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22 GE Zenith Controls
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ZTSCT / ZBTSCT Operation and Maintenance Manual (71R-5000A)
Testing (cont’d)
Emergency Service
Procedure for Extended
Parallel Time
ZTSCT Transfer Switch
If Source 2 breaker shunt trip was triggered after
an extended parallel time (malfunction) occurred.
Follow these steps to open the transfer switch.
1) Disconnect all power sources from the transfer
switch by opening all line breakers
(Source 1 and Source 2).
2) Open the cabinet door and turn the disconnect
switch to the INHIBIT position.
3) Remove the service access cover on the left hand
side of the transfer switch.
4) The manual operator and the manual handle will
now be exposed. Insert the handle into Source 2
side operator. Open Source 2 side contacts.
5) Close the cabinet door.
6) Energize Source 1 to supply the load until
further repairs can be done.
ZBTSCT Transfer/Bypass Switch
a. Auto Location:
Removal of closed transition transfer switch after
Source 2 breaker shunt trip.
1) Disconnect all power sources from bypass-
isolation transfer switch.
2) Open the bottom cabinet door and turn the
Disconnect Switch (DS) to the INHIBIT position.
3) Remove the service access cover on
the left hand side of the transfer switch.
4) The manual operator and the manual handle will
now be exposed. Insert the handle into Source 2
side manual operator. Open Source 2
side contacts.
5) Close bottom cabinet door.
6) Energize Source 1 power.
7) Close the bypass contacts (BN).*
8) Isolate the transfer switch.*
9) Remove the transfer switch from the bypass-
isolation transfer switch as indicated on the
bypass instruction label to inspect and repair.
10)Re-install the transfer switch after maintenance
with contacts closed to the same source as the
bypass switch. Reinstall the manual handle in its
holder and the service access cover on the left
side of the transfer switch.
11)Re-connect the transfer switch to AUTO.*
b.Auto Location:
Removal of the closed transition transfer switch if
Source 1 and Source 2 contacts remain open.
1) Close the bypass switch into the available source.*
2) Turn the DS to INHIBIT. Remove the transfer
switch service access cover. Close the transfer
switch into the same source as the bypass switch.
(Incorrect sequencing is prevented by the
interlocks while the transfer switch is in AUTO only.)
3) Remove the transfer switch from the bypass-
isolation transfer switch to inspect and repair.*
c. Test Location:
Removal of the closed transition transfer switch if
both Source 1 and Source 2 contacts remain open.
1) Close the bypass switch contacts (BN) as
indicated on the bypass instruction label
on the cabinet door.
2) Disconnect all power sources from bypass-isolation
closed transition transfer switch.
3) Open bottom cabinet door. Turn the Disconnect
Switch (DS) to the INHIBIT position.
4) Remove the service access cover on the left side
of the transfer switch.
5) The manual operator and the manual handle will
not be exposed. Insert the handle into Source 1
side and close Source 1 contacts.
6) Close the bottom cabinet door.
7) Energize Source 1 power.
8) Remove the automatic transfer switch from the
bypass-isolation transfer switch.*
9) Re-install the transfer switch after maintenance
with contacts closed to the same source as the
bypass switch. Reinstall the manual handle in
its holder and the service access cover on the
left side of the transfer switch.
10)Re-connect the transfer switch to AUTO.*
* As described in the following Sequence of Operation in this manual.
DANGER
HAZARDOUS VOLTAGE
(Can Cause Severe Injury or Death)
Turn OFF all power before installation, adjustment, or removal of transfer switch or any of its components.