Refrigerant Machine Operator Certification Practice Test

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| By Catherine Halcomb

Catherine Halcomb

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1/100 Questions

THE AMOUNT OF REFRIGERANT THAT FLOWS THROUGH THE ORIFICE PLATE IS DETERMINED BY:
- THE NUMBER OF ECONOMIZER STAGES
- THE NUMBER OF COMPRESSION STAGES
- TEMPERATURE OF REFRIGERANT IN THE HIGH SIDE
- DIFFERENCE IN PRESSURE BETWEEN HIGH AND LOW SIDES

About This Quiz

Industrial refrigerant machine operators seem to be simple people within the production chain but essentially are very important. Take up the quiz below and see how good you are as a refrigerant machine operator. This test consists of 100 most important questions that will help you clear the certification exam of the same. All the best.

Refrigerant Machine Operator Certification Practice Test - Quiz

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2.

UNLOADERS ARE USED TO:
- INCREASE CAPACITY
- STOP FLOW OF REFRIGERANT WITHOUT STOPPING
- REDUCE CAPACITY
- START FLOW OF REFRIGERANT THROUGH SYSTEM
Correct Answer

A. REDUCE CAPACITY

Explanation

Unloaders are used to reduce capacity in a refrigeration system. This means that they are designed to decrease the amount of refrigerant flowing through the system, which in turn reduces the cooling capacity. Unloaders are typically used in situations where the cooling load is lower than the system's maximum capacity, allowing for energy savings and improved efficiency. By reducing the capacity, unloaders help to match the system's output to the actual cooling demand, preventing unnecessary energy consumption.

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14
3.

SEMI-HERMETIC COMPRESSORS MAY BE BETTER TO USE THAN HERMETIC COMPRESSORS BECAUSE HERMETIC COMPRESSORS:
- ARE FULLY ENCLOSED AND CANNOT BE SERVICED ON SITE
- ARE EASIER TO GET TO
- ARE MORE DIFFICULT TO GET TO
- ARE MORE EXPENSIVE
Correct Answer

A. ARE FULLY ENCLOSED AND CANNOT BE SERVICED ON SITE

Explanation

Semi-hermetic compressors may be better to use than hermetic compressors because hermetic compressors are fully enclosed and cannot be serviced on site. This means that if there is any issue or malfunction with a hermetic compressor, it cannot be repaired or maintained on site and would require the compressor to be completely replaced. In contrast, semi-hermetic compressors can be serviced and repaired on site, which can save time and money in case of any problems.

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14
4.

WHEN CONDUCTING A ROUTINE TOUR OF PLANT OPERATION A RMO OBSERVES A SIGNIFICANT INCREASE IN SUPERHEAT TEMP. FOR THE REFRIGERATING FLUID ENTERING A RECIPROCATING COMPRESSOR. OF THE FOLLOWING THE MOST LIKELY CAUSE FOR THIS CONDITION IS
- SCALE PARTICLES LODGED IN THE TEV VALVE
- UNRAVELING OF THE INSULATION PROTECTING THE TEV VALVE THERMAL BULB
- BUILD-UP OF NONCONDENSABLES IN THE CONDENSER
- OVERCHARGE OF REFRIGERANT
Correct Answer

A. SCALE PARTICLES LODGED IN THE TEV VALVE

Explanation

The most likely cause for the significant increase in superheat temperature for the refrigerating fluid entering a reciprocating compressor is scale particles lodged in the TEV valve. Scale particles can restrict the flow of refrigerant, leading to a decrease in the amount of refrigerant entering the evaporator coil. This results in a higher superheat temperature, as the refrigerant is not able to absorb enough heat from the surrounding air before entering the compressor.

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12
5.

A ROOM THERMOSTAT CONTROLS THE LIQUID LINE SOLENOID VALVE IN THIS COMMERCIAL REFRIGERATION SYSTEM. THE COMPRESSOR IS ACTIVATED BY:
- THE HIGH PRESSURE CUT IN
- THE LOW SIDE PRESSURE STAT
- THE THERMOSTATIC EXPANSION VALVE
- THE THERMOSTAT THAT ACTIVATES THE SOLENOID VALVE
Correct Answer

A. THE LOW SIDE PRESSURE STAT

Explanation

The correct answer is the low side pressure stat. In a commercial refrigeration system, the room thermostat controls the liquid line solenoid valve. The compressor is activated by the low side pressure stat, which monitors the pressure on the low side of the system. When the pressure drops below a certain level, the low side pressure stat sends a signal to the compressor to activate and maintain the desired pressure in the system.

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13
6.

WHILE MONITORING THE OPERATION OF A RECIPROCATING REFRIGERATING UNIT YOU OVERSEE THAT THE CYCLING TIMES ARE NORMAL, COMPRESSOR COMPRESSION AND TEMP ARE THE ONLY READING THAT ARE OUTSIDE THE NORMAL RATE. UNDER THESE CONDITIONS SERVICE REQUIREMENTS WOULD INDICATE INSPECTING FOR
- FAULTY MACHINE CONTROL
- PROPER REFRIGERATION CHARGE
- FAULTY COMPRESSOR VALVES
- POOR CONDENSER OPERATION / DIRTY TUBES
Correct Answer

A. FAULTY COMPRESSOR VALVES

Explanation

Based on the information provided, the cycling times of the refrigerating unit are normal, indicating that the machine control is functioning properly. The only readings that are outside the normal rate are compressor compression and temperature. This suggests that there may be an issue with the compressor valves, as faulty valves can affect the compression and temperature of the unit. Therefore, inspecting for faulty compressor valves would be the appropriate service requirement in this situation.

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11
7.

WHICH OF THE FOLLOWING ASHRAE SAFETY GROUPS IS THE MOST DANGEROUS?
- A1
- A2
- B2
- B3
Correct Answer

A. B3

Explanation

The correct answer is B3. In the ASHRAE safety groups classification, B3 represents refrigerants that are highly flammable and have a higher risk of explosion. This makes them the most dangerous among the given options. A1 and A2 represent non-toxic and non-flammable refrigerants, while B2 represents refrigerants that are toxic but not flammable.

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6
8.

YOU ARE AN RMO ASSIGNED TO FACILITY WHERE A REFRIGERANT HAS BEEN RECENTLY CHANGED FROM A FLAMMABLE REFRIGERANT TO R-22, AT THE MOMENT YOU ARE PLANNING TO BRAZE METAL. ON SUCH MAKING A REPAIR IN THE MACHINERY ROOM, UNDER THESE CIRCUMSTANCES YOU:
- MUST ENSURE THE FLAME IS ENCLOSED AND VENTED TO OPEN AIR
- MAY MAKE REPAIRS AT LEAST 25 FEET FROM THE REFRIGERANT UNIT
- MAY MAKE REPAIRS WITHOUT ANY RESTRICTIONS IF THE REFRIGERATING UNIT IS SHUT DOWN
- MAY NOT MAKE REPAIR UNDER ANY CIRCUMSTANCES
Correct Answer

A. MUST ENSURE THE FLAME IS ENCLOSED AND VENTED TO OPEN AIR

Explanation

When working in a facility where the refrigerant has been changed from a flammable refrigerant to R-22, it is important to ensure safety while brazing metal. The correct answer states that the flame must be enclosed and vented to open air. This means that when making repairs, the flame should be contained within a safe enclosure and any fumes or gases produced should be directed outside to prevent any potential hazards. This is necessary to prevent the risk of fire or explosion due to the presence of the flammable refrigerant in the facility.

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6
9.

AN OPERATOR HAS BEEN ASSIGNED TO RUN A CENTRIFUGAL COMPRESSOR. OF THE FOLLOWING ACTIONS A CAPACITY CONTROL IS MOST LIKELY TO ACHIEVE IS THROUGH
- BYPASS DISCHARGE GAS
- ADJUSTMENT OF THE IMPELLER INLET GUIDE PRE-ROTATION VANES
- CONDENSER PRESSURE VARIATION
- ADDING RE-EXPANSION VOLUME
Correct Answer

A. ADJUSTMENT OF THE IMPELLER INLET GUIDE PRE-ROTATION VANES

Explanation

Adjusting the impeller inlet guide pre-rotation vanes is the most likely action to achieve capacity control in a centrifugal compressor. The impeller inlet guide pre-rotation vanes control the flow of gas into the impeller, which in turn affects the compressor's capacity. By adjusting these vanes, the operator can regulate the amount of gas entering the compressor and therefore control its capacity. This allows the operator to match the compressor's output to the required demand, ensuring efficient operation.

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11
10.

A RMO NEEDED TO VARY THE FLOW OF REFRIGERANT IN A SYSTEM. A CONTINUOUS VARIATION IN THE FLOW OF THE SYSTEM DOES NOT INCLUDE THE:
- SOLENOID VALVE
- HIGH SIDE FLOAT
- THERMAL EXPANSION VALVE
- CAPILLARY TUBE
Correct Answer

A. SOLENOID VALVE

Explanation

A solenoid valve is a device that controls the flow of fluid by using an electromagnetic solenoid. In this case, the question states that the RMO needed to vary the flow of refrigerant in a system. The other three options, high side float, thermal expansion valve, and capillary tube, are all components commonly used in refrigeration systems to regulate and control the flow of refrigerant. Therefore, the solenoid valve is the odd one out as it is not specifically mentioned in relation to varying the flow of refrigerant.

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7
11.

AN OPERATOR HAS BEEN ASSIGNED TO A LARGE RECIPROCATING MACHINE WITHOUT UNLOADERS OF THE FOLLOWING SAFETY PROPER PROCEDURE FOR STARTING MACHINE IS.
- FILTER SUCTION AND DISCHARGE VALVES
- SUCTION VALVE AND DISCHARGE BYPASS BOTH OPEN
- SUCTION BYPASS AND DISCHARGE VALVE BOTH OPEN
- DISCHARGE BYPASS AND SUCTION VALVE BOTH CLOSED
Correct Answer

A. SUCTION VALVE AND DISCHARGE BYPASS BOTH OPEN

Explanation

The correct answer is to have the suction valve and discharge bypass both open. This is the proper procedure for starting the machine without unloaders. By having the suction valve open, it allows the machine to draw in the necessary fluid or gas. Opening the discharge bypass allows the fluid or gas to bypass the discharge valve, preventing any potential pressure buildup or damage to the machine. This ensures a safe and efficient start-up of the reciprocating machine.

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15
12.

AN OPERATOR HAS BEEN ASSIGNED TO RUN A RECIPROCATING COMPRESSOR. THE FOLLOWING ACTION CAPACITY CONTROL WOULD MOST LIKELY BE ACHIEVED THROUGH:
- OPENING THE SUCTION VALVES WITH SOME FORM OF CONTROL
- CONTROLLING THE DISCHARGE PRESSURE
- CHANGING THE STROKE AND ADDING RE-EXPANSION VOLUME
- RETURNING THE DISCHARGE GAS TO SUCTION
Correct Answer

A. OPENING THE SUCTION VALVES WITH SOME FORM OF CONTROL

Explanation

The most likely way to achieve capacity control in a reciprocating compressor is by opening the suction valves with some form of control. By controlling the opening of the suction valves, the amount of gas entering the compressor can be regulated, thus controlling the capacity of the compressor. This allows for precise control and adjustment of the compressor's output based on the demand or process requirements.

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10
13.

IF A CENTRIFUGAL COMPRESSOR IS BEING USED IN A REFRIGERATION SYSTEM, AND IS AFFECTED BY THE CONDENSER, THE CONDENSER MAY BE IMPROVED BY:
- INCREASING THE AMOUNT OF SUPERHEAT
- INCREASING THE AMOUNT OF SUB-COOLING
- DECREASE THE AMOUNT OF SUPERHEAT
- DECREASE THE AMOUNT OF SUB-COOLING
Correct Answer

A. INCREASING THE AMOUNT OF SUB-COOLING

Explanation

Increasing the amount of sub-cooling in the condenser of a refrigeration system can improve the performance of a centrifugal compressor. Sub-cooling refers to cooling the refrigerant below its saturation temperature after it has condensed. By increasing the amount of sub-cooling, the refrigerant leaving the condenser will be at a lower temperature, which will increase the density of the refrigerant. This higher density refrigerant will result in increased mass flow rate and improved compressor efficiency.

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4
14.

AN OPERATOR IS USING A SLING PSYCHROMETER TO MEASURE DRY AND WET BULB TEMP ON A ROOF OF A BUILDING WHERE THE COOLING TOWER IS LOCATED. IF DURING THE DAY THE TEMP REMAINS CONSTANT, AND WET BULB DROPS BY 5°F, AND ALL OTHER CONDITIONS REMAIN UNCHANGED, THE OPERATOR SHOULD SEE:
- HIGH COOLING WATER BEING RETURNED
- RISE IN CONDENSER HEAD PRESSURE
- LOWER COOLING WATER TEMPERATURE RETURN
- NO NOTICEABLE EFFECT OF THE COOLING TOWER TEMP BEING RETURNED
Correct Answer

A. LOWER COOLING WATER TEMPERATURE RETURN

Explanation

If the wet bulb temperature drops by 5°F while the dry bulb temperature remains constant, it indicates that the air surrounding the cooling tower has become drier. This decrease in humidity means that the cooling tower is able to evaporate more water, resulting in a lower cooling water temperature return. Therefore, the operator should expect to see a lower cooling water temperature return in this scenario.

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4
15.

UPON BEING ASSIGNED TO A FACILITY DURING INSPECTION OF THE FACILITY, YOU FIND THERE HAS BEEN FAILURE TO MAINTAIN WATER TREATMENT. INSPECTING THE CONDENSER WATER, THE FIRST EVIDENCE WOULD MOST LIKELY BE:
- DECREASE IN SUPER HEAT TEMP ENTERING COMPRESSOR
- AN INCREASE IN COMPRESSOR HEAD PRESSURE
- AN INCREASE IN THE FLOW RATE OF NONCONDENSABLES
- CONDENSER TO METERING DEVICE FROZEN
Correct Answer

A. AN INCREASE IN COMPRESSOR HEAD PRESSURE

Explanation

Upon being assigned to a facility during inspection, if there has been a failure to maintain water treatment, the first evidence that would most likely be observed when inspecting the condenser water is an increase in compressor head pressure. This is because the failure to maintain water treatment can lead to the accumulation of contaminants in the condenser water, which can reduce the heat transfer efficiency. As a result, the compressor would have to work harder to maintain the desired pressure, leading to an increase in head pressure.

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8
16.

WHAT IS THE PURPOSE OF THE RECOVERY TANK WHEN OPERATING A REFRIGERANT MACHINE?
- TO COOL THE REFRIGERANT
- TO STORE EXCESS REFRIGERANT
- TO FILTER IMPURITIES FROM THE REFRIGERANT
- TO INCREASE COMPRESSOR EFFICIENCY
Correct Answer

A. TO STORE EXCESS REFRIGERANT

Explanation

The recovery tank in a refrigerant machine is primarily used to store excess refrigerant that is removed from a system during maintenance or servicing. This prevents the release of refrigerant into the atmosphere and allows for safe storage and disposal.

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3
17.

A RMO WOULD EXPECT A RELIEF VALVE TO START FUNCTIONING (FOR THE SECTION OF REFRIGERATING SYSTEM BEING PROTECTED) AT A PRESSURE MOST CLOSEST TO:
- 5% OVER DESIGN PRESSURE
- THE DESIGN PRESSURE
- RECOMMENDED OPERATING PRESSURE FOR NORMAL COOLING CONDITIONS
- 20% BELOW DESIGN PRESSURE
Correct Answer

A. THE DESIGN PRESSURE

Explanation

A relief valve is a safety device used in refrigerating systems to prevent overpressure. It is designed to open and release excess pressure when the pressure in the system exceeds a certain threshold, known as the design pressure. Therefore, a RMO (Refrigeration Maintenance Operator) would expect a relief valve to start functioning at the design pressure, as this is the pressure at which it is designed to activate and protect the system. The other options, such as 5% over design pressure or 20% below design pressure, are not accurate because the relief valve should only open when the pressure reaches the design pressure.

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6
18.

WHEN CHARGING A SYSTEM WITH LIQUID REFRIGERANT WITH A SET OF MANIFOLD GAUGES, WHAT POSITION ARE THE VALVES ON THE MANIFOLD?
- HIGH AND LOW VALVES BACKSEATED
- HIGH AND LOW VALVES FRONTSEATED
- HIGH SIDE BACKSEATED, LOW SIDE FRONTSEATED
- HIGH SIDE FRONTSEATED, LOW SIDE BACKSEATED
Correct Answer

A. HIGH SIDE BACKSEATED, LOW SIDE FRONTSEATED

Explanation

The correct answer is HIGH SIDE BACKSEATED, LOW SIDE FRONTSEATED. When charging a system with liquid refrigerant using a set of manifold gauges, the high side valve should be backseated (closed) and the low side valve should be frontseated (open). This allows the liquid refrigerant to flow into the low side of the system and prevents it from flowing into the high side prematurely.

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9
19.

ON THE LIQUID LINE, WHICH IS THE CORRECT ORDER OF THE PLACEMENT OF ACCESSORIES?
- SOLENOID VALVE, SIGHT-GLASS, AND DRIER
- DRIER, SIGHT-GLASS, AND SOLENOID VALVE
- DRIER, SOLENOID VALVE, AND SIGHT-GLASS
- NONE OF THE ABOVE
Correct Answer

A. DRIER, SIGHT-GLASS, AND SOLENOID VALVE

Explanation

The correct order of placement for accessories on the liquid line in a refrigeration system is as follows:
Drier: This is placed first to remove any moisture and contaminants from the refrigerant, ensuring that the system operates efficiently and preventing damage to other components.
Sight-glass: Positioned next, this allows for visual inspection of the refrigerant to check for adequate flow and the presence of bubbles, which can indicate a shortage of refrigerant or the presence of air in the system.
Solenoid Valve: Placed last, this controls the flow of refrigerant to the evaporator, helping to regulate the cooling process and ensuring that the system operates only when needed.

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8
20.

DURING A PARTICULAR ROUND AN OPERATOR NOTICES THAT THE SUCTION LINE AND PART OF THE COMPRESSOR ARE FROSTED, THE MOST LIKELY CAUSE OF THE CONDITION IS
- NOT ENOUGH REFRIGERANT IN SYSTEM
- EXPANSION VALVE OPEN TOO WIDE
- THE COMPRESSOR IS RUNNING CONTINUALLY
- COMPRESSOR VALVES ARE LEAKING
Correct Answer

A. EXPANSION VALVE OPEN TOO WIDE

Explanation

The most likely cause of the condition is that the expansion valve is open too wide. When the expansion valve is open too wide, it allows too much refrigerant to flow into the evaporator, causing the suction line and part of the compressor to frost over. This can result in reduced cooling capacity and potential damage to the compressor.

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9
21.

TXV POWER HEADS ARE COLOR CODED TO MATCH REFRIGERANT CHARGE IN THE SYSTEM. WHAT COLOR WOULD THE POWER HEAD HAVE IF IT WAS CHARGE WITH R-22?
- ORANGE
- GREEN
- YELLOW
- WHITE
Correct Answer

A. GREEN

Explanation

The power head of a TXV (Thermal Expansion Valve) is color coded to indicate the type of refrigerant charge in the system. In this case, if the power head was charged with R-22 refrigerant, it would be color coded as GREEN.

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2
22.

WHEN CHARGING AN R-12 RECIPROCATING REFRIGERATION SYSTEM, AN OPERATOR WOULD WANT TO USE WARM WATER TO INCREASE THE RELEASE RATE OF REFRIGERANT FROM THE DRUM. TO PERFORM THIS OPERATION THE WATER TEMP. SHOULD NOT EXCEED THE DEGREE °F OF
- 80°F
- 90°F
- 110°F
- 130°F
Correct Answer

A. 90°F

Explanation

Using warm water helps to increase the release rate of refrigerant from the drum when charging an R-12 reciprocating refrigeration system. However, the water temperature should not exceed 90°F. Temperatures higher than this could potentially cause the refrigerant to vaporize too quickly, leading to inefficient charging and potential damage to the system.

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3
23.

ACCORDING TO THE SAFETY HAND BOOK, HOW MUCH REFRIGERANT CAN BE RECOVERED INTO A 60 LB CONTAINER?
- 60 LBS
- 45 LBS
- 30 LBS
- 15 LBS
Correct Answer

A. 45 LBS

Explanation

According to the safety hand book, a 60 lb container can hold up to 45 lbs of refrigerant for recovery. This means that it is safe to recover and store up to 45 lbs of refrigerant in a container of this size.

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2
24.

DURING A WALK THROUGH OF THE ENGINE ROOM THE RMO NOTICES EXCESSIVE SUPERHEAT AT THE EVAPORATOR OUTLET, THIS WOULD MOST LIKELY BE CAUSED BY:
- STARVED EVAPORATOR
- LEAK IN SYSTEM
- LOW REFRIGERANT CHARGE
- ANY OF THE ABOVE
Correct Answer

A. ANY OF THE ABOVE

Explanation

Excessive superheat at the evaporator outlet can be caused by any of the above options: a starved evaporator, a leak in the system, or a low refrigerant charge. A starved evaporator occurs when there is not enough refrigerant flowing into the evaporator coil, leading to insufficient cooling. A leak in the system can result in a loss of refrigerant, causing a decrease in cooling capacity. A low refrigerant charge means that there is not enough refrigerant in the system, leading to inadequate cooling. Therefore, any of these issues can cause excessive superheat at the evaporator outlet.

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7
25.

IN AN OPERATING PLANT USING RECIPROCATING COMPRESSORS, THE EFFICIENCY OF ONE OF THE COMPRESSORS HAS DECREASED. ONE OF THE FOLLOWING MAY BE THE CAUSE OF THIS
- LIGHT SUCTION VALVE SPRINGS
- HIGH SUCTION PRESSURE
- LEAK IN THE SUCTION VALVE
- LOW SUCTION PRESSURE
Correct Answer

A. LEAK IN THE SUCTION VALVE

Explanation

A possible explanation for the decrease in efficiency of the compressor could be a leak in the suction valve. If there is a leak in the suction valve, it can result in a loss of suction pressure, which can negatively impact the compressor's performance. This can lead to a decrease in efficiency as the compressor has to work harder to maintain the desired pressure levels.

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1
26.

ORIFICE PLATES MAY BE USED AS A METERING DEVICE COMPONENT IN A CENTRIFUGAL SYSTEM. THE VESSEL WHICH THEY ARE CONTAINED IN CAN ALSO SERVE AS
- VAPOR RECYCLING UNIT
- AN ECONOMIZER
- REFRIGERANT CLEANER
- EVAPORATOR
Correct Answer

A. AN ECONOMIZER

Explanation

Orifice plates can be used as a metering device component in a centrifugal system. In addition to this, the vessel in which they are contained can also serve as an economizer. An economizer is a device that helps in improving the efficiency of a system by utilizing waste heat or energy. In this case, the vessel containing the orifice plates can be designed in such a way that it recycles and utilizes the waste heat or energy generated by the system, thereby serving as an economizer.

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1
27.

WITH RESPECT TO FIRE SAFETY, THE ANSI/ASHRAE REFRIGERANT SAFETY CLASSIFICATION THAT IS MOST DANGEROUS IS
- A1
- B2
- A3
- B1
Correct Answer

A. A3

Explanation

The correct answer is A3. In fire safety, the ANSI/ASHRAE refrigerant safety classification that is most dangerous is A3. This classification indicates that the refrigerant is highly flammable, posing a significant risk of fire. It is important to handle and store A3 refrigerants with extreme caution, following proper safety protocols to prevent accidents and ensure the safety of individuals and property.

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28.

AT THE CONDENSER, REFRIGERANT ENTERS AS
- HIGH PRESSURE GAS AND LEAVES AS LOW PRESSURE LIQUID
- HIGH PRESSURE GAS AND LEAVES AS HIGH PRESSURE LIQUID
- SUPERHEATED GAS AND LEAVES AS HIGH TEMPERATURE LIQUID
- HIGH TEMPERATURE GAS AND LEAVES AS SUPERHEATED GAS
Correct Answer

A. HIGH PRESSURE GAS AND LEAVES AS HIGH PRESSURE LIQUID

Explanation

The correct answer is "HIGH PRESSURE GAS AND LEAVES AS HIGH PRESSURE LIQUID." At the condenser, the refrigerant enters as a high-pressure gas and undergoes a cooling process. This cooling causes the refrigerant to condense and transform into a high-pressure liquid. Therefore, the refrigerant leaves the condenser as a high-pressure liquid.

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4
29.

WHAT SAFETY GROUP DOES AMMONIA BELONG?
- GROUP 2, B2
- GROUP 1, A1
- GROUP 3, B1
- BOTH A1 AND B1
Correct Answer

A. GROUP 2, B2

Explanation

Ammonia belongs to safety group 2, B2. This classification indicates that ammonia is a hazardous substance that can cause both immediate and long-term health effects. It is important to handle and store ammonia with caution to prevent any accidents or harm to individuals.

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2
30.

ACCORDING TO NYC FIRE CODE CLASSIFICATION OF REFRIGERANT, AMMONIA WOULD FALL UNDER WHICH GROUP?
- GROUP 1
- GROUP 2
- GROUP 3
- GROUP 4
Correct Answer

A. GROUP 2

Explanation

According to the NYC Fire Code classification of refrigerants, ammonia would fall under Group 2.

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3
31.

WHICH TYPE OF PUMP IS CONSIDERED A NON-POSITIVE DISPLACEMENT PUMP?
- RECIPROCATING
- ROTORY, SCREW
- SCROLL
- CENTRIFUGAL
Correct Answer

A. CENTRIFUGAL

Explanation

A non-positive displacement pump is a type of pump that does not trap and move a fixed amount of fluid with each cycle. Instead, it uses centrifugal force to move the fluid through the pump. A centrifugal pump works by converting rotational energy from a motor into kinetic energy in the liquid being pumped. This kinetic energy then creates pressure and pushes the fluid out of the pump. Therefore, a centrifugal pump is considered a non-positive displacement pump.

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6
32.

IF THE ELIMINATOR PLATES LOCATED BELOW THE FAN IN AN INDUCED DRAFT-COOLING TOWER HAVE BECOME CLOGGED, OF THE FOLLOWING THIS WOULD MOST LIKELY RESULT IN:
- DAMAGE TO FAN BLADES
- INCREASE IN COOLING TOWER WATER TEMP BEING RETURNED
- DECREASE IN MAKEUP WATER REQUIREMENTS
- A DROP IN WET BULB TEMP
Correct Answer

A. INCREASE IN COOLING TOWER WATER TEMP BEING RETURNED

Explanation

If the eliminator plates located below the fan in an induced draft-cooling tower have become clogged, it would most likely result in an increase in cooling tower water temperature being returned. The eliminator plates are responsible for removing water droplets from the air stream before it is discharged from the cooling tower. If these plates are clogged, they will not be able to effectively remove the water droplets, leading to a higher temperature in the water being returned to the cooling tower.

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6
33.

CONVERT 18" VACUUM TO PSIA
- 7.7
- 0.6
- 5.9
- 23.5
Correct Answer

A. 5.9
34.

SUPERHEATED VAPOR PROTECTS THE COMPRESSOR AGAINST LIQUID INTAKE. WHAT WOULD THE RMO NOTICE IF COMPRESSOR WAS RECEIVING LIQUID?
- HEAD PSI DROPPING TO LOW
- DECREASE THE CAPACITY OF THE COMPRESSOR AND REFRIGERATION SYSTEM
- NON-CONDENSABLES ARE MORE PRONE TO COLLECT IN THE SYSTEM
- FROST MAY DEVELOP IN THE SUCTION LINE
Correct Answer

A. FROST MAY DEVELOP IN THE SUCTION LINE

Explanation

If the compressor was receiving liquid, it would cause the refrigerant in the suction line to be colder than normal. This can lead to the formation of frost in the suction line. Frost formation is an indication that the refrigerant is not in its ideal state and can cause a decrease in the compressor's efficiency. Therefore, the presence of frost in the suction line would be noticed by the RMO as a potential issue with the compressor receiving liquid instead of superheated vapor.

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5
35.

IF AN ELECTRIC MOTOR IS REWOUND TO CUT RESISTANCE BY 1/2, ALL OTHER FACTORS BEING EQUAL, THE MOTOR POWER WOULD:
- REDUCE BY 1/2
- INCREASE BY A FACTOR OF 2
- STAY THE SAME
- INCREASE BY A FACTOR OF 4
Correct Answer

A. INCREASE BY A FACTOR OF 2

Explanation

If an electric motor is rewound to cut resistance by 1/2, all other factors being equal, the motor power would increase by a factor of 2. This is because power is directly proportional to the square of the current, and reducing the resistance by 1/2 would result in a doubling of the current. Therefore, the power output of the motor would increase by a factor of 2.

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4
36.

AT THE PLANT WHERE YOU ARE EMPLOYED A REFRIGERATING UNIT IS BEING TAKEN OUT OF SERVICE FOR MAJOR REPAIRS AND THAT YOU HAVE BEEN ASSIGNED TO WITHDRAW REFRIGERANT FOR STORAGE IN A 40 GALLON CONTAINER. ACCORDING TO THE NYC FIRE HANDBOOK, THE MAXIMUM QUANTITY OF REFRIGERANT IN GALLONS THAT YOU MAY LEGALLY FILL EACH CONTAINER WITH UNDER ANY CIRCUMSTANCES IS:
- 36
- 30
- 24
- 32
Correct Answer

A. 30

Explanation

According to the NYC Fire Handbook, the maximum quantity of refrigerant in gallons that can be legally filled in each container under any circumstances is 30.

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2
37.

ASSUME AN OPERATOR IS ABLE TO OBSERVE R-11, WATER AND LUBRICATING OIL TOGETHER AT 70°F. UNDER THESE CONDITIONS, THE WATER, MOISTURE, AND FLUIDS WOULD SETTLE IN THE CONTAINER FROM TOP TO BOTTOM IN WHAT ORDER?
- WATER, OIL, REFRIGERANT
- OIL, REFRIGERANT, WATER
- REFRIGERANT, OIL, WATER
- OIL, WATER, REFRIGERANT
Correct Answer

A. REFRIGERANT, OIL, WATER

Explanation

In a container where R-11 (a type of refrigerant), water, and lubricating oil are all present at 70°F, the substances will separate based on their densities. R-11, which is denser than air but less dense than water or oil, will float on top of water but under the oil. Water, being denser than both oil and R-11, will settle at the bottom of the container. Oil, which is less dense than water but more dense than R-11, will float on top of the water but below the refrigerant. Thus, from top to bottom, the layers would be refrigerant (R-11), oil, and water.

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38.

A RMO WAS INSTRUCTED TO CHARGE A 60 TON PLANT WITH R-134A REFRIGERANT. THE OPERATOR WOULD MOST LIKELY FIND THE CHARGING VALVE ON THE:
- HIGH PRESSURE SIDE OF THE EQUIPMENT
- LOW PRESSURE SIDE OF THE EQUIPMENT
- DISCHARGE SIDE OF THE EQUIPMENT
- RECIEVER
Correct Answer

A. LOW PRESSURE SIDE OF THE EQUIPMENT

Explanation

The operator would most likely find the charging valve on the low pressure side of the equipment because when charging a refrigerant, it is typically done on the low pressure side to ensure proper distribution and avoid overcharging the system. Charging on the high pressure side can lead to overpressurization and potential damage to the equipment. The discharge side and receiver are not typically used for charging refrigerant.

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39.

WHEN CHANGING WATER TO ICE, WHAT MUST BE REMOVED?
- SPECIFIC HEAT
- SUPER HEAT
- LATENT HEAT
- SENSIBLE HEAT
Correct Answer

A. LATENT HEAT

Explanation

When changing water to ice, latent heat must be removed. Latent heat is the heat energy required to change the state of a substance without changing its temperature. In the case of water turning into ice, latent heat is released as the water molecules lose energy and slow down, causing them to form a solid structure. Therefore, to change water to ice, the latent heat needs to be removed from the water.

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40.

WHEN OPERATING A REFRIGERATION MACHINE CONDENSER USING R-22 REFRIGERANT, UNDER NORMAL CONDITIONS THE OPERATOR OBSERVES THAT THE COOLING WATER IS BEING SUPPLIED AT 85°F AND LEAVING AT 95°F. GIVEN THIS INFORMATION, THE CORRESPONDING COMPRESSOR HEAD PRESSURE IN PSI SHOULD BE MOST NEARLY:
- 113
- 313
- 213
- 13
Correct Answer

A. 213

Explanation

Under normal conditions, the cooling water temperature leaving the condenser should be higher than the temperature entering it. This is because the condenser removes heat from the refrigerant, causing the water temperature to increase. Since the cooling water is being supplied at 85°F and leaving at 95°F, it indicates that the condenser is effectively removing heat from the refrigerant. The corresponding compressor head pressure in PSI should be most nearly 213, as it is the only option that aligns with the given information and indicates proper cooling operation.

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41.

WHEN PROPERLY PURGING YOU SHOULD
- PURGE AT RAPID RATE
- PURGE WITH COMPRESSOR ON
- STOP WHEN PRESSURE CEASES TO DROP
- RUN THE CONDENSER AS MUCH AS POSSIBLE
Correct Answer

A. STOP WHEN PRESSURE CEASES TO DROP

Explanation

When properly purging, you should stop when the pressure ceases to drop. This means that all the air or gas that needed to be removed from the system has been successfully purged. Continuing to purge after the pressure has stopped dropping would be unnecessary and potentially wasteful.

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42.

A RECIPROCATING REFRIGERATION COMPRESSOR CYLINDER HAS A 12" BORE AND 16" STROKE, THE VOLUME OF REFRIGERANT IN CUBIC INCHES WOULD BE CLOSER TO
- 1204
- 1002
- 1808
- 1406
Correct Answer

A. 1808

Explanation

The volume of a cylinder can be calculated using the formula V = πr^2h, where r is the radius of the cylinder and h is the height or stroke. In this case, the radius is half of the bore, so it would be 6 inches. The stroke is given as 16 inches. Plugging these values into the formula, we get V = π(6^2)(16) = 1808 cubic inches. Therefore, the volume of refrigerant in the cylinder would be closer to 1808 cubic inches.

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43.

A RUPTURE DISC IN A CENTRIFUGAL REFRIGERATING MACHINE IS NORMALLY LOCATED ON THE
- CONDENSER
- ECONOMIZER
- COMPRESSOR DISCHARGE
- EVAPORATOR
Correct Answer

A. EVAPORATOR

Explanation

The rupture disc in a centrifugal refrigerating machine is normally located on the evaporator. The evaporator is responsible for absorbing heat from the surroundings and evaporating the refrigerant, thus cooling the system. Placing the rupture disc on the evaporator ensures that any excessive pressure buildup in the system is released at the point where the refrigerant is being evaporated. This helps to prevent any potential damage or failure of the evaporator due to high pressure, ensuring the safe operation of the refrigerating machine.

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6
44.

INITIAL O.A.T. IS 50°F. YOU HAVE BEEN INFORMED THAT THE O.A.T. HAS DROPPED 10°C. THE TEMPERATURE IN °F IS -
- 32
- 28
- 40
- 18
Correct Answer

A. 32

Explanation

This suggests if the O.A.T. was approximately 50°F before the drop, after a decrease of 18°F, it would be around 32°F.

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23
45.

GIVEN A REFRIGERATION SYSTEM WHICH INCLUDES A FORCED DRAFT COOLING TOWER, AN ECONOMIZER AND CHILLED WATER AS THE COOLING MEDIUM, THE HEAT THAT IS REMOVED FROM THE BUILDING IS FINALLY REJECTED:
- AS HEAT OF EVAPORATION OF THE COOLING TOWER
- IN THE ECONOMIZER
- IN THE EVAPORATOR
- CONDENSER WATER OUTLET
Correct Answer

A. AS HEAT OF EVAPORATION OF THE COOLING TOWER

Explanation

The heat that is removed from the building is finally rejected as heat of evaporation of the cooling tower. This means that the cooling tower uses the process of evaporation to remove heat from the building. As the water in the cooling tower evaporates, it absorbs heat from the building, thereby cooling the building. This heat is then released into the atmosphere as the water vaporizes, thus rejecting the heat from the building.

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46.

FROST APPEARING ON THE SUCTION LINE AND PART OF THE COMPRESSOR IS CAUSED BY?
- SLUGGING COMPRESSOR
- FLOODED EVAPORATOR
- STARVED EVAPORATOR
- UNINSULATED SUCTION LINE
Correct Answer

A. FLOODED EVAPORATOR

Explanation

Frost appearing on the suction line and part of the compressor is caused by a flooded evaporator. When the evaporator is flooded, it means that there is an excess amount of refrigerant entering the evaporator coil. This can happen due to issues such as a faulty expansion valve or a malfunctioning liquid line solenoid valve. The excess refrigerant in the evaporator causes the suction line and part of the compressor to become colder than normal, leading to the formation of frost.

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47.

A PUMP AFFECTS THE PRESSURE OF A FLUID OR GAS BY:
- REDUCING PRESSURE
- RAISING PRESSURE
- REGULATING PRESSURE
- STABILIZING PRESSURE
Correct Answer

A. RAISING PRESSURE

Explanation

A pump affects the pressure of a fluid or gas by raising it. When a pump is operated, it creates a pressure difference that forces the fluid or gas to move from an area of lower pressure to an area of higher pressure. This increase in pressure allows the fluid or gas to be transported or used for various purposes, such as in water supply systems, hydraulic systems, or air compression systems. Therefore, the correct answer is "RAISING PRESSURE."

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48.

THE BULB TO A TXV HAS FALLEN OFF AND THE ROOM IS AT 85°F. THE EVAPORATOR WOULD?
- STARVE
- FLOOD
- INCREASE SUPERHEAT
- RESPOND NORMALLY
Correct Answer

A. FLOOD

Explanation

If the bulb to a TXV has fallen off and the room is at 85°F, the evaporator would flood. The TXV (Thermal Expansion Valve) regulates the flow of refrigerant into the evaporator coil based on the temperature sensed by the bulb. Without the bulb, the TXV cannot accurately control the refrigerant flow, leading to an excessive amount of refrigerant entering the evaporator coil. This causes flooding, where the evaporator becomes overwhelmed with liquid refrigerant, leading to inefficient cooling and potential damage to the system.

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2
49.

A VERTICAL 12" WATER PIPE FROM THE ROOF HAS A PRESSURE GAUGE READING OF 120 PSI. HOW TALL IS THE PIPE?
- 277 FEET
- 1,440 INCHES
- 1,440 FEET
- 277 INCHES
Correct Answer

A. 277 FEET

Explanation

The pressure gauge reading of 120 PSI indicates the pressure at the base of the vertical water pipe. The height of the pipe can be determined using the principle of hydrostatic pressure. The pressure of a fluid at a certain depth is directly proportional to the height of the fluid column above it. Since the pressure at the base of the pipe is 120 PSI, and the standard atmospheric pressure is 14.7 PSI, the pressure due to the height of the water column is 120 - 14.7 = 105.3 PSI. By converting this pressure to feet of water column using the conversion factor of 2.31 feet of water column per PSI, we get 105.3 * 2.31 = 242.4 feet. However, since the question asks for the height of the pipe and not the water column, we need to add the height of the water column to get the total height of the pipe, which is 242.4 + 34 = 277 feet. Therefore, the correct answer is 277 feet.

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1

Quiz Review Timeline (Updated): Aug 10, 2024 +

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Current Version
Aug 10, 2024

Quiz Edited by
ProProfs Editorial Team
Feb 08, 2014

Quiz Created by
Catherine Halcomb

Refrigerant Machine Operator Certification Practice Test

THE AMOUNT OF REFRIGERANT THAT FLOWS THROUGH THE ORIFICE PLATE IS DETERMINED BY:

Quiz Preview

UNLOADERS ARE USED TO:

SEMI-HERMETIC COMPRESSORS MAY BE BETTER TO USE THAN HERMETIC COMPRESSORS BECAUSE HERMETIC COMPRESSORS:

WHEN CONDUCTING A ROUTINE TOUR OF PLANT OPERATION A RMO OBSERVES A SIGNIFICANT INCREASE IN SUPERHEAT TEMP. FOR THE REFRIGERATING FLUID ENTERING A RECIPROCATING COMPRESSOR. OF THE FOLLOWING THE MOST LIKELY CAUSE FOR THIS CONDITION IS

A ROOM THERMOSTAT CONTROLS THE LIQUID LINE SOLENOID VALVE IN THIS COMMERCIAL REFRIGERATION SYSTEM. THE COMPRESSOR IS ACTIVATED BY:

WHILE MONITORING THE OPERATION OF A RECIPROCATING REFRIGERATING UNIT YOU OVERSEE THAT THE CYCLING TIMES ARE NORMAL, COMPRESSOR COMPRESSION AND TEMP ARE THE ONLY READING THAT ARE OUTSIDE THE NORMAL RATE. UNDER THESE CONDITIONS SERVICE REQUIREMENTS WOULD INDICATE INSPECTING FOR

WHICH OF THE FOLLOWING ASHRAE SAFETY GROUPS IS THE MOST DANGEROUS?

YOU ARE AN RMO ASSIGNED TO FACILITY WHERE A REFRIGERANT HAS BEEN RECENTLY CHANGED FROM A FLAMMABLE REFRIGERANT TO R-22, AT THE MOMENT YOU ARE PLANNING TO BRAZE METAL. ON SUCH MAKING A REPAIR IN THE MACHINERY ROOM, UNDER THESE CIRCUMSTANCES YOU:

AN OPERATOR HAS BEEN ASSIGNED TO RUN A CENTRIFUGAL COMPRESSOR. OF THE FOLLOWING ACTIONS A CAPACITY CONTROL IS MOST LIKELY TO ACHIEVE IS THROUGH

A RMO NEEDED TO VARY THE FLOW OF REFRIGERANT IN A SYSTEM. A CONTINUOUS VARIATION IN THE FLOW OF THE SYSTEM DOES NOT INCLUDE THE:

AN OPERATOR HAS BEEN ASSIGNED TO A LARGE RECIPROCATING MACHINE WITHOUT UNLOADERS OF THE FOLLOWING SAFETY PROPER PROCEDURE FOR STARTING MACHINE IS.

AN OPERATOR HAS BEEN ASSIGNED TO RUN A RECIPROCATING COMPRESSOR. THE FOLLOWING ACTION CAPACITY CONTROL WOULD MOST LIKELY BE ACHIEVED THROUGH:

IF A CENTRIFUGAL COMPRESSOR IS BEING USED IN A REFRIGERATION SYSTEM, AND IS AFFECTED BY THE CONDENSER, THE CONDENSER MAY BE IMPROVED BY:

AN OPERATOR IS USING A SLING PSYCHROMETER TO MEASURE DRY AND WET BULB TEMP ON A ROOF OF A BUILDING WHERE THE COOLING TOWER IS LOCATED. IF DURING THE DAY THE TEMP REMAINS CONSTANT, AND WET BULB DROPS BY 5°F, AND ALL OTHER CONDITIONS REMAIN UNCHANGED, THE OPERATOR SHOULD SEE:

UPON BEING ASSIGNED TO A FACILITY DURING INSPECTION OF THE FACILITY, YOU FIND THERE HAS BEEN FAILURE TO MAINTAIN WATER TREATMENT. INSPECTING THE CONDENSER WATER, THE FIRST EVIDENCE WOULD MOST LIKELY BE:

WHAT IS THE PURPOSE OF THE RECOVERY TANK WHEN OPERATING A REFRIGERANT MACHINE?

A RMO WOULD EXPECT A RELIEF VALVE TO START FUNCTIONING (FOR THE SECTION OF REFRIGERATING SYSTEM BEING PROTECTED) AT A PRESSURE MOST CLOSEST TO:

WHEN CHARGING A SYSTEM WITH LIQUID REFRIGERANT WITH A SET OF MANIFOLD GAUGES, WHAT POSITION ARE THE VALVES ON THE MANIFOLD?

ON THE LIQUID LINE, WHICH IS THE CORRECT ORDER OF THE PLACEMENT OF ACCESSORIES?

DURING A PARTICULAR ROUND AN OPERATOR NOTICES THAT THE SUCTION LINE AND PART OF THE COMPRESSOR ARE FROSTED, THE MOST LIKELY CAUSE OF THE CONDITION IS

TXV POWER HEADS ARE COLOR CODED TO MATCH REFRIGERANT CHARGE IN THE SYSTEM. WHAT COLOR WOULD THE POWER HEAD HAVE IF IT WAS CHARGE WITH R-22?

WHEN CHARGING AN R-12 RECIPROCATING REFRIGERATION SYSTEM, AN OPERATOR WOULD WANT TO USE WARM WATER TO INCREASE THE RELEASE RATE OF REFRIGERANT FROM THE DRUM. TO PERFORM THIS OPERATION THE WATER TEMP. SHOULD NOT EXCEED THE DEGREE °F OF

ACCORDING TO THE SAFETY HAND BOOK, HOW MUCH REFRIGERANT CAN BE RECOVERED INTO A 60 LB CONTAINER?

DURING A WALK THROUGH OF THE ENGINE ROOM THE RMO NOTICES EXCESSIVE SUPERHEAT AT THE EVAPORATOR OUTLET, THIS WOULD MOST LIKELY BE CAUSED BY:

IN AN OPERATING PLANT USING RECIPROCATING COMPRESSORS, THE EFFICIENCY OF ONE OF THE COMPRESSORS HAS DECREASED. ONE OF THE FOLLOWING MAY BE THE CAUSE OF THIS

ORIFICE PLATES MAY BE USED AS A METERING DEVICE COMPONENT IN A CENTRIFUGAL SYSTEM. THE VESSEL WHICH THEY ARE CONTAINED IN CAN ALSO SERVE AS

WITH RESPECT TO FIRE SAFETY, THE ANSI/ASHRAE REFRIGERANT SAFETY CLASSIFICATION THAT IS MOST DANGEROUS IS

AT THE CONDENSER, REFRIGERANT ENTERS AS

WHAT SAFETY GROUP DOES AMMONIA BELONG?

ACCORDING TO NYC FIRE CODE CLASSIFICATION OF REFRIGERANT, AMMONIA WOULD FALL UNDER WHICH GROUP?

WHICH TYPE OF PUMP IS CONSIDERED A NON-POSITIVE DISPLACEMENT PUMP?

IF THE ELIMINATOR PLATES LOCATED BELOW THE FAN IN AN INDUCED DRAFT-COOLING TOWER HAVE BECOME CLOGGED, OF THE FOLLOWING THIS WOULD MOST LIKELY RESULT IN:

CONVERT 18" VACUUM TO PSIA

SUPERHEATED VAPOR PROTECTS THE COMPRESSOR AGAINST LIQUID INTAKE. WHAT WOULD THE RMO NOTICE IF COMPRESSOR WAS RECEIVING LIQUID?

IF AN ELECTRIC MOTOR IS REWOUND TO CUT RESISTANCE BY 1/2, ALL OTHER FACTORS BEING EQUAL, THE MOTOR POWER WOULD:

ASSUME AN OPERATOR IS ABLE TO OBSERVE R-11, WATER AND LUBRICATING OIL TOGETHER AT 70°F. UNDER THESE CONDITIONS, THE WATER, MOISTURE, AND FLUIDS WOULD SETTLE IN THE CONTAINER FROM TOP TO BOTTOM IN WHAT ORDER?

A RMO WAS INSTRUCTED TO CHARGE A 60 TON PLANT WITH R-134A REFRIGERANT. THE OPERATOR WOULD MOST LIKELY FIND THE CHARGING VALVE ON THE:

WHEN CHANGING WATER TO ICE, WHAT MUST BE REMOVED?

WHEN OPERATING A REFRIGERATION MACHINE CONDENSER USING R-22 REFRIGERANT, UNDER NORMAL CONDITIONS THE OPERATOR OBSERVES THAT THE COOLING WATER IS BEING SUPPLIED AT 85°F AND LEAVING AT 95°F. GIVEN THIS INFORMATION, THE CORRESPONDING COMPRESSOR HEAD PRESSURE IN PSI SHOULD BE MOST NEARLY:

WHEN PROPERLY PURGING YOU SHOULD

A RECIPROCATING REFRIGERATION COMPRESSOR CYLINDER HAS A 12" BORE AND 16" STROKE, THE VOLUME OF REFRIGERANT IN CUBIC INCHES WOULD BE CLOSER TO

A RUPTURE DISC IN A CENTRIFUGAL REFRIGERATING MACHINE IS NORMALLY LOCATED ON THE

INITIAL O.A.T. IS 50°F. YOU HAVE BEEN INFORMED THAT THE O.A.T. HAS DROPPED 10°C. THE TEMPERATURE IN °F IS -

GIVEN A REFRIGERATION SYSTEM WHICH INCLUDES A FORCED DRAFT COOLING TOWER, AN ECONOMIZER AND CHILLED WATER AS THE COOLING MEDIUM, THE HEAT THAT IS REMOVED FROM THE BUILDING IS FINALLY REJECTED:

FROST APPEARING ON THE SUCTION LINE AND PART OF THE COMPRESSOR IS CAUSED BY?

A PUMP AFFECTS THE PRESSURE OF A FLUID OR GAS BY:

THE BULB TO A TXV HAS FALLEN OFF AND THE ROOM IS AT 85°F. THE EVAPORATOR WOULD?

A VERTICAL 12" WATER PIPE FROM THE ROOF HAS A PRESSURE GAUGE READING OF 120 PSI. HOW TALL IS THE PIPE?