What phase is this class?
8
r- 404a is sold in what colored tank?
Orange
What is the nominal size of pipe or tubing?
The approximate inside diameter
What material is most commonly used today for hot water piping in houses?
CPVC
Copper tubing that comes in rigid, straight lengths is called?
Hard copper
The outside diameter of schedule 40 black iron pipe is approximately?
1/4 inch larger than the pipe's nominal size
What material is used for natural gas piping?
Iron pipe
What material is used for refrigerant piping heating, air conditioning, and refrigeration systems?
Copper tubing
What is the difference between a flare for an R-410A system and a flare for an R-22 system?
Flares for R-410A systems have a larger cone
What material is used for air conditioning drain line?
PVC
What material is most commonly used today for cold water piping in houses?
PVC
What is galvanized iron pipe?
Galvanized iron pipe is dipped in zinc to make it resistant to corrosion
Why are pipe threads tapered?
The taper allows pipe threads to tighten and seal..
The preferred tool for cutting PVC pipe is?
A plastic tubing shear.
What is the purpose of annealing copper tubing?
To allow the tubing to be formed without cracking or buckling.
Hard copper tubing can be joined by?
Soldering and brazing.
ACR copper tubing is...?
Type L, dehydrated copper tubing.
The preferred method of cutting copper tubing for a refrigeration system is with?
A tubing cutter
Types of copper tubing in order of wall thickness from light to heavy are?
M, L, and K
The most accurate dimension on pipe and tubing is?
The outside diameter
What is the difference between schedule 40 and schedule 80 iron pipe?
Schedule 80 has a heavier wall than schedule 40
What is it recommended that an acetylene cylinder valve never be opened more than 1/2 turn?
To allow rapid shutoff in the case of an accident
Why are acetylene cylinders only used in the upright position?
To prevent acetone from being pulled out of the cylinder
How can technicians protect themselves from hot sparks produced by most welding processes?
Wear heavy protective clothing, gloves, and eye protection
What is the difference between welding and brazing?
The base metal is melted in welding and not during brazing
What are the two most common sizes of oxygen cylinders used in HVAC/R trades?
22ft cubed and 55 ft cubed
What material should clothes worn during welding be made of?
100% cotton
What is the advantage of an oxyacetylene torch compared to an air acetylene torch?
It is a more intense flame that heat the parts faster
Why are face shields worn during arc welding?
To protect from the strong UV light
Why is it illegal to operate a torch with an acetylene pressure greater than 15 PSI?
Risk of explosion
What are the two most common sizes of acetylene cylinders used in HVAC/R
MC and B cylinders
The difference between brazing and soldering is:
Brazing occurs at higher temperature than soldering
Why are the stubs on compressors and filter driers harder to braze than copper pipe?
They have a thin copper coating that is easily oxidized my overheating
Common welding processes for joining sheet metal include:
Resistance spot welding and gas metal arc welding
What procedure is used when heating a brazed copper joint?
Heat the fitting first then heat the pipe
Why are air acetylene, air mapp, or air butane torches preferred over oxyacetylene for copper pipe?
Oxyacetylene can easily over heat the pipe.
Oxyacetylene torches cut metal by:
A high pressure stream of pure oxygen oxidizes the heated metal.
What is the purpose of the acetylene and oxygen regulators?
to reduce tank pressures and maintain steady pressures.
Electrical connections are soldered with?
Electric soldering iron
Why are copper fittings cleaned before brazing
To remove oxides
What type of energy is used to circulate refrigerant in an absorption refrigeration cycle?
Heat
Based on evap coil temp, what are 4 areas the commercial refrigeration equipment is grouped into?
High, Medium, Low and cryogenic temps
A fluid cooled by direct refrigeration is used to transfer cooling to a distant area when cooling is needed is:
Secondary refrigerant
What is the advantage of using multiple compressors on a supermarket rack system?
System capacity can match refrigerant loads which vary greatly
When a cascade system starts:
the high stage compressor starts 1st to lower the evap temp before starting the low stage compressor.
Why is a check valve installed in the suction line of the lowest temp coil in a multiple evap system?
To prevent refrigerant migration from the higher temp and pressure coil to lower temp and pressure coil.
A system that achieves extremely low evap temps by using the evap of one refrigeration system to cool the condenser of another refrigeration system is called:
A cascade system
Evaporative cooling is commonly used in commercial applications in:
Greenhouses
What is expendable refrigerant?
Refrigerant that is released to the atmosphere after the cooling operation is completed.
What refrigeration component makes it possible to use a single stage compressor to control multiple cases of different temps?
Evaporator pressure regulator
What is the normal storage temperature for food items like milk, cheese, fresh fruits and vegetable?
From 32 degrees to 40 degrees fahrenhait
Using multiple parallel compressors makes the use of multiple refrigerants possilbe
Compound multistage compressor system
The lowest evaporator coil temperature that traditional mechanical compression systems can attain is approximately?
-40 degrees fahrenhait
A system that maintains temperatures of -250F and below is a
Cryogenic system
What component is used between stages of a compound compression system?
An intercooler
When multiple compressors are installed in parallel on the same refrigeration system, provisions must be made to insure that?
The oil level is correct in all compressors
Three common methods of controlling evaporator temperature are
Conventional thermostat, a suction pressure cut-out control, or an evaporator pressure regulator
What is the purpose of the door switch on a walk in freezer?
To prevent warm air from entering the case by shutting off the fans when the door is opened.
The defrost cycle is normally terminated?
Based on either temperature, pressure, or time
When a reach in cooler or freezer is not located near a drain evaporator condensate is....
Drained into a heated pan which evaporates the water
The components of a self contained system
Are all selected and assembled by the equipment manufacturer
How is the refrigeration system powered on the trailer mounted systems?
A separate diesel engine
Defrost on a medium temperature case is normally accomplished
By leaving the case fans operating and shutting off the compressor
A refrigerated case that maintains a temperature of 28 degrees would be classified as?
A medium temperature system
Why does compressed air require a drier?
Compressing the air raises the saturation temperature and dew point of the air
Which type of compressors is NOT normally used on liquid chillers?
Rotary
Defrost on a low temperature case is normally accomplished?
By shutting off the compressor and energizing electric defrost heaters
The normal fluid temperature drop through a chiller is
10 degrees fahrenhait
A built-up refrigeration system has system components that
Are all selected and assembled by the installing contractor
The first step in selecting commercial refrigeration equipment for a new install is to
Perform a heat load calculation to determine the required BTU capacity of the system
Products for refrigerated food-storage can are listed in three different groups by physical construction and size as being
small, medium, or large
Why would a 35 degree Fahrenheit medium temperature case need to defrost?
The coil temperature for a 35 degree Fahrenheit box operates below freezing
What type of systems normally use crankcase pressure regulators?
Low temperature refrigeration applications such as walk-in and reach-in freezers
What does an evaporator pressure regulator do?
It will not allow in the evaporator pressure to drop below its setpoint, even if the suction pressure is low
What does a crankcase pressure regulator do?
It will not allow the compressor suction pressure to rise above the CPR setpoint
A suction-to-liquid line heat exchanger
Increases both superheat and subcooling
What is the switching action of a fan cycling head pressure control?
Close on pressure rise
Which refrigeration device would most likely be installed in the discharge line leaving the compressor to prevent liquid refrigerant from draining from a raised condenser into the compressor head?
A check valve
Moisture indicators are normally part of
A sightglass
Where in the system is an oil separator installed?
In the discharge line leaving the compressor
In most commercial refrigeration systems, most of the excess refrigerant that is not being used is stored in
The liquid reciever
A flow control device that stops or allows the flow of a refrigerant in a refrigeration system based on an electric signal in
A solenoid valve
High side pressure can be maintained on a water-cooled condenser using
A water regulator valve
Why is it necessary to have controls for maintaining a minimum high side pressure on outdoor aircooled condensers?
Refrigeration metering devices require a minimum pressure drop to operate
The advantage of ball valves over other types of manual refrigeration valves is that they
Offer less resistance to flow
What is the advantage of using restaurant refrigeration systems with remote condensing units instead of self contained units?
The equipment does not add heat to the kitchen
Refrigeration capacity is unaffected, but the food hydration cycles are decrease
Medium temperature multi-deck open display cases
Compared to a traditional rack system, a protocol system
Has less refrigerant piping
How does increased store humidity affect the operation of the refrigerated cases?
Operating time increases and efficiency decreases due to increased coil frosting.
How does air from air conditioning vents affect open display cases?
It disrupts the case's air curtain, causing them to rise in temperature.
Typical low temperature supermarket rack systems maintain a saturated suction temperature of?
-25 degrees
How do open display cases maintain the temperature within the case without any doors?
A curtain of cold air separates the product from the warmer store air.
Why is it important for open display cases to be loaded according to the manufacturer's instructions?
Incorrect product placement can disturb the case's air curtain.
Compare the installation cost of multiple cases with a separate condensing unit for each refrigerated case versus a rack system.
The rack system generally will have a lower installed cost.
Besides maintaining the proper temperature, all draft beer dispensers must be able to....
Maintain the keg pressure and be easily cleanable.
What type of compressors do protocol refrigeration systems use?
Hermetic reciprocating
Why does some carbon dioxide gas need to be added to a draft beer system?
To maintain the pressure required to dispense the beer.
To manually defrost a frozen evaporator coil, technicians should...
Use a heat gun to accelerate the melting of the ice.
The coil of a current relay used with small single phase compressors should have a resistance of approximately?
1 ohm
When checking the resistance of the compressor start winding, the technician's multimeter shows?
The winding is open
When troubleshooting single phase compressor motors, it is important that the technician....
Check the start relay, start capacitor, and run capacitor
To check for electrical potential at a switch or a load, technicians use a
Voltmeter
A reciprocating compressor with leaking valves will operate with?
A low amp draw, high suction pressure, and low head pressure.
Why should the temperature inside the compressor be kept under 300 degrees fahrenhait
Because the compressor oil starts to break down above 300 degrees fahrenhait
Where is an EPR located
Downstream from the evaporator