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SECTION 3 BYPASSING & ISOLATING
3--1
BYPASSING
This procedure explains how to Bypass the closed
Automatic Transfer Switch contacts. Bypassing is re-
quired before the ATS can be tested or isolated. The
Bypass Switch must be in the AUTOMATIC POS (posi-
tion) and the Isolation Handle must be in the connected
position (turned clockwise until it stops). The CON-
NECTED light should be on.
1. Observe which Automatic Transfer Switch CLOSED
ON light is on (NORMAL or EMERGENCY) on the
STATUS INDICATOR panel. This light indicates the
source connected to the load.
2. Bypas s to the same source connected to the load as
foll ow s (selec t direction). See F igur e 3-1, Fig ure 3-2 ,
and Figu re 3-3.
Figure 3-1. Bypass Handle.
To By pa ss N or ma l S o ur ce
Push in the Bypass
Handle then turn it
counterclockwise to
BYPASS POS.TheBy-
pass Switch CLOSED
ON NORM AL light
should come on. *
Figure 3-2. Bypass to Normal.
To By pa ss E mer g en cy S o ur ce
Figure 3-3. Bypass to Emergency.
Pull out the Bypass
Han dl e then turn it
counterclockwise to
BYPASS POS.TheBy-
pass Switch CLOSED
ON EM ERGENCY
light should come on. *
The Automatic Transfer Switch can now be put in the
TEST or OPEN posit ion. See ISOLATING.
*NOTE: When Acc. 66A is specified, the
handle operation is reversed. Follow
instruction on the door.
ISOLATING
This procedure explains how to isolate the Automatic
Transfer Switch. Isolating is required before any service
work can be performed on the ATS. Observe the ATS
POSITION lights on the STATUS INDICATOR panel.
1. Bypass the closed Automatic Transfer Switch
contacts. See BYPASSING.
2. Isolate the Automatic Transfer Switch as follows.
Refer to Figure 3-4 and Figure 3-5.
Isolation Handle
installed through
enclosure door
Figure 3-4. Isolation Handle.
Bypass–Isolation S witch is energized.
Do not touch isolation contact fingers;
shock, burns, or death could result.
To Isolate the Automatic Transfer Switch
a. Open the encl osure door and r emove the Isolation
Handl e stored on the right side of the c arriage
frame. Close the door. Insert the Isolation Hand le
into the shaft (throu g h the door).
b. Turn Isolation Handle counterclockwise (about 6
or 7 t urns) until the TEST light comes on.
c. Continue turningIsolation Handle co unterclock-
wise (approximately 10 or 11 turns) until it stops
and DISCONNECTED light comes on, TEST
light off.
d. Remove I s o lat i o n Handl e and stor e it inside th e
enclosure on the right s ide o f the c arriage frame.
Figure 3-5. Isolated (DISCONNECTED) ATS.
The Transfer Switch can now be removed for inspectio n
and maintenance. See page 3–2.