Guardian 4721, Repair Manual

Page: 56 / 115

PROCEDURE:
1. With the generator shut down, set the generator’s AUTO-
OFF-MANUAL switch to OFF.
2. Set the generator’s main circuit breaker to OFF or
“Open”.
3. Turn off the “Utility” power supply to the transfer switch,
using whatever means provided (such as a utility source
main line breaker).
DANGER: DO NOT ATTEMPT MANUAL
TRANSFER SWITCH OPERATION UNTIL ALL
POWER VOLTAGE SUPPLIES TO THE
SWITCH HAVE BEEN POSITIVELY TURNED
OFF. FAILURE TO TURN OFF ALL POWER
VOLTAGE SUPPLIES MAY RESULT IN
EXTREMELY HAZARDOUS AND POSSIBLY
LETHAL ELECTRICAL SHOCK.
4. In the transfer switch enclosure, locate the manual trans-
fer handle. Handle is retained in the enclosure with a
wing stud. Remove the wing stud and handle.
5. See Figure 3. Insert the un-insulated end of the handle
over the transfer switch operating lever.
a. Move the transfer switch operating lever up to
actuate the load contacts to the “Utility” position,
i.e., load connected to the “utility” source.
b. Actuate the operating lever down to move the
load contacts against the “Standby” contacts,
i.e., load connected to the “Standby” source.
6. Repeat Step 5 several times. As the transfer switch oper-
ating lever is moved slight force should be needed until
the lever reaches its center position. As the lever moves
past its center position, an over-center spring should
snap the moveable load contacts against the stationary
“Standby” or “Utility” contacts.
7. Finally, actuate the main contacts to their “Utility” power
source side, i.e., load contacts against the “Utility” con-
tacts (upward movement of the operating lever).
RESULTS:
1. If there is no evidence of binding, sticking, excessive
force required, replace the standby closing coil (C2).
2. If evidence of sticking, binding, excessive force required
to move main contacts, find cause of binding or sticking
and repair or replace damaged part(s).
TEST 5- TEST LIMIT SWITCH XB1
DISCUSSION:
Standby power source voltage must be available to
the standby closing coil in order for a “transfer to
standby” action to occur. To deliver that source volt-
age to the coil, limit switch XB1 must be closed to the
“Standby” power source side. If the limit switch did not
get actuated or has failed open, the source voltage
will not be available to the closing coil and transfer to
“Standby” will not occur.
!
PART 3
Page 52
“V-TYPE” PREPACKAGED
TRANSFER SWITCHES
SECTION 3.4
DIAGNOSTIC TESTS
Figure 3. Manual Transfer Switch Operation
MANUAL
TRANSFER
HANDLE
TRANSFER
SWITCH
OPERATING
LEVER
MANUAL
TRANSFER
HANDLE
TRANSFER
SWITCH
OPERATING
LEVER
LOAD CONNECTED TO
UTILITY POWER SOURCE LOAD CONNECTED TO
STANDBY POWER SOURCE