Section 3.4 - Diagnostic Tests; Introduction; Safety; Transfer Switch Troubleshooting - Generac Power Systems 7 kW NG Repair Manual

Section 3.4
Diagnostic Tests

INTRODUCTION

This section familiarizes the service technician with acceptable
procedure for the testing and evaluation of various problems
that can occur on pre-packaged transfer switches. Use this
section in conjunction with Section 3.3, "Troubleshooting Flow
Charts." The numbered tests in this section correspond with
those of Section 3.3.
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 products 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.

TRANSFER SWITCH 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 transfer switch doing?
• What was the transfer switch supposed to do?
• Does the transfer switch have the same fault consistently,
and when does it occur?
• Who is controlling it?
• Exactly what is occurring?
• When is it happening?
• Why would this happen?
• How would this happen?
• What type of test will either prove or disprove the cause of
the fault?
Page 76
PART 3
TEST 20 – CHECK VOLTAGE AT TERMINAL
LUGS E1 AND E2
Discussion
In automatic mode to transfer to the "Standby" position, the
standby closing coil (C2) energizes utilizing generator output.
Transfer to "Standby" cannot occur unless generator voltage is
available to the transfer switch.
If the generator is not producing the correct voltage it will
shutdown on an under or over-voltage alarm and thus will not
be running.
Two procedures have been provided in the event that the
generator is already running in a Utility failure. It is not required
to complete both procedures.

Be careful! High and dangerous voltages are present at
terminal lugs E1 and E2 when the generator is running.
Avoid contact with high voltage terminals or dangerous
and possible lethal electrical shock may result. Do not
perform this voltage test while standing on wet or damp
ground, while barefoot, or while hands or feet are wet.
Procedure: Generator Running in Utility Failure, Switch did not
Transfer
1. Set Volt-Ohm-Milliammeter (VOM) to measure AC voltage.
2. If the Generator engine has started automatically (due to
a Utility failure) and is running, check the position of the
Generator main line circuit breaker. The circuit breaker
must be set to its "Closed" position. After confirming
that the Generator main circuit breaker is set to the
"Closed" position, verify the voltage at the transfer switch
CONTACTOR terminal lugs E1 and E2 with an accurate
AC VOM. The meter should indicate generator line-to-line
voltage.
Procedure: Generator Shutdown
1. Set the AUTO-OFF-MANUAL switch to the OFF position.
2. Set Volt-Ohm-Milliammeter (VOM) to measure AC voltage.
3. Disconnect Utility voltage from the transfer switch.
4. Verify the CONTACTOR is in the "Utility" position.
5. Verify the Generator main line circuit breaker (MLCB) is in
the "Closed Position".
6. Set the AUTO-OFF-MANUAL switch to the MANUAL
position.
7. If transfer to the "Standby" position does NOT occur,
check the voltage across terminal lugs E1 and E2. The
VOM should indicate generator line-line voltage.
TRANSFER SWITCH