Hvac midterm morning

The two general categories of metering devices are: (A) Fixed and modulating. B) High pressure and low pressure. C) Pressure-reducing and pressure-increasing. D) Copper and brass.

(A) Fixed and modulating.

3) The system capacity of an air conditioner with a fixed metering device: A) Is at its maximum when the indoor and outdoor temperatures are the same. (B) Decreases when the indoor wet bulb temperature rises. C) Increases when the indoor wet bulb temperature rises. D) Is fixed regardless of the indoor wet bulb temperature.

(B) Decreases when the indoor wet bulb temperature rises.

To increase superheat on a thermostatic expansion valve, the adjusting stem should be: A) Removed B) Back-seated (CTurned clockwise D) Turned counterclockwise

(CTurned clockwise

Which of the following is the standard saturated temperature drop in the suction ine? A) 2 F B) 7°F C) 12°F D) 0 F

A)2

1) For which of the following measurements is area used? A) Depth B) Sarfaces ) C)Volume D) Lines

B) Sarfaces

40) When applied to systems with air-cooled condensers, what is the lowest outside D35°F pressure control? ambient temperature at which balanced-port valves can typically work without head A) 15°F B) 25°F C) 45°F D) 35 F

D) 35F

Where is the suction line temperature read when adjusting a TEV? A) As close as possible to the TEV bulb B) As close as possible to the discharge service valve C) At the inlet of the evaporator D) At the inlet of the compressor

A) As close as possible to the TEV bulb.

What is the advantage of balanced-port TEVS? A) Balanced port valves can retain good control over a wider range of operating conditions. B) Balanced port valves equalize on the off cycle, making it easier converted from extemally equalized valves to internally for the compressor to start. C) Balanced port valves can be equalized simply by capping the equalizer port. D) Balanced port valves can be installed upside down.

A) Balanced port valves can retain good control over a wider range of operating conditions.

Technicians should be careful when brazing lines to evaporator coils that have preinstalled thermostatic expansion valves because the heat from brazing the lines: A) Can overheat the TEV bulb and destroy the valve. B) Alters the chemical makeup of the bulb charge and changes its physical properties C) Can catch the refrigerant on fire. D) Can weld the sensing bulb to the suction line.

A) Can overheat the TEV bulb and destroy the valve.

38) A device used to evenly distribute mixtures of liquid and vapor refrigerant leaving the TEV to multiple evaporator circuits is called a: B) Refrigerant header. A) Refrigerant distributor. D) Refrigerant junction. C) Refrigerant manifold.

A) Refrigerant distributor.

What two pieces of information are necessary to measure the TEV superheat? A) The suction line temperature and pressure B) The liquid line and suction line temperatures C) The valve body temperature and the bulb temperature D) The evaporator inlet and outlet temperatures

A) The suction line temperature and pressure.

15) A biflow expansion valve: A)designed to allow refrigerant flow in both directions. B) Can be used with two different refrigerants. C) Provides flow out of two ports simultaneously, eliminating the need for a refrigerant distributor. D) Has both a low flow and a high flow setting.

A) designed to allow refrigerant flow in both directions.

22) In an air conditioner with a fixed metering device, a decrease in the outdoor ambient causes: A) increased system superheat. B) No appreciable change in either system capacity or superheat. C) Increased system capacity. D) Decreased system superheat.

A) increased system superheat.

What are the parts of a distributor? A) nozzle, conical divider, and multiple holes around the divider cone B) A conical divider with multiple holes only C) A nozzle with multiple holes only D) A nozzle, handle, and piston with only one hole in the nozzle

A) nozzle, conical divider, and multiple holes around the divider cone

What advantages do orifice-type metering devices have over capillary tubes? A) They adjust to changing operating conditions. B )They are easy to change. C) They are more efficient. D) They equalize during the off cycle.

B ) They are easy to change.

11) Internally equalized thermostatic expansion valves: A) Are constructed so that the pressures across the needle seat are equal. BMeasure the evaporator pressure through a passageway inside the valve. C) Allow the system pressures to equalize on the off cycle. D) Can be used on any type of system.

B )Measure the evaporator pressure through a passageway inside the valve.

Refrigerant leaves the metering device: A) As a subcooled liquid. B) As a saturated mixture of liquid and vapor. C)In the same physical state that it entered. D) As a superheated gas.

B) As a saturated mixture of liquid and vapor.

Which of the following problems can be caused by restrictions in the capillary tubes? B) lOW suction pressure A) Low box temperature C) Low suction line temperature D) High suction pressure

B) LOW suction pressure

Automatic expansion valves are similar in operating concept to: A) Fixed restrictions. B) Pressure regulators. C) Manual valves. D) Electronic expansion

B) Pressure regulators.

Thermostatic expansion valves respond to changes in: A) Subcooling. B) Superheat. C) Temperature. D) Pressure.

B) Superheat.

Why is it dangerous to drill out orifices in metering devices? A) The metal is too soft to drill through. B) The orifices are conical in shape. C) The metal is too hard to drill through. D) The orifices are rectangular in shape.

B) The orifices are conical in shape.

21) Which of the following metering devices can respond to changes in system conditions? C) Fixed restriction D)Orifice A) Capillary tube B) Thermostatic expansion valve

B) Thermostatic expansion valve.

Which of the following best describes the purpose of a distributor? B) To equally distribute refrigerant A) To equally distribute superheated liquid C) To equally distribute cooling water D) To equally distribute gas

B) To equally distribute refrigerant.

47) A system with a loose TEV sensing bulb would most likely: A) Have a lower-than-normal evaporator pressure. B) Have a low superheat. C) Have a high superheat. D) Need adjusting to compensate for the poor bulb installation.

B) have a low superheat

Thermostatic expansion valves are designed to maintain a constant: A) Pressure. B) Superheat. C) Temperature. D) Flow

B) superheat

The operation of a thermostatic expansion valve can best be described A) Evaporator pressure = evaporator pressure + bulb pressure. B) Bulb pressure + evaporator pressure = spring pressure. C )Bulb pressure = evaporator pressure + spring pressure. D) Spring pressure = bulb pressure + evaporator pressure.

C )Bulb pressure = evaporator + spring pressure.

Besides distributing the refrigerant evenly, a refrigerant distributor also: A) Filters the refrigerant. B) Agitates the refrigerant to flash off as much as possible. C) Creates a pressure drop across the distributor, D) Lubricates the system by infusing small quantities of refrigerant oil.

C) Creates a pressure drop across the distributor.

A restricted inlet screen on a TEV can cause A) High suction pressure,superheat, and low subcooling B) Low suction pressure, low super heat and low subcooling. C) Low suction pressure, high superheat, and high subcooling. D) High suction pressure, high superheat, and low subcoomng.

C) Low suction pressure, high superheat, and high subcooling.

Which type of metering device used on flooded evaporators opens to admit more liquid refrigeran into the evaporator when the liquid level in the evaporator drops? A) High-side float B) Electronic expansion valve C) Low-side float D) Automatic expansion valve

C) Low-side float

Automatic expansion valves are good at maintaining a constant: A) Density. B) Viscosity. C )Temperature. D) Flow.

C) Temperature

Which metering device used on flooded evaporators opens when more refrigerant condenses,enabling the refrigerant to flow into the evaporator? A) Low-side float B) Automatic expansion valve C)High-side float D) Electronic ernancion ulı

C) high-side float

What senses the line temperature in electronic expansion valves? A) Bimetallic snap disks B) Magnetically ballasted electronic bulbs C) Thermistors D) Magnetic induction thermal energy sensors

C) thermistors

Two types of fixed metering devices are: A) Pressure-reducing and pressure-increasing. B) Copper and brass. C)Capillary tubes and orifices. D) High-pressure and low-pressure.

C)Capillary tubes and orifices.

When the heat load on the evaporator increases, the automatic expansion valve: A) Sends a signal to the electronic control board indicating the change. B) Does nothing because AEVS are not modulating devices. C)Closes to keep the pressure from increasing. D) Opens to feed more refrigerant.

C)Closes to keep the pressure from increasing.

Which type of metering device is able to respond to changes in system operations? A) Fixed valves B) Fixed metering devices C )Modulating metering devices D) Hand-operated expansion valves

C)Modulating metering devices

One operating advantage of fixed-restriction metering devices over expansion valv A) Easier to adjust. B) Higher operating efficiency. C) Improved system control. D) Can be used with low starting torque compressor motors.

D) Can be used with low starting torque compressor motors.

The most common application of the high-side float controls is: A) Freezers. B) Window units. C) Residential air conditioners. D) Large chillers.

D) Large chillers.

Why do standard-design thermostatic expansion valves need a minimum pressure drop to operate correctly? A) The internal adjustment springs have a minimum required torsion B) To ensure that the pin seats tightly during operation C) The bulb will not sense temperatures below 100 psig D) The pressure difference across the pin acts as an opening force

D) The pressure difference across the pin acts as an opening force.

9) To increase the evaporator pressure, the adjustment on top of an automatic expansion valve should be: A) Turned on. C) Turned off. B) Turned counterclockwise. D) Turned clockwise.

D) Turned clockwise.

The space in a room is measured by: A) Square feet. B) Inches. C) 9 Feet. D) Cubic feet

D) cubic feet

How can moisture in the refrigeration system affect the metering device? contact of the expansion valve bulb. operation of the metering device. A) Water will improve the thermal B) Water in the system improvesoperating of the metering device theough hidronic cooling C) Water will not affect metering device operation. D) Water can freeze up at the metering device, causing a restriction.

D) water can freeze up at the metering device causing a restriction

A TEV with a dead power element will operate: A) With a low superheat. B) With a higher-than-normal evaporator pressure. C) Correctly until an adjustment is made to the valve. D) With a high superheat.

D) with a high superheat

As refrigerant passes through the metering device, it: A) Drops in temperature but not in pressure. B) Drops in pressure, but not in temperature. C) Increases in pressure and temperature. D)Drops in pressure and temperature.

D)Drops in pressure and temperature.

What is the purpose of TEV sensing bulbs with a limited, or gas charge? A) They reduce the amount of refrigerant in the system because of the limited ch B) Gas-charged bulbs regulate better with systems experiencing liquid line flash C) They produce a maximum operating pressure at high operating superheat. D )They save on installation cost by reducing the amount of charge in the TEV br

They produce a maximum operating pressure at high operating superheat.