METERING DEVICE

1. The TXV is controlled by      Ans 

                    (A)       Coil temperature.

(B)       The difference between gas temperature and the temperature corresponding to the gas pressure.

(C)       The difference between gas pressure and the pressure corresponding to the gas tempera­ture.

(D)       Coil pressure.

2. The feeler bulb of a TXV is located      Ans 

                    (A)      Before the evaporator

(B)      After the evaporator

(C)      Midway along the evaporator

3. The three operating pressures of the TXV valve are      Ans 

                    (A)      Evaporator pressure, spring pressure, and suction pressure.

(B)      Evaporator pressure, bulb pressure, and con­denser pressure.

(C)      Evaporator pressure, spring pressure, and discharge pressure.

             (D)          Evaporator pressure, spring pressure, and bulb pressure

4. If a refrigerating system does NOT react to an ad­justment of the TXY it may be due to      Ans 

          (A)       noncondensable gases in the system. 

             (B)       insufficient condenser water flow.

             (C)       an oil-logged coil or evaporator

(D)          Excessive motor speed.

5. In a compression refrigeration system, if the capil­lary line on the remote bulb of the TXV breaks and the charge is lost, the valve      Ans 

                    (A)      Remains open.

                          (B)       operates erratically.

                          (C)       shuts off completely; closes.

                          (D)      first closes, then opens.

6. Thermostatic expansion valves are rated in      Ans 

                    (A)      Superheat settings.

(B)      Horsepower

(C)      Tons of refrigeration.

                                (D)      All the above.

7.    TXV ratings are based on       Ans 

 (A)             Slightly sub cooled liquid entering the valve.

(B)             Vapor-free saturated liquid entering the valve.

(C)             Liquid with a small amount of vapor entering the valve.

(D)             100 F sub cooled liquid entering the valve.

8.    If the feeler bulb of a TXV valve were moved to the center of the evaporator, you would get      Ans 

               (A)             More than 100 superheat.

(B)             Less than 100 superheat.

(C)             No effect on superheat.

9.     An external equalizer is used on an evaporator with a pressure drop of     Ans 

               (A)    Less than 2 pounds.

(B)    More than 2 pounds.

(C)    Less than 10 pounds.

10.   A thermostatic expansion valve with a static set­ting of 70 superheat would have a field setting of     Ans 

              (A)   7  deg superheat

B)     0  deg superheat

(C)    4  deg superheat

(D)   11 deg superheat

11.   If the bulb of a TXV is installed right after the ex­pansion valve, it is installed      Ans 

               (A)             Correctly.

(B)             Incorrectly.

(C)             In accordance with manufacture's require­ments.

12.   If you open the adjustment of a TXV you       Ans 

               (A)    Raise the suction pressure.

(B)    Lower the suction pressure.

(C)    Raise the superheat.

13.   A thermostatic expansion valve was factory set at 0 degrees superheat. How much was the field setting?       Ans 

               (A)   0-3 deg

(B)      3-5 deg

                (C)       4-8 deg

              (D)    10-15 deg  

14.   A TEV is attached to a finned evaporator coil with the bulb clamped to the suction line. In normal op­eration, the suction gas will leave this coil most nearly in the state of        Ans 

                     (A)    0-5 deg F  superheat.

                          (B)   7~10 deg superheat.

                          (C)   0~15 deg superheat.

                          (D)  15~20 deg superheat.

15.   A direct expansion cooling coil has a TXV. If the load variations are wide and subject to rapid change, the valve should be set for superheat from         Ans 

                          (A)                    1-3⁰F.

                          (B)                     3-5 deg F

                          (C)                   7~9 deg F

                          (D)                10-15⁰F.

  16.   In a refrigeration system, the bulb of the TEV is clamped in the middle of the evaporator coil. When operative the probability is that?     Ans 

                          (A) the vapor boiled off will be 100 percent saturated.

                          (B) the superheat in the evaporator will decrease.

                          (C) the superheat in the evaporator will increase.

                          (D)    the liquid leaving the TEV will be hot.

  17.   A TEV shipped from the factory has a static super­heat setting of      Ans 

(A)             3⁰F

(B)             5⁰F

(C)             7⁰F

(D)             10⁰   

18. The static setting of a TXV is set       Ans 

                                                          (A)     in the factory.

                                                          (B)     by the operator

                                                          (C)      in the field.

                                                          (D)     all of the above.

19.       What is the purpose of an external equalizer on a TEV?      Ans 

                           (A)             It lubricates the coil of the TEV.

                           (B) It equalizes the pressure in the evaporator.

                          (C) It eliminates the effect of the pressure drop across the evaporator

                          (D) None of the above

20.   Assume a TXV is set for 100 superheat. This means the gas passing the remote bulb is at~     Ans 

                    (A)    above the temperature of the evaporator refrigerant.

(B)    below the temperature of the evaporator)refrigerant.

(C)    above the temperature of the ambient~ temperature.

(D)    below the temperature of the ambient temperature.

  21.   In a particular air conditioning system using a refrigerant distributor is not necessary. In case a TXV with an external equalizer should be used when the pressure drop through the evaporator is       Ans 

                    (A)    .5 psi.

(B)    1.00 psi.

(C)    1.5 psi.

(D)    2.5 psi.

  22.   A thermostatic expansion valve in a refrigeration system      Ans 

                    (A)             Regulates the pressure in the evaporator.

(B)             Regulates the compressor pressure.

(C)             Regulates the flow of refrigerant to the precooler.

(D)             Modulates and controls the flow of refrigerant to the evaporator

  23.   If the external equalizer line of a TXV is disconnected from the evaporator, which of the following might result?      Ans 

                    (A)    No refrigeration

(B)    Excess refrigeration

(C)    Higher head pressure

(D)    Higher suction pressure

  24.   What is the highest pressure that can be exerted on a  Freon system's TXV bulb (vapor charge) with a  saturated temperature of 60 deg ,on the suction line?     Ans 

                    (A)    55

(B)    70

(C)    100

(D)    Higher

  25.   When using a TXV in a Freon system with temperature range of +40 to 0, what type charge would you use in a remote bulb?     Ans 

                    (A)    Gas charge

(B)    Gas cross charge

(C)    Liquid charge

(D)    Liquid cross charge

26. Superheat is heat added     Ans 

                          (A)      To change liquid to vapor

(B)      To raise the temperature of water

(C)      After all liquid has been changed to vapor

(D)      To increase pressure.

  27. An automatic expansion valve system on a vari­able loads causes    Ans 

                          (A)      A flooded evaporator on high loads.

(B)      No apparent change in operation.

(C)      An overloading of the compressor motor.

(D)      A starved evaporator at high loads.

  28. One main disadvantage of an automatic expansion valve is that it     Ans 

                          (A)      Requires a critical charge of refrigerant.

(B)      Is only used on domestic refrigerators.

(C)      Cannot adapt to variable loads.

(D)      All the above.

  29. A high load affects the operation of a constant pressure expansion valve by     Ans 

                          (A)      Causing overload.

(B)      Requiring an external equalizer.

(C)      Starving the evaporator

(D)      All the above.

  30. Of the following, which component is found in a direct expansion valve system?      Ans 

                          (A)      Float valve

(B)      Needle valve

(C)      Globe valve

(D)      Gate valve

  31. An expansion valve is built most nearly like a     Ans 

                           (A)      Shut-off valve.

(B)      Pressure-reducing valve.

(C)      Blow-off valve.

(D)      Double-seated globe valve.

  32. What causes the drop in temperature and pressure as liquid refrigerant passes through the expansion valve?      Ans 

                          (A)      The superheat of the refrigerant

(B)      The change in the rate of flow of the refrig­erant

(C)      The partial evaporation of refrigerant as it passes through the valve

(D)      The temperature and pressure of the refriger­ant in the liquid line

  33.   The subcooling effect of a liquid refrigerant just before the expansion valve would result in     Ans 

                         (A)           Increased refrigeration effect.

                (B)           Increased refrigerant density.

               (C)           Increased miscibility of the oil.

               (D)     None of the above.

  34.   The automatic expansion valve maintains constant pressure at the     Ans 

                        (A)     Condenser inlet.

               (B)     Evaporator inlet.

              (C)     Liquid line.

             (D)      Condenser outlet.

  35.   Which of the following is also referred to as a backward operating valve'?      Ans 

                     (A)    Thermal expansion valve

           (B)     Hand expansion valve

           (C)     Low side float

          (D)     Automatic expansion valve

  36.   What controls the operation of a high-side float?     Ans 

                   (A)           Accumulator

          (B)           Evaporator

         (C)           Condenser and receiver

         (D)           Evaporator and condenser

  37.   In a high-side float, frost on the suction line indi­cates     Ans 

                  (A)           Recharging the refrigerant is necessary.

             (B)    an excessive amount of refrigerant is in the system.

         (C)        Noncondensibles are in the system.

         (D)        There is a leak in the system.

  38.   On a refrigeration system with a high-side float-metering device, what happens if the float fills with liquid refrigerant and sinks?     Ans 

                 (A)     The evaporator starves.

        (B)     The evaporator floods.

        (C)     The compressor stalls.

        (D)     The condenser starves.

  39.   In a flooded evaporator using an accumulator and float valve, flash gas    Ans 

                 (A)     Passes directly into the evaporator

        (B)     Passes directly into the suction line.

        (C)     Does not occur

        (D)     Stays in the receiver

  40. A flooded system with a low-side float uses a ther­mostat that controls the liquid tine solenoid valve. The thermostat is satisfied and the room continues to cool down due to      Ans 

                           (A)      A drop in head pressure.

(B)      The pumping out of the low side.

(C)      All the above.

(D)      None of the above.

  41. One advantage of a tow-side float system is that it       Ans 

                          (A)      Requires a large amount of refrigerant.

(B)      Can be used with a water-cooled condenser

(C)      Eliminates flash gas in the evaporator

(D)      Can be used with a low starting torque mo­tor

  42. One disadvantage of a low-side float valve is that it       Ans 

                          (A)      Is nonadjustable.

(B)      Requires a large amount of refrigerant.

(C)      Is very expensive.

(D)      Cannot be used on multiple systems.

  43. In a flooded system, a low-side float is used as a metering device. If the float fills with liquid refrig­erant and sinks, this     Ans 

                           (A)      Starves the evaporator

(B)      Floods the evaporator

(C)      Stalls the compressor

(D)      Raises the evaporator temperature.

  44. Flash gas forms in the     Ans 

                          (A)      Compressor

(B)      Condenser

(C)      Evaporator

(D)      Heat exchanger

  45. The flash gas loss at the expansion valve is ap­proximately      Ans 

                          (A)      2 percent.

(B)      5 percent.

(C)      22 percent.

(D)      12 percent.

  46. What does a high superheat mean?       Ans 

                           (A)      Hooded evaporator

(B)      Starved evaporator

(C)      Pressure increase

(D)      Motor speed too high

47.   What does a low superheat indicate?       Ans 

                    (A)    Flooded evaporator

(B)    Starved evaporator

(C)   Pressure increase

(D)    Motor speed too low

  48.   An R-12 refrigeration system has a gas-charged thermostatic expansion valve. The standard maxi­mum operating pressure (MOP) for this valve at 600 F, saturated evaporator pressure, is      Ans 

                      (A)    55 psig.

 (B)    70 psig.

 (C)    lOO psig.

 (D)    150  psig.

  49.   Which of the following distributors are not used with an external equalizer thermostatic expansion valve'?     Ans 

                     (A)             Manifold type

(B)             Venturi type

(C)             Centrifugal type

(D)             Pressure-drop type

  50.   Thermal expansion valves are generally rated at stated suction temperatures in      Ans 

                    (A)    Tons of refrigeration effect.

(B)    Pounds per minute of refrigerant pumped.

(C)    Pounds per hour of refrigerant pumped.

(D)    Cubic feet per minute pf refrigerant pumped

  51.    An electric expansion valve that operates with a heater motor and a thermistor has a control volt of      Ans 

                    (A)    6 volts.

(B)    12 volts.

(C)    24 volts.

(D)    110 volts.

  52.   On an operating electric expansion valve, if the thermistor senses superheat on the suction line. result is      Ans 

                    (A)    It modulates to the closed position.

(B)    It throttles to the open position.

(C)    Insulation at the thermistor stabilizes the valve.

(D)    It increases the resistance to the heater mo­tor