Generac Power Systems 20 kW LP manual Test 37 Check Utility Sensing Voltage at the Circuit Board

Section 3.4

Diagnostic tests

Part 3

Transfer switch

240 VAC

TEST POINTS

N2

N1

Figure 9. Terminal Block Test Points

Test 37 – Check Utility Sensing Voltage at the Circuit Board

Discussion:

If the generator starts and transfer to STANDBY occurs in the automatic mode when acceptable UTILITY source voltage is available at the terminal block, the next step is to determine if sensing voltage is reaching the printed circuit board.

Note: The System Ready LED will flash in AUTO or UTILITY LOST will display on the panel.

Procedure:

1.Set the AUTO-OFF-MANUAL switch to OFF.

2.Disconnect the N1/N2 connector in the control panel (see Figure 6).

3.Set a VOM to measure AC voltage.

4.Connect one meter test lead to Wire N1. Connect the other meter test lead to Wire N2. Approximately 240 VAC should be measured. See Figure 9.

Results:

1.If voltage was measured in Step 4 and the pin connec- tions are good, replace the circuit board.

2.If voltage was NOT measured in Step 4, repair or replace Wire N1/N2 between connector and terminal block.

Test 38 – Check Utility SENSE Voltage

The N1 and N2 terminals in the transfer switch deliver utility voltage “sensing” to a circuit board. If voltage at the terminals is zero or low, standby generator startup and transfer to the “Standby” source will occur auto- matically as controlled by the circuit board. A zero or low voltage at these terminals will also prevent retransfer back to the “Utility” source.

Procedure:

With utility source voltage available to terminal lugs N1 and N2, use a VOM to test for utility source line- to-line voltage across terminal locations N1 and N2 terminals. Normal line-to-line utility source voltage should be indicated.

N1A N2A
A	A	A
F1	F2	F3
B	B	B
N1	N2	T1

Figure 10. Transfer Switch Fuse Block

RESULTS:

1.If voltage reading across the N1 and N2 terminals is zero or low, refer to Flow Chart.

2.If voltage reading is good, refer to Flow Chart.

Test 39 – Check Voltage at Terminal

Lugs N1, N2

DISCUSSION:

If source voltage is not available to N1/N2 terminals, automatic startup and transfer to STANDBY will occur when the generator AUTO-OFF-MANUAL switch is set to AUTO. This test will prove that “Utility” voltage is available to those terminals, or is not available.

*AND DANGEROUS VOLTAGES ARE PRESENT AT TERMINAL LUGS N1/N2. CONTACT WITH HIGH VOLTAGE TERMINALS WILL RESULT IN DANGEROUS AND POSSIBLY LETHAL ELECTRICAL SHOCK. DO NOT ATTEMPT THIS TEST WHILE STANDING ON WET OR

DAMP GROUND, WHILE BAREFOOT, OR WHILE HANDS OR FEET ARE WET.DANGER: PROCEED WITH CAUTION! HIGH

Procedure:

1.Make sure that all main line circuit breakers in the utility line to the transfer switch are “On” or “Closed.”

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