WISCONSIN HVAC QUALIFIER EXAM – Questions And Answers
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1. A service technician arrives at a commercial facility where a packaged rooftop heat
pump is failing to maintain setpoint in heating mode. Ambient outdoor temperature is 35
degrees Fahrenheit. The technician observes heavy frost accumulation strictly on the lower
half of the outdoor coil while the upper half remains clear. What is the most probable cause
of this operating condition?
A. A complete electrical failure of the reversing valve solenoid coil.
B. A partial loss of refrigerant charge or restricted liquid line filter drier causing uneven evaporator feed.
C. Excessive indoor airflow blowing across the supply ductwork.
D. A stuck-open crankcase heater causing premature oil boiling.
Correct Answer: B. A partial loss of refrigerant charge or restricted liquid line filter drier
causing uneven evaporator feed.
Rationale: When an air-source heat pump operates in heating mode, the outdoor coil functions
as an evaporator. A partial refrigerant undercharge or liquid line restriction typically results
in a pressure drop and starvation across a portion of the coil surface, leading to localized frost
formation instead of uniform frosting. Option A would prevent mode switching entirely, option
C would impact indoor temperature distribution rather than outdoor coil frost patterns, and
option D affects compressor oil temperature during off cycles.
2. A residential gas-fired warm-air furnace fails to ignite. During troubleshooting, the
technician notes that the draft inducer motor runs, the pressure switch closes successfully,
the hot surface igniter glows brightly, but the main gas valve never energizes. Using a
digital multimeter, the technician measures 24 volts across the gas valve terminals during
the trial for ignition, yet gas does not flow. What is the definitive conclusion?
A. The flame rollout switch is tripped.
B. The main gas valve redundant internal solenoid or electrical winding is defective.
C. The limit switch is open on the high-temperature side.
D. The indoor blower motor capacitor has failed open.
Correct Answer: B. The main gas valve redundant internal solenoid or electrical winding is
defective.
,Rationale: Voltage across the gas valve terminals indicates that the ignition control module is
correctly sending the 24V signal to open the valve. If voltage is present and stable but no gas
flows, the internal electrical coil of the valve is open or mechanically bound. Options A, C, and
D would interrupt power upstream or prevent the control module from sending the ignition
voltage in the first place.
3. When sizing residential branch ductwork according to ACCA Manual D guidelines, an
HVAC designer calculates an equivalent length of 150 feet for a specific supply run,
including all friction losses from fittings, elbows, and straight duct. If the design friction
rate is set at 0.08 inches W.C. per 100 feet, what is the total friction loss for this run?
A. 0.080 inches W.C.
B. 0.120 inches W.C.
C. 0.150 inches W.C.
D. 0.300 inches W.C.
Correct Answer: B. 0.120 inches W.C.
Rationale: Total friction loss is calculated by multiplying the design friction rate (in inches
W.C. per 100 feet) by the total equivalent length divided by 100. Thus, 0.08 multiplied by (150 /
100) equals 0.120 inches W.C. Options A, C, and D represent mathematical miscalculations of
the proportionality formula.
4. A technician is performing routine maintenance on a commercial rooftop variable air
volume (VAV) air handling unit. The system utilizes a direct-expansion (DX) cooling coil
with a thermostatic expansion valve (TXV). The technician notes that the superheat
measured at the evaporator outlet is 4 degrees Fahrenheit, and the compressor is
experiencing liquid slugging. Which adjustment or corrective action should be taken?
A. Increase the TXV superheat setting by turning the adjustment stem clockwise.
B. Decrease the TXV superheat setting by turning the adjustment stem counterclockwise.
C. Add 5 pounds of liquid refrigerant to the system receiver.
D. Lower the indoor fan speed to reduce sensible heat ratio.
Correct Answer: A. Increase the TXV superheat setting by turning the adjustment stem
clockwise.
Rationale: Low superheat (below 8 to 12 degrees Fahrenheit) indicates that too much liquid
refrigerant is entering the evaporator, risking compressor liquid slugging. Turning the TXV
adjustment stem clockwise increases spring tension, decreases refrigerant flow, and raises
superheat. Counterclockwise rotation decreases superheat, worsening the condition.
, 5. A contractor is designing a mechanical ventilation system for a tightly sealed commercial
office building located in Wisconsin, complying with ASHRAE Standard 62.1. The design
must account for outdoor air rates based on occupant density and floor area. Which
primary parameter dictates the minimum outdoor airflow required for the breathing zone?
A. Total building square footage alone without regard to occupancy type.
B. The combined summation of outdoor air flow rates per person based on occupancy category and per
square foot of floor area.
C. The total cooling capacity of the rooftop air conditioner in tons.
D. The maximum electrical amperage draw of the lighting panels.
Correct Answer: B. The combined summation of outdoor air flow rates per person based on
occupancy category and per square foot of floor area.
Rationale: ASHRAE Standard 62.1 ventilation rate procedure calculates minimum breathing
zone outdoor air using both a people component (RP multiplied by number of occupants) and
an area component (RA multiplied by floor area). Options A, C, and D do not dictate fresh air
ventilation requirements under standard indoor air quality codes.
6. A technician is troubleshooting a 3-phase, 480V scroll compressor on a commercial
chiller that hums loudly for a few seconds upon call for cooling and then trips the internal
thermal overload protector. Using a clamp-on multimeter, the technician measures locked
rotor amperage (LRA) across all three legs during startup, but the compressor fails to
rotate. What is the most likely mechanical fault?
A. The compressor internal scroll set is locked or mechanically seized due to lack of lubrication.
B. The indoor thermostat subbase is programmed for heat pump mode instead of cooling.
C. The outdoor ambient thermistor is reading 20 degrees too high.
D. The economizer damper is stuck in the fully open position.
Correct Answer: A. The compressor internal scroll set is locked or mechanically seized due
to lack of lubrication.
Rationale: When a 3-phase compressor hums and draws locked rotor amps without turning
before tripping on overload, it indicates mechanical seizure (locked scroll members or
bearings). Options B, C, and D would prevent the control circuit from energizing the
compressor contactor rather than causing an electrical locked-rotor condition at the motor
terminals.
7. An HVAC contractor is sizing a gas-fired boiler for a hydronic baseboard heating system
in a residential dwelling in Wisconsin. The calculated design heat loss is 80,000 BTU/h.
| Verified And Well Detailed Answers Plus Rationales |
Guaranteed Pass | Latest Exam Update | Exam Prep | Study
Guide | Practice Test | Download Instant Pdf
1. A service technician arrives at a commercial facility where a packaged rooftop heat
pump is failing to maintain setpoint in heating mode. Ambient outdoor temperature is 35
degrees Fahrenheit. The technician observes heavy frost accumulation strictly on the lower
half of the outdoor coil while the upper half remains clear. What is the most probable cause
of this operating condition?
A. A complete electrical failure of the reversing valve solenoid coil.
B. A partial loss of refrigerant charge or restricted liquid line filter drier causing uneven evaporator feed.
C. Excessive indoor airflow blowing across the supply ductwork.
D. A stuck-open crankcase heater causing premature oil boiling.
Correct Answer: B. A partial loss of refrigerant charge or restricted liquid line filter drier
causing uneven evaporator feed.
Rationale: When an air-source heat pump operates in heating mode, the outdoor coil functions
as an evaporator. A partial refrigerant undercharge or liquid line restriction typically results
in a pressure drop and starvation across a portion of the coil surface, leading to localized frost
formation instead of uniform frosting. Option A would prevent mode switching entirely, option
C would impact indoor temperature distribution rather than outdoor coil frost patterns, and
option D affects compressor oil temperature during off cycles.
2. A residential gas-fired warm-air furnace fails to ignite. During troubleshooting, the
technician notes that the draft inducer motor runs, the pressure switch closes successfully,
the hot surface igniter glows brightly, but the main gas valve never energizes. Using a
digital multimeter, the technician measures 24 volts across the gas valve terminals during
the trial for ignition, yet gas does not flow. What is the definitive conclusion?
A. The flame rollout switch is tripped.
B. The main gas valve redundant internal solenoid or electrical winding is defective.
C. The limit switch is open on the high-temperature side.
D. The indoor blower motor capacitor has failed open.
Correct Answer: B. The main gas valve redundant internal solenoid or electrical winding is
defective.
,Rationale: Voltage across the gas valve terminals indicates that the ignition control module is
correctly sending the 24V signal to open the valve. If voltage is present and stable but no gas
flows, the internal electrical coil of the valve is open or mechanically bound. Options A, C, and
D would interrupt power upstream or prevent the control module from sending the ignition
voltage in the first place.
3. When sizing residential branch ductwork according to ACCA Manual D guidelines, an
HVAC designer calculates an equivalent length of 150 feet for a specific supply run,
including all friction losses from fittings, elbows, and straight duct. If the design friction
rate is set at 0.08 inches W.C. per 100 feet, what is the total friction loss for this run?
A. 0.080 inches W.C.
B. 0.120 inches W.C.
C. 0.150 inches W.C.
D. 0.300 inches W.C.
Correct Answer: B. 0.120 inches W.C.
Rationale: Total friction loss is calculated by multiplying the design friction rate (in inches
W.C. per 100 feet) by the total equivalent length divided by 100. Thus, 0.08 multiplied by (150 /
100) equals 0.120 inches W.C. Options A, C, and D represent mathematical miscalculations of
the proportionality formula.
4. A technician is performing routine maintenance on a commercial rooftop variable air
volume (VAV) air handling unit. The system utilizes a direct-expansion (DX) cooling coil
with a thermostatic expansion valve (TXV). The technician notes that the superheat
measured at the evaporator outlet is 4 degrees Fahrenheit, and the compressor is
experiencing liquid slugging. Which adjustment or corrective action should be taken?
A. Increase the TXV superheat setting by turning the adjustment stem clockwise.
B. Decrease the TXV superheat setting by turning the adjustment stem counterclockwise.
C. Add 5 pounds of liquid refrigerant to the system receiver.
D. Lower the indoor fan speed to reduce sensible heat ratio.
Correct Answer: A. Increase the TXV superheat setting by turning the adjustment stem
clockwise.
Rationale: Low superheat (below 8 to 12 degrees Fahrenheit) indicates that too much liquid
refrigerant is entering the evaporator, risking compressor liquid slugging. Turning the TXV
adjustment stem clockwise increases spring tension, decreases refrigerant flow, and raises
superheat. Counterclockwise rotation decreases superheat, worsening the condition.
, 5. A contractor is designing a mechanical ventilation system for a tightly sealed commercial
office building located in Wisconsin, complying with ASHRAE Standard 62.1. The design
must account for outdoor air rates based on occupant density and floor area. Which
primary parameter dictates the minimum outdoor airflow required for the breathing zone?
A. Total building square footage alone without regard to occupancy type.
B. The combined summation of outdoor air flow rates per person based on occupancy category and per
square foot of floor area.
C. The total cooling capacity of the rooftop air conditioner in tons.
D. The maximum electrical amperage draw of the lighting panels.
Correct Answer: B. The combined summation of outdoor air flow rates per person based on
occupancy category and per square foot of floor area.
Rationale: ASHRAE Standard 62.1 ventilation rate procedure calculates minimum breathing
zone outdoor air using both a people component (RP multiplied by number of occupants) and
an area component (RA multiplied by floor area). Options A, C, and D do not dictate fresh air
ventilation requirements under standard indoor air quality codes.
6. A technician is troubleshooting a 3-phase, 480V scroll compressor on a commercial
chiller that hums loudly for a few seconds upon call for cooling and then trips the internal
thermal overload protector. Using a clamp-on multimeter, the technician measures locked
rotor amperage (LRA) across all three legs during startup, but the compressor fails to
rotate. What is the most likely mechanical fault?
A. The compressor internal scroll set is locked or mechanically seized due to lack of lubrication.
B. The indoor thermostat subbase is programmed for heat pump mode instead of cooling.
C. The outdoor ambient thermistor is reading 20 degrees too high.
D. The economizer damper is stuck in the fully open position.
Correct Answer: A. The compressor internal scroll set is locked or mechanically seized due
to lack of lubrication.
Rationale: When a 3-phase compressor hums and draws locked rotor amps without turning
before tripping on overload, it indicates mechanical seizure (locked scroll members or
bearings). Options B, C, and D would prevent the control circuit from energizing the
compressor contactor rather than causing an electrical locked-rotor condition at the motor
terminals.
7. An HVAC contractor is sizing a gas-fired boiler for a hydronic baseboard heating system
in a residential dwelling in Wisconsin. The calculated design heat loss is 80,000 BTU/h.
