Generac 04674-2, 04673-2 Manual Transfer Operation, ‹ 3.5.2 Transfer Back to Utility Power Source

Section 3 — Operation

Air-cooled 7 kW, 12 kW and 15 kW Generators

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 60 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 a standby source.

C.Standby Voltage Sensor

•This sensor monitors generator AC output volt- age. When the voltage has reached 50 percent of the nominal rated voltage, transfer to standby can occur.

D.Utility Voltage Pickup Sensor

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

E.Retransfer Time Delay

•This timer runs for about 15 seconds.

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

•Retransfer to utility power source then occurs.

F.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.

3.5MANUAL TRANSFER OPERATION

‹3.5.1 TRANSFER TO GENERATOR POWER SOURCE

To start the generator and activate the transfer switch manually, proceed as follows:

1.Set the generator’s main circuit breaker to its OFF (or open) position.

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

3.Turn OFF the utility power supply to the transfer switch using the means provided (such as a utility main line circuit breaker).

DANGER

Do not attempt to activate the transfer switch manually 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 fatal elec- trical shock.

4.Use the manual transfer handle inside the trans- fer switch to move the main contacts to their “Standby” position, i.e., loads connected to the standby power source (Figure 3.2).

5.To crank and start the engine, set the AUTO/OFF/ MANUAL switch to MANUAL.

6.Let the engine stabilize and warm up for a few minutes.

7.Set the generator’s main circuit breaker to its ON (or closed) position. The standby power source now powers the loads.

Figure 3.2 – Manual Transfer Switch Operation

‹3.5.2 TRANSFER BACK TO UTILITY POWER SOURCE

When utility power has been restored, transfer back to that source and shut down the generator. This can be accomplished as follows:

1.Set the generator’s main circuit breaker to its OFF (or open) position.

2.Let the engine run for a minute or two at no-load to stabilize the internal temperatures.

3.Set the generator’s AUTO/OFF/MANUAL switch to its OFF (or open) position. The engine should shut down.

4.Check that utility power supply to the transfer switch is turned OFF.

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