Refrigeration and HVAC Fundamentals, Exams of Refrigeration and Air Conditioning

Download Refrigeration and HVAC Fundamentals and more Exams Refrigeration and Air Conditioning in PDF only on Docsity! REF-B 2024/2025 PRACTICE EXAM QUESTIONS WITH 100% CORRECTLY SOLVED ANSWERS. What is a jurisdiction? -- Correct Answer ✔✔ Each province and territory is its own jurisdiction Explain the intent of the regulation's governing the operation of boilers and pressure equipment? -- Correct Answer ✔✔ To give the director or administrator of the department or branch or government a means of evolving, within the framework of the intent of the act, to meet changes in technology, concept, and the use of those variables listed within the scope of the act. Is it more difficult to change an act or a regulation? -- Correct Answer ✔✔ The main or primary document is an "act" which must be passed through the jurisdictional legislature. The act then has "regulations" which are pursuant to the enforcement of the act. These regulations are usually under the governance of an official of the government rather than the actual legislature. As a result, it is much easier to have changes made to a regulation than it is to have changes made to an act. What jurisdictional item or legislation is most important to a person interning time make power engineering a career choice? -- Correct Answer ✔✔ Power engineers acts and regulations What two Canadian national codes have been adopted by all jurisdictions -- Correct Answer ✔✔ CSA B51 and CSA B52 List some of the penalties which may be applied to the holder of a certificate of competency -- Correct Answer ✔✔ The regulation will also refer to penalties which may be listed in the pertinent jurisdictional act. These can be fines, certificate suspensions, certificate cancellations, imprisonment. List types of pressure vessels discussed in the CSA B51 section entitled "pressure vessels" -- Correct Answer ✔✔ Blowoff vessels, hot water tanks, hydropneumatics tanks, and cushion tanks Explain the two purposes of the CSA B52 code -- Correct Answer ✔✔ To provide for the safe design, construction, installation, operation, and repair of refrigerating and air conditioning equipment and systems, and related equipment. To promote uniform requirements among the provinces and territories. Describe the purpose of ASME Section VI - recommended rules for the care and operation of heating boilers and explain how this purpose is achieved. -- Correct Answer ✔✔ This code contains rules that have been compiled to assist operators of heating boilers in maintaining their plants in as safe a condition as possible. These rules apply to the boiler proper and to pipe connections up to and including the value of valves required by the ASME code. Rules are also given covering auxiliary equipment in so far as safety is concerned What recommended procedures are covered in ASME Section VI - recommended rules for the care and operation of heating boilers pertaining to the treatment of water in steam and hot water heating boilers? -- Correct Answer ✔✔ These recommended procedures cover the treatment of water in steam and hot water boilers. They cover boiler water troubles, chemicals used, function of chemicals, treatment alternatives, blowdown, feeders, and procedures Which of the following items are covered in the appendix or the ASME Boiler and Pressure Vessel Code, Section IV - Heating Boilers? a) approval of new materials under code b) porosity charts for weld radiography c) manufacturer's data report forms and guides d) all of the above -- Correct Answer ✔✔ D The temperature at which a liquid refrigerant evaporates is dependent on the _____ -- Correct Answer ✔✔ Temperature and pressure of the refrigerant in the evaporator Latent heat may be defined further with respect to the states or the substance changing phase. Name the type of latent heat required to change ice from a solid state to a liquid state or from a liquid state to a solid state. -- Correct Answer ✔✔ Fusion Explain how the temperature at which a refrigerant boils in a refrigeration system is controlled. -- Correct Answer ✔✔ Controlled by having an expansion valve at the inlet of the evaporator and a thermostat on the medium to be cooled. Based on the set point of the thermostat, the slow rate through the expansion valve is controlled A body travels 1000 m in 65 seconds. What is it's velocity? A) 14.79 m/s B) 15.12 m/s C) 15.38 m/s D) 22.25 m/s -- Correct Answer ✔✔ C A body is moving north at 15 m/s and 7 seconds later it has a velocity of 40 m/s in the same direction. What was the acceleration of the body? A) 3.57 m/s/s B) 5.25 m/s/s C) 2.84 m/s/s D) 4.56 m/s/s -- Correct Answer ✔✔ A A mass of 250 kg is accelerated at 17 m/s/s. What force is required to achieve this acceleration? A) 34.2 kN B) 43.5 kN C) 425 N D) 4.25 kN -- Correct Answer ✔✔ D A body with a mass of 75 kg is allowed to fall freely to the ground. What gravitational force is acting on the mass? A) 539.45 N B) 1.39 kN C) 735.75 N D) 626.55 N -- Correct Answer ✔✔ C A hydraulic plunger has an area of 0.10 m*m and a force of 200 N acts in it. What is the pressure exerted on the plunger? A) 1.64 kPa B) 750 Pa C) 1.84 kPa D) 2 kPa -- Correct Answer ✔✔ D Potential energy is the ability of a body to do work by virtue of its A) pressure B) position C) force D) acceleration -- Correct Answer ✔✔ B If a welding electrode has the following identifying number E7015 what does the 70 represent? A) 70 mm B) 70000 psi C) 70000 kPa D) best angle to be used when welding -- Correct Answer ✔✔ B With straight polarity the welding electrode is connected to A) the positive terminal B) either terminal C) the negative terminal D) a good ground -- Correct Answer ✔✔ C Submerged arc welding is A) an oxyacetylene welding process B) an AC electric welding process C) a DV welding process D) an AC or DC electric welding process -- Correct Answer ✔✔ D Braze welding is used extensively in the repair of ________ and ________ parts A) wrought iron, cast iron B) stainless steel, carbon steel C) aluminum, white metal D) cast iron, malleable iron -- Correct Answer ✔✔ D A method of testing a weld which is quick easy and inexpensive is the A) fluorescent penetrant method B) visual method C) ultrasonic method D) dye penetrant method -- Correct Answer ✔✔ B When using radiographic inspections defects such as cracks and porosity show up as _________ on the photographic paper A) hairline cracks B) pinholes C) slag inclusion D) darker shadows -- Correct Answer ✔✔ D The method of detection that is effective and widely used to detect leaks in the welded joints of tanks and containers is A) hydrostatic test B) ultrasonic test C) fluorescent penetrant D) magparticle -- Correct Answer ✔✔ C A gas pocket or weld cavity caused by gas or moisture trapped in a weld is called a A) blow hole B) crack C) crater D) root crack -- Correct Answer ✔✔ A A reducing flame is one which is rich in A slight leakage is desired between the pump shaft and packing of the majority of pumps in order to A) prevent the ingress of atmospheric air B) increase the pump capacity and efficiency C) prevent wearing of the wear rings D) lubricate the services E) prevent the pump from vapor locking -- Correct Answer ✔✔ D Flexible coupling's will compensate for A) overheating of packing B) axle shaft misalignment C) bearing failure D) shaft eccentricity due to a badly bent shaft E) impeller imbalance -- Correct Answer ✔✔ B Proper priming and venting of a pump is important especially if A) the medium being pumped is high temperature B) the medium being pumped contains suspended solids C) the pump has a stuffing box and lantern ring D) a mechanical seal is used E) oil or other low flash point lubricant is being pumped -- Correct Answer ✔✔ D Most pump failures and damage occur A) after about six months of continuous service B) due to vapor binding C) during initial start up D) due to wrong rotation E) because of in adequate operator training -- Correct Answer ✔✔ C A plugged impeller symptom or result will be A) air leaks in suction line and stuffing boxes B) wrong direction of rotation C) loss of prime D) an overheated stuffing box E) no liquid being delivered -- Correct Answer ✔✔ E List for advantages of mechanical seals when compared with packing glands -- Correct Answer ✔✔ Less maintenance is required, there is no wear to the shaft or shaft sleeve, leakage is reduced to a minimum, allows design of very high temperature and pressure applications Two ways in which a pump and motor shop can be out of alignment Are -- Correct Answer ✔✔ Angular misalignment axial misalignment For power plants materials used for the manufacturing of pipes must be A) cast iron B) seamless stainless steal C) suited to the operating conditions of the piping system D) case hardened -- Correct Answer ✔✔ C Copper and copper alloy piping and tubing is not used in powerplants when ______ is a prime factor A) pressure B) metallurgy C) temperature D) fluid commodities -- Correct Answer ✔✔ C Pipe fittings which are not clearly identified should be A) marked by the local boiler inspector B) hydrostatically tested C) used in low pressure service D) rejected -- Correct Answer ✔✔ D The type of pipe flange gasket not in normal use today is the A) full face B) ring joint C) flat ring D) graphite -- Correct Answer ✔✔ D Gaskets are used in pipe flange joints to A) prevent leakage because of small imperfections in the flange face B) allow for pipe expansion between each flanged joint C) make up for the misalignment of the pipe D) provide cushioning in the event of water hammer -- Correct Answer ✔✔ A A good rule of thumb to use for the spacing of pipe supports in a piping system is every A) 10 m B) 7.5 m C) 5 m D) 3 m -- Correct Answer ✔✔ D The kind of valve that has minimum wire drawing and seat erosion is the A) ball valve B) globe valve C) check valve D) gate valve -- Correct Answer ✔✔ B To ensure safe and continuous operation of a pressure reducing valve the valve station should have A) a safety valve on the downstream side B) a bypass loop downstream safety valve and a downstream pressure gauge C) the piping to the station made of at least schedule 80 piping D) a Y strainer immediately after the valve -- Correct Answer ✔✔ B What is the maximum temperature for which a non-special alloy steel valve can be used A) 343°C B) 425°C C) 925°C D) 650°C -- Correct Answer ✔✔ D Pressure and or temperature rating of a fitting is known as the A) material designation B) identification of the type of construction material In order to protect the driver a start stop air compressor should be equipped with A) an intercooler B) an automatic blowdown system C) safety heads D) pre-start automatic unloading E) manual cylinder bleed Petcocks -- Correct Answer ✔✔ D The two general types of air compressors are -- Correct Answer ✔✔ Positive displacement, dynamic Describe the operation of a centrifugal compressor -- Correct Answer ✔✔ Similar to a centrifugal pump air is drawn into the compressor impeller and then discharged through a diffuser into a volute shaped casing. the speed of the impeller causes the air to be discharged into the casing at a high velocity where the speed is suddenly reduced causing an increase in pressure Heat exchangers used to cool the air between stages of an air compressor are called -- Correct Answer ✔✔ Intercoolers List three benefits of using an air receiver in an air compression system -- Correct Answer ✔✔ Acts as a reservoir for the storage of compressed air, dampens pulsation in the compressed air system, provides a point for moisture and oil to separate from the compressed air What are the particles that make up a molecule referred to as -- Correct Answer ✔✔ atoms And electric toaster has 9 A flowing at 115 V what is the wattage -- Correct Answer ✔✔ 1.035 kW What amount of electrical current can cause death -- Correct Answer ✔✔ 250 milliamps What causes a fluorescent light to flickering on and off accompanied by a shimmering effect during lighting periods -- Correct Answer ✔✔ Lamp life has been reached and needs to be replaced Which of the following are the common types of electric motor housings A) Open drip proof housing B) splash proof housing C) totally enclosed housing D) all of the above -- Correct Answer ✔✔ D Which of the following agencies is not responsible for testing of appliances A) ASME B) CSA C) ULC D) UL -- Correct Answer ✔✔ A The ideal commercial refrigerant should -- Correct Answer ✔✔ Be environmentally friendly The property which has to be known for the calculation of the size of control valve and piping is -- Correct Answer ✔✔ Density Which of the following is not a physical property of refrigerant A) toxicity B) odor C) leakage tendency D) density E) explosiveness -- Correct Answer ✔✔ D In which Canadian publication or refrigerant officially classified according to their toxicity and flammability -- Correct Answer ✔✔ CSA B-52 mechanical refrigeration code Describe the term standard conditions as it applies to refrigerants and state the values which are considered as standard -- Correct Answer ✔✔ Standard conditions are used as an indication of the difference in the thermodynamic properties of various refrigerants by comparing them at a standard temperature and pressure. the standard conditions are 30°C in the condenser and -15°C in the evaporator. the saturation pressure for the various refrigerant at these temperatures are then used for comparison Describe the two problems that can result from water absorption into the refrigerant -- Correct Answer ✔✔ Water in the refrigerant will freeze in the evaporator coil's expansion valve and possibly in the suction valves of the compressor causing reduced heat exchange in the evaporator and flow restrictions in the valves. water can also react with some refrigerant and compressor oil's to form acidic substances which will result in corrosion of the systems Describe the difference between a direct and indirect refrigeration system -- Correct Answer ✔✔ The direct system is one in which the evaporator is in direct contact with the material or space being refrigerated the indirect system is one that uses refrigerant to cool a liquid such as Brine or water this brine or water is the b circulated by means of a pump to the material or space being refrigerated Explain how compression refrigeration system temperatures and pressures are related -- Correct Answer ✔✔ For the low pressure part of the system the first consideration is the temperature required for the medium to be cooled the next consideration is the evaporation temperature of the liquid refrigerant in order to get sufficient heat transferred from the medium to be cooled to the liquid refrigerant the evaporation temperature should be well below that of the medium thus the pressure in the evaporator must be such that the evaporation temperature is 5 to 10°C below the desired temperature of the medium to be cooled for the high-pressure part of the system the condensing temperature of the vapour has to be higher than that of the cooling medium therefore the pressure of the vapour has to be such that it's condensing temperature is 15 to 20°C higher than the temperature of the cooling medium capacity of the refrigeration system. It will also cause the compressor to operate at higher than usual temperature, which could result in compressor damage if the faulty valves are not repaired in time. Large ammonia refrigeration compressors commonly use a packing gland to seal between the crank shaft and casing. Explain how this gland is lubricated. -- Correct Answer ✔✔ A lantern ring is placed between the two sets of packing. Lubrication oil is pumped to this ring, which distributes the oil between the rotating shaft and the packing. Describe the operation of a centrifugal compressor -- Correct Answer ✔✔ The centrifugal compressor consists essentially of a bladed wheel or impeller, which rotates at high speed. The impeller is surrounded by a volute shaped casing, and in many cases, by a ring of diffuser vanes in addition to the casing. The refrigerant vapour from the suction line is drawn into the center or eye of the impeller. From there the vapour is forced radially outwards to the impeller periphery by the action of centrifugal force due to the rapidly rotating impeller. The vapour leaves the impeller at high velocity, and then flows through the nozzle- shaped channels (diffusers) where some of the velocity is converted into pressure. Then the vapour passed through the volute casing where a further conversion of velocity into pressure takes place. Write down the formula that is used to determine the piston displacement of a refrigeration compressor and explain the meaning of each term. -- Correct Answer ✔✔ V = A * L * N * R V = volume in m^3/min A = cross sectional area of cylinder in m^2 L = length of stroke in m N = number of cylinders R = revolutions per minute What type of evaporator contains only a small amount of liquid refrigerant at any given time? -- Correct Answer ✔✔ Dry or expansion What kind of an evaporator can be easily cleaned and defrosted manually without interrupting the cooling process -- Correct Answer ✔✔ Plate surface Which type of condenser users the least amount of cooling water? -- Correct Answer ✔✔ Evaporative The purpose of a condenser in a refrigeration system is to? -- Correct Answer ✔✔ To remove the latent heat from the refrigerant What are two disadvantages of flooded evaporators -- Correct Answer ✔✔ Require more refrigerant, require more space What are two methods of reducing liquid carryover with flooded shell and tube evaporators? -- Correct Answer ✔✔ Mist eliminators, surge drums Natural draft cooling towers operate most effectively in large open spaces and -- Correct Answer ✔✔ Where wind is relatively constant A bypass valve, which prevents water flow over the fill of a tower during cold weather, should not be closed until the water temperature reaches -- Correct Answer ✔✔ 27°C Scaling is not as severe in towers when compared to boilers because -- Correct Answer ✔✔ Temperatures are not as high List four factors that affect the rate of heat transfer in a Cooling tower -- Correct Answer ✔✔ Relative velocity of both the air and water during contact Area of water surface in contact with air Length of contact time between air and water Difference between inlet water temperature and inlet air wet bulb temperature (relative humidity of air) Cooling towers are divided into two classes according to the method of air circulation. These classes are: -- Correct Answer ✔✔ Natural circulation, mechanical circulation Dissolved and suspended solids can build up in a closed cooling tower system as the water evaporates. This build-up is controlled by -- Correct Answer ✔✔ Bleeding a portion of the water from the system continuously State the cause of the following problems associated with cooling towers: 1) deposit of airborne particles 2) scaling 3) corrosion 4) biological fouling 5) wood deterioration -- Correct Answer ✔✔ 1) dust in atmospheric air that becomes entrained in cooling tower water 2) hardness forming salts in the cooling water consisting of calcium and magnesium compounds 3) pH level below 8.5 and dissolved oxygen (since the water is constantly circulated through the tower dissolved oxygen is high) 4) algae, fungi and bacterial growth 5) delignification due to attack by chlorine and alkaline solutions and biological attack of wood cellulose The simple control which restricts the flow of liquid from the condenser to the evaporator and maintains a pressure differential between the two units because of its length and small bore is called -- Correct Answer ✔✔ Capillary tube The type of operation which stops the compressor when the desired low temperature of the substance to be cooled is reached and starts the compressor up again when the temperature rises to a set level is called -- Correct Answer ✔✔ Intermittent How is the capacity of a reciprocating compressor controlled -- Correct Answer ✔✔ Cylinder unloaders, cylinder bypass, hot gas bypass What two checks can be used to determine if charging of a refrigeration system is complete -- Correct Answer ✔✔ Recommended weight from the manufacturer and sight glass on the receiver To avoid liquid slugging in a direct expansion evaporator after shutting down a reciprocating or rotary compressor refrigerating system which of the following measures needs to be taken? A) pump down the compressor B) fill the compressor with liquid refrigerant C) fill the evaporator with refrigerant vapour D) open all the suction valves on the connecting condenser line E) discharge all the condenser refrigerant into the evaporator -- Correct Answer ✔✔ A Checking the condition of electrical starters and contactors is categorized under what maintenance schedule -- Correct Answer ✔✔ Annual Checking the operation of the compressor lube oil pump, as well as the cooling coil, heater and oil reservoir level is -- Correct Answer ✔✔ Weekly maintenance List ten benefits that are realized by implementation of a preventative maintenance system in a refrigeration plant -- Correct Answer ✔✔ - more dependable service from the equipment -increased operating efficiency and a reduction in energy consumption -elimination or reduction of major breakdown repairs -reduction of overall maintenance costs -efficient scheduling of maintenance operations -reduces spare parts inventory required -control of labour and material costs -better mean of identifying causes of breakdowns -extended life expectancy of plant and equipment -accumulation of history records for each piece of equipment Concentration of the lithium bromide can be most easily controlled by what means -- Correct Answer ✔✔ Controlling the temperature in the generator During seasonal start up when should the purge pump be started -- Correct Answer ✔✔ 30 minutes after the start-up Explain why crystallization in a lithium bromide absorption refrigeration system is undesirable -- Correct Answer ✔✔ It can block piping, it can block passages, it can restrict flow Describe the steps that are taken to add octyl alcohol wetting agent to a lithium bromide system -- Correct Answer ✔✔ Connect a charging tube to the access valve located in top of the concentrator sump. Raise the open end of the tube and fill it with distilled water to remove all the air. Place the open end of the tube in a flask containing the recommended amount of alcohol. With the unit in operation slowly open the access valve allowing the alcohol to be drawn into the system quickly close the valve the instant that the last of the alcohol leaves the flask The temperature of the concentrated solution in a lithium bromide absorption refrigeration system may drop after the unit is shut down for an extended period. Explain how crystallization is avoided during this time. -- Correct Answer ✔✔ During the shutdown of the unit there is a dilution step where the dilute and concentrated solution are mixed together to produce and intermediate solution which will not crystallize as the temperature drops while the unit is shut down Air is approximately what composition by volume? -- Correct Answer ✔✔ 79% nitrogen 21% oxygen The volume of standard air is -- Correct Answer ✔✔ 0.833 kg/m^3 of dry air The difference between the wet and dry bulb readings is called the -- Correct Answer ✔✔ wet-bulb depression The term __________ applies to the percentage of moisture in the air as compared to the amount of moisture that the air can hold at a specific temperature -- Correct Answer ✔✔ Relative humidity The values of standard temperature and pressure of air that are used for evaluating air handling equipment are -- Correct Answer ✔✔ 1 kg of dry air at 21°C and 101 kPa abs The body needs considerable time to adjust when moving from one space to another when temperature and humidity conditions vary widely. This may be described as a) shock effect b) comfort zone c) comfort condition d) effective temperature e) air/motion effect -- Correct Answer ✔✔ A Which of the following statements about effective temperature is true? A) it can be easily determined by using a thermometer B) relative humidity does not affect the relative temperature C) for each combination air velocity remains the same D) the test involved people all dressed in different amounts of clothing for each combination E) charts with metric units cannot be used for making adjustments in SI units -- Correct Answer ✔✔ C Effective temperature can be defined as a measure of comfort which involves the combined effects of the dry bulb temperature relative humidity and site movement. T or F -- Correct Answer ✔✔ True Which of the following is not a centrifugal fan? A) backward inclined fan wheel B) forward curved fan wheel C) the propeller fan Steam grid humidifier used in are conditioning systems achieve humidification by -- Correct Answer ✔✔ injecting steam in the supply air stream Which of the following option is used to control the temperature of the spray water in an air washer? A) only part of the spray water is recirculated and hot or cold water is added as needed B) the spray water is recirculated through a heat exchanger and is either heated or cooled by hot or chilled water C) heating or cooling coil is directly mounted in the sump of the washer D) all of the above -- Correct Answer ✔✔ D A factor limiting the number of find that can be used on coils is -- Correct Answer ✔✔ Direction the fluid is flowing in the tube A counterflow coil is less efficient than a parallel flow coil? T or F -- Correct Answer ✔✔ False Face velocity is the -- Correct Answer ✔✔ Average velocity of the air flowing over the face area of the fin surface The purpose of a vacuum breaker used with steam coils is to -- Correct Answer ✔✔ Prevent possible freezing caused by a vacuum or negative pressure in the steam coil The purpose of the flow switch or sail switch used with hot water coils is to -- Correct Answer ✔✔ Close the outside air dampers and stop the fan if the flow of water is interrupted due to pump failure or closing of the hand valve Which steam trap is preferred for use with steam coils operating at low and medium steam temperatures -- Correct Answer ✔✔ Float and thermostatic trap The inverted bucket trap is used when the steam pressure is -- Correct Answer ✔✔ Higher than 172 kPa A modulating valve can be used for a steam coil when the air inlet temperature is below 1.5 C? T or F -- Correct Answer ✔✔ False To offset the heat gain through the building’s exterior shell from solar radiation, the atmosphere surrounding the building and internal sources of heat what is required? -- Correct Answer ✔✔ A cooling system When a system draws in only room air, conditions it, and then returns it into the room, it is called -- Correct Answer ✔✔ Full recirculation The unitary air conditioning system which used a direct expansion refrigeration system to provide cooling and dehumidification in a local area without ductwork is called -- Correct Answer ✔✔ Window air conditioner Which of the following statements about multi zone systems is true? A) the cooling coils are installed in line B) the dampers are our of phase by ten degrees C) when the hot deck is fully opened the cold deck is fully closed D) the system cannot operate a humidifier E) all of the above -- Correct Answer ✔✔ C The supply temperature of the cold deck air in a dual duct system is 12.5 C? T or F -- Correct Answer ✔✔ True A system used extensively in hotels and motels due to its minimal space requirement, relatively low initial cost, and high degree of individual zone control is called a) a hydronic heat pump system b) an induction system c) a variable volume system with perimeter heating d) a fan coil unit with make up air system e) a compartmental atomizing system -- Correct Answer ✔✔ D The funds available for the air conditioning portion of the building refers to which factor of system selection? a) Building function b) Capital cost c) Building layout d) Operating costs e) Maintenance requirements -- Correct Answer ✔✔ B Which system provides the best control for room conditions on a year round basis? -- Correct Answer ✔✔ Four pipe arrangement The recovery system which has a capillary wick structure consisting of fine circumferential striations machined on its external surface is called a a) heat valve b) runaround system c) heat pump d) thermal wheel e) heat pipe -- Correct Answer ✔✔ E What is the maximum capacity of a heat pipe? -- Correct Answer ✔✔ When the evaporator is lowered below the horizontal The C.O.P. Of a heat pump increases as the outside air temperature drops? T or F -- Correct Answer ✔✔ False To provide a two position damper equipped with a fan that provides 100% outdoor air with a ratio of damper opening what is required? -- Correct Answer ✔✔ A gradual switch In severely cold weather what adjustment must be made to properly preheat the outside air? a) The temperature controller's throttling range must be increased b) The outdoor damper should be closed c) Two separate preheater coils should be installed d) Damper must be heated If the power element of a thermostatic expansion valve lost its charge the result would be -- Correct Answer ✔✔ A starved evaporator In a two stage ammonia refrigeration system which compressor should commonly be started first -- Correct Answer ✔✔ The high side compressor A surge drum of a flooded system is used to -- Correct Answer ✔✔ Separate the vapour from the liquid for the suction gas that returns to the compressor, accept the flash gas from the make up liquid In an ammonia flooded evaporator oil could gather in the evaporator at the lowest point because -- Correct Answer ✔✔ Oil is heavier and it has a higher boiling point than ammonia What can happen when you isolate a pipe or vessel that is almost 100% full of liquid refrigerant? -- Correct Answer ✔✔ If it has a relief valve the valve may open to relieve over pressure from absorbing heat with no room for expansion, a rupture may occur due to a hydrostatic condition if the ammonia absorbs enough heat, if an explosion situation occurs you could have a major emergency on your hands plus possible injuries or fatalities Hey flowing through a copper bar with one end in a fire is an example of heat flow by -- Correct Answer ✔✔ Conduction A cold storage room is 150' by 80' by 35' what is the volume -- Correct Answer ✔✔ 420,000 cubic feet If an ammonia receiver will hold 1000 pounds of liquid at 90 F when completely filled the max capacity for this receiver is -- Correct Answer ✔✔ 800 pounds What condition which can be monitored in the engine room indicates evaporator temperature? -- Correct Answer ✔✔ Suction pressure A back pressure regulator is -- Correct Answer ✔✔ A pressure controller To check a leak in an ammonia piping system typically you use -- Correct Answer ✔✔ A sulfur stick or pH paper What is the common cause of liquid slip over in an ammonia refrigeration system? -- Correct Answer ✔✔ Over feeding the liquid to a DX evaporator, a solenoid valve leaking to the make up line, too great of a heat load on the evaporator too fast The pressure/temperature relationship for ammonia, obtained from a PT chart is only good when the ammonia in the section you are metering is -- Correct Answer ✔✔ In a saturated condition When using a screw compressor with an oil separated a heater should -- Correct Answer ✔✔ Shut on and off as needed according to the oil temperature set point An ammonia liquid line has liquid trapped and it's temp is starting to rise. How much with the psig pressure rise for every one degree F of heat exposure -- Correct Answer ✔✔ 100-150 pounds psig Ammonia is on the EPA toxic chemical list? T or F -- Correct Answer ✔✔ True A high pressure cut out switch -- Correct Answer ✔✔ Should never be jumped How are temperature and heat related -- Correct Answer ✔✔ Temperature is a measure of the intensity of the heat in an object What causes liquid slugging -- Correct Answer ✔✔ The compressor drawing in lubricating oil from the suction line, the compressor drawing in liquid ammonia from the suction line, a rapid lowering of suction pressure at the compressor, drawing in lubrication oil or ammonia What must the operating engineer do in the event of liquid slugging -- Correct Answer ✔✔ Shut of the compressor Where should you manually purge the non condensables from you system -- Correct Answer ✔✔ From the highest point of the condenser with the compressor shut off or the condenser isolated What is the principle advantage and disadvantage of ammonia as a refrigerant -- Correct Answer ✔✔ It is readily available but toxic What is the difference between a unit cooler and a blast freezer -- Correct Answer ✔✔ Unit coolers are not installed in freezers, air velocity, more tonnage of equipment per square foot During a hot gas defrost cycle -- Correct Answer ✔✔ High pressure gas from the compressor discharge is piped through the evaporator What is the tax gas/flash gas in operating an ammonia refrigeration system -- Correct Answer ✔✔ 15% Compressors are sized based on what requirement -- Correct Answer ✔✔ CFM requirement What is fluid friction or vapour resistance -- Correct Answer ✔✔ The loss of pressure as the fluid/vapour interacts with the inner walls of the pipe In a DX or dry expansion coil evaporator the refrigerant should leave ______ -- Correct Answer ✔✔ In a superheated vapour state In a recirculation system where is it important to keep a constant pump pressure? -- Correct Answer ✔✔ At the metering valve evaporation inlet Which evaporator has the least amount of fins spaced per inch for the operational duties it performs? -- Correct Answer ✔✔ A blast freezer evaporator