Table of Contents
Advertisement
5.4 Stab fingers and vertical bus
Look for wear of the tin plating where the unit stab
fingers engage the vertical bus. The plating is part of
the environmental protection system. Oxide and/or
other films can form on exposed bus resulting in a
poor contact.
Lubricate stab connection points with an approved
lubricant. These parts must be replaced when the
plating is worn to the point where copper can be
seen because contact resistance becomes higher,
increasing the heat generated at the contact point.
5.5 Recommended tightening
torques
When making bolted assemblies, the following
considerations should be generally followed.
The tightening torques are determined by the
size of hardware used.
1. Metal-to-metal – Apply standard tightening
torque as listed:
Recommended tightening torques
Thread size
Torque (lbf-in)
8 - 32
20
10 - 32
27 - 32
1/4 - 20
75
5/16 - 18
100
3/8 - 16
247
1/2 - 13
613
2. Metal-to-insert molded in compound part
– Apply 2/3 of standard tightening torque.
3. Compound-to-compound – Apply 1/2 of
standard tighten in torque.
4. Control Terminals – 11 lbf-in.
5. Tighten box type incoming cable lug set screws
to the recommended values shown on the circuit
breaker or device. If no label is present the
recommended value is 85 lbf-ft.
6. Tighten bolted bus connections to 20 lbf-ft.
7. 400 A and 600 A fixed mounted unit clamp
assembly bolts should be tightened to 35 lbf-ft.
5.6 Disconnect operating
handle adjustment
Hazardous voltage.
Will cause death or serious
personal injury.
Disconnect power before working on
this equipment.
In rare circumstances, such as when changing a
circuit breaker or a fusible switch or when a unit
is taken apart, it may be necessary to adjust the
disconnect operating handle. (The Siemens fusible
disconnect switch for 30 A, 60 A, 100 A, and 200 A
ratings does not require adjustment.)
1. Perform all disconnect operating handle
adjustments with the unit removed from the
motor control center or in the"test" position.
2. The adjustable link rod can adjust to increase or
decrease its overall length by rotating the sleeve.
By rotating the sleeve clockwise the length is
increased and by rotating it counterclockwise
the length is decreased. A hex nut is provided as
part of the adjustable link rod and is tightened
against the sleeve to prevent it from going out
of adjustment. The hex nut must be loose and
sufficiently away from the sleeve to allow it to
rotate during the adjustment of the handle.
On
Trip
Off
Park
Figure 68
tiastar™ Motor Control Centers Instruction Manual Maintenance
37
Advertisement
Table of Contents
