R4 Troubleshooting Refrigeration

R4 Troubleshooting Refrigeration
R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1 9/14/2018 R4 Troubleshooting Refrigeration #2 System Problems © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Quick Review of the Refrigeration Cycle
R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1 9/14/2018 Quick Review of the Refrigeration Cycle The following slides review the cycle of a standard air conditioning system: Condenser Rejects heat as refrigerant vapor condenses to a liquid Metering device Reduces pressure and temperature of liquid Evaporator Absorbs heat from space as refrigerant vaporizes Compressor Increases vaporized refrigerant pressure and temperature System heat is sent to the condenser to be rejected © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1
Typical A/C System R-22 9/14/2018 Fixed Metering Device 69 psig 278 psig 175º 40º 60º 125º CONDENSER 125º EVAPORATOR 115º 40º Refrigeration Cycle for a Typical R22 A/C System High Side: High pressure vapor leaves the compressor at a high temperature. When it enters the condenser it first gets rid of the sensible heat of compression and motor heat it picked up in the compressor. This is known as de-superheating. Once it gets rid of that sensible heat it reaches its condensing temperature. In our example, when the vapor has reached 125º it starts condensing into a liquid (changes state) as it rejects the latent heat it picked up in the evaporator. Any additional cooling of the liquid before it leaves the condenser without a change of state is called subcooling. It often picks up additional subcooling in the liquid line before the metering device. Low Side: As it passes through the metering device the high temperature liquid drops in pressure and temperature as it changes to a dense vapor containing tiny droplets of liquid. About 25% of the liquid flashes off dropping the temperature of the remaining liquid from 115º to 40º. That temperature (evaporating temperature) remains the same through the evaporator absorbing latent heat from the refrigerated space as it boils off. When all the refrigerant is boiled off, or vaporized, it is now a “saturated vapor”. Any additional heat it picks up after that is called superheat because only sensible heat can be absorbed when there is no change of state. The vapor continues through the suction line picking up superheat until it gets to the compressor where the cycle starts all over. 50º AMBIENT AIR 95o RETURN AIR 75o © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Typical A/C System R-22 9/14/2018 Total Superheat 20° Fixed Metering Device 69 psig 278 psig Super Heated Vapor 175º 40º 60º 125º Evaporation Starts CONDENSER Condensing Starts 125º EVAPORATOR Fully Evaporated 115º 40º Fully Condensed Liquid Coil Superheat 10° 50º Sub-Cooled Liquid AMBIENT AIR 95o RETURN AIR 75o © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Review of TEV Operation
R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1 9/14/2018 Review of TEV Operation Meters refrigerant Maintains superheat Opening force: Bulb pressure Closing forces: Evaporator pressure Adjustable spring © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Expansion Valve Detail
R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1 SPORLAN 9/14/2018 Expansion Valve Detail Typical A/C Using R22 278 psig 40º EVAPORATOR 40º Low Side: As the liquid refrigerant passes through the metering device the high temperature liquid changes to a low temperature vapor because of the pressure drop caused by the metering device. About 25% of the liquid flashes off, dropping the temperature of the remaining liquid from 115 to 40 deg. That temperature (evaporating or saturation temperature) remains the same through the evaporator as it absorbs latent heat from the refrigerated space. When all refrigerant is boiled off, or vaporized, it is now a “saturated vapor”. Any more heat it picks up after that is called superheat and it can only be sensible heat because there is no further change of state. 69 psig 50º RETURN AIR 75o © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Expansion Valve Detail
R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1 9/14/2018 Expansion Valve Detail 50º = 84 psig Pressure on diaphragm Typical A/C Using R22 278 psig 40º EVAPORATOR Evaporator 40º = 69 psig closing pressure 40º In the enlarged expansion valve illustration we start with the thermal sensing bulb. In this example, when the suction lines increases in temperature to 50° the refrigerant in the bulb boils off, increases in pressure to 84#, and pushes down on a diaphragm in the valve head. The diaphragm pushes down on two pins that move the needle away from the valve seat allowing refrigerant to flash off into the evaporator. The closing forces that keep the valve from opening too wide and flooding the evaporator are (1) the evaporator pressure (at 40 ° the pressure is 69#) and (2) the spring pressure. The superheat spring pressure is adjusted at the factory to provide the difference needed to maintain a constant flow of refrigerant at a certain superheat for the required application (A/C, medium temperature, or low temperature freezer). In this example it would be the difference between the pressures at 50° and 40° (50° - 40° = 10° Superheat) or (84# – 69# = 15#) 69 psig 50º Spring pressure to maintain equilibrium is: 84 psig – 69 psig = 15 psig RETURN AIR 75o © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Diagnosing 9 System Problems TEV and Fixed Metering Devices
R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1 9/14/2018 Diagnosing 9 System Problems TEV and Fixed Metering Devices 1. Undercharge of refrigerant 2. Overcharge of refrigerant 3. Dirty Condenser 4. Air in the system 5. Inefficient compressor 6. Restricted metering device 7. Restriction in the liquid line after the receiver 8. Restriction in the liquid line before the receiver 9. Dirty or iced evaporator, dirty filter, or low air flow © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Undercharge of Refrigerant Fixed metering device
R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1 9/14/2018 Undercharge of Refrigerant Fixed metering device Evaporator: Lower temperature Lack of refrigerant, low pressure, low temperature High superheat Limited refrigerant boiled off quickly Condenser: Little heat from the evaporator Low subcooling Lack of refrigerant to subcool © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Low Charge 9/14/2018 Fixed Metering Device: 40 psig 180 psig 69 psig 278 psig 80º 18º 60º 40º 125º 18º 90º CONDENSER 95º EVAPORATOR Low Refrigerant Charge Cap tube, fixed metering device system LOW is the key word for this condition. Since there is insufficient refrigerant in the system, there is a low load. Therefore, there is LOW HEAD PRESSURE, LOW SUCTION PRESSURE, LOW AMP DRAW, and LOW CONDENSER SUBCOOLING. The only thing that is HIGH is SUPERHEAT because the small amount of refrigerant boils off early in the evaporator and the only heat that is picked up is the sensible heat which accounts for the high superheat. 95º 40º 115º 70º 50º AMBIENT AIR 95o A/C System R-22 RETURN AIR 80o © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Undercharge of Refrigerant TEV System
R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1 9/14/2018 Undercharge of Refrigerant TEV System Evaporator: Lower temperature Lack of refrigerant, low pressure, low temperature High superheat Limited refrigerant boiled off quickly Condenser: Little heat from the evaporator Low subcooling Lack of refrigerant to subcool © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Low Charge 9/14/2018 TEV System: 40 psig 180 psig 69 psig 278 psig 80º 18º 60º 40º TEV 125º 18º CONDENSER 95º EVAPORATOR Along with the same symptoms as the cap tube system a low charge in a TEV system will also produce BUBBLES in the SIGHT GLASS. A word of caution about sight glasses, one installed horizontally can show half full or bubbles during low load conditions, yet the system is fully charged! This won’t show up in a sight glass that’s installed in a vertical liquid line. 95º 40º 115º 70º 50º AMBIENT AIR 95o A/C System R-22 RETURN AIR 80o © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Overcharge of Refrigerant Fixed metering device
R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1 9/14/2018 Overcharge of Refrigerant Fixed metering device Condenser: High temperature Excess refrigerant taking up condensing space High subcooling More liquid for sensible cooling Evaporator: High pressure liquid is forced through metering device Low superheat Refrigerant is flooding through the evaporator © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Overcharge of Refrigerant
R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1 Overcharge of Refrigerant 9/14/2018 Fixed Metering Device: 120 psig 360 psig 69 psig 278 psig 70º 70º 60º 40º 145º 125º CONDENSER 145º EVAPORATOR 125º Overcharge of Refrigerant CAP TUBE System A cap tube system has a critical charge. This means the condenser can contain all the refrigerant in the system and the compressor will be able to handle the liquid returning without too much trouble. However, an excessive overcharge will cause extremely high head, which will trip high pressure controls, or cause internal relief valves to blow, and also make the compressor cycle on overload. A CAP TUBE system cannot tolerate anything above a 10% OVERCHARGE. It will have HIGH SUCTION pressures and NO SUPERHEAT, probably flooding the compressor. If you’re not sure whether it’s air in the system or an overcharge pull out all the refrigerant, evacuate the system, and weigh in the proper amount of refrigerant per the manufacturers specs, or name plate. This should solve either problem and is usually quicker than sitting there scratching you head trying to figure out what it might be. LOOK FOR: An inexperienced tech who doesn’t know how to diagnose a system without dumping refrigerant into it. They may have mistaken a high load situation as an indication of a problem. Cap tube systems do not drop in temperature as quickly as TEV systems, nor do they handle heavy loads. For example, a cap tube system reach-in freezer that was loaded with food that was frozen, but was allowed to rise to about 25 degrees, may take 24 hours or more to bring it down to 0 degrees. 125º 40º 70º 115º 70º 50º AMBIENT AIR 95o A/C System R-22 RETURN AIR 80o © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Overcharge of Refrigerant TEV System
R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1 9/14/2018 Overcharge of Refrigerant TEV System Condenser: High temperature Excess refrigerant taking up condensing space High subcooling More liquid for sensible cooling Evaporator: Slightly higher temperature High condensing pressure pushing liquid through valve Normal superheat TEV tries to maintain suction line temperature © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Overcharge of Refrigerant
R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1 9/14/2018 TEV System: 85 psig 360 psig 69 psig 278 psig 70º 50º 60º 40º TEV 145º 145º CONDENSER 145º EVAPORATOR 125º Overcharge of Refrigerant TEV System This is about the same as air in the system: HIGH HEAD PRESSURE and HIGH SUBCOOLING. An excessive overcharge will cause extremely high head, which will trip high pressure controls, or cause internal relief valves to blow, and also make the compressor cycle on overload. A TEV system will try to maintain a NORMAL to SLIGHTLY HIGH SUCTION PRESSURE and NORMAL SUPERHEAT. If you’re not sure whether it’s air in the system or an overcharge start pulling refrigerant from the system until the sight glass shows bubbles. Put some back in until the glass clears. If the pressures return to normal it was an overcharge, especially if the subcooling returns to normal. If the pressures don’t settle down, there is probably air in the system. LOOK FOR: Someone who charged the system in mild or cold weather. An inexperienced tech may have mistaken a half full horizontal sight glass at low load conditions as a sign of low charge. Or he may have mistaken bubbles in the glass for low charge, when it was during start up or some other high loading situation causing the expansion valve to open wide. If the system runs fine, but goes out on high pressure when trying to pump down, the receiver may not be large enough, or the pump-down solenoid may have to be moved closer to the evaporator so the entire liquid line does not have to be emptied during pump-down. Note: Always charge a system under high load conditions. This may require blocking off some of the condenser air flow. If the system is using a Head Pressure Regulating valve check with the condensing unit manufacturer on charging in ambients over 75°. If this is not possible, a “rule of thumb” when charging in warm weather is to charge to a clear sight glass, then add another 25%. Make sure you pump it down to see if the receiver will hold it all. NOTE: double check with the manufacturer of the system to verify proper charging. 120º 50º 115º 40º 60º 50º AMBIENT AIR 95o A/C System R-22 RETURN AIR 80o © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Dirty condenser Fixed metering device
R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1 9/14/2018 Dirty condenser Fixed metering device Condenser: Higher temperature Heat cannot be rejected Normal subcooling High pressure forces refrigerant out of condenser Evaporator: Higher temperatures High pressure forces refrigerant through evaporator Low superheat Refrigerant doesn’t have a chance to boil off © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Dirty Condenser 9/14/2018 Fixed Metering Device: 120 psig 360 psig 69 psig 278 psig 70º 70º 60º 40º 145º 125º CONDENSER 145º EVAPORATOR 125º Dirty Condenser (low or restricted air through the coil) CAP TUBE System If air cannot cool the condenser than the condensing pressures will rise, but the SUBCOOLING will remain about NORMAL. The HIGH HEAD PRESSURE will result in lower efficiencies which lowers the refrigerant flow rate. This will prevent the evaporator from keeping up with the space heat load and high suction pressures will result. On a CAP TUBE system there will be HIGH SUCTION PRESSURES also because the higher condensing pressures will FORCE more refrigerant through the cap tube raising evaporator pressures. Because of this there will be NO SUPERHEAT resulting in FLOODING back to the compressor. LOOK FOR: Dirt and grease on the condenser. Use a cleaner and lots of water volume and pressure. Note, on small refrigeration units the cardboard cover and fan venturi MUST be in place or the air will go around, rather than through the condenser. On WATER COOLED UNITS an additional measurement is the leaving condenser water temperature. This water temperature should be only 10° less than the condensing temperature. On tower systems you can check inlet to outlet water temperature. It should be a 10° difference, or more. Also, check for proper flow rate of water for that type of water-cooled system. 135º 40º 70º 115º 70º 50º AMBIENT AIR 95o A/C System R-22 RETURN AIR 80o © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Dirty Condenser TEV System
R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1 9/14/2018 Dirty Condenser TEV System Condenser: Higher temperature Heat cannot be rejected Normal subcooling Evaporator: Slightly higher temperature A little more refrigerant pushing through valve Normal superheat TEV is trying to maintain superheat © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Dirty Condenser 9/14/2018 TEV System: 85 psig 360 psig 69 psig 278 psig 70º 50º 60º 40º TEV 145º 125º CONDENSER 145º EVAPORATOR 125º Dirty Condenser (low or restricted air through the coil) TEV System If air cannot cool the condenser than the condensing pressures will rise, but the SUBCOOLING will remain about NORMAL. The HIGH HEAD PRESSURE will result in lower efficiencies which lowers the refrigerant flow rate. This will prevent the evaporator from keeping up with the space heat load and high suction pressures may result. Depending on the severity of the blocked condenser, it is best to say that SUCTION PRESSURES will be NORMAL to SLIGHTLY HIGH for a TEV SYSTEM because the sensing bulb is trying to maintain the SUPERHEAT within a NORMAL RANGE. LOOK FOR: Dirt and grease on the condenser. Use a cleaner and lots of water volume and pressure. Note, on small refrigeration units the cardboard cover and fan venturi MUST be in place or the air will go around, rather than through the condenser. On WATER COOLED UNITS an additional measurement is the leaving condenser water temperature. This water temperature should be only 10° less than the condensing temperature. On tower systems you can check inlet to outlet water temperature. It should be a 10° difference, or more. Verify proper flow rate through the water-cooled condenser for that type system. 135º 50º 115º 40º 60º 50º AMBIENT AIR 95o A/C System R-22 RETURN AIR 80o © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Air (non-condensable) in the system Fixed metering device
R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1 9/14/2018 Air (non-condensable) in the system Fixed metering device Condenser: High temperature Air takes up space, less room for condensing High subcooling Great difference between high condensing temperature and leaving liquid Evaporator: High pressure liquid is forced through the metering device NO superheat Liquid is flooding through evaporator © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Air in the System 9/14/2018 Fixed Metering Device: 120 psig 360 psig 69 psig 278 psig 70º 70º 60º 40º 125º CONDENSER 145º 145º EVAPORATOR 125º Air in the System - CAP TUBE System Non-condensables (air) in the system will become trapped in the condenser because the liquid seal in the bottom of the condenser prevents the air from leaving. The air takes up valuable space which leaves a smaller area for discharge gases to de-superheat, condense, and subcool. To reject heat the head pressures must increase. The elevated condensing temperatures and pressures make the liquid in the bottom of the condenser hotter. There will be a greater temperature difference between the liquid and the ambient, which the heat is rejected into. Remember, subcooling is a temperature difference between the condensing temperature and the liquid temperature at the condenser outlet. The higher subcooling does not necessarily mean there is more liquid in the bottom of the condenser. It just means there is a greater difference, or drop, in temperature of the same amount of liquid. This is one of the main differences between a dirty condenser and air in the system: VERY HIGH SUBCOOLING. Since this type of system has a relatively small charge of refrigerant it does not make since to spend a lot of time on diagnosing air or overcharge. The most productive action is to recover the refrigerant, check for leaks, and weigh in the proper charge. If everything returns to normal you have solved the problem and saved both time and money. The rest of the symptoms are the same as a CAP TUBE system with a dirty condenser: HIGH HEAD PRESSURES, HIGH SUCTION pressures, and NO SUPERHEAT. Watch for flooding back to the compressor. LOOK FOR: Leaks on the suction side that have pulled air into the system. Prior repairs by someone who used poor charging, evacuating, or recovery procedures. 105º 40º 70º 115º 70º 50º AMBIENT AIR 95o A/C System R-22 RETURN AIR 80o © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Air (non-condensables) in the system TEV System
R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1 9/14/2018 Air (non-condensables) in the system TEV System Condenser: High temperature Air takes up space, less room for condensing Very high subcooling Great difference between high condensing temperature and leaving liquid Evaporator: Slightly higher temperature High condensing pressure pushing through valve Normal superheat TEV tries to maintain suction line temperature © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Air in the System 9/14/2018 TEV System: 85 psig 360 psig 69 psig 278 psig 70º 50º 60º 40º TEV 125º 125º CONDENSER 145º 145º EVAPORATOR 125º Air in a TEV System Non-condensables (air) in the system will become trapped in the condenser because the liquid seal in the bottom of the condenser prevents the air from leaving. The air takes up valuable space which leaves a smaller area for discharge gases to de-superheat, condense, and subcool. To reject heat the head pressures must increase. The elevated condensing temperatures and pressures make the liquid in the bottom of the condenser hotter. There will be a greater temperature difference between the liquid and the ambient, which the heat is rejected into. Remember, subcooling is a temperature difference between the condensing temperature and the liquid temperature at the condenser outlet. The higher subcooling does not necessarily mean there is more liquid in the bottom of the condenser. It just means there is a greater difference, or drop, in temperature of the same amount of liquid. This is one of the main differences between a dirty condenser and air in the system: VERY HIGH SUBCOOLING. The rest of the symptoms are the same as a TEV system with a dirty condenser or overcharge: HIGH HEAD PRESSURES, NORMAL to HIGH SUCTION pressures. Diagnostic NOTE: To determine whether its an overcharge or if its air in the system, turn off the compressor, but leave the condenser fan running. An overcharged system will start to drop within a minute. However, a system with air in it may take as much as 5 minutes to start dropping. LOOK FOR: Leaks on the suction side that have pulled air into the system. Prior repairs by someone who used poor charging, evacuating, or recovery procedures. It is best to pull the refrigerant, evacuate, and put in new refrigerant. Also, a new system that did not have the nitrogen holding charge evacuated has non-condensables in the system. 100º 50º 115º 40º 60º 50º AMBIENT AIR 95o A/C System R-22 RETURN AIR 80o © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

9/14/2018 Inefficient Compressor (bad valves or rings) TEV or Fixed metering device Condenser: Discharge pressure is LOW Leaking valves or rings can’t increase discharge pressure Normal subcooling Refrigerant not moving, most remains in the condenser/receiver Evaporator: Suction pressure is HIGH Discharge pressure is blowing back into suction High superheat Evaporator starving because compressor is not pumping NOTE: Only time discharge is low & suction high © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Inefficient Compressor
R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1 Inefficient Compressor 9/14/2018 Fixed Metering & TEV: 100 psig 200 psig 69 psig 278 psig 100º 60º 60º 40º 100º 125º CONDENSER 60º 125º 100º EVAPORATOR 85º 40º Inefficient compressor An inefficient compressor is one that just doesn’t provide the pressures it should. This can be caused by bad suction or discharge valves, worn rings or piston, or damaged cylinder walls. NOTE: This is the only condition that will show up with HIGH SUCTION and LOW HEAD PRESSURE pressures. The discharge gases are recycled in and out of the cylinder resulting in low refrigerant flow rate to the condenser, hence LOW HEAD PRESSURE and LOW compressor AMP DRAW. The same high pressure vapor will most likely slip back into the compressor crankcase causing HIGH SUCTION pressure. If the damage is severe the crankcase will heat up, making the dome of a hermetic compressor HOT. The BEST WAY TO CHECK the compressor is to close off the suction line (front seat the suction service valve). A good compressor should pump it into at least a 10” vacuum within 30 seconds. If it does pull into a vacuum, shut it off and see if the pressures start rising within 2 minutes. If they do, that means the high discharge pressures are leaking back into the crankcase. LOOK FOR: Flooding, slugging, or refrigerant migration problems. Compressor overheating from low charge, restrictions, or condenser air flow problems. Check for acids and sludge caused by moisture in the system. 115º 90º 50º AMBIENT AIR 95o A/C System R-22 RETURN AIR 80o © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Partially restricted fixed metering device
R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1 9/14/2018 Partially restricted fixed metering device Evaporator: Lower temperature Lack of refrigerant, lower pressure, lower temperature High superheat Limited refrigerant boils off quickly Condenser: Little heat from the evaporator High subcooling Refrigerant not used in evap is stored in condenser © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

“Partially” restricted cap tube
R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1 “Partially” restricted cap tube 9/14/2018 Fixed metering device: 40 psig 226 psig 69 psig 278 psig 80º 18º 60º 40º 110º 18º 125º CONDENSER 110º EVAPORATOR 125º Partially restricted Cap Tube system A partial restriction on a cap tube system is rare because the cap tube is so small it usually plugs fully restricting the flow of refrigerant. But, just in case you get to it before that time here is what you may find: A restriction will starve the evaporator and compressor of refrigerant. This causes LOW SUCTION PRESSURES with HIGH SUPERHEAT. The greater the restriction the lower the suction pressures, it may even be pulling a vacuum if the restriction is severe enough. On a CAP TUBE system the restriction will cause the liquid refrigerant to back up into the condenser (because it does not have a receiver to store the excess refrigerant that is not being used). Therefore, the SUBCOOLING is HIGH because the liquid stays in the condenser longer. The HEAD PRESSURE should be normal to only slightly high because this is a critically charged system that does not have enough refrigerant to flood the condenser. However, if the head pressure is high it is probably due to the previous technician who misdiagnosed the problem and added refrigerant attempting to raise the suction pressure. LOOK FOR: Moisture in the system turning to ice. Wax, sludge, or particles of desiccant. Note: Usually the restriction is just at the inlet of the cap tube. The most efficient way to handle problem is to remove the refrigerant, replace the filter-drier, cut off the first couple inches of the cap tube, evacuate to 500 microns, and weigh in the proper charge. This works about 90% of the time. However, if it doesn’t just replace the entire cap tube. 90º 40º 115º 70º 50º AMBIENT AIR 95o A/C System R-22 RETURN AIR 80o © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Partially Restricted TEV
R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1 9/14/2018 Partially Restricted TEV Evaporator: Lower temperature Lack of refrigerant, lower pressure, lower temperature High superheat Limited refrigerant boiled off quickly Condenser: Little heat from the evaporator Normal subcooling Refrigerant not used in evap is stored in the receiver © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Partially Restricted TEV
R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1 Partially Restricted TEV 9/14/2018 TEV System: 40 psig 210 psig 69 psig 278 psig 80º 18º 90º 40º 60º TEV 105º 18º 125º CONDENSER 105º EVAPORATOR 125º 40º Restricted metering device Partially restricted TEV A restriction will starve the evaporator and compressor of refrigerant. This causes LOW SUCTION PRESSURES with HIGH SUPERHEAT. The greater the restriction the lower the suction pressures, it may even be pulling a vacuum if the restriction is severe enough. On an EXPANSION VALVE system the condensing section will have LOW HEAD PRESSURE, NORMAL SUBCOOLING, and LOW compressor AMP DRAW because there is not much of a load. LOOK FOR: Inlet screen on TEV may be partially clogged. Moisture in the system turning to ice at the TEV needle seat. If a hot wet rag will warm the valve enough to thaw it, just replace the drier. Wax or sludge from moisture in the system. Particles of desiccant from the filter-drier. 95º 115º 70º 50º AMBIENT AIR 95o A/C System R-22 RETURN AIR 80o © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Restriction in liquid line after the receiver TEV System
R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1 9/14/2018 Restriction in liquid line after the receiver TEV System Evaporator: Lower temperature Lack of refrigerant, low pressure, low temperature High superheat Limited refrigerant boils off quickly Condenser: Little heat from the evaporator Normal subcooling Refrigerant not used in the evap is stored in receiver © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Restriction After the Receiver
R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1 9/14/2018 TEV System: Restriction After the Receiver 40 psig 210 psig 69 psig 278 psig 80º 75º 18º 60º 40º TEV 105º 18º 125º CONDENSER 105º EVAPORATOR 125º 40º Restriction AFTER the receiver This only applies to TEV systems because cap tube systems do not have receivers. However, the conditions would be similar to a cap tube system with a restricted cap tube. Contrary to what many technicians believe, NOT ALL restrictions result in high head pressures. It depends on where the restriction is located. The symptoms of restrictions AFTER the receiver are similar to a restricted metering device: starved evaporator and compressor resulting in LOW HEAD and LOW SUCTION pressures with HIGH SUPERHEAT in the evaporator. Other than kinked tubing, the most likely place for a restriction is in the drier because it is clogged up with debris. If so, the site glass will be bubbling and there will be more than a 3° temperature drop from the inlet to the outlet of the drier. NOTE: For R22, R404A, & R502 (high pressure systems) the liquid line filter drier should be replaced if the pressure drop through it is over 10#. Use an electronic thermometer to check the difference between inlet and outlet. If the difference is over 3° that is equal to about 10#, so replace the filter drier. If the restriction is after the drier the temperature of the liquid line within 12” of the evaporator will be less than the ambient temperature around the line. There may be a noticeable cool spot or frost on the liquid line at the point of restriction. LOOK FOR: Restricted filter drier, kinked liquid line, or restricted liquid line solder joint (¼” liquid lines are easy to block when brazing). 95º 115º 70º 50º AMBIENT AIR 95o A/C System R-22 RETURN AIR 80o © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Restriction in liquid line before the receiver TEV System
R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1 9/14/2018 Restriction in liquid line before the receiver TEV System Evaporator: Lower temperature Lack of refrigerant, low pressure, low temperature High superheat Limited refrigerant boils off quickly Condenser: High temperature / pressure Liquid backs up in condenser taking up space High subcooling Liquid not moving, just subcooling © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Restriction Before the Receiver
R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1 Restriction Before the Receiver 9/14/2018 TEV System: 40 psig 360 psig 69 psig 278 psig 80º 18º 60º 40º TEV 145º 18º 125º CONDENSER 145º EVAPORATOR 125º 75º Restriction BEFORE the receiver This is rare, but it seems many service technicians like to blame some mysterious restriction in the condenser because they can’t figure out what else it could be. So, we will look at this kind of situation. Like the restriction after the receiver the evaporator and compressor are starved for refrigerant. This will always cause LOW SUCTION pressures and HIGH SUPERHEAT in the evaporator. The sight glass will be bubbling, or may be empty if the restriction is severe. However, the location of this restriction will cause HIGH HEAD PRESSURE. The receiver is not storing the excess liquid refrigerant so it backs up into the condenser. The liquid takes up a lot of room in the condenser so the head pressure starts rising. The condensing pressure may get high enough to trip out the high pressure control or cause the compressor to blow off on its internal relief safety valve. The liquid can’t get out of the condenser so HIGH SUBCOOLING results. LOOK FOR: Kinked lines before the receiver, damaged condenser coil U-bends, or bad solder joints (especially at ¼” line fittings at the inlet of the receiver). 110º 40º 115º 70º 50º AMBIENT AIR 95o A/C System R-22 RETURN AIR 80o © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Dirty or iced evaporator, low air flow Fixed metering device
R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1 9/14/2018 Dirty or iced evaporator, low air flow Fixed metering device Evaporator: Lower temperature Refrigerant can’t boil Low superheat Refrigerant not boiling off Condenser: Little heat from the evaporator Normal subcooling Adequate amount of refrigerant © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Dirty or Iced Evaporator Dirty Filter Low Air Flow
R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1 9/14/2018 Fixed Metering Device: Dirty or Iced Evaporator Dirty Filter Low Air Flow 55 psig 225 psig 69 psig 278 psig 30º 30º 60º 40º 110º 125º CONDENSER 110º EVAPORATOR 125º Dirty or iced evaporator, dirty air filter (a/c system), or low air flow due to fan motor problems. CAP TUBE SYSTEM Restricted air through the evaporator is the reason for all of the above conditions. As a result the refrigerant in the evaporator will not vaporize. This shows up through LOW SUCTION PRESSURES and LOW SUPERHEAT, and a COLD COMPRESSOR. As the coil starts freezing the vapor in the coil moves further down the pipe looking for heat to absorb. It eventually turns the suction line and compressor dome into extended evaporators. The CONDENSING PRESSURES are LOW because the pressure does not need to elevate much to reject the small amount of heat load to the ambient air. The DISCHARGE TEMPERATURE will be LOW because liquid entrained in the suction gas is being vaporized by the compressor. As a result the AMP DRAW could be a little HIGH due to more work required by the compressor because of the higher density suction gas. LOOK FOR: Dirty filter, dirty coil, dirty blower, fan motor problems, or Tstat set too low. In addition, on a refrigerator or freezer check for frequent door openings or gasket problems, blockage of coil by paper or plastic, over-stocking of product blocking the coil, warm product, defrost problems, or drain blocked or iced up. On freezers, if there is no p-trap on the drain, warm outside air can cause coil icing. 100º 30º 115º 40º 30º 50º AMBIENT AIR 95o A/C System R-22 RETURN AIR 80o © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Dirty or iced evaporator, low air flow TEV system
R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1 9/14/2018 Dirty or iced evaporator, low air flow TEV system Evaporator: Lower temperature Refrigerant can’t boil Low to normal superheat TEV tries to maintain superheat Condenser: Little heat from the evaporator Normal subcooling Adequate amount of refrigerant © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Dirty or Iced Evaporator Dirty Filter Low Air Flow
R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1 9/14/2018 TEV System: Dirty or Iced Evaporator Dirty Filter Low Air Flow 55 psig 225 psig 69 psig 278 psig 45º 30º 60º 40º TEV 110º 125º CONDENSER 110º EVAPORATOR 125º 40º Dirty or iced evaporator, dirty filter (a/c system), or low air flow due to fan motor problems. TEV SYSTEM Restricted air through the evaporator is the reason for all of the above conditions. As a result the refrigerant in the evaporator will not vaporize. This shows up through LOW SUCTION PRESSURES and LOW SUPERHEAT, and a COLD COMPRESSOR. As the coil starts freezing the vapor in the coil moves further down the pipe looking for heat to absorb. Unlike the cap tube system, the TEV sensing bulb will try to maintain superheat. This helps control the flooding, but there will be a lower superheat and eventually some flooding could occur. The CONDENSING PRESSURES are LOW because the pressure does not need to elevate much to reject the small amount of heat load to the ambient air. The DISCHARGE TEMPERATURE will be LOW because liquid entrained in the suction gas is being vaporized by the compressor. As a result the AMP DRAW could be a little HIGH due to more work required by the compressor because of the higher density suction gas. LOOK FOR: Dirty filter, dirty coil, dirty blower, fan motor problems, or Tstat set too low (a common problem, but often overlooked). In addition, on a refrigerator or freezer look for: frequent door openings or gasket problems , blockage of coil by paper or plastic, over-stocking of product blocking the coil, warm product (high load), defrost problems, or drain blocked or iced up. On freezers, if there is no p-trap on the drain, warm outside air can cause coil icing. 100º 30º 115º 35º 50º AMBIENT AIR 95o A/C System R-22 RETURN AIR 80o © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Getting the right information
R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1 9/14/2018 Getting the right information To diagnose a problem you must know: The type of system How it should operate How it is currently operating The following slide is an example of a form that can be helpful. © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

System Information 9/14/2018 Pressures & Temperatures: (Makes calculations easy) A X B Y A-B Y-X C Z C-B Z-Y System Components & Accessories: Current Operation & Condition: Pressures and Temperatures: Diagnosing a system is futile unless the tech knows the system temperatures. It is imperative to take pressures and convert them to temperatures. Then take the proper line temperatures. Calculating the differences results in determining the system’s evaporator TD, superheat, condenser split, and subcooling. If the tech knows what they are supposed to be, he can begin to diagnose why they are different. System Components and Accessories: By checking off these spaces on the form the tech will determine the type of system. It will help the tech answer the first question, “What is it supposed to be doing?” Current Conditions and Operation: Filling in these spaces makes the tech ask, “What is it doing?” Additional information relative to compressor operation: If the compressor is having trouble starting the most obvious are electrical problems and starting components. Also, suction and discharge temperatures can verify many problems from a flooded evaporator to a starving evaporator to damaged compressor valves. Additional information relative to compressor operation: © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Exercise in using the Diagnostic Chart
R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1 9/14/2018 Exercise in using the Diagnostic Chart Assume the following conditions of a problem system: Low condensing temperature Low subcooling Low evaporator temperature High superheat Use the chart to find the problem: Circle ALL X’s for the conditions that apply to the system Total the X’s in each column The problem is the column with the most X’s Note: XCT applies only to cap tube systems (fixed metering) XEV applies only to TEV systems © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Determine which symptoms apply, then circle all the X’s in the row for each symptom. R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1 9/14/2018 Diagnostic Chart Total all the X’s in each column. The column with the most X’s in the problem. Ex: Condensing temp. is low LOW X X X X X Ex: Subcool is low LOW X Ex: Evap temp. is low LOW X X X X X Ex: Superheat is high HIGH X X X X X Ex: Sight glass is bubbling X X X BUBBLING 2 3 5 2 4 3 LOW CHG © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Printable Information Sheets
R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1 9/14/2018 Printable Information Sheets The following two slides can be printed out for use in lab work or on the job. Hopefully, they will be a help in diagnosing system problem. © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

Diagnostic Chart (for print outs)
R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1 9/14/2018 Diagnostic Chart (for print outs) © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

System Information (for print outs)
R4 Troubleshooting Refrigeration - Subject 2 System Problems v1.1 System Information (for print outs) 9/14/2018 © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

9/14/2018 End of Troubleshooting System Problems © 2004 Refrigeration Training Services - R4 Subject 2 Troubleshooting System Problems v1.2 © 2004 Refrigeration Training Services No reproduction or unauthorized use allowed

R4 Troubleshooting Refrigeration

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