Generac Power Systems CorePower 6/7 kW 60 Hz Diagnostic Repair Manual page 34

Section 2.4
Diagnostic Tests
INTRODUCTION
This section familiarizes the service technician with acceptable
procedure for the testing and evaluation of various problems that
can occur on the standby generators with air-cooled engines. Use
this section in conjunction with Section 2.3, "Troubleshooting Flow
Charts." The numbered tests in this section correspond with those
of Section 2.3.
Some test procedures in this section may require the use of
specialized test equipment, meters or tools. Most tests can be
performed with an inexpensive Volt-Ohm-Meter (VOM). An AC
frequency meter is required where frequency readings must be
taken. To measure AC loads it is acceptable to use a clamp-on
ammeter.
Testing and troubleshooting methods covered in this section are
not exhaustive. No attempt has been made to discuss, evaluate
and advise the home standby service trade of all conceivable
ways in which service and trouble diagnosis must be performed.
Accordingly, anyone who uses a test method not recommended
herein must first satisfy himself that the procedure or method he
has selected will jeopardize neither his nor the product's safety.
SAFETY
Service personnel who work on this equipment should be aware
of the dangers of such equipment. Extremely high and dangerous
voltages are present that can kill or cause serious injury. Gaseous
fuels are highly explosive and can ignite by the slightest spark.
Engine exhaust gases contain deadly carbon monoxide gas that
can cause unconsciousness or even death. Contact with moving
parts can cause serious injury. The list of hazards is seemingly
endless.
When working on this equipment, use common sense and remain
alert at all times. Never work on this equipment while you are
physically or mentally fatigued. If you do not understand a
component, device or system, do not work on it.
AC TROUBLESHOOTING
It is always good practice to continue to ask questions during the
troubleshooting process. When evaluating the problem asking
some of these questions may help identify the problem quicker.
• What is the generator supposed to do?
• What fault (Alarm) is shutting the generator down?
• Is the fault a symptom of another problem?
• Does the generator have the same fault consistently?
• When does the fault occur?
• Why would this happen?
• How would this happen?
• What type of test will either prove or disprove the cause of the
fault?
TEST 1 – CHECK MAIN CIRCUIT BREAKER
Discussion
Often the most obvious cause of a problem is overlooked. If the
generator main line circuit breaker is set to OFF or "Open", no
electrical power will be supplied to electrical loads. If loads are
not receiving power, perhaps the main circuit breaker is open or
has failed.
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PART 2
Procedure
The generator main circuit breaker is located in the external
customer connection box. If loads are not receiving power, make
sure the breaker is set to "On" or "Closed".
If you suspect the breaker may have failed, it can be tested as
follows (see Figure 21):
1. Set a Volt-Ohm-Meter (VOM) to its "R x 1" scale and zero
the meter.
2. With the generator shut down, disconnect all wires from the
main circuit breaker terminals, to prevent interaction.
3. With the generator shut down, connect one VOM test probe
to the Wire 11 (Blue) terminal of the breaker and the other
test probe to the Wire E1 terminal.
4. Set the breaker to its "On" or "Closed" position. The VOM
should read CONTINUITY.
5. Set the breaker to its OFF or "Open" position and the VOM
should indicate INFINITY.
6. Repeat Steps 4 and 5 with the VOM test probes connected
across the Wire 44 (Black) terminal and the E2 terminal.
Results
1. If the circuit breaker tests good, refer back to flow chart.
2. If the breaker tests bad, it should be replaced.
11 (BLUE)
E1
Figure 21. Generator Main Circuit Breaker Test Points
TEST 4 – FIXED EXCITATION /ROTOR AMP
DRAW TEST
Discussion
Supplying a fixed DC current to the rotor will induce a magnetic
field in the rotor. With the generator running, this should create a
proportional voltage output from the stator windings.
AC GENERATORS
44 (BLACK)
LINE
LOAD SIDE
E2