Commercial Air Conditioning EXAM QUESTIONS AND ANSWERS 100% CORRECT

How a pump down system works - ANSWERthe thermostat will open at the set temperature it controls the liquid line solenoid valve the valve will close and the system will pump down and the low pressure switch will open and turn off the compressor see unit 21 pump down cycle and unit 25/ 25.18 automatic pumpdowm systems No oil trap in the discharge line can cause - ANSWERcompressor valve damage if the condenser is on the roof no oil getting back to the compressor see internet oil trap If the txv bulb becomes loose the low side and high pressure will - ANSWERboth go up the valve will open and let more refrigerant in the evaporator causing the high side to rise see unit 24 / 24.8 Low air flow over the evaporator will cause - ANSWERa low suction pressure low superheat low head pressure and the room will be warm see unit 29 inefficient evaporator In a water cooled condenser the water and the refrigerant - ANSWERflow in opposite directions see unit 22/ figure 22.3 A plugged equalization line or oil level regulator on a large ton compressor can cause the - ANSWERcompressor to lock up because no oil coming back to the compressor see page 465 modern ref. What compressor can handle a small amount of liquid refrigerant - ANSWERa scroll