Asco — Arcing Contact Replacement

For these Asco models: G7ATB, G962.

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Procedure

1. Remove the movable arcing contact. Use needlenose pliers and a screwdriver to remove the spring pin from the spring stud. Then remove the flat washer, spring guide, and contact spring. Next use a 3/8" socket wrench to remove (ccw) two Sems screws from the pigtails attached to the main movable contact. Now remove arcing contact retainer and the movable arcing contact.
2. Remove the stationary arcing contact. Use a 3/8" socket wrench to remove (ccw) two Sems screws holding the arcing contact (and arc chute support plate) to the main contact pivot block. Then remove the stationary arcing contact.
3. Install new stationary arcing contact. Install a new stationary arcing contact and the arc chute support plate onto the main contact pivot block. Use a 3/8" socket wrench (cw) to secure it with two Sems screws. Tighten both screws to 66 in-lbs (5.5 ft-lbs) torque.
4. Install new movable arcing contact. Put two drops of Loctite 222 (service removable threadlocker) to the lead threads of the adjustment screw. Then install the adjustment screw through the new movable arcing contact until it protrudes 1/8". Now install the movable arcing contact onto the movable main contact so that the spring stud goes through the arcing contact and its pivot points fit into the two depressions (in main contact). Finally, install the arcing contact spring, spring guide, flat washer, and spring pin.
5. Reconnect the pigtails and shunts to the contact. Place the arcing contact retainer over the movable arcing contact and between the shunts and pigtails. Install two Sems screws through the arcing pigtail lugs, arcing contact retainer, and main contact shunt lugs into the main movable contact. Use a 3/8" socket wrench to tighten the two screws (cw) to 66 in-lbs (5.5 ft-lbs) torque.
6. Adjust arcing contacts. After all arcing contacts (both stationary and movable) have been installed, contact adjustment is required.

Source: manual:G962 and G7ATB Transfer Switches.pdf. Figures and steps are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.