Page 1 of 110
First Class Stationary Air Conditioning - 636-LA
Contractor Exam COMPLETE QUESTIONS AND
DETAILED SOLUTIONS LATEST UPDATE THIS YEAR-
JUST RELEASED
Summarized Exam Coverage
1. HVAC Theory: Basic thermodynamics, refrigeration cycles, psychrometrics, heat transfer.
2. Refrigeration Systems: Components, refrigerants, absorption, and troubleshooting techniques.
3. Air Conditioning Equipment: Air handlers, coils, condensing units, chillers, packaged systems.
4. Electrical & Controls: Motors, relays, thermostats, safety devices, wiring diagrams.
5. Installation Practices: Piping, ductwork, brazing, refrigerant charging, evacuation, leak testing.
6. Maintenance & Troubleshooting: Preventive maintenance, diagnostic readings, common
failures.
7. Codes & Safety: Louisiana contractor regulations, OSHA, EPA Section 608, fire and confined
space
1.
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A technician finds the evaporator coil frozen solid in a rooftop unit. What is the first step to correct the
problem?
A. Turn off the system and check airflow restrictions, filter condition, and blower operation
B. Add refrigerant immediately
C. Increase condenser fan speed
D. Replace the coil
Answer: A
Rationale: Frozen evaporators are often caused by airflow restrictions; airflow must be corrected before
adding refrigerant.
2.
During maintenance, a contractor notices low refrigerant pressure on a R-410A system. What is the
correct procedure?
A. Check for leaks using approved leak detection methods, repair, and recharge system
B. Increase compressor speed
C. Only document the low pressure
D. Add water to system lines
Answer: A
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Rationale: Low pressure usually indicates a leak; adding refrigerant without repair is unsafe and non-
compliant.
3.
A client complains that the air conditioning unit is cycling frequently. What is the most likely cause?
A. Improper thermostat location, short cycling due to oversized equipment or low airflow
B. High refrigerant charge
C. Clean coil
D. Dirty exterior paint
Answer: A
Rationale: Short cycling is often due to oversized equipment, improper controls, or airflow issues.
4.
While inspecting a split system, the technician finds oil residue near the compressor. What does this
indicate?
A. Potential refrigerant leak at the compressor or fittings requiring repair
B. Normal operation
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C. Only oil lubrication needed
D. Dirty air filter
Answer: A
Rationale: Oil leakage is a common sign of refrigerant leaks and must be addressed immediately.
5.
During startup, the contractor finds the compressor not running. Voltages are correct. What should be
checked next?
A. Inspect the contactor, overload relay, and control circuit for faults
B. Replace refrigerant
C. Adjust airflow
D. Paint unit for identification
Answer: A
Rationale: Electrical control faults or overloads are the primary causes of a non-running compressor.
6.
First Class Stationary Air Conditioning - 636-LA
Contractor Exam COMPLETE QUESTIONS AND
DETAILED SOLUTIONS LATEST UPDATE THIS YEAR-
JUST RELEASED
Summarized Exam Coverage
1. HVAC Theory: Basic thermodynamics, refrigeration cycles, psychrometrics, heat transfer.
2. Refrigeration Systems: Components, refrigerants, absorption, and troubleshooting techniques.
3. Air Conditioning Equipment: Air handlers, coils, condensing units, chillers, packaged systems.
4. Electrical & Controls: Motors, relays, thermostats, safety devices, wiring diagrams.
5. Installation Practices: Piping, ductwork, brazing, refrigerant charging, evacuation, leak testing.
6. Maintenance & Troubleshooting: Preventive maintenance, diagnostic readings, common
failures.
7. Codes & Safety: Louisiana contractor regulations, OSHA, EPA Section 608, fire and confined
space
1.
, Page 2 of 110
A technician finds the evaporator coil frozen solid in a rooftop unit. What is the first step to correct the
problem?
A. Turn off the system and check airflow restrictions, filter condition, and blower operation
B. Add refrigerant immediately
C. Increase condenser fan speed
D. Replace the coil
Answer: A
Rationale: Frozen evaporators are often caused by airflow restrictions; airflow must be corrected before
adding refrigerant.
2.
During maintenance, a contractor notices low refrigerant pressure on a R-410A system. What is the
correct procedure?
A. Check for leaks using approved leak detection methods, repair, and recharge system
B. Increase compressor speed
C. Only document the low pressure
D. Add water to system lines
Answer: A
, Page 3 of 110
Rationale: Low pressure usually indicates a leak; adding refrigerant without repair is unsafe and non-
compliant.
3.
A client complains that the air conditioning unit is cycling frequently. What is the most likely cause?
A. Improper thermostat location, short cycling due to oversized equipment or low airflow
B. High refrigerant charge
C. Clean coil
D. Dirty exterior paint
Answer: A
Rationale: Short cycling is often due to oversized equipment, improper controls, or airflow issues.
4.
While inspecting a split system, the technician finds oil residue near the compressor. What does this
indicate?
A. Potential refrigerant leak at the compressor or fittings requiring repair
B. Normal operation
, Page 4 of 110
C. Only oil lubrication needed
D. Dirty air filter
Answer: A
Rationale: Oil leakage is a common sign of refrigerant leaks and must be addressed immediately.
5.
During startup, the contractor finds the compressor not running. Voltages are correct. What should be
checked next?
A. Inspect the contactor, overload relay, and control circuit for faults
B. Replace refrigerant
C. Adjust airflow
D. Paint unit for identification
Answer: A
Rationale: Electrical control faults or overloads are the primary causes of a non-running compressor.
6.
