Section 5 Commercial Refrigeration Unit 25 Special Refrigeration
![Section 5: Commercial Refrigeration Unit 25: Special Refrigeration System Components Section 5: Commercial Refrigeration Unit 25: Special Refrigeration System Components](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-1.jpg)
![Objectives • After studying this unit, you should be able to: – Distinguish between Objectives • After studying this unit, you should be able to: – Distinguish between](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-2.jpg)
![Objectives (cont’d. ) – Describe electrical controls that apply to refrigeration – Describe off-cycle Objectives (cont’d. ) – Describe electrical controls that apply to refrigeration – Describe off-cycle](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-3.jpg)
![The Four Basic Components • Must have a compressor, condenser, expansion device, and evaporator The Four Basic Components • Must have a compressor, condenser, expansion device, and evaporator](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-4.jpg)
![Mechanical Controls • Mechanical controls start, stop, or modulate fluid flow to increase system Mechanical Controls • Mechanical controls start, stop, or modulate fluid flow to increase system](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-5.jpg)
![Two-Temperature Controls • Two-temperature operation is utilized when there are multiple evaporators in the Two-Temperature Controls • Two-temperature operation is utilized when there are multiple evaporators in the](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-6.jpg)
![Figure 25– 1 Two-temperature operation. Two evaporators are operating on one compressor. One evaporator Figure 25– 1 Two-temperature operation. Two evaporators are operating on one compressor. One evaporator](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-7.jpg)
![Evaporator Pressure Control • Evaporator pressure regulator (EPR) – Prevents the pressure in an Evaporator Pressure Control • Evaporator pressure regulator (EPR) – Prevents the pressure in an](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-8.jpg)
![Multiple Evaporators • An EPR is needed in the suction line of each evaporator Multiple Evaporators • An EPR is needed in the suction line of each evaporator](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-9.jpg)
![Figure 25– 5 Evaporators piped together and one compressor used to maintain a suction Figure 25– 5 Evaporators piped together and one compressor used to maintain a suction](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-10.jpg)
![Electric Evaporator Pressure Regulator (EEPR) Valves • Provide more accurate control – Located at Electric Evaporator Pressure Regulator (EEPR) Valves • Provide more accurate control – Located at](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-11.jpg)
![Crankcase Pressure Regulator (CPR) • Located close to the compressor – Prevents compressor from Crankcase Pressure Regulator (CPR) • Located close to the compressor – Prevents compressor from](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-12.jpg)
![Figure 25– 10 The CPR valve throttles the vapor refrigerant entering the compressor. There Figure 25– 10 The CPR valve throttles the vapor refrigerant entering the compressor. There](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-13.jpg)
![Adjusting The CPR Valve • Procedure: – Best adjusted under a high load condition Adjusting The CPR Valve • Procedure: – Best adjusted under a high load condition](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-14.jpg)
![Relief Valves • Release refrigerant from a system when a high-pressure condition exists – Relief Valves • Release refrigerant from a system when a high-pressure condition exists –](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-15.jpg)
![Low Ambient Controls • Used on systems that are operated year round to maintain Low Ambient Controls • Used on systems that are operated year round to maintain](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-16.jpg)
![Fan-Cycling Head Pressure Control • Device opens on a drop in head pressure, turning Fan-Cycling Head Pressure Control • Device opens on a drop in head pressure, turning](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-17.jpg)
![Fan Speed Control for Controlling Pressure • As the outside temperature drops, the fan Fan Speed Control for Controlling Pressure • As the outside temperature drops, the fan](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-18.jpg)
![Air Volume Control for Controlling Head Pressure • Utilizes piston-controlled shutters and/or dampers – Air Volume Control for Controlling Head Pressure • Utilizes piston-controlled shutters and/or dampers –](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-19.jpg)
![Figure 25– 17 (A) Installation using dampers to vary the air volume instead of Figure 25– 17 (A) Installation using dampers to vary the air volume instead of](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-20.jpg)
![Condenser Flooding for Controlling Head Pressure • Flooding valves cause liquid refrigerant to move Condenser Flooding for Controlling Head Pressure • Flooding valves cause liquid refrigerant to move](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-21.jpg)
![Condenser Splitting for Controlling Head Pressure • Splitting: – Another way to reduce the Condenser Splitting for Controlling Head Pressure • Splitting: – Another way to reduce the](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-22.jpg)
![The Solenoid Valve • Used to start or stop refrigerant flow – Normally open The Solenoid Valve • Used to start or stop refrigerant flow – Normally open](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-23.jpg)
![The Solenoid Valve (cont’d. ) Figure 25– 21 The solenoid valve installed in the The Solenoid Valve (cont’d. ) Figure 25– 21 The solenoid valve installed in the](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-24.jpg)
![Pressure Switches • Start and stop current flow to components – Low pressure switch: Pressure Switches • Start and stop current flow to components – Low pressure switch:](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-25.jpg)
![Low-Pressure Switch • Can be used as low-charge protection and space temperature control – Low-Pressure Switch • Can be used as low-charge protection and space temperature control –](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-26.jpg)
![Low-Pressure Control Applied as a Thermostat • Control will cut off the compressor when Low-Pressure Control Applied as a Thermostat • Control will cut off the compressor when](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-27.jpg)
![Figure 25– 25 When a compressor that is larger than the electrical rating of Figure 25– 25 When a compressor that is larger than the electrical rating of](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-28.jpg)
![Automatic Pump-Down Systems • Sequence of shut-down operation: – Normally closed liquid-line solenoid valve Automatic Pump-Down Systems • Sequence of shut-down operation: – Normally closed liquid-line solenoid valve](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-29.jpg)
![Automatic Pump-Down Systems (cont’d. ) • Sequence of startup operation: – When the box Automatic Pump-Down Systems (cont’d. ) • Sequence of startup operation: – When the box](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-30.jpg)
![High-Pressure Control • Prevents compressor from operating at high head pressures – Control opens High-Pressure Control • Prevents compressor from operating at high head pressures – Control opens](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-31.jpg)
![Low-Ambient Fan Control • Starts and stops the condenser fan motor in response to Low-Ambient Fan Control • Starts and stops the condenser fan motor in response to](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-32.jpg)
![Oil Pressure Safety Control • Larger compressors use with oil pumps – Pump connected Oil Pressure Safety Control • Larger compressors use with oil pumps – Pump connected](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-33.jpg)
![Defrost Cycle • Any evaporator that operates below the freezing point of water needs Defrost Cycle • Any evaporator that operates below the freezing point of water needs](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-34.jpg)
![Medium-Temperature Refrigeration • Defrost: – Typical box temperature ranges from 34°F to 45°F – Medium-Temperature Refrigeration • Defrost: – Typical box temperature ranges from 34°F to 45°F –](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-35.jpg)
![Random or Off-Cycle Defrost • Coil defrosts using box temperature air compressor cycles off Random or Off-Cycle Defrost • Coil defrosts using box temperature air compressor cycles off](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-36.jpg)
![Planned Defrost • Defrost is controlled by a timer • System goes into defrost Planned Defrost • Defrost is controlled by a timer • System goes into defrost](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-37.jpg)
![Low-Temperature Evaporator Design • Box and coil temperatures are both below 32°F • Coil Low-Temperature Evaporator Design • Box and coil temperatures are both below 32°F • Coil](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-38.jpg)
![Defrost Using Internal Heat (Hot Gas and Cool Gas Defrost) • Hot gas from Defrost Using Internal Heat (Hot Gas and Cool Gas Defrost) • Hot gas from](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-39.jpg)
![Figure 25– 35 Hot gas defrost Figure 25– 35 Hot gas defrost](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-40.jpg)
![External Heat Type of Defrost • Usually accomplished with electric heaters mounted to the External Heat Type of Defrost • Usually accomplished with electric heaters mounted to the](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-41.jpg)
![Defrost Termination and Fan Delay Control • Single pole, double throw switch – Terminates Defrost Termination and Fan Delay Control • Single pole, double throw switch – Terminates](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-42.jpg)
![Defrost Termination and Fan Delay Control Figure 25 -37 A sensor used with the Defrost Termination and Fan Delay Control Figure 25 -37 A sensor used with the](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-43.jpg)
![Refrigeration Accessories • Accessories are devices that improve system performance and service functions • Refrigeration Accessories • Accessories are devices that improve system performance and service functions •](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-44.jpg)
![Receivers • Located in the liquid line – The device stores liquid refrigerant – Receivers • Located in the liquid line – The device stores liquid refrigerant –](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-45.jpg)
![The King Valve on the Receiver • Located in the liquid line between the The King Valve on the Receiver • Located in the liquid line between the](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-46.jpg)
![The King Valve on the Receiver (cont’d. ) Figure 25– 41 A king valve The King Valve on the Receiver (cont’d. ) Figure 25– 41 A king valve](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-47.jpg)
![Filter Driers • Located in the liquid line – Removes dirt, moisture, and acid Filter Driers • Located in the liquid line – Removes dirt, moisture, and acid](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-48.jpg)
![Refrigerant Check Valves • Allows refrigerant to flow in only one direction – Can Refrigerant Check Valves • Allows refrigerant to flow in only one direction – Can](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-49.jpg)
![Refrigerant Sight Glasses • Installed in the liquid line • Enables the technician to Refrigerant Sight Glasses • Installed in the liquid line • Enables the technician to](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-50.jpg)
![Liquid Refrigerant Distributors • Used on multi-circuit evaporators • Located at the outlet of Liquid Refrigerant Distributors • Used on multi-circuit evaporators • Located at the outlet of](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-51.jpg)
![Heat Exchangers • In the suction line leaving the evaporator • Suction and liquid Heat Exchangers • In the suction line leaving the evaporator • Suction and liquid](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-52.jpg)
![Heat Exchangers (cont’d. ) Figure 25 -47 Heat exchangers (A) Plain liquid-to-suction type (B) Heat Exchangers (cont’d. ) Figure 25 -47 Heat exchangers (A) Plain liquid-to-suction type (B)](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-53.jpg)
![Suction Line Accumulators • Located in the suction line, close to the compressor – Suction Line Accumulators • Located in the suction line, close to the compressor –](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-54.jpg)
![Figure 25– 48(B) A suction-line accumulator with heat exchanger Figure 25– 48(B) A suction-line accumulator with heat exchanger](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-55.jpg)
![Suction-Line Filter Driers • Located in the suction line • Good compressor protection • Suction-Line Filter Driers • Located in the suction line • Good compressor protection •](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-56.jpg)
![Suction Service Valves • Normally attached to the compressor – Valve positions • • Suction Service Valves • Normally attached to the compressor – Valve positions • •](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-57.jpg)
![Discharge Service Valves • Located in the discharge line – Normally attached to the Discharge Service Valves • Located in the discharge line – Normally attached to the](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-58.jpg)
![Refrigeration Line Service Valves • Hand-operated specialty valves used for service purposes • Used Refrigeration Line Service Valves • Hand-operated specialty valves used for service purposes • Used](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-59.jpg)
![Diaphragm Valves • Same internal flow pattern as a “globe” valve • Can be Diaphragm Valves • Same internal flow pattern as a “globe” valve • Can be](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-60.jpg)
![Ball Valves • Straight-through valve with little pressure drop • Advantage is that it Ball Valves • Straight-through valve with little pressure drop • Advantage is that it](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-61.jpg)
![Oil Separators • Installed in the discharge line – Separates oil from the refrigerant Oil Separators • Installed in the discharge line – Separates oil from the refrigerant](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-62.jpg)
![Vibration Eliminators • Often necessary to protect the tubing at the suction and discharge Vibration Eliminators • Often necessary to protect the tubing at the suction and discharge](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-63.jpg)
![Pressure Access Ports • Installed to take pressure readings at various points in the Pressure Access Ports • Installed to take pressure readings at various points in the](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-64.jpg)
![Crankcase Heat • Prevents refrigerant from migrating to the oil in the off cycle Crankcase Heat • Prevents refrigerant from migrating to the oil in the off cycle](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-65.jpg)
![Summary • Additional components enhance system operation • The EPR is used on multiple Summary • Additional components enhance system operation • The EPR is used on multiple](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-66.jpg)
![Summary (cont’d. ) • The CPR provides a limit to the pressure that can Summary (cont’d. ) • The CPR provides a limit to the pressure that can](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-67.jpg)
![Summary (cont’d. ) • Common low ambient controls include fan cycling, shutters, dampers and Summary (cont’d. ) • Common low ambient controls include fan cycling, shutters, dampers and](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-68.jpg)
![Summary (cont’d. ) • Pressure witches open and close in response to sensed pressures Summary (cont’d. ) • Pressure witches open and close in response to sensed pressures](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-69.jpg)
![Summary (cont’d. ) • Defrosting medium temperature refrigeration systems can be accomplished with planned, Summary (cont’d. ) • Defrosting medium temperature refrigeration systems can be accomplished with planned,](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-70.jpg)
![Summary (cont’d. ) • Receivers are refrigerant storage tanks located at the outlet of Summary (cont’d. ) • Receivers are refrigerant storage tanks located at the outlet of](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-71.jpg)
![Summary (cont’d. ) • Check valves ensure that refrigerant flows in only one direction Summary (cont’d. ) • Check valves ensure that refrigerant flows in only one direction](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-72.jpg)
![Summary (cont’d. ) • Accumulators help liquid refrigerant boil before it enters the compressor Summary (cont’d. ) • Accumulators help liquid refrigerant boil before it enters the compressor](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-73.jpg)
- Slides: 73
![Section 5 Commercial Refrigeration Unit 25 Special Refrigeration System Components Section 5: Commercial Refrigeration Unit 25: Special Refrigeration System Components](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-1.jpg)
Section 5: Commercial Refrigeration Unit 25: Special Refrigeration System Components
![Objectives After studying this unit you should be able to Distinguish between Objectives • After studying this unit, you should be able to: – Distinguish between](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-2.jpg)
Objectives • After studying this unit, you should be able to: – Distinguish between mechanical and electrical controls – Explain how and why mechanical controls function – Describe an automatic pumpdown system – Define low ambient operation
![Objectives contd Describe electrical controls that apply to refrigeration Describe offcycle Objectives (cont’d. ) – Describe electrical controls that apply to refrigeration – Describe off-cycle](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-3.jpg)
Objectives (cont’d. ) – Describe electrical controls that apply to refrigeration – Describe off-cycle defrost – Describe random and planned defrost – Explain temperature-terminated defrost – Describe the various refrigeration accessories – Describe the low-side and high-side components
![The Four Basic Components Must have a compressor condenser expansion device and evaporator The Four Basic Components • Must have a compressor, condenser, expansion device, and evaporator](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-4.jpg)
The Four Basic Components • Must have a compressor, condenser, expansion device, and evaporator • Other components enhance operation • Controls can be electrical, mechanical, or electromechanical devices
![Mechanical Controls Mechanical controls start stop or modulate fluid flow to increase system Mechanical Controls • Mechanical controls start, stop, or modulate fluid flow to increase system](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-5.jpg)
Mechanical Controls • Mechanical controls start, stop, or modulate fluid flow to increase system effectiveness • Can be operated by pressure, temperature, or electricity • Almost always found in the piping
![TwoTemperature Controls Twotemperature operation is utilized when there are multiple evaporators in the Two-Temperature Controls • Two-temperature operation is utilized when there are multiple evaporators in the](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-6.jpg)
Two-Temperature Controls • Two-temperature operation is utilized when there are multiple evaporators in the system – These evaporators typically operate at different temperatures – The pressures are therefore different – Two-temperature operation is normally accomplished with mechanical valves
![Figure 25 1 Twotemperature operation Two evaporators are operating on one compressor One evaporator Figure 25– 1 Two-temperature operation. Two evaporators are operating on one compressor. One evaporator](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-7.jpg)
Figure 25– 1 Two-temperature operation. Two evaporators are operating on one compressor. One evaporator operates at 20°F (18. 4 psig), the other at 30°F (26. 1 psig)
![Evaporator Pressure Control Evaporator pressure regulator EPR Prevents the pressure in an Evaporator Pressure Control • Evaporator pressure regulator (EPR) – Prevents the pressure in an](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-8.jpg)
Evaporator Pressure Control • Evaporator pressure regulator (EPR) – Prevents the pressure in an evaporator from dropping below a predetermined pressure – Two pressures control the valve • Spring pressure – pushes to close the valve • Evaporator pressure – pushes to open the valve – Evaporator superheat may be high when the EPR is closed
![Multiple Evaporators An EPR is needed in the suction line of each evaporator Multiple Evaporators • An EPR is needed in the suction line of each evaporator](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-9.jpg)
Multiple Evaporators • An EPR is needed in the suction line of each evaporator except the lowest temperature coil • EPR valves are equipped with Schrader valves to read evaporator pressure • Multiple EPRs can be set at different pressures so each evaporator can be maintained at a different temperature
![Figure 25 5 Evaporators piped together and one compressor used to maintain a suction Figure 25– 5 Evaporators piped together and one compressor used to maintain a suction](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-10.jpg)
Figure 25– 5 Evaporators piped together and one compressor used to maintain a suction pressure for the lowest-pressure evaporator. Evaporators that have pressures higher than the true suction pressure of the lowest evaporator all have EPR valves set to their individual needs
![Electric Evaporator Pressure Regulator EEPR Valves Provide more accurate control Located at Electric Evaporator Pressure Regulator (EEPR) Valves • Provide more accurate control – Located at](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-11.jpg)
Electric Evaporator Pressure Regulator (EEPR) Valves • Provide more accurate control – Located at the evaporator outlet – Used on single or multiple systems – Microprocessor senses case discharge air temperature – Designed to maintain discharge air temperature in the refrigerated case – Controlled by a bipolar step motor
![Crankcase Pressure Regulator CPR Located close to the compressor Prevents compressor from Crankcase Pressure Regulator (CPR) • Located close to the compressor – Prevents compressor from](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-12.jpg)
Crankcase Pressure Regulator (CPR) • Located close to the compressor – Prevents compressor from overloading on start-up – Provides a limit to the pressure that can enter the compressor – Referred to as a close on rise of outlet (CRO) valve – Resembles an EPR valve
![Figure 25 10 The CPR valve throttles the vapor refrigerant entering the compressor There Figure 25– 10 The CPR valve throttles the vapor refrigerant entering the compressor. There](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-13.jpg)
Figure 25– 10 The CPR valve throttles the vapor refrigerant entering the compressor. There will be a pressure drop across the valve when the evaporator is too warm. This valve is adjusted and set up using the compressor full-load amperage on a hot pulldown. The CPR valve can be set to throttle the suction gas to the compressor and prevent a high suction pressure on the compressor side of the valve that will not allow the compressor to overload. When the refrigerated box temperature is pulled down to the design range, the suction gas in the evaporator will be the same as the pressure at the compressor because the valve is wide open
![Adjusting The CPR Valve Procedure Best adjusted under a high load condition Adjusting The CPR Valve • Procedure: – Best adjusted under a high load condition](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-14.jpg)
Adjusting The CPR Valve • Procedure: – Best adjusted under a high load condition • An ammeter should be used to set the valve • Excessive amperage indicates that too much refrigerant is entering the compressor • Turning the adjusting screw into the valve reduces the refrigerant pressure returning to the compressor • Turning the screw out of the valve increases it
![Relief Valves Release refrigerant from a system when a highpressure condition exists Relief Valves • Release refrigerant from a system when a high-pressure condition exists –](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-15.jpg)
Relief Valves • Release refrigerant from a system when a high-pressure condition exists – Spring-loaded type • Located in the vapor space • Resets after opening – One-time type • Fittings filled with low-temperature solder • Usually located in the suction line near the compressor
![Low Ambient Controls Used on systems that are operated year round to maintain Low Ambient Controls • Used on systems that are operated year round to maintain](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-16.jpg)
Low Ambient Controls • Used on systems that are operated year round to maintain head pressure – Fan cycling, fan speed control, air volume control, and condenser flooding – Intended to simulate design operating conditions – Help to keep the system’s operating pressures within desired ranges
![FanCycling Head Pressure Control Device opens on a drop in head pressure turning Fan-Cycling Head Pressure Control • Device opens on a drop in head pressure, turning](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-17.jpg)
Fan-Cycling Head Pressure Control • Device opens on a drop in head pressure, turning condenser fan off • Device closes on a rise in head pressure, turning condenser fan on • Fan cycling causes large variances in the head pressure • Best used on systems with multiple fans
![Fan Speed Control for Controlling Pressure As the outside temperature drops the fan Fan Speed Control for Controlling Pressure • As the outside temperature drops, the fan](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-18.jpg)
Fan Speed Control for Controlling Pressure • As the outside temperature drops, the fan slows down to reduce the amount of airflow through the condenser coil • As the outside temperature rises, the fan speeds up to increase airflow through the condenser • Some controls monitor the refrigerant’s condensing temperature
![Air Volume Control for Controlling Head Pressure Utilizes pistoncontrolled shutters andor dampers Air Volume Control for Controlling Head Pressure • Utilizes piston-controlled shutters and/or dampers –](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-19.jpg)
Air Volume Control for Controlling Head Pressure • Utilizes piston-controlled shutters and/or dampers – As the head pressure drops, the shutters close, reducing airflow – Reduced airflow raises the head pressure – During periods of warm ambient temperatures, the dampers are fully open to maximize airflow through the condenser coil
![Figure 25 17 A Installation using dampers to vary the air volume instead of Figure 25– 17 (A) Installation using dampers to vary the air volume instead of](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-20.jpg)
Figure 25– 17 (A) Installation using dampers to vary the air volume instead of fan speed. This is accomplished with a refrigerant-operated damper that operates the shutters. This application modulates the airflow and gives steady head pressure control. (B) If more than one fan is used, the first fans can be cycled off based on ambient temperature. Care should be taken that the condenser fan will not be overloaded when the shutters are placed at the fan outlet
![Condenser Flooding for Controlling Head Pressure Flooding valves cause liquid refrigerant to move Condenser Flooding for Controlling Head Pressure • Flooding valves cause liquid refrigerant to move](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-21.jpg)
Condenser Flooding for Controlling Head Pressure • Flooding valves cause liquid refrigerant to move from the receiver to the condenser in cold weather – Systems with flooding valves have oversized receivers to hold excess refrigerant charge in warm weather – The valve is closed when outdoor temperature is high (refrigerant directed to the condenser)
![Condenser Splitting for Controlling Head Pressure Splitting Another way to reduce the Condenser Splitting for Controlling Head Pressure • Splitting: – Another way to reduce the](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-22.jpg)
Condenser Splitting for Controlling Head Pressure • Splitting: – Another way to reduce the amount of extra refrigerant charge – Split the condenser into two separate and identical condenser circuits – Controlled by a pilot-operated, three-way solenoid valve installed in the discharge line from the compressors
![The Solenoid Valve Used to start or stop refrigerant flow Normally open The Solenoid Valve • Used to start or stop refrigerant flow – Normally open](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-23.jpg)
The Solenoid Valve • Used to start or stop refrigerant flow – Normally open (NO) or normally closed (NC) – Snap-acting valves (open or closed) – Valves must be installed with the arrow pointing in the direction of flow – Often used in conjunction with automatic pump down cycles – Valve position controlled by a solenoid coil
![The Solenoid Valve contd Figure 25 21 The solenoid valve installed in the The Solenoid Valve (cont’d. ) Figure 25– 21 The solenoid valve installed in the](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-24.jpg)
The Solenoid Valve (cont’d. ) Figure 25– 21 The solenoid valve installed in the correct position. Most valves use gravity to seat the valve, and the magnetic force raises the valve off its seat. If the valve is installed on its side or upside down, the valve will not seat when deenergized
![Pressure Switches Start and stop current flow to components Low pressure switch Pressure Switches • Start and stop current flow to components – Low pressure switch:](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-25.jpg)
Pressure Switches • Start and stop current flow to components – Low pressure switch: closes on a rise in pressure – High pressure switch: opens on a rise in pressure – Low ambient control: closes on a rise in pressure – Oil safety switch: opens on a rise in pressure
![LowPressure Switch Can be used as lowcharge protection and space temperature control Low-Pressure Switch • Can be used as low-charge protection and space temperature control –](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-26.jpg)
Low-Pressure Switch • Can be used as low-charge protection and space temperature control – Low-charge protection • Cut-out pressure set well below normal • Cut out pressure should be set above atmospheric pressure to prevent atmosphere from being pulled into the system • Prevents system from operating in a vacuum • Control is normally reset automatically
![LowPressure Control Applied as a Thermostat Control will cut off the compressor when Low-Pressure Control Applied as a Thermostat • Control will cut off the compressor when](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-27.jpg)
Low-Pressure Control Applied as a Thermostat • Control will cut off the compressor when the pressure equals the system pressure that corresponds to a temperature about 15° cooler than desired box temperature • Control is rated by pressure range and current draw of the contacts
![Figure 25 25 When a compressor that is larger than the electrical rating of Figure 25– 25 When a compressor that is larger than the electrical rating of](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-28.jpg)
Figure 25– 25 When a compressor that is larger than the electrical rating of the pressure control contacts is encountered, the compressor has to be started with a contactor. The wiring diagram shows how this is accomplished.
![Automatic PumpDown Systems Sequence of shutdown operation Normally closed liquidline solenoid valve Automatic Pump-Down Systems • Sequence of shut-down operation: – Normally closed liquid-line solenoid valve](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-29.jpg)
Automatic Pump-Down Systems • Sequence of shut-down operation: – Normally closed liquid-line solenoid valve controlled by a thermostat • Thermostat opens when desired box temperature is reached • The solenoid is de-energized and closes • Compressor continues to pump refrigerant • The suction pressure drops, so low-pressure control opens and controls compressor operations
![Automatic PumpDown Systems contd Sequence of startup operation When the box Automatic Pump-Down Systems (cont’d. ) • Sequence of startup operation: – When the box](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-30.jpg)
Automatic Pump-Down Systems (cont’d. ) • Sequence of startup operation: – When the box temperature rises, thermostat closes – The liquid-line solenoid is energized – Refrigerant flows to the evaporator – When the low-side pressure increases, the low-pressure control closes – The compressor is once again energized
![HighPressure Control Prevents compressor from operating at high head pressures Control opens High-Pressure Control • Prevents compressor from operating at high head pressures – Control opens](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-31.jpg)
High-Pressure Control • Prevents compressor from operating at high head pressures – Control opens on a rise in pressure – Can be automatically or manually reset – Should be set at a pressure higher than the normal operating head pressure – Manual reset controls provide better equipment protection
![LowAmbient Fan Control Starts and stops the condenser fan motor in response to Low-Ambient Fan Control • Starts and stops the condenser fan motor in response to](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-32.jpg)
Low-Ambient Fan Control • Starts and stops the condenser fan motor in response to head pressure • Starts the condenser fan motor when the head pressure rises • This setting should be lower than the set point on the high-pressure control
![Oil Pressure Safety Control Larger compressors use with oil pumps Pump connected Oil Pressure Safety Control • Larger compressors use with oil pumps – Pump connected](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-33.jpg)
Oil Pressure Safety Control • Larger compressors use with oil pumps – Pump connected to compressor crankshaft • Oil forced through holes in the crankshaft – Measures net oil pressure • Net oil pressure = pump outlet pressure – suction pressure – Has a time delay built into the control to allow oil pressure to build up – Internal overloads also controlled
![Defrost Cycle Any evaporator that operates below the freezing point of water needs Defrost Cycle • Any evaporator that operates below the freezing point of water needs](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-34.jpg)
Defrost Cycle • Any evaporator that operates below the freezing point of water needs defrosting • Develops a layer of frost and entrained air referred to as “hoar frost” • Increased by humidity levels and air flow amounts • Medium and low temperature range methods of defrosting
![MediumTemperature Refrigeration Defrost Typical box temperature ranges from 34F to 45F Medium-Temperature Refrigeration • Defrost: – Typical box temperature ranges from 34°F to 45°F –](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-35.jpg)
Medium-Temperature Refrigeration • Defrost: – Typical box temperature ranges from 34°F to 45°F – Coil temperatures are normally 10° to 15°F cooler than the box – Coil will be operating below 32°F but box will be above 32°F – Air in box is used to defrost the coil in the off cycle defrost
![Random or OffCycle Defrost Coil defrosts using box temperature air compressor cycles off Random or Off-Cycle Defrost • Coil defrosts using box temperature air compressor cycles off](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-36.jpg)
Random or Off-Cycle Defrost • Coil defrosts using box temperature air compressor cycles off on thermostat • Evaporator fan will continue to run while the compressor is off • Air in box defrost coil • Coil defrosts whenever compressor cycles off
![Planned Defrost Defrost is controlled by a timer System goes into defrost Planned Defrost • Defrost is controlled by a timer • System goes into defrost](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-37.jpg)
Planned Defrost • Defrost is controlled by a timer • System goes into defrost at predetermined times • Defrost cycle is initiated during low load periods • Systems in retail establishments often go into defrost when the store is closed
![LowTemperature Evaporator Design Box and coil temperatures are both below 32F Coil Low-Temperature Evaporator Design • Box and coil temperatures are both below 32°F • Coil](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-38.jpg)
Low-Temperature Evaporator Design • Box and coil temperatures are both below 32°F • Coil defrosted using internal or external heat • Air in the box cannot be used to defrost the evaporator coil – Internal heat: hot gas from the compressor – External heat: electric strip heaters
![Defrost Using Internal Heat Hot Gas and Cool Gas Defrost Hot gas from Defrost Using Internal Heat (Hot Gas and Cool Gas Defrost) • Hot gas from](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-39.jpg)
Defrost Using Internal Heat (Hot Gas and Cool Gas Defrost) • Hot gas from compressor’s discharge – Discharge gas is directed into the evaporator – A hot gas solenoid defrost initiated by a timer – Defrost is ended by time or coil temperature – Evaporator fan is de-energized during defrost – Compressor runs during defrost – Refrigerant condenses in the evaporator • Cool gas comes from top of the receiver
![Figure 25 35 Hot gas defrost Figure 25– 35 Hot gas defrost](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-40.jpg)
Figure 25– 35 Hot gas defrost
![External Heat Type of Defrost Usually accomplished with electric heaters mounted to the External Heat Type of Defrost • Usually accomplished with electric heaters mounted to the](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-41.jpg)
External Heat Type of Defrost • Usually accomplished with electric heaters mounted to the evaporator coil – Defrost is initiated by a timer – Defrost is terminated by either time or coil temperature – Evaporator fan is de-energized during defrost – Compressor is de-energized during defrost
![Defrost Termination and Fan Delay Control Single pole double throw switch Terminates Defrost Termination and Fan Delay Control • Single pole, double throw switch – Terminates](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-42.jpg)
Defrost Termination and Fan Delay Control • Single pole, double throw switch – Terminates defrost when all frost removed – When ice has been removed, the evaporator surface temperature increases • The control senses this increase in temperature and the system is put back into refrigeration mode mechanically – When the coil temperature drops to the set point temperature, the fan is energized
![Defrost Termination and Fan Delay Control Figure 25 37 A sensor used with the Defrost Termination and Fan Delay Control Figure 25 -37 A sensor used with the](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-43.jpg)
Defrost Termination and Fan Delay Control Figure 25 -37 A sensor used with the timer in Figure 25– 36. The sensor has three wires; it is a single-pole–double-throw device. It has a hot contact (made from common to the terminal that is energized on a rise in temperature) and a cold contact (made from common to the terminal that is energized when the coil is cold). This control is in either the hot or the cold mode. It is often referred to as a defrost termination and fan delay (DTFD) switch. Courtesy Ferris State University. Photo by John Tomczyk
![Refrigeration Accessories Accessories are devices that improve system performance and service functions Refrigeration Accessories • Accessories are devices that improve system performance and service functions •](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-44.jpg)
Refrigeration Accessories • Accessories are devices that improve system performance and service functions • Each system does not have all the accessories
![Receivers Located in the liquid line The device stores liquid refrigerant Receivers • Located in the liquid line – The device stores liquid refrigerant –](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-45.jpg)
Receivers • Located in the liquid line – The device stores liquid refrigerant – Refrigerant leaves receiver as 100% liquid – A dip tube is used to remove bottom liquid – Must be used on condenser flooding valves – Found on systems with automatic or thermostatic expansion valves – Not found on critically charged (capillary tube) systems
![The King Valve on the Receiver Located in the liquid line between the The King Valve on the Receiver • Located in the liquid line between the](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-46.jpg)
The King Valve on the Receiver • Located in the liquid line between the receiver and expansion device – Normally the valve is back seated – Valve can be front seated in order to pump system down – Has a service port to enable readings – Must be cracked off the back seat to take pressure readings
![The King Valve on the Receiver contd Figure 25 41 A king valve The King Valve on the Receiver (cont’d. ) Figure 25– 41 A king valve](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-47.jpg)
The King Valve on the Receiver (cont’d. ) Figure 25– 41 A king valve piped in the circuit. The back seat is open to the gauge port when the valve is front seated. This valve has to be back seated for the gauge to be removed if refrigerant is in the system
![Filter Driers Located in the liquid line Removes dirt moisture and acid Filter Driers • Located in the liquid line – Removes dirt, moisture, and acid](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-48.jpg)
Filter Driers • Located in the liquid line – Removes dirt, moisture, and acid from the refrigeration system – Desiccant: activated alumina, molecular sieve, silica gel – Can be permanent or replaceable core type – Connected to system with either solder joints or flare connections
![Refrigerant Check Valves Allows refrigerant to flow in only one direction Can Refrigerant Check Valves • Allows refrigerant to flow in only one direction – Can](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-49.jpg)
Refrigerant Check Valves • Allows refrigerant to flow in only one direction – Can be either the ball type or magnetic type – Must be installed with the arrow pointing in the direction of refrigerant flow – Installed at the outlet of the lowest temperature coil on multi-evaporator systems
![Refrigerant Sight Glasses Installed in the liquid line Enables the technician to Refrigerant Sight Glasses • Installed in the liquid line • Enables the technician to](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-50.jpg)
Refrigerant Sight Glasses • Installed in the liquid line • Enables the technician to determine if a solid column of liquid is reaching the expansion device • Can also be supplied with a moisture indicator • Usually installed after the filter drier
![Liquid Refrigerant Distributors Used on multicircuit evaporators Located at the outlet of Liquid Refrigerant Distributors • Used on multi-circuit evaporators • Located at the outlet of](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-51.jpg)
Liquid Refrigerant Distributors • Used on multi-circuit evaporators • Located at the outlet of the expansion device • Designed to allow equal refrigerant flow to all evaporator circuits • Some distributors are made with side inlets used for hot gas defrost
![Heat Exchangers In the suction line leaving the evaporator Suction and liquid Heat Exchangers • In the suction line leaving the evaporator • Suction and liquid](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-52.jpg)
Heat Exchangers • In the suction line leaving the evaporator • Suction and liquid lines are connected to allow heat to transfer between them • Increases the amount of subcooling in the liquid entering the expansion device • Prevents liquid from moving through the suction line into the compressor
![Heat Exchangers contd Figure 25 47 Heat exchangers A Plain liquidtosuction type B Heat Exchangers (cont’d. ) Figure 25 -47 Heat exchangers (A) Plain liquid-to-suction type (B)](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-53.jpg)
Heat Exchangers (cont’d. ) Figure 25 -47 Heat exchangers (A) Plain liquid-to-suction type (B) Capillary tube fastened to the suction line; it accomplishes the same thing as the heat exchanger
![Suction Line Accumulators Located in the suction line close to the compressor Suction Line Accumulators • Located in the suction line, close to the compressor –](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-54.jpg)
Suction Line Accumulators • Located in the suction line, close to the compressor – Prevents liquid refrigerant from entering the compressor – Gives liquid a place to boil off before entering compressor – Sometimes, the liquid line is routed through the accumulator to help boil away any liquid and also increase liquid subcooling
![Figure 25 48B A suctionline accumulator with heat exchanger Figure 25– 48(B) A suction-line accumulator with heat exchanger](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-55.jpg)
Figure 25– 48(B) A suction-line accumulator with heat exchanger
![SuctionLine Filter Driers Located in the suction line Good compressor protection Suction-Line Filter Driers • Located in the suction line • Good compressor protection •](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-56.jpg)
Suction-Line Filter Driers • Located in the suction line • Good compressor protection • Must be installed when system has become contaminated • Usually have two pressure ports to read the pressure drop across the device
![Suction Service Valves Normally attached to the compressor Valve positions Suction Service Valves • Normally attached to the compressor – Valve positions • •](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-57.jpg)
Suction Service Valves • Normally attached to the compressor – Valve positions • • Back-seated: normal operating position Front-seated: used for pump down & service Mid-seated: used for system evacuation Cracked off the back seat: used for taking pressure readings, charging refrigerant into the system, or removing refrigerant from the system
![Discharge Service Valves Located in the discharge line Normally attached to the Discharge Service Valves • Located in the discharge line – Normally attached to the](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-58.jpg)
Discharge Service Valves • Located in the discharge line – Normally attached to the compressor – Used as a gauge port and to valve off the compressor for service – Same positions as the suction service valve – This valve should not be front-seated when the compressor is running except during closed-loop capacity tests
![Refrigeration Line Service Valves Handoperated specialty valves used for service purposes Used Refrigeration Line Service Valves • Hand-operated specialty valves used for service purposes • Used](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-59.jpg)
Refrigeration Line Service Valves • Hand-operated specialty valves used for service purposes • Used in any line that may have to be valved off for any reason • Two types: the diaphragm valve and the ball valve
![Diaphragm Valves Same internal flow pattern as a globe valve Can be Diaphragm Valves • Same internal flow pattern as a “globe” valve • Can be](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-60.jpg)
Diaphragm Valves • Same internal flow pattern as a “globe” valve • Can be tightened by hand enough to hold back high pressures • Installed into the system with either a flare or soldered connection
![Ball Valves Straightthrough valve with little pressure drop Advantage is that it Ball Valves • Straight-through valve with little pressure drop • Advantage is that it](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-61.jpg)
Ball Valves • Straight-through valve with little pressure drop • Advantage is that it can be opened or closed easily because it only takes a 90° turn to either open or close it • Known as a “quick open or close” valve
![Oil Separators Installed in the discharge line Separates oil from the refrigerant Oil Separators • Installed in the discharge line – Separates oil from the refrigerant](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-62.jpg)
Oil Separators • Installed in the discharge line – Separates oil from the refrigerant and returns the oil to the compressor – Oil drops fall to the bottom of the separator – Oil level raises a float and opens a valve – Difference between high- and low-side pressures push oil back to the compressor – Device needs to be kept warm
![Vibration Eliminators Often necessary to protect the tubing at the suction and discharge Vibration Eliminators • Often necessary to protect the tubing at the suction and discharge](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-63.jpg)
Vibration Eliminators • Often necessary to protect the tubing at the suction and discharge lines • Eliminated on small compressors successfully with vibration loops • Large tubing requires special vibration eliminators constructed with a bellowstype lining and a flexible outer protective support
![Pressure Access Ports Installed to take pressure readings at various points in the Pressure Access Ports • Installed to take pressure readings at various points in the](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-64.jpg)
Pressure Access Ports • Installed to take pressure readings at various points in the system • Line piercing valves can be installed while the system is running • Can be saddle type or solder type • Can either have a Schrader pin or a small valve
![Crankcase Heat Prevents refrigerant from migrating to the oil in the off cycle Crankcase Heat • Prevents refrigerant from migrating to the oil in the off cycle](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-65.jpg)
Crankcase Heat • Prevents refrigerant from migrating to the oil in the off cycle • Prevents oil from foaming and being pumped out of the compressor • Crankcase heat is needed during the off cycle and is sometimes controlled by a set of normally closed contacts that open when the compressor is energized
![Summary Additional components enhance system operation The EPR is used on multiple Summary • Additional components enhance system operation • The EPR is used on multiple](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-66.jpg)
Summary • Additional components enhance system operation • The EPR is used on multiple evaporator systems to maintain different pressures in each evaporator • EPR valves are located in all evaporators except the lowest pressure evaporator
![Summary contd The CPR provides a limit to the pressure that can Summary (cont’d. ) • The CPR provides a limit to the pressure that can](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-67.jpg)
Summary (cont’d. ) • The CPR provides a limit to the pressure that can enter the compressor • Relief valves release refrigerant from a system when a high-pressure condition exists • Low ambient controls are used on refrigeration systems that operate year round
![Summary contd Common low ambient controls include fan cycling shutters dampers and Summary (cont’d. ) • Common low ambient controls include fan cycling, shutters, dampers and](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-68.jpg)
Summary (cont’d. ) • Common low ambient controls include fan cycling, shutters, dampers and condenser flooding • Solenoid valves are used to start and stop the flow of refrigerant (snap-acting valve) • Liquid line solenoids are used as part of the automatic pump down cycle
![Summary contd Pressure witches open and close in response to sensed pressures Summary (cont’d. ) • Pressure witches open and close in response to sensed pressures](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-69.jpg)
Summary (cont’d. ) • Pressure witches open and close in response to sensed pressures • Pressure switches can be operational or safety devices • The oil pressure safety control ensures that compressors operate with sufficient oil pressure
![Summary contd Defrosting medium temperature refrigeration systems can be accomplished with planned Summary (cont’d. ) • Defrosting medium temperature refrigeration systems can be accomplished with planned,](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-70.jpg)
Summary (cont’d. ) • Defrosting medium temperature refrigeration systems can be accomplished with planned, random or off-cycle defrost • Defrosting low temperature refrigeration systems is accomplished with hot discharge gas (internal) or electric strip heaters (external)
![Summary contd Receivers are refrigerant storage tanks located at the outlet of Summary (cont’d. ) • Receivers are refrigerant storage tanks located at the outlet of](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-71.jpg)
Summary (cont’d. ) • Receivers are refrigerant storage tanks located at the outlet of the condenser • Receivers are equipped with service valves that can be back-seated, cracked off the backseat, mid-seated, or frontseated • Filter driers remove dirt, moisture, and acid from the refrigeration system
![Summary contd Check valves ensure that refrigerant flows in only one direction Summary (cont’d. ) • Check valves ensure that refrigerant flows in only one direction](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-72.jpg)
Summary (cont’d. ) • Check valves ensure that refrigerant flows in only one direction • Refrigerant distributor allow equal amounts of refrigerant flow to all circuits • Suction line/liquid line heat exchangers increase subcooling and help ensure that 100% vapor enters the compressor
![Summary contd Accumulators help liquid refrigerant boil before it enters the compressor Summary (cont’d. ) • Accumulators help liquid refrigerant boil before it enters the compressor](https://slidetodoc.com/presentation_image_h/e8ca19c32603c3d8f421543c91a2efec/image-73.jpg)
Summary (cont’d. ) • Accumulators help liquid refrigerant boil before it enters the compressor • Oil separators help remove oil from the hot vapor that is discharged from the compressor • Crankcase heat helps boil refrigerant from the oil in the compressor crankcase
Defrost using internal heat is accomplished using
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