Chapter 11 Working with refrigerants

To perform a triple evacuation, a technician pulls vacuum then charges the system with dry nitrogen to a pressure of ______.

0 to 3 psig

Most refrigeration systems have a subcooling value between _____°F

10°F and 20°F

If a systems recommended testing pressures are not known, the pressure should not exceed ______ when testing with carbon dioxide or nitrogen.

170 psig

A deep vacuum evacuation uses a vacuum pump to create a pressure of ______.

250 microns

A refrigeration system is leak free if deep vacuum pressure holds steady around _____ or less.

500 microns

Some refrigerant cylinders have a liquid level switch that turns off recovery machine when the cylinder is _____ full.

80%

Active recovery method use ____ to recover refrigerant from a system.

A recovery machine

A system leak might be indicated by ____.

A. A lack of cooling B. Low suction and head pressure C. All of the above D. None of the above C. All of the above

Checking a system's refrigerant charge is important because an improper charge can ______.

A. Lead to compressor damage B. Reduce system capacity and efficiency C. Waste electrical energy D. All of the above D. All of the above

What are the two methods for recovery?

Active recovery & passive recovery

Superheat may be described as the amount of heat _____.

Added to a refrigerant after it has evaporated

If a system using a capillary tube or fixed orifice metering device has low superheat, then the system has ____.

An excessive refrigerant charge "over charged"

A vacuum causes moisture in a system to evaporate by lowering the pressure in the system, which in turn Lowers the ______ of any moisture in the system.

Boiling point

A _____ Cylinder holds a small amount of refrigerant, usually around 5 Lbs or less.

Charging

Adding refrigerant to a system is called ______.

Charging

Passive recovery may involve using the ____ to pump refrigerant out of the system.

Compressor

Subcooling is equal to ____ temperature minus liquid line temperature.

Condenser saturation

Which method of evacuation is most effective at removing moisture from a system?

Deep vacuum

What are the two methods for evacuation?

Deep vacuum & triple evacuation

Superheat is equal to the suction line temperature minus _____ temperature.

Evaporator saturation

True or false? A professional technician always confirms the identity of a refrigerant by smelling and tasting it rather than relying on cylinder color alone?

False

True or false? During passive recovery, raising the temperature of a recovery cylinder causes more refrigerant to flow from the system to the cylinder.

False

There should always be a _____ between the refrigeration system and the recovery machine to protect against contamination.

Filter-dryer

To perform liquid recovery, a recovery machine must be equipped with a _____ that flashes liquid refrigerant into vapor.

Filter-dryer

Checking refrigerant charge by superheat is normally done on systems using ______.

Fixed orifice or Capillary tube metering device

Which of the following is NOT a likely indication that the system may need to be charged with more refrigerant?

High head pressure

To charge a system with liquid refrigerant, a technician should charge refrigerant into the ______.

High side

If a vacuum must be pulled for a long time and must be left unattended by a technician, it is good practice to install a solenoid valve between the system and the vacuum pump. Such a solenoid valve should be wired ______ with the vacuum pump.

In parallel

The first valve to front seat when performing a pump-down is the _____.

King valve

Vacuum pump service lines should have a ______ to increase evacuation efficiency.

Large diameter

The quickest method of refrigerant charging is ______ charging.

Liquid charging

Some recovery cylinders have a _____ that shuts the recovery machine off to prevent overfilling the cylinder.

Liquid level switch

Performing a pump-down involves moving all the refrigerant in a system to the ____.

Liquid receiver

When brazing to repair a system leak, the nitrogen should be _____ in order to create a good brazing point.

Low pressure and flowing

When liquid charging a zeotrope into the low-side which device is installed to prevent liquid refrigerant from entering the compressor from the low-side?

Metering device

During vapor recovery, the low and high-side service valves should be ____.

Mid-positioned

A continuous flow of _____ is passed through a system during brazing to prevent the formation of oxidation.

Nitrogen

Which type of gas should be used to pressurize a system to check for leaks?

Nitrogen "inert gas"

Which part of epoxy resin should be heated in order to harden?

One-part

All leak detection methods involve applying ____ to a refrigeration system.

Pressure

To pull a deep vacuum as quickly as possible, what should a technician do regarding Schrader valves?

Pull the schrader pin

It is always necessary to _____ the refrigerant in a system before repairing a leaking connection by brazing.

Recover

During push-pull liquid recovery, the recovery cylinder vapor valve is connected to the _____.

Recover machine inlet

The push-pull liquid recovery method pulls vapor refrigerant from the ____.

Recovery cylinder

Subcooling may be described as the amount of heat _____.

Removed from a refrigerant after it has condensed

When pulling a vacuum, it is best to use hoses that are _____.

Short with wide diameter

What is the superheat of a system with a suction line temperature of 52°F, low-side pressure corresponding to 34°F, and a liquid line temperature of 100°F?

Suction line temperature 52°F - low pressure (Evaporator saturation) to 34°F: 52°F-34°F = 18°F

If a refrigeration system has a capillary tube metering device the ____ method should be used to check the charge in the system.

Superheat

When retrofitting a refrigeration system from one refrigerant to another, the following are likely to need replacing, except for the _____.

System thermostat

The total recovery cylinder weight is equal to the maximum refrigerant weight plus the _____ of the cylinder.

Tare weight

When pulling a vacuum, a technician can observe the gas laws in action. For example, in a refrigeration system, as pressure drops, _______.

Temperature drops

To retrofit a system, a technician should contact ______ to identify which components need to be replaced.

The original equipment manufacturer

Checking refrigerant by subcooling is normally done on systems using _____.

Thermostatic expansion valves

True or false? A two part epoxy compound should only be purchased on an as-needed basis due to its limited shelf life.

True

To check whether a recovery cylinders liquid level switch is working, connect the switch to a recovery machine and recovery cylinder set up, turn on the machine, and then ______.

Turn the recovery cylinder upside-down

Liquid recovery should be used in combination with ____ in order to remove a system's entire refrigerant charge.

Vapor recovery

The maximum amount of refrigerant that can be stored in a recovery cylinder is equal to 80% of the cylinder's ____ by weight.

Water capacity

The proper charge of refrigerant in a system is best specified in terms of the refrigerant's ______.

Weight