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discuss the procedure for a burn victim in the vicinity of energized electrical equipment
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what would provide the best protection from gas leaking from a refrigeration unit?
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Basic Refrigeration

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QuestionAnswer
discuss the procedure for a burn victim in the vicinity of energized electrical equipment secure power, check vitals, provide comfort
what would provide the best protection from gas leaking from a refrigeration unit? SCBA
Define a refrigeration ton. 1200 BTU per hour.
describe the heat gained per. pound of refrigerant in the evaporator. refrigeration effect
describe total heat. latent & sensible = total
what kind of heat causes a change in temp sensible heat
describe the heat compression. heat removed by condenser from refrigent
define latent heat change in state
what is specific heat heat required per. unit mass to change one degree
define sensible heat molecular motion seen on a thermometer.
In the refrigeration cycle, where will we find superheated vapor? Inlet outlet of compressor
What is the metering device in a refrigeration system? TXV = saturated liquid vapor mix
Describe the refrigerant when it leaves the metering device of the system. Reducing flash gas
Why due we sub cool the refrigerant prior to the TXV? To increase refrigerant effect by reducing flash gas.
What does the pressure in the control tubing of a TXV spend on? Superheat in the tail coil.
Describe the condition when liquid is forced back to the compressor. Flood back (liquid returning to the compressor)
Where does the refrigerant absorb the latent heat of vaporation? Evaporator.
Describe where the latent heat of condensation is removed. Condenser.
What PPE should be worn when handling contaminated oil? Rubber gloves.
Define liquid slugging. Liquid coming back to compressor from evaporator.
What is short cycling? Frequent starting & stopping in a compressor.
If some refrigerants are burned, what is the result? Odor,compressor burn out ,contamination in oil.
Describe the methods to determine if there is moisture in the refrigerant. Color change in the moisture indicator.
Why do we install sight glass in the liquid line? To see moisture, state of change.
What causes frost on the compressor suction line? TXV (metering device) stuck open.
What causes the crankcase to sweat? Flood back (liquid return to compressor)
What do you check first when the compressor doesn't start? Power, fuses
What will result from the oxidation of the lube oil due to overheating? Sludge
What causes crankcase oil to foam? Refrigerant boiling out of solution with the oil
What do we do to prevent flashing in the liquid line? Sub cooling in condenser.
When does an automatic compressor restart? Suction pressure increases.
What causes the low pressure cutout switch to actuate? Low refrigerant pressure.
What will happen if excessive foam occurs in the crankcase? Bearing over heating.
What will cause the release of refrigerant from the oil/refrigerant mixture? Sudden reduction of pressure at start up.
Define the refrigeration system between the expansion value & the compressor. Low side
What components separate the high side from the low side? Compressor, metering device
What does the compressor do? Circulate refrigerante
What will cause the suction line temperature to increase? Heat load increase
What occurs to the temperature of the refrigerant as it passes through the TXV? Decreases to the lowest point
What will most likely occur if the evaporator coil becomes covered with frost? Short cycle
What would cause high head pressure at the compressor Dirty condenser coils
What will prevent the compressor from starting? low refrigerant level will not cause L/P switch to acturate
What problems are assoc. with excessive circ of the lubricating oil with the refrigerant? Evap temp will rise, too much oil in the system
Describe the operation of a refrigeration unit that is low on refrigerant? Frequent cycling continuous starting
List the methods to determine if a unit is low on refrigerant Bubbles in the sight glass
Describe the procedure to add refrigerant to the low side of an A/C system. Add as a vapor to the suction side service value.
Describe the procedure for charging refrigerant. purge charging line
What are the sources of moisture in a low pressure refrigeration system? leaking tubes
Describe the procedure for admitting fresh air to a HVAC for the greatest efficiency. As little as possible for proper ventaliation
What is the purpose of dehumidifiers in an A/C system? Remove moisture
What type of refrigerant is R-12 CFC
The ozone layer protects the earth from UV
What chemical found in the upper stratosphere indicate that the ozone layer is being destroyed Chlorine Monoxide
The state of the refrigerant leaving the condenser of a refrigerant system is? h/t, h/p sub cooled liquid
Refrigerant entering the compressor of a refrigeration system is a : L/T, L/P superheated vapor
Refrigerant entering the metering or expansion device of a refrigeration system is a : H/T, H/P, sub cooled liquid
The low pressure gage is color coded Blue
The component that changes a low pressure vapor to a high pressure vapor is: Compressor
When heat is moved, the temp of the substance it moved from: Drops
List the components that are contained in all mechanical refrigeration. Metering Device, Evaporated, Compress, Condenser
List the four basic categories for the use of mechanical refrigeration Comfort, Refrigeration, Process, Cryogenics (low temp work)
As the temp of any substance increase, the molecules which make it up vibrate: Faster
When a substance changes state from a liquid to a gas, the spacing of its molecules: Increase greatly
One pound of refrigerant will take up the most space in what state Gas
List several good thermal insulator & therefore poor conductor? Polystyrene = poor conductor Copper, Aluminum = good thermal insulator
To the refrigerant technician the most important type of heat is: Latent
As 32°F liquid water is heated we witness: Sensible, Latent, Sensible
A fluid (liquid or gas) is called saturated when: It contains all the heat it can w/out change of state
In terms of refrigeration language, the water we drink is: Sub cooled
The difference between a D-X coil & a cooler is: D-X coil = cools air A Coolers = cools liquid
Your electric temp probe shows that the temp of the refrigerant in an evaporator is 40°F. It's condition is: Need the pressure to determine refrigerant condition
Describe the shell on a chiller Casing that encloses the evaporator & condenser
Created by: Rafael Leon
 

 



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