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Maintenance
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16.0 MAINTENANCE
Minimal periodic maintenance of the STS2/PDU is required. As with all electrical distribution compo-
nents, the system should be regularly inspected for electrical connection integrity, signs of excessive
temperatures, dirt accumulation and proper system operation.
16.1 Proper Tightening of Nuts and Bolts
The recommended tightening torque for all nuts and bolts is as shown below, unless otherwise
labeled. All power connections are designed to remain at proper torque throughout the lifetime of the
unit.
16.2 Testing the STS2/PDU
The STS2/PDU includes comprehensive system alarms and fault detection to identify operational
problems. To increase the degree of confidence of proper system operation, periodic transfer tests can
be easily performed. For instructions for changing the preferred source and switching sources, see
10.2 - Manual Transfer / Preferred Source Selection.
16.3 Changing the Air Filter
A standard furnace filter is installed behind the air intake in the front door. The air intake allows air
to circulate to cool the unit. Replace the filter when it becomes dirty and impedes air flow. The fre-
quency of changing or cleaning the filter depends on the location in which the unit is located. The size
of the filter is 1 x 25 x 25 in. (254 x 635 x 635mm).
!
WARNING
Only qualified service personnel should perform maintenance on the STS2/PDU.
Lethal voltages exist inside the unit during normal operation.
The unit is supplied by multiple AC power sources. Disconnect and lock out all power sources
before working inside unit.
Table 29 Torque tightening
Bolt Shaft Size
Grade 5 - Imperial
Grade 8.8 - Metric
Electrical Connections with
Belleville Washers
in-lb
(pound-inch)
N-m
(Newton-meter)
in-lb
(pound-inch)
N-m
(Newton-meter)
10-32253354
1/4-20 53 6 80 9.0
5/16-18 107 12 180 20.4
3/8-16 192 22 240 27.1
1/2-13 428 48 480 54.3
Table 30 Branch circuit breakers
Current Rating
in-lb
(pound-inch)
N-m
(Newton-meter)
Up to 30 Amp 35 4.0
40 to 100 Amp 45 5.1