Asco — Main and Arcing Contact Assembly Replacement

For these Asco models: G7ATB, G962.

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Procedure

1. Remove the contact supports from both sides. Use a 1/2" box or open-end wrench to remove (ccw) four Sems screws (left & right, upper & lower). Then remove the two contact supports that run vertically between the Normal and Emergency movable contact assemblies.
2. Disconnect the crank arm from the shaft. Use a 1/2" socket wrench to remove (ccw) two nuts with lock washers from each shaft clamp. Then remove the loose clamp from the shaft. Save all hardware.
3. Remove the movable contact assembly. Use a 1/2" socket wrench with 12" extension to remove (ccw) two nuts with lock washers from base of each movable contact assembly.
4. Remove the stationary contact assembly. Use a 3/8" socket wrench to remove (ccw) two Sems screws from the top (or bottom) of each stationary contact assembly. Then use a 1/2" socket wrench with 12" extension to remove (ccw) two nuts with lock washers from the base of each main stationary contact assembly.
5. Install the new stationary contact assembly. Position the new main stationary contact assembly onto the two 5/16" studs. Use a 1/2" socket wrench with 12" extension to install (cw) two nuts with lock washers to secure the assembly. Tighten to 132 in-lbs (11 ft-lbs) torque.
6. Install arc chute support plate & arcing contact. Use a 3/8" socket wrench to install (cw) two Sems screws through the new arc chute plate and new stationary arcing contact to the top (or bottom) of each new stationary contact assembly. Tighten to 66 in-lbs (5.5 ft-lbs) torque.
7. Install the new movable contact assembly. Position the new movable contact assembly onto the two 5/16" studs. Use a 1/2" socket wrench with 12" extension to install (cw) two nuts with lock washers to secure the assembly. Tighten to 132 in-lbs (11 ft-lbs) torque.
8. Connect new movable contact assembly to shaft. Position the new movable contact assembly (black drive arm) under the shaft. Then position the metal half clamp over the front and install two bolts (from opposite side). Use a 1/2" wrench to install (cw) two nuts with lock washers to secure each clamp. Tighten the clamp nuts to 132 in-lbs (11 ft-lbs) torque.
9. Adjust the arcing and main contacts. After all movable and stationary contact assemblies 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.