RACT Unit 25 Overview

Question 1

Mechanical Controls:

1. Start, stop, or modulate fluid flow and can be operated by ________ or _________

Answer 1

1. pressure or temperature or other means

2. piping

Question 2

Evaporator Pressure Regulator (EPR):

1. Prevents the pressure in an evaporator from ______ below a predetermined pressure
2. Positioning controlled by ____ pressures which are ________ pressure and ______ pressure
3. Also referred to as _____ on rise of ____ pressure
4. Only establish a ________ pressure and do not hold a _______ pressure or limit maximum pressure

Answer 2

1. dropping
2. two, evaporator and spring pressure
3. open on rise of inlet pressure valves
4. minimum, do not hold a constant

Question 3

Multiple Evaporator Systems:

1. Single compressor with _______ evaporators

EPR Valves:

2. Allow each evaporator to operate at its own ________ and __________
3. Are equipped with ______ valves to allow gauge readings on the evaporator side of the valve
4. Common suction-line pressure can be obtained at the compressor ________ valve

Answer 3

1. multiple
2. at its own pressure and temperature
3. schrader
4. service valves

Question 4

Electric Evaporator Pressure-Regulating (EEPR) Valves:

1. Provide more accurate _________
2. Designed to maintain _______ air temperature in the refrigerated case
3. Controlled by a bipolar ______ motor

Locations:

4. Single evaporator: evaporator _______
5. Multiple Evaporators: suction line before the common suction ________

Answer 4

1. Control
2. discharge
3. bipolar stepper motor
4. outlet
5. suction line before the common suction header

Question 5

Crankcase Pressure Regulator:

1. Resembles an ____ valve
2. Located close to the __________
3. Keeps a low-temperature compressor from overloading during a ___ ____down
4. Referred to as a ____ on rise of _____ valve
5. Controlled by crankcase (outlet) pressure and its _______ pressure

Answer 5

1. EPR
2. Compressor
3. during a hot pull down
4. close on rise of outlet (CRO) valve
5. spring pressure

Question 6

Adjusting the CPR Valve:

1. Should be accomplished on a hot pulldown or at least when the compressor has enough load that it is trying to run ________
2. It is important to use an _______ on the compressor while adjusting the CPR valve to ensure that the amperage draw of the compressor does not exceed the full load amperage rating

Answer 6

1. overloaded

2. ammeter

Question 7

Oil Separators:

1. Installed in the ________ line
2. Separate oil from the refrigerant and return the oil to the compressor _________
3. Oil drops fall to the bottom of the ________
4. Oil level raises a float and opens a ______
5. Difference between _____ and ___-side pressures push oil back to the compressor
6. Another type is the ______ oil separator
7. Device needs to be kept ______

Answer 7

1. discharge line
2. crankcase
3. separator
4. opens a valve
5. high and low side
6. helical oil separator
7. warm

Question 8

Vibration Eliminators:

1. Often necessary to protect the tubing at the ______ and ________ lines
2. Eliminated on small compressors successfully with _______ loops
3. Large ______ requires special vibration eliminators constructed with a bellows-type lining and a flexible outer protective support

Answer 8

1. suction and discharge lines
2. vibration loops
3. large tubing

Question 9

Crankcase Heat:

The crankcase heater;

1. Designed to help combat refrigerant ________
2. Holds oil in the compressor’s crankcase at a temperature _______ than the coldest part of the system

Common in air-conditioning systems

3. Can be applied in _______ ways
4. Only needed (and desired) during the ____ _____

Answer 9

1. migration
2. higher
3. several
4. during the off-cycle

Question 10

Oil Pumps:

1. Larger compressors have ______ oiling systems that usually have over __ horsepower
2. Contain an oil pump located at the end of the compressors _______
3. Keyed into the compressors ________
4. Can be of the gear or _______ type
5. Squeezes the oil to a ______ pressure which is referred to as the ___ oil pressure

Answer 10

1. forced oiling systems that usually have over 3 horsepower
2. crankshaft
3. crankshaft
4. gear or eccentric type
5. higher pressure which is referred to as the net oil pressure

Question 11

Low Ambient Controls:

1. Used on systems that are operated year round to maintain _____ pressure

Methods used to keep the head pressure at an acceptable level;

2. Fan cycling using a _______ control
3. ___ speed control
4. Air volume control using ______ and fan cycling
5. Condenser _______ and condenser _______

Answer 11

1. maintain head pressure
2. fan cycling using pressure control
3. fan speed control
4. air volume control using shutters and fan cycling
5. condenser flooding and condenser splitting

Question 12

Fan-Cycling Head Pressure Controls:

1. Device opens on a drop in head pressure, turning condenser fan ____
2. Device closes on a rise in _____ pressure, turning the condenser fan ___
3. Fan cycling causes large _______ in the head pressure
4. One application is the use of _______ fans

Answer 12

1. off
2. rise in head pressure, turning condenser fan on
3. large variances
4. multiple fans

Question 13

Fan Speed Control for Controlling head pressure

1. As the outside temperature _____, the fan slows down
2. As the outside temperature rises, the fan speeds ___
3. Some controls monitor the refrigerants condensing __________
4. Newer generation systems use ____, to control condenser fan motor speed

Answer 13

1. drops
2. up
3. temperatures
4. VFD’s

Question 14

Air volume Control for controlling head pressure:

1. accomplished with a piston-driven ______ controlled with the ____-pressure refrigerant
2. When there are multiple fans, the first fans can be cycled off using ________, and the shutter can be used on the _____ fan

Answer 14

1. piston-driven damper controlled with high-pressure refrigerant
2. using temperature, shutter can be used on the last fan

Question 15

Condenser Flooding and Condenser Splitting for controlling head pressure:

1. Condenser flooding devices cause liquid refrigerant to move from an oversized receiver to the condenser in ____ weather
2. And requires a large amount of refrigerant to flood the _______ in the winter
3. Splitting is another way to reduce the amount of extra ________ charge
4. It splits the condenser into two separate _______ condenser circuits

Answer 15

1. in cold weather
2. condenser
3. extra refrigerant charge
4. two separate identical

Question 16

Pressure Switches and Controls: Start and stop current flow to components;

1. Low pressure switch: _____ on rise in pressure
2. High pressure switch: ____ on rise in pressure
3. Low ambient control: _____ on rise in pressure
4. Oil safety switch: has a _____ delay; _____ on rise in pressure

Answer 16

1. closes
2. opens
3. closes
4. time delay, opens

Question 17

Low pressure control applied as a thermostat:

1. Can be set to operate the compressor the maintain the space temperature in the cooler and to serve as a ___-charge protection as well
2. No interconnecting wires must be installed between the inside of the cooler and the _______ unit
3. Control is rated by pressure range and ______ draw of the contacts

Answer 17

1. low charge
2. condensing unit
3. current draw

Question 18

High-pressure control:

1. Prevents compressor from operating at high _____ pressures
2. Opens on a ______ in pressure
3. Can be automatically or manually ______
4. Control cut-in point must be above the pressure corresponding to the _______ temperature
5. Some have a fixed differential of ___psig
6. Some manufacturers specify a manual ______

Answer 18

1. head
2. rise
3. reset
4. ambient
5. 50psig
6. reset

Question 19

Oil Pressure Safety Control:

1. Larger compressors use with _____ pumps
2. Pump is connected to compressor _______ and oil is forced through ______ in crankshaft
3. Measures ___ oil pressure

Answer 19

1. oil pumps
2. crankshaft, holes
3. net

Question 20

The Solenoid Valve:

1. Valve position controlled by a solenoid ______
2. Normally ____ or normally ______
3. Used to control ______ or _______ flow
4. Valves must be installed with arrow pointing in direction of ______

Answer 20

1. coil
2. open or closed
3. liquid or vapour flow
4. flow

Question 21

Automatic Pumpdown systems: Sequence of pumpdown operation;

1. Normally closed liquid-line solenoid valve controlled by a _________
2. Thermostat opens when desired ____ temperature is reached
3. The solenoid deenergizes and _______
4. Comp continues to pump ref downstream of closed solenoid valve to the high side causing low side pressure to _____

Answer 21

1. thermostat
2. box temp
3. closes
4. drop

Question 22

Automatic Pumpdown Systems: Call for Cooling:

1. When box temp rises, thermostat ______
2. Liquid line solenoid is _______
3. Refrigerant flows to _______
4. when low side pressure increases, the low pressure control _____
5. the compressor is once again _______

Answer 22

1. closes
2. energized
3. evaporator
4. closes
5. energized

Question 23

Medium-Temp Refrigeration:

1. Box temperature ranges from __F to 45F
2. Coil temps are normally 10 to ___F cooler than the box
3. Coil temp as low as ___F

Answer 23

1. 34 to 45F
2. 10 to 15F
3. 19F

Question 24

Random or Off-Cycle Defrost:

1. Most _______ type of defrost
2. Occurs when refrigeration system has enough reserve capacity to cool more than the _____ requirement
3. Air in the cooler can defrost ice from the coil and evaporator fans continue to ___

Answer 24

1. common
2. load
3. run

Question 25

Planned Defrost: 1. Defrost is controlled by a ______ 2. System goes into defrost at predetermined _____ 3. Defrost cycle is initiated during low _____ periods 4. Systems in retail establishments often go into defrost when the store is ______

Answer 25

1. timer 2. times 3. load 4. closed

Question 26

Low-Temp Evaporator Defrost: 1. Low-temperature evaporators operate below _________ 2. Must have planned ______ 3. _____ must be added, ______ or ________ heat

Answer 26

1. freezing 2. defrost 3. heat must be added, internal or external heat

Question 27

External Heat Defrost: 1. Usually accomplished with _______ heaters mounted to the evaporator coil 2. Timer controls the following events: - Stopping evaporator fan and compressor - Energizing electric heaters and drain pan heaters 3. Temp sensor may be used to terminate _______

Answer 27

1. electric 2. 3. defrost

Question 28

Defrost Termination and Fan Delay Control: 1. Temperature-activated, single-pole-double-throw switch controlled by a remote _______ bulb

Answer 28

sensing

Question 29

Refrigeration Accessories are devices that improve system _______ and service functions

Answer 29

performance

Question 30

Receivers: 1. Tank-like device located in the _______ line 2. Used to store liquid ________ after it leaves the condenser and should be ______ than the condenser 3. May be installed upright or __________ 4. Refrigerant must enter the _____ of the receiver and be taken from the _____ to ensure it is 100% liquid

Answer 30

1. liquid 2. refrigerant, lower 3. horizontally 4. top, bottom

Question 31

King Valve on the Receiver: 1. Located in the liquid line between the receiver and _________ valve 2. Normally the valve is ____seated 3. Has a _______ port to enable readings 4. Many systems also contain a _______ valve which stops and starts liquid flow

Answer 31

1. expansion valve 2. backseated 3. service port 4. solenoid valve

Question 32

Liquid-Line Filter Driers 1. Located in the ______ line 2. Removes foreign matter from the __________ 3. Connected with _______ or _______ connections

Answer 32

1. liquid 2. refrigerant 3. solder or flare

Question 33

Refrigerant Sight Glasses: 1. Normally located anywhere liquid flow exists and anywhere it can serve a _______ 2. When installed just prior to expansion device it enables technician to determine if a solid column of________ is reaching the device 3. When installed at the condensing unit it can help with _________ 4. May be supplied with a moisture _________

Answer 33

1. Purpose 2. liquid 3. troubleshooting 4. indicator

Question 34

Liquid Refrigerant Distributors: 1. Used on multi circuit ________ 2. Located at the ______ of the expansion valve 3. Designed to allow _____ ref to flow to all circuits

Answer 34

1. evaporators 2. outlets 3. equal

Question 35

Heat Exchangers: 1. May be placed in or at the ______ line leaving the evaporator 2. Suction and liquid lines are connected to allow _____ to transfer between them 3. Increase the amount of ________ in the liquid entering the expansion device 4. Prevents liquid refrigerant from moving through the suction line into the __________

Answer 35

1. suction line 2. heat 3. sub cooling 4. compressor

Question 36

Suction Line Accumulators: 1. Prevents liquid refrigerant from entering the __________ 2. Gives liquid a place to ________ before entering the compressor 3. Should have adequate liquid holding ________

Answer 36

1. compressor 2. vaporize 3. capacity

Question 37

Suction-Filter Driers: 1. Good compressor ________ 2. Must be installed when system has become _________ 3. Most have some means for determining the _______ drop across the cores because even a small pressure drop can reduce the _______ of the compressor

Answer 37

1. protection 2. contaminated 3. pressure drop, efficiency

Question 38

Refrigerant Check Valves: 1. Allow refrigerant to flow in ____ direction 2. Can be either the ____ type or magnetic type 3. Must be installed with arrow pointing in the direction of refrigerant _____ 4. Cause some pressure drop, even when ______

Answer 38

1. one 2. ball type 3. flow 4. open

Question 39

Suction Service Valves: 1. Normally attached to the _________ 2. Can never be totally _______ 3. Positions: ____seated, front______ and ___seated

Answer 39

1. compressor 2. closed 3. front-seated, back-seated, mid-seated

Question 40

Discharge Service Valves: 1. Located in the ________ line 2. Used as a gauge port and to valve off the compressor for _______ 3. Should not be ____seated when the compressor is running except during closed-loop capacity tests

Answer 40

1. discharge 2. service 3. front seated

Question 41

Refrigeration Line service valves: 1. Hand-operated speciality valves used for ________ purposes 2. Used in any line that may have to be valved ____ for any reason 3. Two types: Diaphragm valve and ____ valve

Answer 41

1. service 2. off 3. ball valve

Question 42

Diaphragm Valves: 1. Same internal flow pattern as a _____ valve 2. Can be tightened by hand enough to hold back _____ pressures 3. Installed into the system with either a flare or ______ connection

Answer 42

1. globe 2. high 3. flare or soldered

Question 43

Ball Valves: 1. Straight-through valve with little pressure _____ 2. Advantage is that it can be opened or closed easily because it only takes a ___degree turn to either open or close it 3. Known as a “quick open or close” _____

Answer 43

1. drop 2. 90 degree 3. valve

Question 44

Pressure Access Ports: 1. Used for taking pressure readings at places that do not have _____ ports 2. ______ the line when attached 3. Some can be attached while the unit is operating, may be _____ or ______ to the line

Answer 44

1. service 2. pierce 3. bolted or soldered

Question 45

Relief Valves: Release refrigerant from a system when predetermined ____-pressures exist

Answer 45

high