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10 Cards in this Set
- Front
- Back
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Which of the following statements about flow switches is false? a) they are used on chilled water b) they are used as lockout switches when flow is insufficient c) they are operated by the force exerted on a flexible vane immersed in the liquid flowing in the line d) they can only be used to regulate liquid flow e) they can be used to close flow indicator circuits |
d) they can only be used to regulate liquid flow |
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Actuating or secondary controls are used to a) indirectly control changes in operation which are called for by primary controls b) regulate the refrigeration system output when the system limits are reached c) regulate the refrigeration system output when the system limits are exceeded d) control the operation of cooling water e) protect the system from operation beyond set limits |
a) indirectly control changes in operation which are called for by primary controls |
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The safety control, which uses a current transformer with a resistor in the motor circuit, is known as a) high motor temperature cut up b) low oil sump temperature protection c) motor overload protection d) solenoid valve e) high oil temperature cut out |
c) motor overload protection |
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It is not true that: a) humidistat may contain a hygroscopic element b) pressurestat maintains a constant pressure in evaporator c) thermostatic controller works only by the pressure of its bulb effecting on a connected bellows d) bimetal thermostat works only by the change of temperature on a bimetal strip e) pressure actuated control may be used to control the high pressure cut out of the compressor |
c) thermostatic controller works only by the pressure of its bulb effecting on a connected bellows |
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It is not correct that a) expansion valve at the evaporator limits the degree of pump down the evaporator b) a reduction in refrigeration load will cause the high side pressure to drop c) bellows pressure in water regulating valve is balanced by an adjustable spring d) solenoid valves are not used for the regulating of refrigerant flow e) evaporator pressure must not be allowed to drop below a certain level |
a) expansion valve at the evaporator limits the degree of pump down the evaporator |
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A bimetallic element converts temperature changes to mechanical motion by having metals of different a) coefficients of linear expansion b) rates of temperature change c) temperatures d) coefficients of thermal conductivity e) electron velocities |
a) coefficients of linear expansion |
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The operating control which consists of a hygroscopic element is made of a material similar to multiple strands of human hair is called a a) humidistat b) thermostat c) fluid expansion regulator d) pressure-stat e) bimetal element |
a) humidistat |
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Regarding the compressor lubrication and its oil pressure switch, it is not correct that a) failure of a forced lubrication system could cause extensive damage to a refrigeration compressor b) the time delay allows the compressor to operate for about two minutes to establish the required oil pressure differential c) the constants of the differential pressure switch and timer switch are both closed when the compressor is started d) discharge and suction pressures of the compressor are applied to two opposed acting pressure bellows in the oil pressure failure switch e) the oil pressure failre switch shuts down the compressor when the oil pressure drops below the safe minimum limit for longer than a predetermined period |
d) discharge and suction pressures of the compressor are applied to two opposed acting pressure bellows in the oil pressure failure switch |
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What type of control prevents an overly low pressure and low temperature condition in an evaporator? a) a solenoid valve b) a direct acting suction pressure regulator c) low pressure safety cut off d) an evaporator pressure regulator e) a high pressure safety cut out |
d) an evaporator pressure regulator |
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With regard to the high side, the maximum setting for a pressure limiting device on a refrigeration system shall not exceed the high side design pressure by more than: a) 100% b) 75% c) 90% d) 80% e) 50% |
c) 90% |
