.
Repeat this procedure as necessary until the correct dimensions are obtained. Install phase insulator assembly (18,
Figure 5-19) and front cover (1) in accordance with paragraph 5-24, step d (36) and (38).
Figure 5-21. Load Circuit Breaker CB101, Detail of Vacuum Interrupter Assembly