Guardian 4721, Repair Manual

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PART 4
CIRCUIT CONDITION- UTILITY VOLTAGE RESTORED
• Utility source line-to-line voltage is delivered directly to the sensing transformer’s primary winding. A resultant
sensing voltage is then delivered from the transformer’s secondary winding to the control board. It the “Utility”
sensing voltage is above about 80 percent of the nominal rated voltage, the control board will react.
• On restoration of “Utility” source voltage, control board action will turn on a “return to utility timer.”
Page 72
DC CONTROL
LIQUID COOLED
ENGINE UNITS
SECTION 4.2
OPERATIONAL ANALYSIS