This morning I thought we could test your knowledge on the basics of refrigeration and charging practices. I have listed the answers at the bottom ot the page. GOOD LUCK!
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Refrigeration is defined as “the movement of heat from a place it is not wanted to a place it is unobjectionable”.
T F
It is possible to cool air in a house.
T F
Heat flows from:
Cold to hot
Hot to cold
Left to right
Up to down
Another name for evaporator side pressure is:
High side pressure
Low side pressure
Discharge pressure
Head Pressure
Another name for condenser side pressure is:
Low side pressure
Discharge pressure
Back pressure
Static pressure
Which of the following is untrue about the compressor:
Is the heart of the system
Creates the pressure differences necessary between the low and high sides of the system
Pump liquid only
It raises the pressure and temperature of the refrigerant vapor above the ambient temperature
The high and low pressures in a refrigeration system are separated by:
The receiver.
The evaporator.
The metering device.
The filter drier.
The pressure at which the refrigerant changes state from a vapor to a liquid is the:
Evaporation pressure.
Superheat pressure.
Back pressure.
Condensing pressure.
All of the above.
A pressure gauge placed anywhere between the metering device and the compressor (including the compressor crankcase) will read:
The low side or evaporating pressure.
The head pressure.
The total high pressure.
All of the above.
Modern refrigerants exists either in:
The vapor state.
The liquid state.
Answers (a) and (b) are true.
None of the above.
In an operating system, you should have liquid and vapor in the:
Evaporator only.
Condenser only.
Compressor
Evaporator and condenser.
Refrigerant “Conditions” refer to which of the following?
Saturated, superheated, or subcooled.
Pressurized only.
In a complete vacuum.
None of the above.
The heat energy that causes a liquid refrigerant to change to a vapor at a constant saturation temperature for a given pressure is referred to as:
Sensible heat.
Latent heat (hidden heat).
Superheat.
Subcooled.
The temperature/pressure chart is only good when the refrigerant is:
In the liquid state only.
In the vapor state only.
In the superheated state only.
In the liquid and vapor mixed.
Superheat always refers to:
A liquid refrigerant.
A vapor.
A mixture of liquid and vapor.
Both (a) and (c).
Subcooling always refers to:
A vapor below its saturation temperature.
A liquid below its saturation temperature.
The refrigerant that cools the compressor.
The flashing of refrigerant at the metering device.
The basic components of a refrigeration unit are:
Compressor, discharge line, condenser, metering device, receiver, evaporator and suction line.
Filter drier, receiver, high and low sides.
Condenser, discharge line, condenser, metering device, receiver, and suction line.
Compressor, metering device and refrigerant.
In the first few passes of the condenser:
The refrigerant should be de-superheated.
The refrigerant should completely change to a vapor.
The refrigerant should completely change to a liquid.
The pressure should drastically drop.
One of the main functions of a condenser is to:
Change the liquid to a vapor.
Superheat the liquid.
Change the refrigerant vapor to a liquid.
Both a and b.
Subcooling can be defined as:
The cooling effect of an evaporator.
Any sensible heat taken away from 100% saturated liquid.
The superheat that is removed at the top of the condenser.
The cooling of the compressor motor by returning refrigerants.
The component in the refrigeration system used to catch and prevent any liquid from entering the compressor is called the:
The liquid receiver.
The accumulator.
The Bypass solenoid valve.
The filter drier.
The greatest advantage of a TXV over a capillary tube or fixed metering device is:
The cost factor.
The capillary tube can adapt to the load quickly.
The TXV can adapt to the load very quickly.
The TXV can completely stop the refrigerant flow.
The greatest need for “subcooling” the refrigerant is to:
Prevent liquid line flash, thus making the system much more efficient.
Cool the refrigerant suction line.
Prevent liquid from entering the compressor.
To store liquid in the filter drier.
The purpose for a Liquid Pressure Amplification LPA is to:
Increase the superheat.
Increase the liquid pressure.
Help prevent flashing and increase subcooling.
Both b and c are correct.
The refrigerant charge in a TXV remote bulb or power element must:
Be changed when the filter drier is changed.
Be identical to the refrigerant in the system.
Be discharged before it is effective.
Be R-134a.
An External equalizing tube on the TXV is used:
On units with long evaporator.
On units with a pressure drop due to evaporator length.
On all refrigeration applications.
Both a and b are correct.
The factory superheat settings for TXVs used with central air conditioning systems should be:
20 degrees or more.
Less than 5 degrees.
About 10 degrees.
None of the above.
The remote bulb of a TXV should be fastened to the:
Outlet of the TXV, about 6 inches.
Inlet of the TXV, about 6 inches.
Outlet of the condenser and on the superheat line.
None of the above.
The refrigerant passing through a filter drier should be in what state?
Superheated vapor.
Liquid and vapor.
Saturated vapor.
Liquid.
The TXV operates on which of the following pressures?
Remote bulb, spring pressure and superheat.
Remote bulb, spring pressure and evaporator pressure.
Discharge, suction and spring pressures.
All of the above.
At higher loads, a sightglass located in the liquid line will:
Bubble if the system is undercharged.
Have no bubbles.
Be clear.
Turn yellow inside.
Always charge a TXV/receiver/sightglass system under a :
No load condition.
Low load condition.
High load condition.
None of the above.
The initial refrigerant charge into an evacuated system should be made:
Into the compressor as a liquid.
Into the evaporator as a liquid.
A small amount of vapor first, followed by liquid into the high side.
The accumulator.
Compressor superheats should always be:
Between 20 and 30 degrees.
Less than 5 degrees.
Prevented.
Both a and c are correct.
The evaporator temperature on an air conditioning system should be:
40 to 50 degrees F.
No more than 32 degrees F.
More than 50 degrees at all times.
20 to 30 degrees F.
The refrigerant charge on a capillary tube system is:
Not critical on most units.
Very critical on all units.
Critical on some units.
None of the above.
The most accurate method of charging a capillary tube system is to:
Weigh the charge into an empty system.
Check the subcooling system first.
Charge liquid directly into the compressor.
Use the capillary tube subcool method.
An overcharge of refrigerant will result in:
Lower ampere draw for the compressor.
Increased overall efficiency.
Elevated head and suction pressures.
None of the above are correct.
The second best way to charge a capillary tube system is to:
Use the superheat charging table or curve.
Listen to the sounds the compressor makes.
Charge unit and watch for sweating or frost on the suction line.
Add refrigerant until the evaporator gets cold.
An air conditioning system or heat pump must have:
600 cubic feet of air per minute across the evaporator coil.
550 cubic feet of air per minute across the evaporator coil.
400 cubic feet of air per minute across the evaporator coil.
Less than 400.
When using a charging chart on most central air conditioning systems, the following temperatures must be known:
Outdoor dry bulb and superheat.
Indoor wet bulb and superheat.
Indoor wet and dry bulb, outdoor dry bulb, and superheat.
Indoor wet bulb and dry bulb temperatures only.
When charging air conditioning systems with capillary tube or fixed orifice metering devices, the technician should:
Consult with the manufacturer and use their exact method of charging and specifications.
Charge until the unit stops frosting back.
Charge the amount shown on the I.D. tag and add 1 pound for losses.
Turn off most of the registers to slow down the airflow across the evaporator.
ANSWERS
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