Guardian 4721 Repair Manual page 74

SECTION 4.2
OPERATIONAL ANALYSIS
• When the transfer mechanism's main load carrying contacts reach "Neutral" position (disconnected from both
power sources), a mechanical interlock opens limit switch LS3. This opens the circuit to actuating coil (C) and
the coil de-energizes.
• With coil (C) de-energized, spring force closes the main contacts to their "Standby" power source side ("Load"
connected to the "Standby" source).
• As the main contacts close to the "Standby" side, a mechanical interlock actuates limit switches XA1/XB1 to
their terminals A1/A2 side. This action "prepares" the circuit for retransfer back to "Utility".
• Electrical load circuits (T1/T2) are now powered by generator AC output.
Page 70
CIRCUIT CONDITION- FINAL TRANSFER TO STANDBY
DC CONTROL
PART 4
LIQUID COOLED
ENGINE UNITS