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NATE Certified HVAC Professional (CHP-5)
Service Exam | Latest Verified Questions and
Detailed Answers
OVERVIEW DESCRIPTION
This Comprehensive set of multiple choice questions is designed for the NATE Certified
HVAC Professional (CHP-5) Service Exam, a focused assessment within the five-exam
CHP-5 certification pathway. The exam measures advanced diagnostic, repair, and
maintenance competencies through real-world scenarios in planned maintenance,
refrigeration cycle analysis, heating system troubleshooting (gas, electric, and heat
pump), and component-level evaluation of compressors, motors, and controls. It
emphasizes the interpretation of pressure, temperature, and electrical readings to
identify systemic issues. Administered by North American Technician Excellence
(NATE), the CHP-5 structure enables technicians to achieve full NATE certification by
completing smaller, job-specific exams that align closely with on-the-job skill
development.
QUESTION 1
A technician performing planned maintenance on a gas furnace measures a temperature
rise of 70°F. The manufacturer’s specification is 40–65°F. Which action should the
technician take first?
A. Increase the blower speed
B. Decrease the gas manifold pressure
C. Clean the evaporator coil
D. Replace the heat exchanger
CORRECT ANSWER: A
EXPERT RATIONALE:
Excessive temperature rise indicates low airflow across the heat exchanger. Increasing
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blower speed raises CFM, reducing temperature rise to within specification and
preventing limit switch trips.
QUESTION 2
During a planned maintenance check on an air conditioning system, the technician finds
the compressor pulling rated load amps but the suction line is frosting back to the
compressor. The most likely cause is:
A. Overcharge of refrigerant
B. Restricted indoor airflow
C. Faulty condenser fan motor
D. Liquid line restriction
CORRECT ANSWER: B
EXPERT RATIONALE:
Frosty suction line with normal compressor amps typically results from low indoor
airflow (dirty filter, closed registers) causing low suction pressure and evaporator
saturation below freezing. This lowers superheat and can flood the compressor.
QUESTION 3
While auditing the efficiency of a 10-year-old split heat pump, the technician observes a
10°F subcooling value with the system in cooling mode. The outdoor ambient is 85°F,
indoor return 75°F. What does this subcooling indicate?
A. Undercharge
B. Proper charge
C. Overcharge
D. Non-condensables in the system
CORRECT ANSWER: B
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EXPERT RATIONALE:
A target subcooling of around 10°F is typical for a TXV-equipped system under normal
conditions. It indicates a full column of liquid to the metering device and correct
refrigerant charge.
QUESTION 4
Planned maintenance on a rooftop unit with an economizer includes checking the
enthalpy changeover sensor. The sensor prevents use of outdoor air when:
A. Outdoor dry-bulb exceeds 75°F
B. Outdoor air is too humid for free cooling
C. Mixed air temperature is below 55°F
D. Return air CO₂ exceeds 1000 ppm
CORRECT ANSWER: B
EXPERT RATIONALE:
Enthalpy sensors measure both dry-bulb and humidity to determine total heat content.
The economizer locks out when outdoor enthalpy is higher than return air enthalpy,
avoiding adding latent load.
QUESTION 5
When performing a combustion analysis on a natural gas furnace, the technician reads
9.5% O₂ in the flue gas. The manufacturer calls for 6–7.5% O₂. What adjustment is
needed?
A. Increase primary air shutter opening
B. Decrease gas manifold pressure
C. Increase gas manifold pressure
D. Close the primary air shutter slightly
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CORRECT ANSWER: C
EXPERT RATIONALE:
High O₂ indicates excess air, meaning a lean air-fuel mixture. Increasing manifold
pressure delivers more fuel, bringing O₂ down into the acceptable range.
QUESTION 6
During a belt-drive blower inspection, the technician measures belt tension and finds a
deflection of 1.5 inches with 5 lb of force. The manufacturer specifies 0.5-inch deflection
at the same force. The correct action is to:
A. Replace the belt
B. Tighten the motor mount
C. Leave as is; it will wear in
D. Replace the blower pulley
CORRECT ANSWER: B
EXPERT RATIONALE:
Excessive belt deflection indicates insufficient tension. Tightening the motor mount
increases tension, reducing slip and heat generation, matching the specification.
QUESTION 7
In a planned maintenance check of a condensing furnace, the technician inspects the
secondary heat exchanger. What symptom would most indicate a compromised
secondary?
A. Rust flakes in the condensate trap
B. High CO in flue gas
C. Condensate pH of 5
D. Delayed ignition
NATE Certified HVAC Professional (CHP-5)
Service Exam | Latest Verified Questions and
Detailed Answers
OVERVIEW DESCRIPTION
This Comprehensive set of multiple choice questions is designed for the NATE Certified
HVAC Professional (CHP-5) Service Exam, a focused assessment within the five-exam
CHP-5 certification pathway. The exam measures advanced diagnostic, repair, and
maintenance competencies through real-world scenarios in planned maintenance,
refrigeration cycle analysis, heating system troubleshooting (gas, electric, and heat
pump), and component-level evaluation of compressors, motors, and controls. It
emphasizes the interpretation of pressure, temperature, and electrical readings to
identify systemic issues. Administered by North American Technician Excellence
(NATE), the CHP-5 structure enables technicians to achieve full NATE certification by
completing smaller, job-specific exams that align closely with on-the-job skill
development.
QUESTION 1
A technician performing planned maintenance on a gas furnace measures a temperature
rise of 70°F. The manufacturer’s specification is 40–65°F. Which action should the
technician take first?
A. Increase the blower speed
B. Decrease the gas manifold pressure
C. Clean the evaporator coil
D. Replace the heat exchanger
CORRECT ANSWER: A
EXPERT RATIONALE:
Excessive temperature rise indicates low airflow across the heat exchanger. Increasing
,2|Page
blower speed raises CFM, reducing temperature rise to within specification and
preventing limit switch trips.
QUESTION 2
During a planned maintenance check on an air conditioning system, the technician finds
the compressor pulling rated load amps but the suction line is frosting back to the
compressor. The most likely cause is:
A. Overcharge of refrigerant
B. Restricted indoor airflow
C. Faulty condenser fan motor
D. Liquid line restriction
CORRECT ANSWER: B
EXPERT RATIONALE:
Frosty suction line with normal compressor amps typically results from low indoor
airflow (dirty filter, closed registers) causing low suction pressure and evaporator
saturation below freezing. This lowers superheat and can flood the compressor.
QUESTION 3
While auditing the efficiency of a 10-year-old split heat pump, the technician observes a
10°F subcooling value with the system in cooling mode. The outdoor ambient is 85°F,
indoor return 75°F. What does this subcooling indicate?
A. Undercharge
B. Proper charge
C. Overcharge
D. Non-condensables in the system
CORRECT ANSWER: B
,3|Page
EXPERT RATIONALE:
A target subcooling of around 10°F is typical for a TXV-equipped system under normal
conditions. It indicates a full column of liquid to the metering device and correct
refrigerant charge.
QUESTION 4
Planned maintenance on a rooftop unit with an economizer includes checking the
enthalpy changeover sensor. The sensor prevents use of outdoor air when:
A. Outdoor dry-bulb exceeds 75°F
B. Outdoor air is too humid for free cooling
C. Mixed air temperature is below 55°F
D. Return air CO₂ exceeds 1000 ppm
CORRECT ANSWER: B
EXPERT RATIONALE:
Enthalpy sensors measure both dry-bulb and humidity to determine total heat content.
The economizer locks out when outdoor enthalpy is higher than return air enthalpy,
avoiding adding latent load.
QUESTION 5
When performing a combustion analysis on a natural gas furnace, the technician reads
9.5% O₂ in the flue gas. The manufacturer calls for 6–7.5% O₂. What adjustment is
needed?
A. Increase primary air shutter opening
B. Decrease gas manifold pressure
C. Increase gas manifold pressure
D. Close the primary air shutter slightly
, 4|Page
CORRECT ANSWER: C
EXPERT RATIONALE:
High O₂ indicates excess air, meaning a lean air-fuel mixture. Increasing manifold
pressure delivers more fuel, bringing O₂ down into the acceptable range.
QUESTION 6
During a belt-drive blower inspection, the technician measures belt tension and finds a
deflection of 1.5 inches with 5 lb of force. The manufacturer specifies 0.5-inch deflection
at the same force. The correct action is to:
A. Replace the belt
B. Tighten the motor mount
C. Leave as is; it will wear in
D. Replace the blower pulley
CORRECT ANSWER: B
EXPERT RATIONALE:
Excessive belt deflection indicates insufficient tension. Tightening the motor mount
increases tension, reducing slip and heat generation, matching the specification.
QUESTION 7
In a planned maintenance check of a condensing furnace, the technician inspects the
secondary heat exchanger. What symptom would most indicate a compromised
secondary?
A. Rust flakes in the condensate trap
B. High CO in flue gas
C. Condensate pH of 5
D. Delayed ignition
