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Question 1Heating Systems and Equipment

In a conventional gas-fired forced-air furnace, what is the function of the draft inducer assembly?

  1. It pulls combustion gases through the heat exchanger and vents them outdoors Correct answer.
  2. It regulates the manifold gas pressure at the burner orifices
  3. It mixes fresh outdoor air with return air before heating
  4. It circulates conditioned room air through the supply ductwork

Explanation

The draft inducer is a blower mounted on the flue side of the heat exchanger that establishes negative pressure to draw combustion products through the exchanger and out the vent. It operates on the combustion air path, not the airstream. Room-air circulation is handled by the main blower, and gas pressure is set by the manifold regulator.

Question 2Heating Systems and Equipment

A natural gas furnace is rated at 100,000 Btu/h input with an 80% steady-state efficiency. What is the approximate output capacity?

  1. 100,000 Btu/h
  2. 20,000 Btu/h
  3. 125,000 Btu/h
  4. 80,000 Btu/h Correct answer.

Explanation

Output equals input multiplied by the steady-state efficiency: 100,000 x 0.80 = 80,000 Btu/h. The remaining 20,000 Btu/h leaves as stack and jacket losses. Input ratings are not increased by efficiency.

Question 3Heating Systems and Equipment

Which ignition method relies on a silicon carbide or silicon nitride element that heats to incandescence to light the burners?

  1. Direct spark ignition
  2. Intermittent pilot ignition
  3. Hot surface ignition Correct answer.
  4. Standing pilot

Explanation

Hot surface ignition uses a resistive element that glows to ignite the gas. Standing pilots burn continuously, spark ignition uses a high-voltage arc, and intermittent pilots are lit by spark and proven before main burner operation.

Question 4Heating Systems and Equipment

A technician measures a temperature rise across the furnace that is well above the data plate range. Which condition is most likely?

  1. A manifold pressure set too low
  2. A failed high-limit switch stuck open
  3. A restricted return air path or dirty blower wheel Correct answer.
  4. Excessive airflow through the heat exchanger

Explanation

Temperature rise equals the heat added divided by the mass airflow and specific heat. Reduced airflow from a dirty filter, blocked return, or dirty blower raises the rise. Excess airflow lowers the rise, and low manifold pressure reduces heat input and therefore rise.

Question 5Heating Systems and Equipment

What is the primary purpose of a barometric draft regulator on a naturally drafted gas appliance?

  1. To limit the flue draft acting on the appliance to a set value Correct answer.
  2. To cool the flue gases before they enter the chimney
  3. To shut off gas flow if the flue backs up
  4. To increase the draft during cold startup

Explanation

A barometric draft regulator is a hinged damper that opens to admit room air into the flue connector, holding the draft at the appliance near its setpoint. It stabilizes draft against chimney variations rather than creating draft. Spillage protection is a separate safety function.

Question 6Heating Systems and Equipment

In a condensing furnace, what is the purpose of the secondary heat exchanger?

  1. To preheat combustion air entering the burners
  2. To extract latent heat by condensing water vapor from the flue products Correct answer.
  3. To cool the supply air before it enters the duct system
  4. To reduce the flue gas temperature below ambient before venting

Explanation

The secondary exchanger cools the flue products enough that water vapor condenses, releasing latent heat to the airstream and raising efficiency above 90%. The condensate is drained away. It does not preheat combustion air or chill supply air.

Question 7Heating Systems and Equipment

A gas furnace ignites but shuts down after a few seconds, and the technician finds the flame sensor is coated with white oxide. What is the correct action?

  1. Replace the gas valve
  2. Bypass the flame sensor to test the burners
  3. Increase manifold pressure to lengthen the flame
  4. Clean the sensor with steel wool or an abrasive pad Correct answer.

Explanation

A flame sensor must conduct a small current through the flame; oxide buildup insulates it and the control drops out on loss of flame signal. Cleaning restores the signal. Bypassing a safety device is never acceptable, and gas pressure does not correct a sensing fault.

Question 8Heating Systems and Equipment

What is the function of a limit switch in a forced-air gas furnace?

  1. To prove that combustion air is flowing before ignition
  2. To interrupt burner operation if the heat exchanger overheats Correct answer.
  3. To open the gas valve only after the blower starts
  4. To regulate supply air temperature by cycling the blower

Explanation

The high-limit switch is a temperature-actuated safety that opens the burner circuit when the heat exchanger exceeds its safe temperature, typically from low airflow. Blower control is handled by the fan switch, and combustion air proving is handled by pressure switches.

Question 9Heating Systems and Equipment

A hot water boiler system uses zone valves with a single circulator. Which statement describes a typical series-loop piping arrangement?

  1. Each emitter has its own supply and return run back to a manifold
  2. Each zone has a dedicated circulator and no zone valves
  3. Emitters are piped one after another so water flows through each in turn Correct answer.
  4. Water flows through emitters in parallel with equal path lengths

Explanation

In a series loop, water passes sequentially through each emitter, so downstream units receive cooler water and the loop cannot be individually zoned without valves. Home-run or manifold layouts give each emitter its own supply and return. Parallel piping with equal paths describes a reverse-return primary/secondary design.

Question 10Heating Systems and Equipment

What is the purpose of an expansion tank in a closed hydronic heating system?

  1. To remove dissolved oxygen from the system water
  2. To store heated water for domestic use
  3. To increase system pressure at the boiler outlet
  4. To absorb the volume change of water as it is heated Correct answer.

Explanation

Water expands as it heats, and in a closed system that expansion must be accommodated or pressure will rise dangerously. The expansion tank provides a compressible cushion. It does not store domestic water, deaerate, or boost pressure.

Question 11Heating Systems and Equipment

A technician must verify the manifold gas pressure on a natural gas furnace. Where is the pressure measured and what is a common target value?

  1. At the flue outlet, about 1 in. w.c.
  2. At the inlet to the gas valve, about 7 in. w.c.
  3. At the draft hood, about 5 in. w.c.
  4. At the burner orifices, about 3.5 in. w.c. Correct answer.

Explanation

Manifold pressure is measured at the valve outlet or burner manifold, and natural gas furnaces commonly specify about 3.5 in. w.c. Inlet (supply) pressure is typically 7 in. w.c. and is a separate check. Flue and draft hood readings are not manifold pressure.

Question 12Heating Systems and Equipment

Which component prevents the main burner from operating until the inducer has established adequate draft in a mid-efficiency furnace?

  1. The rollout switch
  2. The flame sensor
  3. The fan/limit switch
  4. The pressure switch Correct answer.

Explanation

A pressure switch senses the negative pressure created by the inducer and closes to permit ignition. Rollout switches respond to flame escaping the burner area, the flame sensor proves flame after ignition, and the fan/limit controls the blower.

Question 13Heating Systems and Equipment

A steam heating system's low-water cutoff is found to be plugged with sludge. Why is this critical?

  1. It may fail to shut off the burner when water level drops, risking a dry boiler Correct answer.
  2. It will prevent the circulator from running
  3. It will overfire the burner and crack the boiler sections
  4. It will cause the radiator vents to discharge water

Explanation

The low-water cutoff is the primary safety preventing burner operation with insufficient water. A plugged float chamber can hold the switch closed, allowing the boiler to fire dry and overheat. It does not affect radiator vents or circulator operation.

Question 14Heating Systems and Equipment

What is the function of a thermostatic radiator valve on a hot water heating system?

  1. To limit the maximum system pressure
  2. To balance flow between supply and return mains
  3. To vent air from the radiator as it fills
  4. To throttle flow to the emitter in response to room temperature Correct answer.

Explanation

A thermostatic radiator valve uses a temperature-sensitive actuator to modulate flow to the emitter, providing individual room control. Air venting is done by automatic or manual vents, pressure is limited by a relief valve, and balancing is done with balancing valves.

Question 15Heating Systems and Equipment

A furnace's blower continues to run after the thermostat is satisfied, then stops. Which control most directly determines this off-delay?

  1. The gas valve regulator
  2. The fan switch portion of the fan/limit control Correct answer.
  3. The rollout switch
  4. The high-limit switch

Explanation

The fan switch senses plenum temperature and keeps the blower running after burner shutdown to remove residual heat, then opens when the plenum cools. The limit is a safety, the gas valve regulates fuel, and the rollout switch is a safety for flame spillage.

Question 16Heating Systems and Equipment

Which statement best describes the difference between a direct-vent and a non-direct-vent (Category I) furnace?

  1. Direct-vent units use only outdoor air for combustion and vent through a dedicated two-pipe system Correct answer.
  2. Non-direct-vent units require no vent at all
  3. Direct-vent units must always be condensing
  4. Non-direct-vent units cannot be installed in a basement

Explanation

A direct-vent appliance draws combustion air from outdoors through a dedicated intake and vents through a dedicated pipe, isolating it from indoor air. Category I units use indoor air and vent by natural draft. Direct-vent design is independent of condensing status, and all fuel appliances require venting.

Question 17Heating Systems and Equipment

A technician finds a cracked heat exchanger in a gas furnace. What is the appropriate action?

  1. Seal the crack with high-temperature furnace cement
  2. Red-tag the unit and shut off the fuel supply until repair or replacement Correct answer.
  3. Reduce manifold pressure to limit flue gas leakage
  4. Continue operation until the heating season ends

Explanation

A cracked heat exchanger can allow carbon monoxide into the airstream, so the appliance must be taken out of service immediately. Field repair of the exchanger is not acceptable, and reducing gas pressure does not eliminate the hazard.

Question 18Heating Systems and Equipment

What does a combustion analyzer's carbon monoxide reading of 400 ppm air-free in the flue of a furnace most likely indicate?

  1. Incomplete combustion requiring immediate investigation Correct answer.
  2. A correctly adjusted primary air shutter
  3. Normal operation for a condensing furnace
  4. An overfilled condensate trap

Explanation

Elevated CO in flue products signals incomplete combustion from causes such as insufficient primary air, overfiring, or a restricted flue. Normal readings are far lower. A condensate trap and shutter adjustment are not diagnosed by CO alone, and 400 ppm is not normal.

Question 19Heating Systems and Equipment

Which boiler type is designed to operate with return water cool enough to condense flue gas moisture and therefore requires a condensate drain?

  1. Cast-iron atmospheric boiler
  2. Condensing boiler Correct answer.
  3. Copper-fin baseboard boiler
  4. Steam boiler with a Hartford loop

Explanation

Condensing boilers extract latent heat by cooling flue products below the dew point, producing acidic condensate that must be drained and often neutralized. Cast-iron and copper-fin non-condensing boilers must be protected from sustained condensing conditions.

Question 20Heating Systems and Equipment

A mid-efficiency furnace with a draft hood is installed in a tightly sealed room with no dedicated combustion air. What is the primary risk?

  1. Freezing of the condensate trap
  2. Spillage of flue gases into the room from depressurization Correct answer.
  3. Overheating of the draft inducer motor
  4. Excessive draft causing flame lift

Explanation

Natural-draft appliances need adequate combustion and dilution air; a tight space can depressurize and reverse draft at the hood, spilling flue gases indoors. Flame lift is caused by excessive draft, and condensate traps belong to condensing units.

Question 21Heating Systems and Equipment

What is the purpose of a Hartford loop in a steam boiler piping arrangement?

  1. To provide a condensate drain for the boiler
  2. To regulate steam pressure at the header
  3. To prevent boiler water from draining out through a failed return Correct answer.
  4. To separate air from the steam supply

Explanation

The Hartford loop connects the equalizer and return near the water line so that a leak in the wet return cannot drain the boiler below a safe level. Air separation is done by air vents or separators, and pressure is regulated by the pressuretrol.

Question 22Heating Systems and Equipment

A technician is checking a thermocouple-equipped standing pilot. The pilot flame is steady and blue but the main valve will not open. Which test is most appropriate?

  1. Check the manifold gas pressure at the burners
  2. Measure the temperature rise across the furnace
  3. Measure the thermocouple's millivolt output with the pilot lit Correct answer.
  4. Test the blower capacitor

Explanation

A thermocouple generates a small DC voltage that holds the safety magnet open; if output is low the main valve will not open. Manifold pressure, temperature rise, and blower components are unrelated to pilot safety operation.

Question 23Heating Systems and Equipment

Which condition would cause a furnace's rollout switch to trip repeatedly?

  1. A thermostat set too high
  2. A dirty blower wheel reducing airflow
  3. A low refrigerant charge in the coil
  4. A blocked flue or heat exchanger restricting combustion gas flow Correct answer.

Explanation

Rollout switches are located near the burners and open when flame rolls out of the combustion area, typically because combustion products cannot escape due to a blocked flue or exchanger. Airflow restrictions affect the limit switch, and thermostat setpoint does not cause rollout.

Question 24Heating Systems and Equipment

What is the function of a zone valve in a hydronic system?

  1. To relieve excess pressure in the boiler
  2. To open or close water flow to a zone in response to its thermostat Correct answer.
  3. To mix supply and return water to control temperature
  4. To remove air from the loop during filling

Explanation

A zone valve is an electrically actuated valve that opens on a call from its zone thermostat to allow circulation through that zone. Pressure relief, mixing, and air removal are handled by separate devices.

Question 25Heating Systems and Equipment

A gas furnace has a flashing diagnostic LED indicating a pressure switch fault. The inducer runs but the switch does not close. Which is the most likely cause?

  1. A failed flame sensor
  2. A faulty thermostat
  3. A blocked condensate drain or vent pipe Correct answer.
  4. A loose blower belt

Explanation

A pressure switch that will not close despite inducer operation points to a blocked or restricted vent, intake, or condensate drain that prevents the required pressure differential. Flame sensing, thermostat, and blower issues produce different symptoms.

Question 26Heating Systems and Equipment

Which type of heat exchanger is commonly found in a warm-air gas furnace?

  1. Plate-fin
  2. Fire-tube
  3. Clamshell Correct answer.
  4. Shell-and-tube

Explanation

Clamshell heat exchangers are the most common design in residential warm-air gas furnaces; combustion gases pass through the clamshell sections while supply air passes over the exterior.

Question 27Heating Systems and Equipment

What is the primary function of the gas valve in a gas-fired furnace?

  1. To regulate the flow of gas to the burners Correct answer.
  2. To mix gas with air before combustion
  3. To ignite the gas-air mixture
  4. To sense the presence of a flame

Explanation

The gas valve controls the on/off and modulating flow of gas to the burner manifold, thereby regulating firing rate.

Question 28Heating Systems and Equipment

In a forced-air furnace, what is the purpose of the blower compartment door switch?

  1. To activate the door open indicator light
  2. To adjust blower speed based on door position
  3. To disable furnace operation when the door is removed Correct answer.
  4. To turn on the blower when the door is opened

Explanation

The door switch is a safety interlock that breaks power to the furnace controls when the blower compartment door is removed, preventing operation with the compartment open.

Question 29Heating Systems and Equipment

Which of the following is a common symptom of a faulty hot surface igniter in a gas furnace?

  1. The furnace ignites and then shuts down after a few seconds
  2. The burners light but the blower does not start
  3. The furnace short-cycles on the high-limit switch
  4. The inducer runs but the burners do not light Correct answer.

Explanation

A failed hot surface igniter will not glow hot enough to ignite the gas, so the burners fail to light even though the inducer may run through its sequence.

Question 30Heating Systems and Equipment

A technician measures 3.2 inches of water column manifold pressure on a natural gas furnace that specifies 3.5 inches. What is the most likely effect on combustion?

  1. The furnace will overfire and produce more heat
  2. The furnace will produce less heat output than rated Correct answer.
  3. The furnace will experience flame rollout
  4. The furnace will produce excessive carbon monoxide

Explanation

Manifold pressure below the rating reduces the gas input rate, resulting in lower heat output and a leaner mixture than designed.

Question 31Heating Systems and Equipment

In a hydronic heating system, what is the function of an air separator?

  1. To remove dissolved oxygen from the water
  2. To separate sludge from the water
  3. To separate air bubbles from the water and vent them Correct answer.
  4. To separate the supply and return piping circuits

Explanation

An air separator uses a centrifugal or coalescing design to remove entrained air bubbles from the circulating water so they can be vented, improving heat transfer and reducing noise.

Question 32Heating Systems and Equipment

A hot water boiler system uses a circulator pump with a flow check valve. What is the purpose of the flow check valve?

  1. To prevent gravity circulation when the pump is off Correct answer.
  2. To prevent backflow of domestic water into the boiler
  3. To act as a safety relief valve
  4. To regulate the flow rate through the boiler

Explanation

A flow check valve prevents thermosyphoning (gravity circulation) of heated water when the circulator is not running, which would cause unwanted heating.

Question 33Heating Systems and Equipment

A technician is testing a thermopile in a standing pilot system. The pilot flame is steady, but the thermopile output is only 250 millivolts when 750 millivolts is expected. What is the most likely cause?

  1. The thermocouple is shorted
  2. The pilot orifice is too large
  3. The gas valve is stuck closed
  4. The thermopile is defective or misaligned Correct answer.

Explanation

A thermopile generates voltage when heated by the pilot flame; low output despite a steady flame indicates a faulty thermopile or one not properly positioned in the flame.

Question 34Heating Systems and Equipment

What is the purpose of a barometric draft regulator in a natural draft furnace?

  1. To increase the draft by restricting flue gas flow
  2. To prevent backdraft by closing off the flue
  3. To measure the draft pressure in the flue
  4. To maintain a constant flue draft by admitting room air into the flue Correct answer.

Explanation

A barometric draft regulator opens to admit room air into the flue when draft is excessive, thereby stabilizing the draft to a set value.

Question 35Heating Systems and Equipment

A steam boiler is equipped with a low-water cutoff and a feed water pump. The low-water cutoff is found to be sluggish and not tripping during a test. What is the appropriate action?

  1. Adjust the burner to reduce steam demand
  2. Increase the feed water pressure to clear the blockage
  3. Replace the low-water cutoff immediately
  4. Blow down the low-water cutoff and retest Correct answer.

Explanation

Sluggish operation often results from sediment or sludge in the float chamber; blowing down the cutoff can clear the obstruction and restore proper operation.

Question 36Heating Systems and Equipment

In a two-pipe steam heating system, what is the function of the steam trap?

  1. To vent steam to the atmosphere to control temperature
  2. To add water to the boiler when the level drops
  3. To allow air and condensate to pass while preventing steam from escaping Correct answer.
  4. To regulate the pressure of steam entering the radiator

Explanation

A steam trap is designed to discharge condensate and air but close when steam reaches it, keeping steam in the system.

Question 37Heating Systems and Equipment

A technician is performing a combustion analysis on a condensing furnace and reads 9% CO2 and 6% O2 in the flue gas. What does this indicate?

  1. Excessive excess air and possible dilution Correct answer.
  2. Proper combustion with optimal efficiency
  3. A cracked heat exchanger
  4. Insufficient combustion air

Explanation

Low CO2 and high O2 readings indicate a large amount of excess air, which dilutes the flue gases and reduces efficiency.

Question 38Heating Systems and Equipment

A technician is troubleshooting a hot water boiler that is not heating the house. The circulator runs, but the boiler water temperature remains low. Which component is most likely at fault?

  1. The pressure relief valve
  2. The expansion tank
  3. The zone valve
  4. The aquastat Correct answer.

Explanation

The aquastat controls the boiler water temperature by cycling the burner; if it fails, the burner may not fire or may fire insufficiently, leaving the water cool.

Question 39Heating Systems and Equipment

A steam boiler has a sight glass showing a water level that is surging and fluctuating widely during operation. What is the most likely cause?

  1. A faulty low-water cutoff
  2. Insufficient boiler water
  3. An oversized steam trap
  4. A dirty or oil-contaminated boiler water Correct answer.

Explanation

Surging water level in a steam boiler often results from impurities or oil in the water causing foaming and priming, which makes the level difficult to read.

Question 40Heating Systems and Equipment

A technician is installing a new furnace and must ensure proper combustion air. The furnace is in a confined space with two permanent openings. According to common code, what is the minimum free area required for each opening if the total input is 100,000 Btu/hr and the openings connect to a ventilated attic?

  1. 200 square inches
  2. 100 square inches Correct answer.
  3. 50 square inches
  4. 25 square inches

Explanation

For vertical ducts or openings to a ventilated attic, each opening must have at least 1 square inch of free area per 4,000 Btu/hr of input. For 100,000 Btu/hr, that is 25 square inches, but the minimum is often 100 square inches for each opening when using the standard 1 square inch per 1,000 Btu/hr rule for horizontal ducts. However, common code (NFPA 54) requires 1 square inch per 4,000 Btu/hr for vertical openings, which equals 25 square inches, but many local codes require a minimum of 100 square inches. The correct answer based on typical exam standards is 100 square inches.

Question 41Cooling and Refrigeration Systems

In a vapor-compression refrigeration cycle, what is the primary function of the compressor?

  1. It lowers refrigerant pressure before the evaporator.
  2. It removes heat from the conditioned space.
  3. It filters moisture and debris from the refrigerant.
  4. It raises the refrigerant pressure so it can reject heat at a higher temperature. Correct answer.

Explanation

The compressor increases refrigerant pressure and temperature so the condenser can reject heat to ambient air. Rejecting heat at a higher temperature than the surroundings is what makes the cycle possible.

Question 42Cooling and Refrigeration Systems

Which component in a refrigeration circuit is responsible for absorbing heat from the space being cooled?

  1. Evaporator Correct answer.
  2. Receiver
  3. Condenser
  4. Expansion valve

Explanation

The evaporator is the heat-exchange coil where low-pressure liquid refrigerant boils and absorbs heat from the surrounding air or product. The condenser rejects heat instead.

Question 43Cooling and Refrigeration Systems

What is the purpose of the metering device in a refrigeration system?

  1. To reduce refrigerant pressure and control flow into the evaporator. Correct answer.
  2. To compress refrigerant vapor before it enters the condenser.
  3. To store excess refrigerant during low-load conditions.
  4. To remove non-condensable gases from the system.

Explanation

The metering device creates a pressure drop between the high side and low side and regulates the amount of refrigerant entering the evaporator. This drop allows the refrigerant to boil at a low temperature.

Question 44Cooling and Refrigeration Systems

In a typical air-conditioning system, heat rejected by the condenser is released to what?

  1. The evaporator coil
  2. The return air duct
  3. The outdoor air or a water loop Correct answer.
  4. The suction line

Explanation

The condenser transfers heat from the refrigerant to an external medium, usually outdoor air or a water loop in water-cooled systems. That rejected heat is the sum of the space heat absorbed plus compressor work.

Question 45Cooling and Refrigeration Systems

What does the term superheat describe at the evaporator outlet?

  1. The amount a vapor is cooled below its saturation temperature.
  2. The temperature difference between condenser air in and out.
  3. The pressure drop across the metering device.
  4. The amount a vapor is heated above its saturation temperature. Correct answer.

Explanation

Superheat is the number of degrees a vapor is above its saturation temperature at a given pressure. At the evaporator outlet it confirms that all liquid has boiled off before reaching the compressor.

Question 46Cooling and Refrigeration Systems

What does subcooling measure in a refrigeration system?

  1. The oil level in the compressor crankcase.
  2. The compressor's running current versus rated current.
  3. How far liquid refrigerant is cooled below its condensing temperature. Correct answer.
  4. How far suction vapor is heated above its boiling point.

Explanation

Subcooling is the number of degrees a liquid is below its saturation temperature at the measured pressure. It is commonly measured at the condenser outlet to verify the liquid seal and charge.

Question 47Cooling and Refrigeration Systems

Why is refrigerant oil important in a compressor?

  1. It absorbs moisture from the refrigerant.
  2. It lubricates moving parts and helps seal clearances. Correct answer.
  3. It raises the evaporating pressure.
  4. It acts as a secondary refrigerant in the condenser.

Explanation

Oil reduces friction on bearings and moving surfaces and helps seal internal clearances to limit blow-by. Proper oil return to the compressor is essential for reliable operation.

Question 48Cooling and Refrigeration Systems

What is the main purpose of a filter-drier in a refrigeration circuit?

  1. To reduce compressor discharge temperature.
  2. To regulate superheat at the evaporator.
  3. To trap debris and absorb moisture from the refrigerant. Correct answer.
  4. To increase refrigerant velocity through the evaporator.

Explanation

A filter-drier removes solid contaminants and chemically absorbs moisture that could form acids or freeze at the metering device. It protects the system from blockages and corrosion.

Question 49Cooling and Refrigeration Systems

A technician measures an evaporator saturation temperature of 40°F and a suction line temperature of 52°F at the evaporator outlet. What is the superheat?

  1. 12°F Correct answer.
  2. 52°F
  3. 92°F
  4. 40°F

Explanation

Superheat equals the actual suction line temperature minus the evaporator saturation temperature. Subtracting 40°F from 52°F gives 12°F of superheat.

Question 50Cooling and Refrigeration Systems

A condenser has a saturation temperature of 110°F and the liquid line at the condenser outlet reads 100°F. What is the subcooling?

  1. 10°F Correct answer.
  2. 210°F
  3. 110°F
  4. 100°F

Explanation

Subcooling is the condensing saturation temperature minus the liquid line temperature. Subtracting 100°F from 110°F yields 10°F of subcooling.