C-20 HVAC – Practice Exam 1

Welcome to your C-20 HVAC - Practice Exam 1

What does low suction pressure combined with normal or high discharge pressure indicate?

What does low suction pressure combined with normal or high discharge pressure indicate?Deselect Answer

This pattern indicates refrigerant overcharge

This pattern indicates low refrigerant charge, a restricted metering device, or insufficient heat load on the evaporator — refrigerant is not absorbing enough heat to maintain normal evaporator pressure

This pattern is normal for heat pump operation in cooling mode

This pattern indicates a failed reversing valve in a heat pump

None

What is the correct PPE for an HVAC technician handling asbestos-containing duct insulation discovered during a renovation?

What is the correct PPE for an HVAC technician handling asbestos-containing duct insulation discovered during a renovation?Deselect Answer

Standard work gloves are sufficient for handling older insulation materials

Stop work, isolate the area, and notify the building owner and general contractor — asbestos abatement requires licensed asbestos abatement contractors, not HVAC technicians, and improper disturbance of asbestos-containing materials violates Cal/OSHA Title 8, Section 1529

Wear a standard N95 dust mask and continue working — asbestos is only dangerous in large quantities

Seal the area with plastic and continue HVAC work while wearing a P100 half-face respirator

None

What must be verified when starting up a gas furnace for the first time?

What must be verified when starting up a gas furnace for the first time?Deselect Answer

Only that the thermostat calls for heat and the burner ignites

Proper gas pressure at the manifold, correct ignition sequence operation, flame sensor function, limit switch operation, flue gas CO2 or CO content, proper temperature rise across the heat exchanger, and that all safety controls operate correctly

Only that the supply air is warmer than the return air

Only the gas valve opens when the thermostat calls for heat

None

What does EPA Section 608 certification allow a technician to do?

What does EPA Section 608 certification allow a technician to do?Deselect Answer

EPA 608 certification allows technicians to install new HVAC equipment only

EPA 608 certification authorizes technicians to purchase and handle refrigerants, perform refrigerant recovery and charging, and service equipment containing refrigerants covered by Section 608 of the Clean Air Act

EPA 608 certification replaces the CSLB C-20 license in California

EPA 608 certification is optional — any person may handle refrigerants without certification

None

What is the correct method for supporting refrigerant tubing installed in an attic or crawl space?

What is the correct method for supporting refrigerant tubing installed in an attic or crawl space?Deselect Answer

Refrigerant tubing may rest freely on insulation without additional support

Refrigerant tubing must be supported at intervals not exceeding 5 feet for copper tubing, using listed straps or hangers that prevent vibration transmission to the structure while maintaining proper slope for oil return on horizontal suction lines

Refrigerant tubing only requires support at each end of the line set

Any support method is acceptable as long as the tubing does not touch the ground

None

What is the correct method for leak testing a refrigerant system after installation?

What is the correct method for leak testing a refrigerant system after installation?Deselect Answer

Pressurize with refrigerant and use a flame-type halide torch to detect leaks

Pressurize the system with dry nitrogen to the manufacturer's recommended test pressure and use electronic leak detectors or soap bubbles at all brazed joints and fittings to locate leaks before adding refrigerant

Add refrigerant and operate the system — any leaks will reveal themselves over time

Pressurize with compressed air and submerge components in water to find leaks

None

What is the most likely cause when a heat pump fails to heat but cools normally?

What is the most likely cause when a heat pump fails to heat but cools normally?Deselect Answer

The compressor has failed — replace immediately

The reversing valve is stuck in the cooling position or its solenoid coil has failed — the system mechanically operates in cooling mode but cannot shift to heating mode

The outdoor fan motor has failed, preventing heat absorption in heating mode

The heat pump requires a refrigerant charge — low charge prevents heating operation only

None

What fall protection is required for HVAC technicians working on rooftop equipment?

What fall protection is required for HVAC technicians working on rooftop equipment?Deselect Answer

No fall protection is required if the equipment is within 6 feet of the roof edge

When working within 6 feet of a roof edge or unprotected opening, fall protection is required — guardrails, personal fall arrest systems, or safety monitoring systems per Cal/OSHA Title 8, Section 1671 et seq.

Fall protection is only required on commercial rooftops above 3 stories

HVAC technicians are exempt from fall protection requirements because they must move freely to service equipment

None

What is the minimum refrigerant line size typically used for a 3-ton residential split system?

What is the minimum refrigerant line size typically used for a 3-ton residential split system?Deselect Answer

3/8-inch liquid line and 1/2-inch suction line

3/8-inch liquid line and 7/8-inch suction line

1/2-inch liquid line and 1-1/8-inch suction line

Line size is always determined by the equipment manufacturer's installation instructions for the specific unit

None

10.

What refrigerant is most commonly used in new residential split-system HVAC equipment installed in California?

What refrigerant is most commonly used in new residential split-system HVAC equipment installed in California?Deselect Answer

R-22 (Freon)

R-410A

R-32

R-134a

None

11.

If an air conditioner produces 24,000 BTU/h of cooling and consumes 2,400 watts of electricity, what is its EER?

If an air conditioner produces 24,000 BTU/h of cooling and consumes 2,400 watts of electricity, what is its EER?Deselect Answer

2.4

9.0

10.0

12.0

None

12.

A customer complains the air conditioner runs continuously but the house never reaches the set temperature. What should be checked first?

A customer complains the air conditioner runs continuously but the house never reaches the set temperature. What should be checked first?Deselect Answer

Replace the thermostat immediately

Verify refrigerant charge (suction and discharge pressures, superheat/subcooling), check airflow (filter condition, supply and return temperatures), verify outdoor unit coil is clean and unobstructed, and confirm the system is properly sized for the load

Increase the thermostat set point and advise the customer to accept higher indoor temperatures

The compressor must be replaced — continuous operation always indicates compressor failure

None

13.

A room has a calculated cooling load of 6,000 BTU/h. What is this load expressed in tons?

A room has a calculated cooling load of 6,000 BTU/h. What is this load expressed in tons?Deselect Answer

0.25 tons

0.5 tons

1.0 ton

1.5 tons

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14.

What action must an HVAC technician take if they discover that a gas appliance they have serviced is producing dangerous levels of carbon monoxide?

What action must an HVAC technician take if they discover that a gas appliance they have serviced is producing dangerous levels of carbon monoxide?Deselect Answer

Note the CO reading in the service report and advise the customer to improve ventilation

Immediately shut off the gas supply to the appliance, advise the occupants to leave the building until the CO level is safe, do not restart the appliance until the cause is identified and corrected, and provide the customer with a written explanation of the unsafe condition

Increase the gas pressure to improve combustion efficiency and reduce CO production

CO production is normal from gas appliances — no action is required unless the alarm has activated

None

15.

What is the difference between a ton of refrigeration and a BTU?

What is the difference between a ton of refrigeration and a BTU?Deselect Answer

A ton and a BTU are the same unit expressed differently

A BTU is the amount of heat needed to raise one pound of water one degree F; a ton of refrigeration equals 12,000 BTU/h — the rate of heat removal equivalent to melting one ton of ice per day

A ton of refrigeration equals 1,000 BTU

BTUs measure heat while tons measure cooling only — they cannot be compared

None

16.

What is the purpose of a load calculation's outdoor design conditions?

What is the purpose of a load calculation's outdoor design conditions?Deselect Answer

Outdoor design conditions determine the equipment's noise rating at maximum load

Outdoor design conditions establish the worst-case temperature and humidity that the system must overcome — used to size equipment so it can maintain indoor comfort during peak load periods

Outdoor design conditions only apply to commercial systems with economizers

Outdoor design conditions are set by the equipment manufacturer for warranty purposes

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17.

What are the typical symptoms of a low refrigerant charge in a residential split-system air conditioner?

What are the typical symptoms of a low refrigerant charge in a residential split-system air conditioner?Deselect Answer

High suction pressure, low superheat, and ice on the suction line

Low suction pressure, high superheat, reduced cooling capacity, and the system running continuously without reaching setpoint

High head pressure and the condenser fan cycling on and off

Normal pressures but reduced airflow indicating a dirty filter

None

18.

How is refrigerant charge verified on a system with a fixed orifice metering device (piston or orifice)?

How is refrigerant charge verified on a system with a fixed orifice metering device (piston or orifice)?Deselect Answer

Verify charge by measuring subcooling at the liquid line

Verify charge using the superheat method — measuring suction line temperature and pressure at the outdoor unit, and comparing calculated superheat to the manufacturer's target superheat chart based on indoor wet-bulb and outdoor dry-bulb temperatures

Fixed orifice systems cannot have their charge verified in the field

Verify charge by measuring the compressor amperage and comparing to nameplate RLA

None

19.

What type of duct is required for HVAC systems in California per the California Mechanical Code?

What type of duct is required for HVAC systems in California per the California Mechanical Code?Deselect Answer

Any duct material is acceptable as long as it is not combustible

Duct systems must be constructed of listed materials appropriate for the application — sheet metal, fiberglass duct board, or flexible duct meeting UL 181 listing requirements — and must be sealed at all joints per California Title 24

Only sheet metal duct is permitted in California residential systems

Duct material selection is the contractor's preference with no code requirements

None

20.

What minimum SEER2 rating is required for new residential split-system air conditioners in California as of 2023?

What minimum SEER2 rating is required for new residential split-system air conditioners in California as of 2023?Deselect Answer

13 SEER2

14 SEER2

15 SEER2

16 SEER2

None

21.

What is the purpose of a pressure switch on a gas furnace inducer assembly?

What is the purpose of a pressure switch on a gas furnace inducer assembly?Deselect Answer

The pressure switch measures outdoor wind speed to adjust furnace output

The pressure switch verifies that the inducer motor is running and creating proper negative pressure in the heat exchanger before the gas valve is allowed to open — preventing combustion gas spillage if the inducer fails

The pressure switch controls the blower speed based on system static pressure

The pressure switch shuts off the gas valve if the filter becomes clogged

None

22.

What is the purpose of an HVAC load calculation before replacing existing equipment?

What is the purpose of an HVAC load calculation before replacing existing equipment?Deselect Answer

Existing equipment capacity should always be matched — no calculation is needed for replacements

To verify the correct equipment size for the existing building — the old equipment may have been improperly sized, and building modifications may have changed the load since original installation

Load calculations are only required for new construction — replacements use the existing equipment nameplate capacity

Load calculations are only required when the homeowner requests a larger system

None

23.

What is the correct procedure when a CO alarm activates while working on a gas furnace?

What is the correct procedure when a CO alarm activates while working on a gas furnace?Deselect Answer

Reset the CO alarm and continue working — false alarms are common

Stop work immediately, evacuate all occupants and workers from the building, call emergency services, ventilate the building by opening doors and windows from outside if safe to do so, and do not re-enter until the source is identified and the CO level is confirmed safe

Increase combustion air ventilation to the furnace and continue monitoring the CO alarm

CO alarms only activate from outdoor sources — a CO alarm during furnace work does not indicate a furnace problem

None

24.

What is the purpose of Manual S in residential HVAC design?

What is the purpose of Manual S in residential HVAC design?Deselect Answer

Manual S provides safety procedures for refrigerant handling

Manual S is the ACCA residential equipment selection procedure — it matches equipment performance data to the calculated loads from Manual J to ensure proper sizing

Manual S covers residential sheet metal duct fabrication standards

Manual S is the California supplement to federal refrigerant regulations

None

25.

When installing a split system with a line set longer than 50 feet, what must be considered?

When installing a split system with a line set longer than 50 feet, what must be considered?Deselect Answer

Line set length has no effect on system performance — any length is acceptable

Additional refrigerant must be added per the manufacturer's specification (typically a small amount per additional foot beyond the rated line set length), and suction line size may need to be increased to maintain adequate velocity for oil return

Longer line sets require larger electrical conductors to compensate for voltage drop

Line sets over 50 feet are prohibited by California code — a packaged unit must be used instead

None

26.

What electrical safety practice is required before working inside an air handling unit?

What electrical safety practice is required before working inside an air handling unit?Deselect Answer

Turn off the thermostat to stop the system — no further de-energization is needed

De-energize the unit at the disconnect switch, verify with a non-contact voltage tester that all circuits are de-energized, and apply a lockout/tagout device to prevent re-energization while work is in progress

Only unplug the control transformer before working inside the air handler

Electrical safety procedures are only required for work on the electrical components — mechanical work inside the unit requires no electrical precautions

None

27.

What is the purpose of a Manual J cooling load calculation's latent component?

What is the purpose of a Manual J cooling load calculation's latent component?Deselect Answer

The latent component determines how much the supply air temperature must be reduced to cool the space

The latent component quantifies the moisture that must be removed from the space — determining the dehumidification capacity required from the cooling equipment

The latent component is only calculated for commercial buildings — residential calculations use sensible load only

The latent component determines the duct sizing for the system

None

28.

What electrical protection is required for HVAC equipment per the National Electrical Code and California Electrical Code?

What electrical protection is required for HVAC equipment per the National Electrical Code and California Electrical Code?Deselect Answer

A dedicated circuit with no special protection requirements

A dedicated circuit with overcurrent protection sized per NEC Article 440 based on the equipment's minimum circuit ampacity and maximum fuse or breaker size listed on the nameplate, plus a disconnecting means within sight of the equipment

HVAC equipment may share circuits with other loads as long as the total load does not exceed the breaker rating

Only a ground fault circuit interrupter is required for outdoor HVAC equipment

None

29.

What is the minimum clearance required around an outdoor condensing unit for proper airflow and service access?

What is the minimum clearance required around an outdoor condensing unit for proper airflow and service access?Deselect Answer

No clearance is required — condenser placement is only an aesthetic decision

Minimum clearances vary by manufacturer but typically require at least 12 to 24 inches on the air inlet sides and 24 to 48 inches on the service access side — always follow the manufacturer's installation instructions

A minimum of 6 feet on all sides is always required

Clearance is only required on the discharge (top) of the unit — sides may be enclosed

None

30.

What is a heating degree day (HDD) and how is it used in HVAC planning?

What is a heating degree day (HDD) and how is it used in HVAC planning?Deselect Answer

The number of days per year when heating equipment must run at full capacity

A measure of how much heating a location requires — calculated as the sum of degrees below 65 degrees F for each day of the year — used to estimate annual fuel consumption and compare climates

The maximum number of hours per day that a heating system should operate

A rating applied to heating equipment based on its output capacity in BTU per degree of temperature difference

None

31.

What is the purpose of a reversing valve in a heat pump system?

What is the purpose of a reversing valve in a heat pump system?Deselect Answer

The reversing valve increases refrigerant flow during defrost operation

The reversing valve changes the direction of refrigerant flow through the outdoor and indoor coils — switching the system between cooling mode (outdoor coil as condenser) and heating mode (outdoor coil as evaporator)

The reversing valve bypasses the expansion valve during heating operation

The reversing valve is a safety device that shuts down the compressor when outdoor temperature drops below freezing

None

32.

What does it mean when an air conditioner's evaporator coil temperature is below 32 degrees F?

What does it mean when an air conditioner's evaporator coil temperature is below 32 degrees F?Deselect Answer

The system is operating correctly — evaporator coil temperatures are always below freezing

The evaporator is operating below the freezing point of water — frost or ice will form on the coil, indicating insufficient airflow, low refrigerant charge, or a metering device problem that requires diagnosis and correction

Below-freezing evaporator temperature is only a concern in cold climates

Below-freezing coil temperature improves dehumidification performance and is desirable in humid climates

None

33.

What is the Heating Seasonal Performance Factor (HSPF) used for?

What is the Heating Seasonal Performance Factor (HSPF) used for?Deselect Answer

HSPF measures the efficiency of gas furnaces during the heating season

HSPF measures the seasonal heating efficiency of heat pumps — the ratio of total heating output in BTU to total electrical energy input in watt-hours over the heating season

HSPF is a measure of heat pump cooling efficiency in the summer

HSPF is the California rating for hydronic heating system efficiency

None

34.

What does it mean when an air conditioning system has normal suction pressure but low discharge pressure?

What does it mean when an air conditioning system has normal suction pressure but low discharge pressure?Deselect Answer

Low discharge pressure with normal suction pressure indicates a refrigerant overcharge

Low discharge pressure with normal suction pressure indicates a compressor that is pumping efficiently on the suction side but losing efficiency in compression — worn rings or leaking discharge valves allow compressed gas to leak back to the suction side

This condition indicates the system needs more refrigerant added immediately

Low discharge pressure indicates the condenser fan motor has failed

None

35.

What is the minimum clearance required between a gas-fired furnace and combustible materials?

What is the minimum clearance required between a gas-fired furnace and combustible materials?Deselect Answer

No clearance is required if the furnace is listed as a zero-clearance appliance

Clearances are established by the furnace manufacturer's listing and installation instructions — they must be followed exactly, as listed clearances are the code-required minimums

A minimum 6-inch clearance is required from all combustibles for any gas appliance

Clearances only apply to the furnace cabinet — supply and return plenums have no clearance requirements

None

36.

What does a dirty air filter cause in an HVAC system?

What does a dirty air filter cause in an HVAC system?Deselect Answer

A dirty filter improves air quality by filtering smaller particles

A dirty filter increases resistance to airflow, reducing the volume of air moved by the blower — causing low suction pressure, possible evaporator freeze-up, reduced system capacity, and higher operating costs

A dirty filter causes higher head pressure but does not affect suction pressure

Dirty filters only affect air quality — they have no effect on system operation

None

37.

What is the minimum safe distance from the blades of an operating condenser fan when performing service?

What is the minimum safe distance from the blades of an operating condenser fan when performing service?Deselect Answer

No minimum distance — condenser fans are guarded and cannot contact service personnel

Keep hands, tools, and clothing away from fan blade path at all times — before reaching into any area near rotating equipment, confirm the equipment is completely de-energized and locked out per LOTO procedures

6 inches is the required safe distance from operating fan blades

Only the blade tips present a hazard — working near the fan hub is always safe

None

38.

What is the correct slope for a horizontal condensate drain line?

What is the correct slope for a horizontal condensate drain line?Deselect Answer

Level is acceptable for condensate drain lines

A minimum slope of 1/4 inch per foot toward the drain terminus to ensure gravity drainage — flat or back-pitched lines allow condensate to pool and overflow the drain pan

A minimum slope of 1 inch per foot is required for all condensate lines

Condensate lines must slope downward at 45 degrees

None

39.

What is the purpose of a psychrometric chart in HVAC design?

What is the purpose of a psychrometric chart in HVAC design?Deselect Answer

To determine refrigerant charge quantities for a given system

To graphically display the thermodynamic properties of moist air — including dry-bulb temperature, wet-bulb temperature, relative humidity, dew point, and enthalpy

To calculate duct friction losses for a given airflow rate

To select the correct filter efficiency for an air handling unit

None

40.

When estimating the cost of an HVAC installation, what should be included beyond equipment and materials?

When estimating the cost of an HVAC installation, what should be included beyond equipment and materials?Deselect Answer

Equipment and materials are the only costs that should be included in a contractor estimate

Labor, equipment, materials, overhead, profit, permit fees, startup and commissioning, and any required accessories such as pad, disconnect, and line set

Only labor and materials — overhead and profit are added by the general contractor

Only the first year's maintenance contract is included in installation cost

None

41.

What is Manual D used for in residential HVAC system design?

What is Manual D used for in residential HVAC system design?Deselect Answer

Diagnosing refrigerant system faults after installation

Designing the residential duct distribution system — sizing supply and return ducts to deliver the correct airflow to each room based on Manual J loads and equipment selection

Determining the correct disconnect switch size for HVAC equipment

Documenting commissioning results for permit closeout

None

42.

What is the purpose of an economizer on a commercial HVAC system?

What is the purpose of an economizer on a commercial HVAC system?Deselect Answer

An economizer recovers heat from exhaust air to preheat incoming outdoor air

An economizer uses outdoor air for free cooling when outdoor conditions are favorable (cool and dry) — reducing or eliminating mechanical cooling compressor operation and saving significant energy

An economizer stores cooling capacity in a thermal mass for peak demand reduction

An economizer is a variable-speed compressor drive that reduces energy during part-load conditions

None

43.

What is the hazard associated with refrigerant R-410A at high concentrations?

What is the hazard associated with refrigerant R-410A at high concentrations?Deselect Answer

R-410A is completely non-toxic and poses no health hazard at any concentration

At high concentrations, R-410A displaces oxygen and causes asphyxiation — it is also heavier than air and can accumulate in low areas. Decomposition products from flames or hot surfaces include hydrogen fluoride, a highly toxic and corrosive gas

R-410A is flammable and explosive at all concentrations

R-410A causes skin burns on direct contact — no inhalation hazard exists

None

44.

What PPE is required when working with chemical coil cleaners on HVAC equipment?

What PPE is required when working with chemical coil cleaners on HVAC equipment?Deselect Answer

No PPE is required for mild coil cleaners

Safety glasses or face shield, chemical-resistant gloves, and appropriate clothing to protect against splashes — alkaline coil cleaners can cause severe eye and skin burns, and acidic cleaners present similar hazards

Only rubber gloves are required for coil cleaner applications

A respirator is the only PPE required for coil cleaning chemicals

None

45.

What is the purpose of a confined space entry procedure when working in crawl spaces or mechanical rooms?

What is the purpose of a confined space entry procedure when working in crawl spaces or mechanical rooms?Deselect Answer

Confined space procedures are only required in spaces below ground level

To identify oxygen deficiency, toxic gas accumulation, or other atmospheric hazards before entry — protect workers from asphyxiation, poisoning, or engulfment in spaces with limited entry and exit that were not designed for continuous occupancy

Confined space procedures only apply to spaces where workers are completely enclosed and cannot see daylight

Mechanical rooms are never confined spaces — they are exempt from confined space requirements

None

46.

What does Manual J refer to in HVAC system design?

What does Manual J refer to in HVAC system design?Deselect Answer

A duct sizing manual published by SMACNA

The ACCA residential load calculation manual used to determine heating and cooling loads for a specific structure

The California mechanical code chapter on equipment sizing

A refrigerant charge calculation guide published by ASHRAE

None

47.

What is the proper method for disposing of refrigerant that cannot be returned to service?

What is the proper method for disposing of refrigerant that cannot be returned to service?Deselect Answer

Pour the refrigerant down a floor drain — it evaporates quickly and causes no environmental harm

Refrigerant must be recovered into an approved recovery cylinder and sent to a reclaimer certified by the EPA — venting, pouring, or other release to the atmosphere is prohibited under EPA Section 608 and subject to significant fines

Refrigerant that is too contaminated to reuse may be vented outdoors in well-ventilated areas

Refrigerant cylinders may be disposed of in standard trash once they are empty — no special disposal is required

None

48.

What is the correct sequence for startup of a new split-system air conditioner?

What is the correct sequence for startup of a new split-system air conditioner?Deselect Answer

Immediately turn on the thermostat and observe operation

Verify electrical connections and voltage, check refrigerant pressures, confirm proper airflow, allow crankcase heater to energize for at least 24 hours before first cooling operation if the compressor has been in storage, then start and measure operating parameters

Add refrigerant before starting to ensure sufficient charge for first operation

Turn on the system and wait 30 minutes before measuring any parameters

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49.

A contractor is estimating a residential HVAC replacement. The job requires 8 hours of labor at $85 per hour, materials totaling $3,200, and a permit fee of $150. If overhead is 20% of direct costs and profit is 15%, what is the approximate total bid price?

$3,950

$4,880

$6,440

$5,610

None

50.

What is the purpose of a TXV (thermostatic expansion valve) in a refrigeration system?

What is the purpose of a TXV (thermostatic expansion valve) in a refrigeration system?Deselect Answer

A TXV increases refrigerant flow during startup to build pressure quickly

A TXV meters refrigerant flow into the evaporator to maintain a consistent superheat at the evaporator outlet, optimizing evaporator coil utilization under varying load conditions

A TXV replaces the compressor in small residential systems

A TXV is a safety device that stops refrigerant flow when the system overheats

None

51.

What is the Sensible Heat Ratio (SHR) and why does it matter for equipment selection?

What is the Sensible Heat Ratio (SHR) and why does it matter for equipment selection?Deselect Answer

SHR is the ratio of refrigerant flow to total system BTU capacity

SHR is the ratio of sensible cooling capacity to total cooling capacity — it must match the building's sensible-to-total load ratio for proper humidity control

SHR is the ratio of supply air temperature to return air temperature

SHR only applies to commercial systems — residential systems do not have a sensible heat ratio

None

52.

When installing a gas furnace, what is required at the flue gas vent connection?

When installing a gas furnace, what is required at the flue gas vent connection?Deselect Answer

Any sheet metal pipe of any gauge is acceptable for furnace venting

The vent connector must be listed for the application (Type B for Category I appliances), properly sloped upward at minimum 1/4 inch per foot toward the chimney or vent termination, and secured with sheet metal screws at each joint

Flexible aluminum foil duct may be used for furnace venting in all applications

The furnace flue connection does not require slope — horizontal venting is equally acceptable

None

53.

What is the minimum ventilation requirement when working with refrigerant in an enclosed mechanical room?

What is the minimum ventilation requirement when working with refrigerant in an enclosed mechanical room?Deselect Answer

No ventilation requirement exists for enclosed spaces with refrigerant systems

Adequate ventilation must be provided to prevent refrigerant concentrations from reaching the ASHRAE-specified refrigerant concentration limit (RCL) — for R-410A this is 0.44 kg per cubic meter — and to maintain oxygen levels above 19.5 percent per Cal/OSHA requirements

A window must be open at all times when working with refrigerant — no other specific requirement exists

Ventilation requirements only apply to refrigerants classified as A2 or A3 (flammable) — A1 refrigerants like R-410A have no ventilation requirements

None

54.

What is the purpose of a secondary condensate drain pan and overflow switch?

What is the purpose of a secondary condensate drain pan and overflow switch?Deselect Answer

A secondary pan collects water for humidifier use

A secondary drain pan catches condensate if the primary drain becomes clogged — an overflow switch in the pan shuts down the cooling system before water overflows and damages ceilings or building materials

Secondary pans are only required for commercial systems above 10 tons

A secondary pan provides an alternative drain path that is always active along with the primary drain

None

55.

What is the hazard associated with operating gas heating equipment in an unventilated space?

What is the hazard associated with operating gas heating equipment in an unventilated space?Deselect Answer

There is no hazard from operating gas equipment without ventilation if the equipment is functioning correctly

Combustion consumes oxygen and produces carbon monoxide — in unventilated spaces, oxygen depletion can cause asphyxiation and carbon monoxide accumulation can cause CO poisoning, which is colorless, odorless, and rapidly fatal at high concentrations

Ventilation is only required for gas equipment rated above 100,000 BTU/h

The hazard is limited to fire risk only — CO poisoning is not possible from properly operating gas equipment

None

56.

What is the correct procedure for cleaning a condenser coil on a residential split system?

What is the correct procedure for cleaning a condenser coil on a residential split system?Deselect Answer

Use a pressure washer from the outside to blast debris from the coil

Rinse the coil from the inside out with a garden hose or low-pressure water after applying listed coil cleaner — rinsing from inside out pushes debris out rather than further into the coil, and avoids bending fin surfaces with excessive pressure

Clean the coil with compressed air from the outside, blowing debris into the coil fins

Condenser coils are self-cleaning and require no periodic maintenance

None

57.

What is a heat pump's Coefficient of Performance (COP)?

What is a heat pump's Coefficient of Performance (COP)?Deselect Answer

COP equals the heat pump's BTU output divided by 3,412 BTU per watt

COP equals the useful heating or cooling output in watts divided by the electrical input in watts — it represents the efficiency multiplier of a heat pump compared to direct electric resistance heating

COP is always less than 1.0 for heat pumps because energy cannot be created

COP equals the SEER divided by 3.412

None

58.

What diagnostic information does measuring the temperature split (return vs. supply air temperature) provide?

What diagnostic information does measuring the temperature split (return vs. supply air temperature) provide?Deselect Answer

The temperature split indicates the refrigerant charge level directly

The temperature split (typically 15 to 22 degrees F for residential air conditioning) indicates overall system heat transfer — a split below 15 degrees F suggests low airflow or low refrigerant charge; a split above 22 degrees F may indicate low airflow with high humidity

The temperature split only indicates filter condition — a high split means a dirty filter

Temperature split measurements are meaningless without also measuring refrigerant pressures

None

59.

What factors are included in a residential heating load calculation per Manual J?

What factors are included in a residential heating load calculation per Manual J?Deselect Answer

Only the square footage of the home and the local design temperature

Conduction heat loss through walls, ceilings, floors, windows, and doors; infiltration losses; duct losses; and internal heat gains from occupants and appliances

Only the insulation R-value and window U-factor

The equipment capacity from the existing system only

None

60.

What California code governs energy efficiency requirements for new HVAC installations in residential buildings?

What California code governs energy efficiency requirements for new HVAC installations in residential buildings?Deselect Answer

The National Electrical Code Article 440

California Title 24, Part 6 — the California Energy Code — which sets minimum efficiency standards and mandatory measures for HVAC systems in new and renovated buildings

The California Mechanical Code Chapter 3 only

Federal ASHRAE 90.1 is the only applicable standard in California

None

61.

What is the Cal/OSHA requirement for workers exposed to hazardous materials such as refrigerant on an HVAC job site?

What is the Cal/OSHA requirement for workers exposed to hazardous materials such as refrigerant on an HVAC job site?Deselect Answer

Workers may handle all refrigerants without training or PPE if they are licensed HVAC technicians

Workers must be trained on the hazards of refrigerants per the Cal/OSHA Hazard Communication Standard (Title 8, Section 5194), have access to Safety Data Sheets, and use appropriate PPE for the specific refrigerant being handled

Only the contractor needs hazardous material training — workers are covered by the contractor's general knowledge

Cal/OSHA has no specific requirements for refrigerant handling — EPA 608 certification is the only requirement

None

62.

What is the correct procedure for brazing refrigerant tubing connections?

What is the correct procedure for brazing refrigerant tubing connections?Deselect Answer

Use soft solder (50/50 tin-lead) for all refrigerant tubing connections

Use silver-alloy brazing filler with nitrogen flowing through the tubing during brazing to prevent oxidation scale formation inside the lines

Braze without nitrogen purge — flux alone prevents internal oxidation

Any welding rod rated above 1,100 degrees F is acceptable for refrigerant tubing

None

63.

What does a higher-than-normal suction pressure combined with lower-than-normal discharge pressure indicate?

What does a higher-than-normal suction pressure combined with lower-than-normal discharge pressure indicate?Deselect Answer

This pattern indicates a refrigerant overcharge

This pattern indicates a worn or leaking compressor — the compressor is not pumping efficiently, resulting in high suction pressure (poor pull-down) and low discharge pressure (poor compression)

This pattern is normal operation in humid weather

This pattern indicates a restriction in the liquid line

None

64.

What Cal/OSHA requirements apply to HVAC technicians working in attics during hot weather?

What Cal/OSHA requirements apply to HVAC technicians working in attics during hot weather?Deselect Answer

No special requirements apply to attic work — technicians are acclimatized from outdoor work

Cal/OSHA Title 8, Section 3395 (Heat Illness Prevention) requires water, shade, rest breaks, and acclimatization — attic temperatures can exceed 150 degrees F in summer, creating extreme heat illness risk requiring additional protective measures

Heat illness prevention only applies when outdoor temperatures exceed 95 degrees F — enclosed attics are exempt

Water and shade are sufficient for all heat conditions — no additional measures are required for attic work

None

65.

What is latent heat in HVAC terminology?

What is latent heat in HVAC terminology?Deselect Answer

Heat that causes a measurable temperature change in air

Heat associated with a change of state (moisture evaporation or condensation) at constant temperature — responsible for humidity removal in cooling systems

The heat content of refrigerant at compressor discharge

The heat produced by electrical resistance in HVAC equipment

None

66.

What is subcooling and what does it indicate about refrigerant charge?

What is subcooling and what does it indicate about refrigerant charge?Deselect Answer

Subcooling is the temperature drop across the condenser coil from inlet to outlet

Subcooling is the temperature of liquid refrigerant below its saturation temperature at the liquid line pressure — proper subcooling (typically 10-15 degrees F) indicates adequate refrigerant charge and ensures liquid (not flash gas) enters the metering device

Subcooling only applies to heat pump systems, not air conditioners

Subcooling is measured at the suction line near the compressor

None

67.

What is the purpose of nitrogen purging during refrigerant system brazing?

What is the purpose of nitrogen purging during refrigerant system brazing?Deselect Answer

Nitrogen pressurizes the system to make brazing easier by keeping tubing rigid

Flowing dry nitrogen through the tubing during brazing prevents the formation of copper oxide scale on the interior tube walls — scale that would circulate through the system and damage compressor valves and clog metering devices

Nitrogen purging is only required for commercial refrigeration systems above 5 tons

Nitrogen purging cools the brazing joint faster, creating a stronger connection

None

68.

What is the correct method for connecting flexible duct to a sheet metal plenum or duct collar?

What is the correct method for connecting flexible duct to a sheet metal plenum or duct collar?Deselect Answer

Use standard cloth duct tape wrapped twice around the connection

The flexible duct inner liner must be pulled back over the duct collar at least 2 inches and secured with a listed clamp — then the outer jacket and insulation are pulled over and secured with a separate listed clamp or UL 181 tape

Insert the flexible duct into the collar opening and rely on compression for the seal

Use sheet metal screws through the flexible duct into the collar

None

69.

What is the purpose of a duct system static pressure test?

What is the purpose of a duct system static pressure test?Deselect Answer

A static pressure test measures the velocity of air through the duct system

A static pressure test measures the air pressure resistance of the duct system — comparing total external static pressure to the equipment's rated static pressure to identify if restrictions exist that reduce airflow and system performance

Static pressure testing is only required for commercial systems above 10 tons

A static pressure test verifies that duct joints are properly sealed

None

70.

What is the purpose of a condensate drain trap on an air handling unit?

What is the purpose of a condensate drain trap on an air handling unit?Deselect Answer

A trap prevents air from bypassing the filter

A trap prevents negative pressure in the drain pan from drawing sewer gases into the air handler and prevents air from being drawn into the negative-pressure section of the air handler through the drain line

A trap is only required when the drain line runs more than 10 feet horizontally

A trap prevents the drain pan from overflowing during heavy condensation periods

None

71.

What is the purpose of duct leakage testing per California Title 24?

What is the purpose of duct leakage testing per California Title 24?Deselect Answer

Duct leakage testing is only required for commercial systems in California

To verify that duct systems meet the maximum allowed leakage rate — excessive duct leakage wastes conditioned air to unconditioned spaces, reducing system efficiency and comfort while increasing energy costs

Duct leakage testing is performed only to satisfy warranty requirements from equipment manufacturers

To measure the total airflow delivered by the air handling unit

None

72.

What type of gas connector is required for connecting a gas appliance to the gas supply piping?

What type of gas connector is required for connecting a gas appliance to the gas supply piping?Deselect Answer

Standard black iron pipe with standard fittings for all appliance connections

A listed flexible gas appliance connector rated for the gas type (natural or LP), with the correct BTU/h capacity for the appliance, and limited to 3 to 6 feet in length per California Plumbing Code requirements

Any flexible metallic tubing may be used as a gas connector regardless of listing

Copper tubing with flare fittings is the preferred connection for all gas appliances

None

73.

What is the purpose of evacuating a refrigerant system before charging?

What is the purpose of evacuating a refrigerant system before charging?Deselect Answer

Evacuation removes excess refrigerant from an overcharged system

Evacuation removes air, moisture, and non-condensable gases from the system using a vacuum pump — moisture causes ice formation at the metering device and acid formation that attacks compressor components

Evacuation is only required for systems using R-410A — older refrigerants do not require evacuation

Evacuation brings the system to atmospheric pressure before refrigerant is added

None

74.

What is the purpose of Manual N in commercial HVAC design?

What is the purpose of Manual N in commercial HVAC design?Deselect Answer

Manual N provides national refrigerant handling regulations for commercial contractors

Manual N is the ACCA commercial load calculation procedure — the commercial equivalent of Manual J for determining heating and cooling loads in commercial buildings

Manual N covers NATE certification requirements for commercial technicians

Manual N is a duct leakage testing standard for commercial buildings

None

75.

A packaged water source heat pump eliminates which component compared to an air-cooled split system?

A packaged water source heat pump eliminates which component compared to an air-cooled split system?Deselect Answer

It eliminates the reversing valve because water-source units do not provide both heating and cooling

It eliminates the air-cooled condenser — heat rejection occurs through a water coil rather than an outdoor air-cooled condenser, allowing the entire unit to be installed indoors

It eliminates the compressor — water source units use absorption refrigeration only

It eliminates the expansion valve because water always provides a constant condensing temperature

None

76.

What is the purpose of a flame sensor (also called a flame rod or rectifier) in a modern gas furnace?

What is the purpose of a flame sensor (also called a flame rod or rectifier) in a modern gas furnace?Deselect Answer

The flame sensor measures the temperature of the supply air to verify the heat exchanger is working

The flame sensor detects the presence of flame by measuring the small DC current that flows through the flame (flame rectification) — if flame is not detected within the trial period, the gas valve closes as a safety measure

The flame sensor monitors the pilot flame in standing pilot furnaces

The flame sensor controls the gas valve modulation rate based on heating demand

None

77.

What causes high head pressure in an air conditioning system?

What causes high head pressure in an air conditioning system?Deselect Answer

Low refrigerant charge always causes high head pressure

High head pressure is caused by: dirty or restricted condenser coil, insufficient condenser airflow, high outdoor ambient temperature, refrigerant overcharge, or non-condensable gases (air) in the system

High head pressure is normal during the first hour of operation

High head pressure only occurs in commercial systems — residential systems cannot develop excessive head pressure

None

78.

What Cal/OSHA requirement governs the use of ladders when accessing rooftop HVAC equipment?

What Cal/OSHA requirement governs the use of ladders when accessing rooftop HVAC equipment?Deselect Answer

Any ladder is acceptable as long as the technician can reach the rooftop

Portable ladders must be inspected before use, secured at the top, extend at least 3 feet above the landing surface, be positioned at the correct angle (4:1 ratio), and meet the weight capacity rating for the user plus tools per Cal/OSHA Title 8, Section 3276

Extension ladders may be used at any angle convenient for the installer

Ladder safety requirements are the building owner's responsibility — not the HVAC technician's employer

None

79.

What type of condensate drain line material is acceptable per the California Mechanical Code?

What type of condensate drain line material is acceptable per the California Mechanical Code?Deselect Answer

Only copper pipe is acceptable for HVAC condensate drainage

Listed materials for condensate drainage include copper, CPVC, PVC, and other materials approved for drain service — material selection depends on the condensate temperature, which can reach 140 degrees F in some heating applications

Only PVC is acceptable for condensate drainage in California

Any plumbing drain pipe material is acceptable without restriction

None

80.

What type of refrigerant line insulation is required on suction lines and why?

What type of refrigerant line insulation is required on suction lines and why?Deselect Answer

Insulation is optional on suction lines — it is only cosmetic

Closed-cell foam insulation rated for the service temperature must be installed on suction lines to prevent condensation and sweating, and to minimize heat gain from the surrounding environment that reduces system efficiency

Fiberglass duct wrap insulation is the required type for refrigerant suction lines

Only suction lines in attics require insulation — suction lines in conditioned spaces need none

None

81.

What EPA regulation governs the handling and recovery of refrigerants?

What EPA regulation governs the handling and recovery of refrigerants?Deselect Answer

OSHA 29 CFR 1910.1000 regulates all chemical handling including refrigerants

EPA Section 608 of the Clean Air Act requires that all refrigerants be recovered before servicing — prohibits venting refrigerants into the atmosphere, and requires technician certification for purchasing and handling refrigerants

California Title 24 contains all refrigerant handling requirements for California contractors

Refrigerant handling is self-regulated by the industry with no federal requirements

None

82.

What is superheat in a refrigeration system and why is it measured?

What is superheat in a refrigeration system and why is it measured?Deselect Answer

Superheat is the temperature increase of refrigerant liquid in the condenser

Superheat is the temperature of refrigerant vapor above its saturation temperature at a given pressure — measured at the suction line to verify the evaporator is fully used and the compressor receives dry vapor, not liquid refrigerant

Superheat is the heat removed from the refrigerant in the expansion valve

Superheat equals the difference between discharge and suction pressure

None

83.

What is the correct way to add refrigerant to an undercharged system?

What is the correct way to add refrigerant to an undercharged system?Deselect Answer

Add refrigerant until the system pressures look normal by comparison to memory

Connect gauges, verify the system is undercharged by measuring superheat or subcooling per the manufacturer's method, recover any contaminated refrigerant if needed, then add the correct refrigerant type in the correct charging method (vapor on suction, liquid on liquid line or per manufacturer) until target superheat or subcooling is achieved

Open the refrigerant cylinder valve fully and allow refrigerant to flow until pressures equalize

Add refrigerant by weight — always add exactly one pound regardless of the amount the system is undercharged

None

84.

What does a thermocouple do in a gas furnace and how is failure identified?

What does a thermocouple do in a gas furnace and how is failure identified?Deselect Answer

A thermocouple measures supply air temperature to control furnace output

A thermocouple generates a small millivolt signal in the presence of a pilot flame — if it fails, the gas valve closes (as a safety function), and the pilot flame cannot be kept lit even when manually held on

A thermocouple is an electronic ignition component used in modern furnaces only

A thermocouple failure causes the furnace to overheat and trip the limit switch

None

85.

What is the design outdoor temperature and why is it important for HVAC sizing?

What is the design outdoor temperature and why is it important for HVAC sizing?Deselect Answer

The highest temperature ever recorded in a location — used to size the absolute maximum capacity system

The outdoor temperature used for equipment sizing calculations — typically the temperature exceeded only 1 to 2.5 percent of hours during the cooling season (99th or 97.5th percentile) — not the extreme historical maximum

The average outdoor temperature throughout the year

The manufacturer's recommended maximum outdoor operating temperature for the selected equipment

None

86.

What is required before opening a refrigerant circuit for repair?

What is required before opening a refrigerant circuit for repair?Deselect Answer

Simply discharge the system pressure into the atmosphere before opening any connections

The system refrigerant must be fully recovered into an approved recovery cylinder using certified recovery equipment — intentional venting is prohibited under EPA Section 608 and Cal/OSHA, and opening a pressurized refrigerant circuit without recovery creates both an environmental violation and a serious personal injury hazard

Recovery is only required for systems containing more than 50 pounds of refrigerant

The system may be opened after pressure is reduced to below 50 psig by running the compressor

None

87.

What personal protective equipment is required when brazing refrigerant tubing?

What personal protective equipment is required when brazing refrigerant tubing?Deselect Answer

No PPE is required for brazing — it is a common HVAC task

Safety glasses or face shield to protect against hot metal spatter, appropriate gloves to handle hot tubing, and fire-resistant clothing — plus a fire extinguisher nearby and fire watch if working near combustible materials

Only leather gloves are required for brazing

A self-contained breathing apparatus is always required for brazing operations

None

88.

What information must be included on a refrigerant recovery cylinder label?

What information must be included on a refrigerant recovery cylinder label?Deselect Answer

Only the type of refrigerant in the cylinder

The refrigerant type, the cylinder's DOT classification, the date of last hydrostatic test, the cylinder's tare weight, and when returning recovered refrigerant — the refrigerant type and that the contents are recovered (not virgin) refrigerant

Recovery cylinders do not require labels if the technician knows what refrigerant was recovered

Only the technician's EPA certification number and date of recovery are required

None

89.

What causes short cycling in a residential air conditioner?

What causes short cycling in a residential air conditioner?Deselect Answer

Short cycling is normal operation — units should cycle on and off frequently

Short cycling (frequent starts and stops in rapid succession) is caused by: refrigerant overcharge, dirty condenser, high head pressure tripping the high-pressure switch, thermostat placed in a poor location, or an oversized system that quickly satisfies the thermostat set point without adequate runtime for dehumidification

Short cycling only occurs in heat pump systems — air conditioners cannot short cycle

Short cycling is always caused by electrical problems in the compressor

None

90.

What is the most likely cause when a gas furnace ignites but shuts off after a few seconds of operation?

What is the most likely cause when a gas furnace ignites but shuts off after a few seconds of operation?Deselect Answer

The gas valve is defective and must be replaced

The flame sensor is coated with carbon deposits and is not generating sufficient signal to prove flame — the furnace control board shuts off the gas valve within the trial period as a safety measure

The inducer motor has failed, causing the pressure switch to open during operation

The heat exchanger is cracked, activating the rollout switch

None

91.

What is the most common cause of frozen evaporator coils?

What is the most common cause of frozen evaporator coils?Deselect Answer

Refrigerant overcharge causes evaporator freeze-up

Insufficient airflow across the evaporator (dirty filter, blocked registers, failed blower motor) or low refrigerant charge — both cause the coil to operate below freezing and moisture to accumulate as ice

A faulty defrost timer causes residential AC evaporator freeze-up

Evaporator coils only freeze in cold weather — summer freeze-up is impossible

None

92.

What is the purpose of a heat exchanger inspection on a gas furnace?

What is the purpose of a heat exchanger inspection on a gas furnace?Deselect Answer

Heat exchanger inspection verifies proper refrigerant charge in the furnace system

Heat exchanger inspection checks for cracks or holes that could allow combustion products (including carbon monoxide) to enter the supply air stream — a cracked heat exchanger is a life-threatening safety hazard requiring immediate furnace shutdown

Heat exchanger inspection is only performed during installation — no periodic inspection is needed

Heat exchanger inspection verifies that the heat exchanger is properly sized for the home's heating load

None

93.

What is the purpose of a commissioning report at the completion of an HVAC installation?

What is the purpose of a commissioning report at the completion of an HVAC installation?Deselect Answer

A commissioning report is only required for commercial systems over 10 tons

To document that the system was installed and verified to operate correctly — including measured airflow, refrigerant charge verification, operating temperatures and pressures, and control system operation — providing a baseline record for future maintenance

To satisfy equipment warranty registration requirements only

To document the equipment model and serial numbers for tax purposes

None

94.

What is the purpose of a crankcase heater on a refrigerant compressor?

What is the purpose of a crankcase heater on a refrigerant compressor?Deselect Answer

The crankcase heater preheats refrigerant before it enters the evaporator

The crankcase heater prevents refrigerant from migrating into and mixing with the compressor oil during off-cycles — refrigerant dissolved in oil causes oil foaming and loss of lubrication at startup

The crankcase heater is a safety device that shuts off the compressor when oil pressure is low

The crankcase heater improves compressor efficiency during operation in cold weather

None

95.

What maintenance should be performed annually on a gas furnace?

What maintenance should be performed annually on a gas furnace?Deselect Answer

Only replacing the filter is needed annually — gas furnaces require no other maintenance

Inspect and clean the heat exchanger, clean the burners, check flue vent for proper draft and leaks, verify gas pressure, test all safety controls, lubricate moving parts if required, replace filter, and perform a combustion analysis to verify safe and efficient operation

Annual maintenance is not required for modern sealed combustion furnaces

Only the air filter and thermostat batteries require annual replacement

None

96.

What is SEER and what does a higher SEER value indicate?

What is SEER and what does a higher SEER value indicate?Deselect Answer

Seasonal Energy Efficiency Ratio — the ratio of total seasonal cooling output in BTU to total seasonal electrical energy input in watt-hours; a higher SEER indicates greater seasonal efficiency

Standard Equipment Efficiency Rating — a fixed test condition efficiency score; higher values indicate noisier operation

System Energy Efficiency Ratio — only applicable to commercial rooftop units

SEER is identical to EER but measured in metric units

None

97.

What is the purpose of a defrost cycle on a heat pump operating in heating mode?

What is the purpose of a defrost cycle on a heat pump operating in heating mode?Deselect Answer

Defrost cycles cool the home periodically to give the compressor a rest

When outdoor temperatures are below approximately 40 degrees F, moisture in the outdoor air freezes on the outdoor coil (now functioning as an evaporator) — the defrost cycle temporarily reverses the system to heat and melt the ice, restoring outdoor coil efficiency

Defrost cycles only occur in commercial heat pump systems — residential units do not frost

The defrost cycle heats the refrigerant lines to prevent freezing during cold weather operation

None

98.

What is the purpose of a dryer/filter in a refrigeration system?

What is the purpose of a dryer/filter in a refrigeration system?Deselect Answer

A dryer/filter increases refrigerant velocity through the metering device

A dryer/filter removes moisture and debris from the liquid refrigerant — moisture causes metering device freeze-up and acid formation that damages compressor components

A dryer/filter is only required after a system has experienced compressor burnout

A dryer/filter regulates refrigerant flow to maintain constant subcooling

None

99.

What is the proper procedure for handling a refrigerant cylinder?

What is the proper procedure for handling a refrigerant cylinder?Deselect Answer

Store cylinders horizontally to prevent valve damage

Keep cylinders upright or at the manufacturer-specified angle, secure them to prevent falling, protect the valve with the cap when not in use, never expose to temperatures above 125 degrees F, and transport in a secured upright position with the valve protected

Fill cylinders from bulk supply using a high-pressure compressor to maximize capacity

Cylinders may be used as rollers or work platforms if needed on a job site

None

100.

What is the purpose of a high-pressure safety switch on a refrigeration system?

What is the purpose of a high-pressure safety switch on a refrigeration system?Deselect Answer

The high-pressure switch starts a second compressor when demand exceeds single-compressor capacity

The high-pressure switch shuts down the compressor when discharge pressure exceeds a safe limit — protecting the compressor and refrigerant circuit from damage caused by excessive head pressure

The high-pressure switch regulates the condensing fan speed to maintain constant head pressure

The high-pressure switch is only required on commercial refrigeration systems above 5 tons

None

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