Study Guide 41

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

10-12°F

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

20°F (17 to 20°F)

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

243

If the suction pressure of an R-22 air-conditioning system is 67 psig and the evaporator outlet temperature is 51°F, what is the evaporator superheat?

39

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

95°F

Where is the correct location for a sight glass in order to check the charge?

Anywhere on the liquid line. Before an expansion device.

Why should a technician visually inspect the equipment before installing gauges?

Check for visual defects.

If a compressor motor locks up, it will _____.

It can trip the breaker, blow the fuse to the unit. If the compressor has a thermal overload it should trip due to the heat from lock up.

Refrigerant undercharge

Low operating pressure (may eventually have frozen evaporator coil)

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

Many factors, leak, low charge, compressor with bad valves

While passing through the condenser, refrigerant is three different states. What are they?

Saturated vapor, subcooled liquid, warm subcooled high pressure liquid...

Why is it recommended to measure by weight the refrigerant charge into the system?

So you don't under or overcharge. To know how much charge you need to put.

Superheated refrigerant is present where in a normally operating system?

Suction & discharge line.

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

To check for problems and prevent from having to pump down the entire system.

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

VOM to start with or an meger (if we have reason to believe there's an insolation break down occurring).

When is it necessary to connect gauges onto a system?

You connect gauges when you believe you may have a reason to need them.

Non-condensable gas in system.

high operating pressures

Refrigerant overcharge.

high operating pressures

Dirty condenser coil.

high operating pressures (dirty condenser coil will cause insufficient condensing)

Defective condenser fan motor.

high operating pressures (due to insufficient amount of condensing going on)

A service valve can be used to _____.

isolate whatever part it controls.

Blocked/dirty filter.

low operating pressures (then could be frozen evaporator coil)

Defective evaporator fan motor.

low operating pressures (then could be frozen evaporator coil)

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

subcooling

Improper system balancing.

uneven cooling