Generac Power Systems 004916-0 Automatic Transfer Operation, Sequence Of Automatic Operation

Section 3 — Operation

Air-cooled 11 kW Generators

‹3.2.2 “OFF” POSITION

This switch position shuts down the engine. This position also prevents automatic operation.

‹3.2.3 “MANUAL” POSITION

Set the switch to Manual to crank and start the engine. Transfer to standby power will not occur unless there is a utility failure.

With the switch set to AUTO, the engine may crank and start at any time without warning. Such automatic starting normally occurs when utility power source voltage drops below a pre- set level or during the normal exercise cycle. To prevent possible injury that might be caused by such sudden starts, always set the switch to OFF and remove the fuses before working on or around the generator or transfer switch. Then, place a “DO NOT OPERATE” tag on the generator panel and on the transfer switch.

3.3AUTOMATIC TRANSFER

OPERATION

To select automatic operation, do the following:

1.Make sure the transfer switch main contacts are set to their “Utility” position, i.e., loads connected to the utility power source (Figure 3.2).

2.Be sure that normal utility power source voltage is available to transfer switch terminal lugs N1 and N2.

3.Set the generator’s AUTO/OFF/MANUAL switch to AUTO.

4.Set the generator’s main circuit breaker to its ON (or closed) position.

With the preceding steps complete, the generator will start automatically when utility source voltage drops below a preset level. After the unit starts, loads are transferred to the standby power source. Refer to Section 3.4, “Sequence of Automatic Operation.”

3.4SEQUENCE OF AUTOMATIC

OPERATION

The generator’s control panel houses a control logic circuit board. This board constantly monitors util- ity power source voltage. Should that voltage drop below a preset level, circuit board action will signal the engine to crank and start. After the engine starts, the circuit board signals the transfer switch to acti- vate and connect load circuits to the standby power supply (load terminal lugs T1/T2 connect to terminal lugs E1/E2).

Upon restoration of utility source voltage above a preset level, generator circuit board action signals the transfer switch to transfer loads back to that power supply. After retransfer, the engine is signalled to shut down.

The actual sequence of operation is controlled by sensors and timers on a control logic circuit board, as follows:

A.Utility Voltage Dropout Sensor

•This sensor monitors utility source voltage.

•If utility source voltage drops below about 70 percent of the nominal supply voltage, the sensor energizes a 15-second timer.

•Once the timer has expired, the engine will crank and start.

B.Engine Warm-up Time Delay

•This mechanism lets the engine warm up for about 10 seconds before the load is transferred to the standby source.

C.Utility Voltage Pickup Sensor

•This sensor monitors utility power supply volt- age. When that voltage is restored above 70 per- cent of the nominal source voltage, a retransfer time delay starts timing.

D.Retransfer Time Delay

•This timer runs for about 15 seconds.

•At end of a 15-second delay, circuit board action de-energizes transfer relay in the transfer switch.

•Retransfer to utility power source then occurs.

E.Engine Cool-down Timer

• When the load is transferred back to utility power source, the engine cool-down timer starts tim- ing.

• The timer will run for about one minute, and the generator will then shut down.

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