Air Conditioning & Refrigeration Technologies
Unit 21 Low temperature food storage applications typically have a temperature range of ________.
*0 to -20 °F*
Unit 22 For every 1 degree rise in suction gas temperature returning to the compressor, there will be a _____ degree rise in the compressor's discharge temperature.
*1*
Unit 24 The four types of TXV bulb charges are:
*1.- Vapor, 2.- vapor cross, 3.- oil, and 4.- oil cross*
Unit 7 Describe each part of the third dimension 1/4 -18 NPT
*1/4 pipe and 18 thread*
Unit 7 What elements make up the metal alloys for brazing filler
*15 to 60% silver*
Unit 7 A common filler material used for brazing is composed of
*15% to 60% silver*
Unit 7 In what size rolls are is soft copper usually available?
*25 ft of 50 ft, diameter 3/16 in to 7/8 in* (It can be special ordered in 100 ft lengths)*
Unit 23 What would be considered a higher-than-normal temperature for a discharge gas line on a reciprocating compressor?
*250°F*
Unit 21 A medium-temperature refrigeration box operates within what temperature range?
*28°F to 40°F*
Unit 23 At what speeds in rpm does a hermetic compressor normally turn?
*3450*
Unit 24 The spring tension on a TXV is factory set for a predetermined superheat of _____ °F.
*8 - 12*
Unit 22 On a system that uses condenser flooding to control head pressure during low ambient conditions, the receiver should be sized so that it is ___________.
*80% full when it contains the entire system charge*
Unit 21 A refrigerant system's evaporator typically runs about _______________ degrees of superheat.
*8°F - 12°F*
Unit 7 One way to reduce the number of solder joints used in a piping system is to use _________.
*A tubing bender to reduce the number of fittings used*
Unit 22 Low ambient controls are used on ___________ to maintain head pressure during low ambient conditions.
*Air-cooled condensers*
Unit 24 A TXV with a liquid charged bulb is usually limited to ____________.
*Applications that have a narrow operating range*
Unit 24 Conditions such as large varying head pressures, widely varying evaporator loads, and very low liquid-line temperatures can be controlled by a(n) _________ TXV.
*Balanced-port*
Unit 21 When liquid refrigerant floods the compressor crankcase, the oil level in the crankcase can drop causing _______.
*Bearing washout*
Unit 23 Open-drive compressors are manufactured in two styles, ____________.
*Belt drive and direct drive*
Unit 7 When copper is cut using a tubing cutter, excess material, called a ________, may be pushed back into the tubing by the cutting wheel.
*Burr*
Unit 24 The _______ does not control superheat, is a fixed-bore device with no moving parts and cannot adjust to load changes.
*Capillary tube*
Unit 21 Refrigerant in the evaporator
*Changes from liquid to vapor*
Unit 7 A type of plastic pipe used in HVAC/R applications that can be used with temperatures up to 180°F at 100 psig is _____________.
*Chlorinated polyvinyl chloride* (CPVC)
Unit 7 Describe the steps for making a good soldered copper tubing/fitting joint.
*Clean the end, then apply Flux. Flux is used to minimize oxidation while the joint is being heated*
Unit 22 A device that passes outside air over water to remove the system heat is a ________
*Cooling tower*
Unit 22 Natural draft, forced draft, and evaporative are all types of __________.
*Cooling towers*
Unit 22 Common construction materials for air-cooled condensers are:
*Copper, steel, and aluminum*
Unit 23 A _________ in a reciprocating compressor transmits the circular motion of the rods into a back-and-forth motion for the pistons.
*Crankshaft*
Unit 21 A low evaporator superheat indicates
*Dirt buildup*
Unit 23 _________ compressors are refrigeration compressors that are available with capacity modulation from 10% to 100%.
*Discus*
Unit 24 The controls of a(n) ____________ use algorithms, a set of electronic instructions, and a proportional integral derivative (PID) controller.
*Electronic expansion valve (EEV)*
Unit 21 The difference in temperature between the boiling refrigerant temperature and the evaporator outlet temperature is known as ___________.
*Evaporator Super-heat*
Unit 24 The bulb of the TXV is mounted on the
*Evaporator outlet*
Unit 24 The three pressures that act to open or close a thermostatic expansion valve (TXV) are _____________ pressure.
*Evaporator, bulb, and spring*
Unit 22 Air-cooled condensers are much more efficient than water-cooled condensers.
*False*
Unit 22 Fan cycling, air shutters or dampers, condenser flooding, and variable-speed (VFD) condenser fan motors are all methods for controlling head pressure in water-cooled condensers.
*False*
Unit 23 A compressor can compress a liquid.
*False*
Unit 22 Any refrigerant receiver should be able to hold all of the system's charge and still have a 25% vapor head for safety.
*False* (Head Pressure Controls)
Unit 22 Condensing temperatures can be reduced by reducing the condenser surface area.
*False* (High-Efficiency Condensers)
Unit 21 Natural-convection evaporators use a blower to force or induce air over the coil to improve the efficiency of the heat exchange.
*False* (Types of Evaporators)
Unit 21 When a refrigerated space has been allowed to warm up considerably, the system must ________.
*Go through a hot pulldown*
Unit 21 Low-temperature evaporator coils __________.
*Have fewer fins per inch than medium temperature evaporator coils*
Unit 22 Condenser flooding is accomplished by _____________ in both mild and cold weather to keep the head pressure constant.
*Having enough refrigerant in the system to flood the condenser*
Unit 24 Which is not a pressure or force acting on a TXV diaphragm?
*Head pressure*
Unit 23 The two housings used for reciprocating compressors are ___________.
*Hermetic and open*
Unit 21 Two common methods for defrosting a low temperature evaporator are __________.
*Hot gas and electric heat*
Unit 7 The size of 1/2 in. would refer to the _________ with regard to copper tubing used in plumbing and heating.
*ID* (inside diameter/ nominal)
Unit 23 What would be done *to increase* the compressor speed on a belt-driven compressor?
*Increase drive pulley size*
Unit 21 When an evaporator experiences a heat-load increase, the suction pressure
*Increases*
Unit 24 The TXV responds to an increased heat load by
*Increasing refrigerant flow*
Unit 7 The standard weight of copper tubing used most frequently in the heating and air-conditioning industry is
*L* (K is the heaviest used for plumbing and heating, M is the lightest, not commonly used and DWV is drain, waste, vent)
Unit 7 ACR copper tubing can be purchased in bundles called __________.
*Line sets*
Unit 21 Flooded evaporators use a(n) ____________ type of expansion device.
*Low-side float*
Unit 7 Describe the procedures for cutting tubings with a tube cutter
*Most often used with soft tubing and smaller diameter. Place the tube in the cutter. Make sure that the cutter is tight. Make sure that it is moderate pressure being applied by the cutter.* (Hacksaws can be used for hard-drawn tubing)*
Unit 7 The size of 1/2 in. would refer to the _________ with regard to ACR copper tubing.
*OD* diameter (ACROD)
Unit 21 Flooding the compressor crankcase with liquid refrigerant can cause ________.
*Oil foaming*
Unit 23 What lubricates the refrigeration compressor?
*Oil*
Unit 23 Which style of compressor uses belts to turn the compressor?
*Open drive*
Unit 7 What is the most common cause of leaking compression fittings?
*Overtightening the compression nut*
Unit 23 The part of the cylinder assembly that is exposed to high-pressure gas during compression is the _________.
*Piston*
Unit 7 Describe the procedure for preparing and threading the end of steel pipe?
*Place the die over the end and make sure that the lines up square with the pipe. Then apply cutting oil to the pipe and turn the die once or twice. Then reverse the die one- quarter. Then rotate the die one or two more turns. Make sure that the pipe is flushed.*
Unit 7 An alternative method used to join pipe that uses manufacturer-specific fittings and tools is called ________.
*Press-on*
Unit 22 A __________ can be piped into the high-side of the system to cycle the condenser fan on and off during a low ambient condition.
*Pressure control*
Unit 24 An automatic expansion valve (AXV) is designed to maintain a constant _________ in the evaporator.
*Pressure*
Unit 7 A __________ is used to remove burrs from the inside of a pipe after it has been cut.
*Reamer*
Unit 23 Which compressor type uses pistons to compress the gas?
*Reciprocating*
Unit 7 The portion of a compression fitting that actually tightens against the tubing to create the leak-free seal is the....
*Ring or ferrule*
Unit 23 Which compressor type uses tapered, machined gear components to trap the gas for compression?
*Screw*
Unit 23 A compressor that has few moving parts, operates quieter than other models and at a higher efficiency is a ____________ compressor.
*Scroll*
Unit 21 When the evaporator removes heat from the air and lowers the temperature of the air, _________.
*Sensible heat is removed from the air*
Unit 7 Describe the procedures for making a flare for joining copper tube
*Slip flare nut over the end, clamp the tube in the flaring, yoke over the flaring block, turn the valve screw down the firmly and inspect flare.*
Unit 7 Why are some ACR tubing lines insulated?
*Some ACR tubing lines are insulated so, that they prevent heat transfer between the fluid in the pipe and the surrounding air. It also prevents condensation from forming on the lines*
Unit 24 The needle and seat of a TXV are normally made of .
*Stainless steel*
Unit 21 The sensible heat that is added to a saturated vapor after all of the liquid has boiled away is referred to as
*Superheat*
Unit 24 The TXV tries to maintain a constant ______ in the evaporator.
*Superheat*
Unit 7 A _______ can be used to join two copper pipes that are to be brazed or soldered.
*Swage*
Unit 7 What type of solder is suitable for moderate temperatures and pressures?
*The type of solder that is suitable for moderate temperatures and pressures is the solder alloy that contains 15% to 60% silvers and alloys that contains phosphorus.*
Unit 21 What is the function of the evaporator in the refrigeration system
*To act as a heat exchanger between air and refrigerant*
Unit 7 When soldering, a flux is used to
*To minimize oxidation while the joint is being heated*
When soldering, a flux is used?
*To minimize oxidation while the joint is being heated*
Unit 24 Factors that can affect the capacity of a TXV are the evaporator temperature, pressure drop across the valve, and temperature of liquid entering the valve.
*True*
Unit 7 The main function of flux is to prevent oxidation from forming on the surface of the tubes being joined.
*True* (Fluxing)
Unit 21 When moisture is removed from the air, latent heat is removed.
*True* (Removing Moisture)
Unit 7 Each V-shaped thread on a steel pipe should have a 45° angle and a taper of 1/16 inch per inch.
*True* (Steel and Wrought Iron Pipe)
Unit 7 Lever and spring are two types of ___________.
*Tubing benders*
Unit 7 Tubing used for air-conditioning installations is usually installed at
*Tubing used for air-conditioning installations is usually installed at low-pressure side*
Unit 23 Two things in the design of a reciprocating compressor that directly affect its efficiency are:
*Valve design and clearance volume*
Unit 23 The ________, located between the head of the compressor and the top of the cylinder wall, holds the suction and discharge flapper valves.
*Valve plate*
Unit 24 A TXV with a ______ charge bulb, sometimes referred to as a critical charge bulb, is often called a maximum operating pressure (MOP) valve.
*Vapor*
Unit 22 __________ systems use water once, it is then piped to a drain.
*Wastewater*
Unit 22 The type of condenser that has the lowest operating head pressure is the _________ cooled condenser.
*Water*
Unit 22 A cooling tower's capacity is governed by what aspect of the ambient air?
*Wet-bulb temperature*
Unit 7 Describe procedures for bending soft copper tubing?
*You can bend the soft copper by hand, whereas larger tubes cannot be bent by hands. Instead, you have to use tools such as tube bending springs or lever type bending tool.*
What is the most common cause of leaking compression fitting
*overtightening*
Unit 23 Connecting rods connect the crankshaft to the valve plate.
False *(Reciprocating Compressor Components)*
Unit 24 The external equalizer line should always be piped to the suction line before the expansion valve sensing bulb.
False *(TXV Function with External Equalizers)*
Unit 23 In a scroll compressor, there are no volumetric losses through gas re-expansion as with piston-type compressors.
True *(New Technology in Compressors)*
Unit 23 Scroll compressors can use radial movement, which allow the compressor to handle small amounts of liquid.
True *(New Technology in Compressors)*
Unit 24 An external-equalized TXV must always be installed when a refrigerant distributor is used because of the distributor's large pressure drop.
True *(TXV Function with External Equalizers)*
Unit 7 List the procedures used when setting up, igniting, and using and air-acetylene unit.
a). *Free the dirt,* b). *connect the regulator,* c). *make sure that torch handle valve is closed*
