# Chap. 51 Heating And Air Conditioning Service

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With the hanging seasons it is important to keep warm in the winter and get some cool air for the summer. This therefore places some importance on understanding how to fit in heating and air conditioning equipment for buildings. Take up the true or false test below and get to see how much you know about these services and what is needed to have a proper functioning one. All the best!

• 1.

### A manifold gauge set can be used during the evacuation of the A/C system.

• A.

True

• B.

False

A. True
Explanation
A manifold gauge set is a tool used to measure the pressure and temperature of the refrigerant in an air conditioning system. During the evacuation process, the manifold gauge set can be connected to the system to monitor the pressure levels and ensure that the system is properly evacuated. This is important because a proper evacuation removes any air or moisture from the system, which can cause damage or reduce the efficiency of the A/C system. Therefore, using a manifold gauge set during the evacuation process is necessary to ensure the A/C system is properly evacuated.

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• 2.

### A manifold gauge set can be used during A/C system diagnosis.

• A.

True

• B.

False

A. True
Explanation
A manifold gauge set is a tool used to measure the pressure and temperature of the refrigerant in an air conditioning system. By connecting the gauges to the high and low pressure sides of the system, technicians can diagnose issues such as low refrigerant levels, blockages, or compressor problems. This allows them to accurately assess the condition of the A/C system and determine the necessary repairs or maintenance needed. Therefore, it is true that a manifold gauge set can be used during A/C system diagnosis.

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• 3.

### Refrigerant condenses quickly when exposed to the atmosphere.

• A.

True

• B.

False

B. False
Explanation
Refrigerant does not condense quickly when exposed to the atmosphere. In fact, refrigerants are designed to be stable and not easily condense at normal atmospheric conditions. They are specifically formulated to operate within a closed system, such as a refrigeration or air conditioning unit, where they can undergo the necessary phase changes to cool or heat the desired space. Therefore, it is incorrect to say that refrigerant condenses quickly when exposed to the atmosphere.

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• 4.

### A manifold gauge set is used to determine both high-side and low-side pressures in the refrigeration system.

• A.

True

• B.

False

A. True
Explanation
A manifold gauge set is a tool used by technicians to measure and monitor the pressure levels in a refrigeration system. It consists of two gauges, one for the high-side pressure and one for the low-side pressure. By connecting the gauges to the appropriate ports in the system, the technician can accurately determine the pressure levels on both sides of the system. This information is crucial for diagnosing any issues or problems with the system and for ensuring that it is operating efficiently. Therefore, the statement that a manifold gauge set is used to determine both high-side and low-side pressures in the refrigeration system is true.

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• 5.

### Warm underhood temperatures produce lower than normal A/C system pressures.

• A.

True

• B.

False

B. False
Explanation
Warm underhood temperatures actually produce higher than normal A/C system pressures. As the temperature under the hood increases, the refrigerant in the A/C system becomes hotter and expands, causing the pressure inside the system to rise. This higher pressure helps in the cooling process by allowing the refrigerant to absorb more heat from the cabin. Therefore, the statement in the question is incorrect.

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• 6.

### A single drop of water in an A/C refrigeration sytsem may cause damage to the system.

• A.

True

• B.

False

A. True
Explanation
Water in an A/C refrigeration system can cause damage because water is not compatible with the refrigerant used in the system. When water enters the system, it can mix with the refrigerant and form acid, which can corrode the metal components of the system. This corrosion can lead to leaks, reduced efficiency, and ultimately, system failure. Therefore, even a single drop of water can potentially cause significant damage to an A/C refrigeration system.

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• 7.

### Refrigerant is lighter than oxygen.

• A.

True

• B.

False

B. False
Explanation
Refrigerant is not lighter than oxygen. In fact, refrigerants have varying densities and can be either lighter or heavier than oxygen. Therefore, the statement is false.

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• 8.

### R-12 is stored in light blue containers.

• A.

True

• B.

False

B. False
Explanation
The statement "R-12 is stored in light blue containers" is false. This means that R-12 is not stored in light blue containers.

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• 9.

### R-134a is stored in yellow containers.

• A.

True

• B.

False

B. False
Explanation
R-134a is not stored in yellow containers.

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• 10.

### High and low pressure fittings must be changed during an R-12 to R-134a conversion.

• A.

Explanation
During an R-12 to R-134a conversion, high and low pressure fittings need to be changed. This is because R-12 and R-134a have different pressure requirements and properties. R-134a operates at higher pressures than R-12, so the fittings need to be able to withstand these higher pressures. Changing the fittings ensures that the system is compatible with the new refrigerant and can operate safely and efficiently.

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• 11.

### Which of the following statements best defines the term 'evacuation'?

• A.

Evacuation is a process in which refrigerant in the system is released.

• B.

Evacuation is a condition that exists when a compressor runs until there is no refrigerant left in the system.

• C.

Evacuation is a process that removes all traces of air, moisture, and refrigerant from the system.

• D.

Evacuation is a process that uses air to force moisture and dirt out of the system.

C. Evacuation is a process that removes all traces of air, moisture, and refrigerant from the system.
Explanation
Evacuation is the process of removing all traces of air, moisture, and refrigerant from a system. This process is essential in HVAC systems to ensure proper functioning and prevent any damage. By removing air, moisture, and refrigerant, the system can be properly sealed and prevent any contaminants from affecting its performance. This process is typically done using a vacuum pump to create a vacuum and pull out any unwanted substances.

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• 12.

### Which of the following statements is not true about orifice tube systems?

• A.

The suction line must be cool to the touch from the evaporator outlet to the compressor.

• B.

The liquid line from the condenser outlet to the orifice tube should be cool.

• C.

The evaporator should feel very cold.

• D.

The accumulator must be cool to the touch.

B. The liquid line from the condenser outlet to the orifice tube should be cool.
Explanation
The correct answer is "The liquid line from the condenser outlet to the orifice tube should be cool." This statement is not true because the liquid line should actually be warm, not cool. The liquid refrigerant flows from the condenser to the orifice tube, and it needs to be warm in order to properly boil and evaporate in the evaporator. Cooling of the liquid line could indicate a problem with the system, such as a restriction or a lack of refrigerant flow.

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• 13.

### When is a manifold gauge set used?

• A.

Explanation
A manifold gauge set is used when working on air conditioning and refrigeration systems. It is used to measure the pressure and temperature of the refrigerant in the system. This allows technicians to diagnose problems, such as low refrigerant levels or blockages, and make adjustments to the system as needed. The gauge set consists of two gauges, one for high pressure and one for low pressure, connected to the system with hoses. By comparing the readings on the gauges to the manufacturer's specifications, technicians can determine if the system is operating properly or if repairs are needed.

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• 14.

### Which of the following cannot cause excessive heat?

• A.

A loose or damaged control cable

• B.

A heater control valve stuck open

• C.

A water flow control valve not opening fully

• D.

A faulty thermostatic fan

C. A water flow control valve not opening fully
Explanation
A water flow control valve not opening fully cannot cause excessive heat because if the valve is not opening fully, it means that the flow of water is restricted, resulting in less water reaching the heater. This would lead to a decrease in heat rather than an increase.

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• 15.

### To charge an air conditioning system while it is running, the refrigerant should be added to the:

• A.

High side

• B.

Low side

• C.

Both A and B

• D.

Neither A nor B

B. Low side
Explanation
When charging an air conditioning system while it is running, the refrigerant should be added to the low side. This is because the low side is the part of the system that is designed to handle the cool, low-pressure refrigerant. Adding refrigerant to the high side could cause damage to the system or result in improper cooling. Therefore, adding refrigerant to the low side ensures that it is properly distributed throughout the system and allows for efficient cooling.

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• 16.

### R-12 refrigerant exposed to an open flame will produce:

• A.

Hydrogen gas

• B.

Hydrofluorocarbon gas

• C.

Hydrochloric gas

• D.

Phosgene gas

D. Phosgene gas
Explanation
When R-12 refrigerant is exposed to an open flame, it will produce phosgene gas. Phosgene gas is a highly toxic substance that was used as a chemical weapon during World War I. It is formed when chlorofluorocarbons (CFCs) like R-12 are burned. Inhaling phosgene gas can cause severe respiratory distress, lung damage, and even death. Therefore, it is crucial to handle and dispose of R-12 refrigerant safely to prevent the release of phosgene gas into the environment.

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• 17.

### R-12 and R-134a:

• A.

Should never be mixed

• B.

May be mixed after a system has been converted from R-12 to R-134a

• C.

Use the manifold gauge sets

• D.

All of the above

A. Should never be mixed
Explanation
R-12 and R-134a should never be mixed because they are two different types of refrigerants with different properties. Mixing them can result in damage to the system and potentially harmful effects. It is important to use the correct refrigerant for each specific system to ensure proper functioning and safety.

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• 18.

### EPA certification is required to:

• A.

Service R-12 A/C systems

• B.

Purchase R-12

• C.

Both A and B

• D.

Neither A nor B

C. Both A and B
Explanation
EPA certification is required to both service R-12 A/C systems and purchase R-12. This means that individuals must have the necessary certification to work on and handle R-12 refrigerant.

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• 19.

### Technician A says evacuating (pumping down) an air conditioning system removes air and moisture from the system. Tcehnician B says evacuating (pumping down) an air conditioning sytem removes dirt particles from the system. Who is correct?

• A.

A only

• B.

B only

• C.

Both A and B

• D.

Neither A nor B

A. A only
Explanation
Evacuating an air conditioning system involves removing air and moisture from the system. This is because air and moisture can interfere with the proper functioning of the system and can cause damage. However, evacuating the system does not remove dirt particles. Dirt particles can be removed through other cleaning methods such as using filters or cleaning the system components. Therefore, Technician A is correct in stating that evacuating the system removes air and moisture, but Technician B is incorrect in stating that it removes dirt particles.

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• 20.

### Technician A says if the suction line to the compressor is covered with thick frost, this might indicate that the expansion valve is flooding the evaporator. Technician B says the formation of frost on the outside of the line or component means there is a restriction to the flow of refrifgerant. Who is correct?

• A.

Explanation
Technician B is correct. The formation of frost on the outside of the line or component indicates a restriction to the flow of refrigerant. This restriction could be caused by various factors such as a clogged filter or a blocked expansion valve. On the other hand, Technician A's statement about the suction line covered with thick frost indicating a flooding expansion valve is not accurate. A flooding expansion valve would result in a lack of frost on the suction line, as the valve would be allowing too much refrigerant into the evaporator.

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