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Terms in this set (22)
1. What is absolute pressure
gauge pressure + atmospheric pressure. scale its weight will be 14.7 pounds. This means every square inch of any surface at sea level has 14.7 pounds of air pressure pushing down on it.
2. Which heat transfer method is achieved using a liquid or gas?
(There are 3 methods of heat transfer conduction, convection and radiation )CONVECTION is the transfer of heat through the flow of liquid or gas caused by a temperature differential.
3. What state is the refrigerant before and after the metering device?
HP sub cooled liquid and LP sub cooled liquid.
4. What is net weight, tare weight and gross weight?
Net weight =weight of the contents in the vessel, tare weight =the empty weight of the vessel, gross weight =combined weight of the vessel plus the weight in the vessel
5. In which compressors do the compressor and drive motor share the same housing?
Hermetic and semi hermetic
6. What are the different types of condensers, when are they most commonly used?
Fin and tube condensers are most commonly used and plate condensers confine to small domestic units.
7. What must happen for an evaporator to achieve peak performance?
8. What is a trap and when is it used in air conditioning?
Builds up the oil to lubricate the compressor
9. What is the duty of a suction line accumulator?
Prevents liquid flood back by accumulating liquid refrigerant.
10. What does a remote bulb thermostat use to sense temperature change?
Refrigerant reacts through temperature pressure
11. What is a check valve used for?
Prevents refrigerant flood back to the compressor. Ensures single direction flow.
12. Which compressor have the motor separated from the compressor?
Open drive compressor
13. What happens when a piston in a reciprocating compressor reaches its lowest point?
Hits a spring that closes the suction line.
14. How does the centrifugal compressor increase pressure difference?
Multiple impeller in a series.
15. Which part in a centrifugal compressor actually compresses the refrigerant?
16. How do u solve to find the compressor displacement?
Piston length times RPM
17. what are throttling valves used for , and what are they used on ?
Controls the capacity on centrifugal compressor system
18. How do you prevent the build up of copper oxide when brazing?
3-5 psi of nitrogen running through a system
19. How do u prevent the migration of liquid refrigerant into the crankcase?
Raise the temperature of theCrankcase
20.how are high and low safety switches installed?
21.what can cause a compressors overload device to open?
Not removing enough heat
22. When measuring voltage to a compressor it should be within what range of the nameplate?
Single phase +- 10% three phase motor 3-5 %
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