Service Section Service Section Technical Training Technical Training December 2004 December 2004 Technical Training Technical Training Technical Training Scroll Compressor Characteristics Scroll Compressor Characteristics Scroll Compressor Characteristics
Scroll Compressor Scroll Compressor Failure Analysis Failure Analysis Technical Training Technical Training Technical Training Scroll Compressor Characteristics Scroll Compressor Characteristics Scroll Compressor Characteristics
Failure Analysis Failure Analysis Technical Training Technical Training Technical Training Scroll Compressor Characteristics Scroll Compressor Characteristics Scroll Compressor Characteristics
Why Do Compressors Fail In The Field? Why Do Compressors Fail In The Field? • Too Hot – Measure discharge temperature • Too Cold – Measure oil sump temperature – Measure discharge temperature • Liquid Compression Technical Training Technical Training Technical Training – Use a crankcase heater • No Oil Or Diluted Oil Scroll Compressor Characteristics Scroll Compressor Characteristics Scroll Compressor Characteristics
Summary Of 10 Returns Summary Of 10 Returns Technical Training Technical Training Technical Training Scroll Compressor Characteristics Scroll Compressor Characteristics Scroll Compressor Characteristics
Overheating Overheating Overheating Overheating Technical Training Technical Training Technical Training Scroll Compressor Characteristics Scroll Compressor Characteristics Scroll Compressor Characteristics
Overheating Overheating • Overheating Problems Occur When The Oil In A Compressor Is Heated To The Point Where It Loses It’s Ability To Lubricate. If The Heat Is High Enough, The Oil Breaks Down Chemically • Compressors Should Operate Within The Safe Limits Of The Discharge Temperature Technical Training Technical Training Technical Training • Oil And Refrigerant Break Down In Severe Overheating And Create CARBON And ACIDS, Which Can Cause Harm Throughout The Entire System Scroll Compressor Characteristics Scroll Compressor Characteristics Scroll Compressor Characteristics
Example Of Overheated Compressor Example Of Overheated Compressor Compressor Severely Overheated – Vacuum Operation Technical Training Technical Training Technical Training Scroll Compressor Characteristics Scroll Compressor Characteristics Scroll Compressor Characteristics
Causes Of Overheating Causes Of Overheating • High Compression Ratios – Low suction pressure • Loss of refrigerant charge • Blocked suction – High discharge pressure • Blocked Condenser • Undersized Discharge Line • Lack Of Sufficient Condenser Air Circulation • Inoperative Fan Motors • Refrigerant Overcharge • Non-Condensables In The System • Recirculation Of Condenser Air Technical Training Technical Training Technical Training – Combination of each • High Return Gas Temperatures – Insufficient insulation of suction lines • Inadequate Compressor Motor Cooling Scroll Compressor Characteristics Scroll Compressor Characteristics Scroll Compressor Characteristics
Discharge Line Temperature Measurement Discharge Line Temperature Measurement • 225 ° F / 107 ° C Discharge Line Temperature MAXIMUM FOR DESIRABLE LIFE • 250 ° F / 121 ° C Discharge Line Temperature DANGER LEVEL - Oil Thins Out At 310-320 °F • 275 ° F / 135 ° C Discharge Line Temperature Technical Training Technical Training Technical Training CERTAIN FAILURE - Oil Breaks Down Completely At 350 °F The discharge line temperature will be 10 °F To 15 °F less than the internal temperature when measured about 6 inches from the service valve on the discharge line Scroll Compressor Characteristics Scroll Compressor Characteristics Scroll Compressor Characteristics
To Control Suction Pressure… To Control Suction Pressure… • Watch For Undersized Evaporator Or Oversized Compressor • Check For Plugged Driers And Make Sure A Solid Column Of Liquid Can Enter The Expansion Device Technical Training Technical Training • Keep The Pressure Drop In The Suction Line Technical Training To A Minimum And Still Maintain Sufficient Velocity For Proper Oil Return Scroll Compressor Characteristics Scroll Compressor Characteristics Scroll Compressor Characteristics
To Control Return Gas Temperature… To Control Return Gas Temperature… • Prevent The Suction Line From Passing Through Hot Spaces • Properly Insulate All Suction Lines Outside The Refrigerated Space Technical Training Technical Training Technical Training Scroll Compressor Characteristics Scroll Compressor Characteristics Scroll Compressor Characteristics
Compressor Temperatures At Normal Load Compressor Temperatures At Normal Load Technical Training Technical Training Technical Training Scroll Compressor Characteristics Scroll Compressor Characteristics Scroll Compressor Characteristics
High Load – Very Hot Weather High Load – Very Hot Weather Technical Training Technical Training Technical Training Scroll Compressor Characteristics Scroll Compressor Characteristics Scroll Compressor Characteristics
Simulations Simulations • To Identify Compressor Condition Due To Blocked Suction Line H.P Pressure and running current reading • Discharge pressure is a little lower than normal L.P • Suction pressure is very low AMP Technical Training Technical Training Technical Training • Running current decreases * Frost grows on evaporator coil Scroll Compressor Characteristics Scroll Compressor Characteristics Scroll Compressor Characteristics
Blocked Suction After 24 Seconds Blocked Suction After 24 Seconds Technical Training Technical Training Technical Training In 24 seconds, scroll temperature has risen by 87°C already above safe limit Scroll Compressor Characteristics Scroll Compressor Characteristics Scroll Compressor Characteristics
Blocked Suction After 48 Seconds Blocked Suction After 48 Seconds Technical Training Technical Training Technical Training Discharge line not very hot – Very low flow Scroll Compressor Characteristics Scroll Compressor Characteristics Scroll Compressor Characteristics
Blocked Suction After 96 Seconds Blocked Suction After 96 Seconds Technical Training Technical Training Technical Training Compressor already seriously damaged at this point. Power input is also rising. Scroll Compressor Characteristics Scroll Compressor Characteristics Scroll Compressor Characteristics
Blocked Suction After 118 Seconds Blocked Suction After 118 Seconds Last data before protector trip Technical Training Technical Training Technical Training Scroll tips worn Thrust face Drive bearing Thrust face damaged damaged damaged Scroll Compressor Characteristics Scroll Compressor Characteristics Scroll Compressor Characteristics
Simulations Simulations • Corrections: – Check system piping and components – Proper air flow across coils – Clean evaporator and condenser surface – Correct refrigerant charge – Insulate suction lines – Fan belt tightening sufficient – Short cycling of cooling air Technical Training Technical Training Technical Training Scroll Compressor Characteristics Scroll Compressor Characteristics Scroll Compressor Characteristics
Simulations Simulations • To Identify Compressor Condition Due To Charging Vapour Into Suction Line H.P Pressure and running current reading • Both high and low pressures are very low L.P • Running current decreases extremely AMP Technical Training Technical Training Technical Training Scroll Compressor Characteristics Scroll Compressor Characteristics Scroll Compressor Characteristics
Split System Charging After 1 Minute Split System Charging After 1 Minute (DLT) 64°C Suction pressure: -0.5 bar = -7 psig Discharge pressure: 6.9 bar = 100 psig Technical Training Technical Training Technical Training Scroll Compressor Characteristics Scroll Compressor Characteristics Scroll Compressor Characteristics
Split System Charging After 4 Minutes Split System Charging After 4 Minutes (DLT) 142°C Suction pressure: 0.1 bar = 2 psig Discharge pressure: 7.9 bar = 115 psig Technical Training Technical Training Technical Training Higher than the safe limit (175°C) Scroll Compressor Characteristics Scroll Compressor Characteristics Scroll Compressor Characteristics
Split System Charging After 8 Minutes Split System Charging After 8 Minutes (DLT) 201°C Suction pressure: 1.6 bar = 23 psig Discharge pressure: 14.4 bar = 209 psig Technical Training Technical Training Technical Training Much too high – Compressor damage Scroll Compressor Characteristics Scroll Compressor Characteristics Scroll Compressor Characteristics
Why Is LP Needed? Why Is LP Needed? • LP Protects Against – Blocked suction – Total loss of charge in off season – Slow vapour charging • LP Acts Instantly And Stops The Compressor – Damage can happen quickly – Temperature sensors on the outside of the pipe have some Technical Training Technical Training Technical Training delay – Temperature sensors are influenced by the ambient Scroll Compressor Characteristics Scroll Compressor Characteristics Scroll Compressor Characteristics
Summary Of 10 Returns – Too Cold Summary Of 10 Returns – Too Cold Technical Training Technical Training Technical Training Scroll Compressor Characteristics Scroll Compressor Characteristics Scroll Compressor Characteristics
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