HVACR System Servicing and Troubleshooting Residential Unit 40

Subcooling occurs in the evaporator as well as the condenser.

The correct answer is 'False'.

As a rule of thumb, the air leaving the evaporator will be about ____ than the air entering the evaporator.

The correct answer is: 17-20° cooler

A typical evaporator superheat reading at the evaporator outlet for a central air-conditioning system on a 95°F day would be ____°F.

The correct answer is: 10-12

Problems in the refrigerant portion of a system are caused by ____.

The correct answer is: any of the above

When checking the electrical circuits of an air-conditioning system, each parallel circuit should be isolated and checked separately.

The correct answer is 'True'.

With a rise in outdoor temperature, the head pressure will rise.

The correct answer is 'True'.

Match the symptom with all possible causes. Note: The choices can be used more than once.

refrigerant overcharge

refrigerant undercharge

blocked/dirty filter

non-condensable gas in system

defective condenser fan motor

defective evaporator fan motor

improper system balancing

dirty condenser coil

The correct answer is:
refrigerant overcharge
- high operating pressures,

refrigerant undercharge
- low operating pressures,

blocked/dirty filter
- low operating pressures,

non-condensable gas in system
- high operating pressures,

defective condenser fan motor
- high operating pressures,

defective evaporator fan motor
- low operating pressures,

improper system balancing
- uneven cooling,

dirty condenser coil
- high operating pressures

The best way to tell if a compressor's discharge line is at the correct temperature is to grab hold of it.

The correct answer is 'False'.

If the metering device malfunctions and gets stuck in the closed position, the compressor could overheat.

The correct answer is 'True'.

To accurately add refrigerant to a system, a condenser ambient temperature of ____°F should be simulated.

The correct answer is: 95

If a compressor motor locks up, it will ____.

a. not start

b. hum and then shut off

c. draw locked rotor amps (LRA)

d. all of the above

The correct answer is: all of the above

A suction line filter/drier should always be installed with a compressor changeout.

The correct answer is 'True'.

The liquid line temperature is used to determine the ____ of a condenser.

The correct answer is: subcooling

The instrument to use to check for a short in the compressor motor winding is a(n) ____.

The correct answer is: ohmmeter

On a 95°F day, the R-22 refrigerant pressure on the high side should be about ____ psig.

The correct answer is: 243

A service valve can be used to ____.

The correct answer is: isolate the refrigerant so the system can be serviced

Superheat occurs in the condenser as well as the evaporator.

The correct answer is 'True'.

If a compressor has a partially shorted winding, it could run for a while, overheat, and shut off.

The correct answer is 'True'.

When would it be beneficial for a technician to pump a system down before servicing?

The correct answer is: when the thermostatic expansion valve needs to be changed