Guardian 4721 Repair Manual page 80

SECTION 4.2
OPERATIONAL ANALYSIS
• When the transfer mechanism's main contacts reach "Neutral" position ("Load" disconnected from both power
sources), limit switch XA1 is opened by a mechanical interlock. This opens the circuit to actuating coil (C). Coil
(C) de-energizes.
• With coil (C) de-energized, spring force completes the transfer action back to the"Utility" side ("Load" connect-
ed to the "Utility" supply).
• Loads are now powered by the "Utility" power source.
• The standby generator is still running and generator AC output voltage is still available to transfer mechanism
Terminal Lugs E1 and E2.
• Following retransfer back to the "Standby" source, an "engine cool down timer" starts timing. This timer will time
for about 1 minute. Purpose of this timer is to allow the engine to run at no-load for about one (1) minute to sta-
bilize internal engine-generator temperatures.
Page 76
CIRCUIT CONDITION- FINAL RETRANSFER TO UTILITY
DC CONTROL
PART 4
LIQUID COOLED
ENGINE UNITS