19 thermal overload and fusible link 20 to prevent a

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Industrial Maintenance
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Chapter 14 / Exercise 7
Industrial Maintenance
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19. Thermal overload and fusible link 20. To prevent a large current draw at one time when initially starting Unit 49 1. Air to air, water to air, air to water, water to water 2. It moves heat from a low-temperature heat source to a higher-temperature heat sink 3. A reversing valve which reverses the direction of refriger- ant flow 4. Air-source heat pumps circulate less refrigerant at low ambient temperatures, and the refrigerant not being used must be stored somewhere. 5. Auxiliary heat is another heat source added to make up the difference between the heat pump capacity and the house load. 6. The solenoid coil controls the pilot valve, which controls the pressure to the ends of the reversing valve. The pres- sure difference between one end of the valve and the other causes the cylinder to shift. The end the valve is shifted to becomes the evaporator, and the other end becomes the high side. 7. EER is a steady-state measurement that doesn’t take into consideration starting, stopping, and different operating conditions. SEER is a seasonal measurement that takes all these factors into account. Review Question Answers 82
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Industrial Maintenance
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Chapter 14 / Exercise 7
Industrial Maintenance
Brumbach/Clade
Expert Verified
8. COP is the ratio of heat out divided by heat in and is measured at one condition. HSPF is a measure of heat per watt and is measured for the entire heating season. 9. Over-under, side by side, wall mount, curb mount, con- vertible 10. Their function (evaporator or condenser) reverses when the unit changes from cooling to heating. 11. Heat is molecular motion, and all molecules are moving until they reach absolute 0 (–460°F). 12. Heat exists down to absolute zero, which is –460°F. Heat will flow only from a higher temperature to a lower temperature. Gases become warmer when compressed. Most matter can be in a solid (ice), liquid (water) or gas (steam) state. The temperature at which a material changes from a liquid to a gas or from a gas to a liquid depends on the pressure at which it is contained 13. Since both coils must function as the evaporator during one of the cycles, they each need a metering device: one for the indoor coil and one for the outdoor coil. 14. Check valves installed in parallel with the metering devices or built into them 15. A biflow valve allows refrigerant flow in both directions. Some meter in both directions while others only meter in one direction and allow free flow in the other. 16. The outdoor fan doesn’t operate in the defrost cycle but the auxiliary heat does. 17. Outdoor coil cooling = condenser Outdoor coil heating = evaporator Indoor coil cooling = evaporator Indoor coil heating = condenser Evaporator condenser Review Question Answers 83
18. Outdoor metering device cooling = bypassed Outdoor metering device heating = active Indoor metering device cooling = active Indoor metering device heating = bypassed 19. In the middle on the side with three large lines 20. The smaller line located by itself 21. The ground water temperature is warmer than the air temperature.

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