[ILM] 104C

Question 1

Thermostats

Answer 1

electromechanical (constant cut-in, thermodisk)

electronic (RTD or thermocouple/processor)

Question 2

constant cut-in thermostat

Answer 2

two position thermostats with a factory set cut-in temp and an adjustable differential

Question 3

thermodisk thermostat

Answer 3

use in medium- and low-temp refrigeration

Question 4

two position thermostat

Answer 4

helps maintain stable temp conditions within a space

Question 5

Proportional control

1. deviation
2. offset
3. differential

Answer 5

1. the length of time it takes for the control point and the setpoint to equalize
2. a sustained difference between the control point and the setpoint
3. the actual separation between cut-in and cut-out temps or pressures in a 2 position control

Question 6

oil failure controls (OFC)

Answer 6

protect refrigeration compressors with built-in oil pumps from damage that insufficient lubrication causes

Question 7

delay-on-make

Answer 7

prevents 2 compressors from starting at the same time by delaying when the 2nd compressor turns on

Question 8

delay-on-break

Answer 8

prevents a short cycling

Question 9

solenoid valve

Answer 9

electromagnetically actuated fluid flow control valve

Question 10

NEVER ENERGIZE a solenoid coil,

Answer 10

if you disconnect it from the solenoid valve, coil damage will occur

Question 11

1. Evap Pressure Regulator (EPR)
2. Compressor Pressure Regulator (CPR)

Answer 11

1. ORI acting valve (Open on Rise of Inlet)
2. CRO acting valve (Close on Rise of Outlet)

Question 12

crankcase heater

Answer 12

prevent refrigerant migration and mixing with the lubricating oil in the compressor’s crankcase during off cycles

suction side of the compressor, always powered on

Question 13

pump down & pump out

Answer 13

cycles to remove liquid refrigerant between the liquid line solenoid & the compressor before the compressor can cycle off

Question 14

pump down system

Answer 14

is designed to prevent refrigerant migration into the evaporator during the off cycle. This helps to protect the compressor and maintain system efficiency.

1. Prevents refrigerant migration and oil dilution.
2. Protects the compressor from liquid slugging.
3. Helps to maintain system efficiency during the off cycle.

Question 15

pump out system

Answer 15

is used to evacuate refrigerant from the entire system, usually for maintenance or repair purposes. This ensures that no refrigerant remains in the system, reducing the risk of leaks and allowing safe access for service.

1. Facilitates safe and efficient maintenance or repair.
2. Ensures no refrigerant is left in the system, reducing environmental impact and safety risks.
3. Prevents short cycling

Question 16

ONLY compressors that have a mechanical oil pump use an oil failure control

T or F

Answer 16

True

Question 17

purpose of fan delay thermostat

Answer 17

prevent the evaporator fans from spraying freshly melted frost and water inside the cabinet when the evaporator is still warm from a defrost cycle