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HVAC EXCELLENCE QUESTIONS AND ANSWERS
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HVAC EXCELLENCE QUESTIONS AND ANSWERS
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HVAC EXCELLENCE QUESTIONS AND ANSWERSHeat which causes a change in temperature of a substance is called - Answers -
sensible heat,
Heat added to a substance without a rise in temperature; (example: liquid refrigerant to
gas) this process la called? - Answers -latent heat
Heat added to the refrigerant in vapor state after the evaporation process is called, -
Answers -superheat
A scroll compressor moves refrigerant by means of; - Answers -involute spirals
The movement of heat by way of fluid or is called; air - Answers -convection
The movement of heat through a solid object is called; - Answers -radiation
The standard unit for measuring the quantity of heat in a substance is - Answers -British
Thermal Unit
A refrigerant gives up heat when it; - Answers -it condenses
Why must refrigerant in the suction line be slightly warmer than the saturation
temperature? - Answers -prevent liquid slugging of the compressor.
It is desirable for refrigerant in the suction line to be slightly superheated in order to; -
Answers -insure liquid refrigerant does not enter the compressor.,
The state of the refrigerant in the suction line should be - Answers -low pressure/ low
temperature vapor
Refrigerant R-134a vapor enters the condenser at 124psig, 100 degrees faranheit, It
leaves as a liquid from the condenser, sub-cooled 20 degrees faranheit, and the
pressure will be approximately - Answers -124 psig
There are 3 basic types of condensers, air cooled, water cooled, and - Answers -
evaporative cooled
10 lbs of refrigerant passing through a water cooled condenser will lose 20 BTU of heat/
pound. If 10#'s of water passes through the condenser with an entering temp of 80
degrees, the temp of the water leaving the condenser is - Answers -100 degrees
faranheit
The heat removed from the refrigerant by the condenser is - Answers -both sensible
and latent heat
, An energy recovery ventilator is - Answers -an air to air heat exhanger to recover heat
Which of hte following can not be used as a low ambient temperature control? -
Answers -Crankcase regulating valves
When testing the efficiency of an air cooled condenser, the refrigerant condensing
temperature should be no more than _____ higher than the entering air temp. - Answers
-30 degrees
The First function a condenser must perform is to ___ the refrigerant before condesing
can occur. - Answers -De-Superheat
A thermostatic expansion valve is designed to maintain - Answers -Constant evaporator
superheat
The thermostatic expansion valve has three operating pressures - Answers -Evaporator,
Spring and Sensing bulb Pressure
When Mounting a thermostatic expansion valve sensor bulb, which of the folling is NOT
true? - Answers -It must be installed lower than the valve body
In an air conditioning system that uses a thermostatic expansion valve, the temperature
of the evaporator outlet will usually be: - Answers -Warmer than the evaporator inlet
An automatic expansion valve is best suited: - Answers -When the system load remains
fairly constant
Which of the following is not true of a capillary tube metering device? - Answers -They
maintain a constant evaporator temperature
A decrease in superheat causes the thermostatic expansion valve to - Answers -Close
A rise in evaporator pressure causes the automatic expansion valve to begin to -
Answers -close
a thermal-electric ( solid state) expansion valveis controlled by - Answers -NTC
Thermistor
In a Direct expansion (DX) evaporator system, the refrigerant enters the evaporator as -
Answers -a mixture of liquid with some "flash gas"
In the Evaporator - Answers -Latent heat is transferred from the refrigerated space to
the refrigerant
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