TVA Ingersoll Rand Sierra Compressor
Operations Continuing Training Tennessee Valley Authority TVA
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Ingersoll Rand Sierra Compressor
Table of Contents
TABLE OF CONTENTS .................................................................................................................. STUDENT OBJECTIVES .............................................................................................................. 3 Airflow Circuit .................................................................................................................................................................................................4 Airend ................................................................................................................................................................................................................ 17 Compression Process............................................................................................................................................................................22 Lubrication.................................................................................................................................................................................................25 Intellisys..................................................................................................................................................................................29
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Ingersoll Rand Sierra Compressor
Student Objectives To review the components of the Pall Filter HLP22.................................................................... To review the correct operation of the Pall Filter HLP22........................................................... To understand the oil flow path of the Pall Filter HLP22................................................................. To understand the air flow path of the Pall Filter HLP22........................................................... To identify the major and minor alarms associated with the Pall Filter HLP22................... To be able to bring up and review the alarm history for the Pall Filter HLP22....................
Air Flow Circuit
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Ingersoll Rand Sierra Compressor
When the inlet control butterfly valve is open air enters the 1st Stage Airend and is compressed to 26-31 PSIG. The air discharges from the Airend via a venturi used to dissipate pressure pulsation. Air then moves from the venturi through the 1st stage
expansion joint and enters the intercooler where it is cooled to 11 degrees centigrade above ambient temperature. Air exits the intercooler through stainless steel piping to a moisture separator (epoxy coated internals). Condensate is removed before the air goes to the 2nd Stage Airend.
The air exits the 2nd Stage Airend into a venturi then the air passes through an expansion joint, this allows some of the turbulence and noise to dissipate. The air then continues to the after
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Ingersoll Rand Sierra Compressor
cooler. There is a check valve to prevent air from back flowing into the 2nd Stage Airend. It is fitted on the after cooler inlet piping. The air temperature is lowered to within 11 degrees centigrade of the ambient air temperature before exiting through a stainless steel pipe, into a moisture separator. The air then flows to the desiccant dryers then to the control air system. There is a blow down silencer to reduce noise levels during unloaded operation.
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Ingersoll Rand Sierra Compressor
Inlet Filter The inlet filter cleans the air prior to the first stage Airend. The filter is 99.5% efficient at (10) micron.
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Ingersoll Rand Sierra Compressor
Inlet ValveÂ
Unloading Valve
Stop Nut Counter Nut
Blowdown Valve Plate
Butterfly Valve
Butterfly Valve Casing
Control Cylinder
Compression Springs
Control Piston Needle Screws
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Ingersoll Rand Sierra Compressor
These are actual pictures of the Inlet Valve Assembly.
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Blow off Valve
Inlet Butterfly Valve
Operating Cylinder
Inlet Valve Assembly
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Ingersoll Rand Sierra Compressor
This is a side view of the first stage, it compresses to 28-41 PSIG
This is a picture of the front of the First Stage Discharge Venturi.
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Ingersoll Rand Sierra Compressor
The flexible piping is made of corrugated stainless steel with exterior stainless steel braiding. This allows for expansion and misalignment during operation.
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Ingersoll Rand Sierra Compressor
The intercooler cools the air prior to the inlet of the Second Stage Airend. The First Stage cooler cools the air to 15.3 degrees Fahrenheit above the ambient temperature on water cooled machines. The Second Stage cooler cools the 2nd stage discharge before the air is discharged from the compressor. There is a relief valve that is set at 45 pounds per square inch that is not shown in this picture. There is a stainless steel pipe to the moisture separator.
The purpose of the intercooler moisture separator is to collect any moisture prior to the second stage Airend. It is specially designed with an epoxy coating on the interior to prevent rust. The purpose of the Aftercooler Moisture Separator is to remove condensed water from the air stream prior to discharge to the dryer.
First Stage Intercooler
2nd Stage Aftercooler Moisture Separator
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Ingersoll Rand Sierra Compressor
The second stage Airend compresses the first stage pressure of 26 to 31 pounds per square inch to the rated package discharge pressure. The purpose of the second stage discharge venturi is to provide pulsation dampening and silencing of the discharge air.
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Ingersoll Rand Sierra Compressor
This shows a cutaway of the second stage venturi
The purpose of the check valve is to isolate the control air system from the compressor; it is a twin flap butterfly type check valve.
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Ingersoll Rand Sierra Compressor
These are actual pictures of a discharge silencer. This shows two applications of the same device, it’s purpose is to dampen pulsations and noise suppression during unloaded operation.
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Ingersoll Rand Sierra Compressor
The 1st and 2nd stage Condensate Valves are located after each of the moisture separators as seen on pages 5 and 6 of this document. Both valves are normally open until the power is applied to the unit. This prevents water from standing in the moisture separator and lines with the unit off. Both valves have Y strainers installed before the valve bodies. The 1st stage Condensate valve also has a check valve before the strainer to prevent backflow during blowdown. The valves are piped separately to prevent interstage problems.
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Ingersoll Rand Sierra Compressor
A moisture separator is located immediately after the intercooler and the after cooler to collect any condensation from the compressed air. The condensate is drained through electrically operated valves. The opening duration of the condensate valves is preset at three seconds and is adjustable between 2 to 20 seconds. The opening between these intervals may be adjusted between 60 and 360 seconds, depending on the ambient temperature. If the environment consists of high temperature and or high humidity, then the interval may have to be reduced to facilitate moisture removal. The factory setting is 180 seconds. To check the operation of the solenoid valves, you should open the manual bypass valves momentarily once per day to check for moisture. For extended shutdown periods, the manual valves should be left open to prevent the accumulation of moisture. Strainers are provided upstream of the condensate valves to prevent any particles from plugging the solenoid valves. Before any maintenance is performed on the strainers or the solenoid valves, the strainer service valves should be closed, in order to isolate them from possible high pressure. The Safety Valve settings for our compressors are as follows. We have a 250 HP motor so the 1st stage is set at 55psig and the 2nd stage is set at 165psig.
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Ingersoll Rand Sierra Compressor
Airend An Airend is the part of the compressor that produces the compressed air. Rotary compression and displacement is achieved by the positive action of the rotating elements in the Airend.
2nd Stage
1st Stage
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Ingersoll Rand Sierra Compressor
The air to be compressed enters the compressor through an opening at the right end of the enclosure. The air travels through a passageway lined with sound absorbing material to the air filter. It then travels through a round flexible hose, the air passes through the inlet valve assembly into the first stage of the compressor.
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Ingersoll Rand Sierra Compressor
Screw dry compressors operate on the positive air displacement principle in a similar way as contact cooled rotary compressors do (Sullair). One shaft rotates both rotors. Oil injection keeps them lubricated and cool just as in the Sullair compressors. Inside the screw compressor casing there are two rotors which rotate in opposite directions. The rotors have specially shaped profile lobes which are helically twisted in an axial direction, comparable to a helically toothed pair of gear wheels. The number of lobes in the 1st stage is: the male rotor has 3 lobes and the female rotor has 4 lobes. The number of lobes in the 2nd stage is: The male rotor has 4 lobes and the female rotor has 6 lobes. Any contact between the rotors is prevented by a pair of timing gears arranged outside the compression chamber. The radial and axial clearances between the rotors and the casing are also very low. Therefore, for increased safety, small projections have been provided on the profile diameter and on the discharge side face ends of the rotors to ensure perfect running.
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Ingersoll Rand Sierra Compressor
The helical rotors compress the air to a pressure of between 25 to 38 psig. The air is discharged into a venturi, which dampens any pressure pulsations that may be present before entering the intercooler.
The intercooler then reduces the air temperature before it enters into the 2nd stage. A safety relief valve is also positioned in this system to guard against an abnormally high interstage pressure. A moisture separator is supplied immediately following the intercooler to remove any condensation that may occur under certain conditions of ambient humidity and temperature. An expansion joint is utilized between the moisture separator and the 2nd stage.
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Ingersoll Rand Sierra Compressor
The 2nd stage further compresses the air to the desired pressure. The pressure pulsations are dampened by the 2nd stage venturi. There is an expansion joint to prevent transmition of any vibrations to the air system. A wafer type check valve is provided to prevent any back flow of air into the compressor. The Aftercooler cools the air to a suitable temperature, while the discharge moisture separator removes significant amounts of condensation. When the desired pressure point is reached, the inlet butterfly valve closes. As the butterfly inlet valve closes the hydraulic cylinder opens the blowdown valve to unload the compressor. The actuator (Hydraulic Cylinder), which opens and closes the inlet, unloading valves, is connected to the lubricating system through the 1SV solenoid valve.
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Ingersoll Rand Sierra Compressor
The Compression Process As rotation of the compressor begins, air is drawn into the pockets between the male rotor lobes and the female rotor lobes. The compression process for the positive displacement group of compressors depends upon reducing the volume of a given amount of air, which thereby increases the air pressure. With further rotation, the leading strip of the male lobe reaches the contour of the female groove and traps the air in the pocket previously formed. The air is moved down the female rotor groove and is compressed as the volume is reduced. When the male rotor lobe reaches the end of the groove, the trapped air is discharged from the Airend. The Airend bearings position the rotor in the center of the Airend housing and prevent rotor movement due to thrust. Sierra Module bearing types include: 4 roller bearings at the Inlet and Discharge and 2 (4 point) aircraft type thrust bearings.
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Ingersoll Rand Sierra Compressor
This is the arrangement of the Airend parts we have covered. This is the 2nd stage Airend. The labyrinth seals perform the task of preventing oil from the lubricating system from getting into the compression zone of the Airend. This is a critical component if we are to maintain oil free dry air.
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Ingersoll Rand Sierra Compressor
Vent holes are supplied to enable us to monitor the condition of the labyrinth seals. By feeling the discharge from these vent holes we can determine if there is any leakage through the seals. There should not be any residue on your fingers.
First Stage Vent Holes
Second Stage Vent Holes
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Ingersoll Rand Sierra Compressor
Lubrication The lubrication system is supplied by the Oil Pump. This oil performs the following functions: 1. Lubrication of the bearings 2. Housing Cooling 3. Operation of the Inlet/ Blow-off Valve
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Ingersoll Rand Sierra Compressor
Orifice
3RV
The oil is drawn through a suction strainer, which is used to filter out large contaminants. The oil proceeds to the suction port on the oil pump and then elevated in pressure to approximately 40 to 60 PSIG. There is a pressure relief valve on the oil pump discharge piping to relieve oil to the sump. This is factory set at 100 PSIG. The oil is discharged to the oil cooler where it’s cooled to approximately 54 to 60°C. A thermally controlled mixing valve is located on the cooler outlet. This valve mixes hot oil, (which bypasses the cooler) and cool oil from the cooler to maintain optimal oil temperature of 54 to 60°C. The oil leaves the thermal mixing valve and proceeds through a 10micron filter, and then is diverted to multiple oil feed points on the two Airends. Pressurized oil is also supplied to the 1SV solenoid valve. It operates the hydraulic cylinder used to load and unload the unit. The oil that has been fed to the bearings is drained from Airends via the oversized drain ports located on the bottom side of the Airends. The oil pressure is controlled by the use of an orifice, sized by the factory located in the oil outlet piping on the 2nd stage Airend housing. The oil level should be maintained at three quarters full with the compressor running.
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Ingersoll Rand Sierra Compressor
3RV Oil Pressure Relief Valve 1SV Solenoid Valve
Oil Filter
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Ingersoll Rand Sierra Compressor
The Breather separates oil mist from the gearcase vapor. It vents into the plenum area. The wire wool filter should be cleaned every 2,000 hours.
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Ingersoll Rand Sierra Compressor
Intellisys The SG Intellisys control system is an exclusive Ingersoll-Rand design, developed for reliable compressor operation. The microprocessor-based controller uses a finger touch membrane for operation of the compressor and setting control parameters. Information about the current operating status is available on a Liquid Crystal Display from a list of temperature, pressure and filter condition readings. The Intellisys monitors the compressor and should any pre-programmed limit be exceeded, the controller automatically displays a warning or issues an alarm to shut the compressor down. A group of pressure and temperature sensors, relays and switches support the decision making process.
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Ingersoll Rand Sierra Compressor
Arrows Small Arrows
Buttons
Display
Start
Unload
Load
Stop
The Start Button will start the compressor if the display shows Ready to Start. The compressor will start and load if there is sufficient demand for air. The Stop Button will activate the unloaded stop sequence. If the compressor is running loaded, it will unload and continue to run unloaded for an adjustable 10 to 30 seconds and then stop. If the compressor is running unloaded and the button is pressed, it will stop immediately. The Unload Button will cause the compressor to unload and remain unloaded. This display will indicate the machine is Running Unloaded, and Mode: Unload. The Load Button will cause the compressor to load if the machine has been started and the Discharge Pressure is less than the Online Pressure. The Up and Down Arrow Buttons have multiple functions relating to the right half of the screen. When lists are presented, the buttons are used to move up and down through the items on the list. The Small Arrows displayed in the upper right corner of the display screen indicate when you can move up (designated by the arrow head pointing up) and/or down (designated by the arrow head pointing down) through the list. The functions of the Display Buttons change and are defined by the words immediately above them in the bottom line of the screen. Such as Main Menu, Status Set etc......
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Ingersoll Rand Sierra Compressor
Warning
When warning occurs, the word Warning will flash on the screen in large letters. The display message would indicate what calls the warning and the reset button appears. A running compressor will continue to run and provide air during a warning. If multiple warnings exist, the small up and down arrows will appear in the upper right corner of the display screen. The multiple warnings can be seen by pressing the up and down arrow buttons. Press and status button will display the Current Status screen. The status button changes to a warning button indicating other warnings still exists. The reset button disappears at this time. Use the up and down arrows to observe the current status items associated with the warning in the display. Pressing the warning button will return the display to the warning screen and the reset button returns. When the cause for the warning has been corrected, press the reset button twice to clear the controller. A warning remains on the screen until it is reset by an operator. Warnings are: • Change Coolant Filter • Change Inlet Filter • Sensor Failure
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Ingersoll Rand Sierra Compressor
These are the warnings listed again with their causes: Change Coolant Filter: This warning will occur at the press differential across the coolant filter exceeds 13 psi and the bearing oil temperature is greater than 110째f. Change Inlet Filter: This will occur in the inlet vacuum (1 AVPT) is greater than 0.7 PSI and the compressor is fully loaded with the inlet valve in the fully open position. Sensor Failure: This will occur if the Intellisys recognizes a missing or broken sensor, sensors affected by this warning are 50PT, 3ATT and 7ATT. The failed sensor will be displayed along with the sensor failure message.
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Ingersoll Rand Sierra Compressor
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Ingersoll Rand Sierra Compressor
ALARM
When an alarm occurs, the word ALARM in large capitals will appear and the display message will indicate what caused the alarm and the Reset Button will appear. A compressor that is running will be shutdown immediately as an ALARM situation arises, causing the Remote Alarm Contacts to change state. The compressor cannot be restarted either manually or automatically, until the Alarm situation has been rectified and the Intellisys Controller reset. An already stopped compressor cannot be started if an Alarm condition exists. Pressing the Status Button will activate the ALARM STATUS screen with the ALARM Button indicating an alarm situation still exists. Alarm status gives a list of operating parameters of the compressor when the ALARM occurred. The value of the parameters can be seen by scrolling using the arrow buttons, pressing the ALARM Button will return to the alarm screen and bring back the RESET BUTTON. The ALARM can be reset by pressing the RESET Button, when the ALARM condition has been rectified. Remember an Alarm will cause the immediate shutdown of the compressor.
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Ingersoll Rand Sierra Compressor
Any of the Current Status readings selected will remain on the display until another status item is chosen. Use the UP or Down buttons at the right of the display to change the selection. There is small arrow prompt within the display indicating which of the two buttons to use. The Y prompt is for the UP button and the B prompt is for the Down button. The C prompt indicates the current status display is somewhere in the middle and either the UP or the Down button can be used.
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Ingersoll Rand Sierra Compressor
Operator Setpoints Operator Setpoints are user adjustable settings in the controller logic that can be changed using the Operator Setpoints Screen. Changes to the Operator Setpoints can be made while the compressor is in operation. The Operator Setpoints listed above can be seen on the screen by moving the UP and DOWN arrow buttons. The SETPOINT Value can be changed by highlighting the item and its value and pressing the Select Button to highlight just that value. When the value is highlighted it can be adjusted by using the UP and DOWN arrows. The CANCEL and SET Buttons appear at this time. Press the SET Button to enter the new value, or press the CANCEL Button to return the value to the setpoint prior to using the arrows. The displayed value will flash twice to indicate it has been entered into the setpoint, and the pair of setpoint items and value display will again be highlighted together. OPERATOR SETPOINTS can be exited by pressing either the STATUS or MAIN MENU buttons. If no buttons are pressed within 30 seconds, the display automatically returns to the CURRENT STATUS screen showing PACKAGE DISCHARGE TEMPERATURE and 1st Stage.
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Ingersoll Rand Sierra Compressor
Operator Setpoint Descriptions Lead/Lag- will control the compressor at the Off/On Line values programmed. The Lag selection will control the compressor at the Off/ ON Line values. OFFLINE PRESSURE- the pressure at which the compressor will unload. ONLINE PRESSURE- the pressure at which the compressor will re-load. Lag Offset- reduces OFF/ON Line values when Lag is selected. Load Delay Time- the time delay period between the ON Line pressure set point achieved and the actual loading of the compressor. Condensate Release- the time period that the condensate solenoid valves 6SV and 9SV open. CONDENSATE INTERVAL-the time period between the operation of the condensate solenoid valves 6SV and 9SV when the compressor is running loaded. STAR/DELTA- determines the period of time before delta transition. (refer to manual) MAX 1ST STAGE TEMPERATURE- an adjustable set point depending on the rated pressure of the unit, and is factory set to the maximum. MAX 2ND STAGE TEMPERATURE- an adjustable set point depending on the rated pressure of the unit, and is factory set to the maximum. DISPLAY CONTRAST- controls the LCD display brightness.
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Ingersoll Rand Sierra Compressor
The Clock Function allows the controller to perform real time control functions. Such as scheduled Start and Stop.
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Ingersoll Rand Sierra Compressor
Pressure Sensor Descriptions: 1AVPT – Inlet Vacuum A pressure sensor having a range between 0 and 15 psi vacuum connected to the Airend inlet to provide vacuum information for the controller. The controller uses inlet vacuum information to confirm the inlet valve is in the correct position for both loaded and unloaded operation. It will also indicate the condition of the inlet air filter for the Intellisys to monitor and warn when necessary. 2 APT – 1st Stage Discharge Pressure and 3 APT – 2nd Stage Discharge Pressure The Airend discharge is monitored for several reasons to include comparison to line pressure during separator element differential check and to provide logic for the controller to position the inlet valve during unloaded operation. The normal unloaded intercooler pressure is maintained at 0 PSI and loaded within a range of 26 to 31 psi to ensure adequate inlet pressure to the 2nd stage to prevent over ratio of the 2nd stage Airend. The normal unloaded 2nd stage discharge pressure is maintained at 0 PSI and loaded to the rated pressure of the machine. This pressure is monitored as the unit unloads to ensure the 2nd stage Airend discharge has blown down to atmosphere ensuring that any over ratio situation is detected and the unit stops in an alarm condition.
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Ingersoll Rand Sierra Compressor
4APT-Package Discharge Pressure This sensor is used to provide information about the discharge pressure just prior to the compressed air leaving the package. The connection is downstream of the Aftercooler and in the top of the moisture separator. Package discharge pressure provides logic to load or unload the compressor. 5OPT- Oil Filter Inlet Pressure and 6OPT- Oil Filter Outlet Pressure Two (2) pressure sensors are used to monitor the lubricant filter differential and the lubricant pressure is monitored continually to ensure that the bearings have a continuous feed of lubricant.
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Ingersoll Rand Sierra Compressor
Temperature Sensors and Descriptions-- 2ATT, 3ATT, 4ATT, 5OTT, 7ATT Temperature sensors are used to monitor temperature changes at various points within the compressor package. They operate on a 12 V DC circuit. As the temperature of the sensor changes either higher or lower, the resistance to the sensor changes a corresponding amount. As the output voltage varies due to the temperature changes, the voltage strength is processed by an analog-to-digital converter within the controller. Depending on the output voltage from the various sensors, the controller makes decisions that may change a number on the panel display, delay a differential pressure reading until the compressor warms up, reposition the inlet valve slightly doing cold unloaded operation, provide WARNING about rising temperature or could possibly shut the compressor down with an ALARM if operating conditions dictate.
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Ingersoll Rand Sierra Compressor
Alarm Messages • • • • • • • •
Sensor Failure 1AVPT (Inlet Vacuum) Sensor Failure 2APT (2nd Stage Inlet Pressure) Sensor Failure 3APT (2nd Stage Discharge Pressure) Sensor Failure 4APT (Package Discharge Pressure) Sensor Failure 6OPT ( Bearing Oil Pressure) Sensor Failure 2ATT (1st Stage Discharge Temperature) Sensor Failure 4ATT (2nd Stage Discharge Temperature) Sensor Failure 5 OTT (Bearing Oil Temperature)
All of the shown sensor failure alarm will cause compressed the shutdown if that sensor is detected by the Intellisys controller to be missing or broken. Causes can be: • A broken wire • A bad transducer • There can be moisture in the transducer or in a temperature sensor. Check Setpoints: This alarm will only occur at power up. It is an indication that some of the Setpoints in the controller out of range and Intellisys reloaded it’s the default values. Invalid Calibration This alarm will only occur doing calibration. An invalid calibration alarm is normally an indication of pressure already being on the sensor. • Bad Transducer • Pressure on the System • Plastic tubing still connected to the transducer. Emergency Stop This alarm is an indication that the emergency stop button has been pressed. Check Control Power/Phase This alarm occurs when the 120 V AC power (connection at P1 – 1) is lost. Cause: • A bad control transformer • Phase monitor malfunction
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Ingersoll Rand Sierra Compressor
Starter Fault 1SL (2SL) This alarm occurs if the auxiliary contact on 1M (1SL) or 1S and 2M (2 SL) is closed and a start is attempted on the compressor. Cause: • The auxiliary contacts bad • EPROM rev 1.5 and above will not display this alarm • A loose wire. Main Motor Overload This alarm indicates that the motor overload switch to the main motor has opened. This condition must exist for at least 3 seconds before the alarm is issued. Cause – check motor current at full load. Fan Motor Overload This alarm indicates that the motor overload switch to the fan motor has opened. This condition must also last at least 3 seconds. High I/C Condensate This alarm will occur if the set point in the options menu called condensate level installed is set to On and intercooler condensate level switch closes for at least 60 seconds. Cause – check the intercondenser drain for proper operation. Inlet Restriction This alarm will occur in the inlet vacuum is greater than 13.3 PSI. This alarm will also occur if the compressor is running and has been loaded for at least 8 seconds, and inlet vacuum is greater than 3 PSI. Cause: • Check the inlet filter • Check for collapsed hoses High Intercooler Pressure This alarm will occur if the compressor is loaded and the 2nd stage Inlet pressure is greater than 43 PSI, and the 1st stage discharge temperature is greater than 410°F. If the compressor is running unloaded this alarm with occur if the 2nd stage Inlet pressure is greater than 10 PSI. The unloaded alarm will only be checked during the 1st 7 seconds of operation. Cause: • Remove the 2nd stage Inlet tubing and view the male and female rotor coating • Review the intercooler tubing for rust in the cooler bonnet. • Clean the intercooler.
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Ingersoll Rand Sierra Compressor
High 2nd Stage Pressure This will occur if the compressor is running and the 2nd stage discharge pressure is greater than 15 PSI above rated pressure. Cause: • The pressure sensor is out of calibration. • There could be electrical noise affecting the sensor. High Line Air Pressure This will also occur if the compressor is running and the package discharge pressure is greater than 15 PSI above the rated pressure. Cause: • Review the remote pressure transducer location. • Check the transducer calibration. Low Bearing Oil Pressure For this alarm to occur the compressor must be running and the oil pressure is less than 34 PSI. This alarm is not checked until the compressor has been running at least 7 seconds and this alone will not be checked the first 8 seconds after the compressor loads. If the oil pressure falls below 34 PSI, there’ll be a 2 second time delay before the alarm comes in. Cause: • Incomplete start Delta transition. • The auxiliary contacts could malfunction. • A low oil level. • The oil relief valve could be out of adjustment. • The oil pump could be bad. High 1st Stage Temperature This alarm will occur if the unit is running and the 1st stage discharge temperature is greater than the high 1st stage discharge temperature set point or the unit is not running and the 1st stage discharge temperature is greater than 95% of the high 1st stage discharge temperature set point. In both cases, the 1st stage discharge temperature cannot exceed the 1st stage discharge temperature set point by 20°F. Cause- The ambient temperature is too high.
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Ingersoll Rand Sierra Compressor
High 2nd Stage Temperature This alarm will occur if the unit is running and the 2nd stage discharge temperature is greater than the high 2nd stage discharge temperature set point or the unit is not running and the 2nd stage discharge temperature is greater than 95% of the high 2nd stage discharge temperature set point. In both cases, the 2nd stage discharge temperature cannot exceed the 2nd stage discharge temperature set point by 20°F. Cause- The ambient temperature is too high High I/C Air Temperature This occurs when the unit is running and the 2nd stage Inlet (intercooler) temperature is greater than 140°F. Cause: • Check the 2nd stage male and female rotor coatings. • Check the intercooler tubing for rust on the bonnet. • Clean the intercooler Excessive Unloaded Run This alarm will occur if the operator has to unload the compressor by pressing the unload button and the compressor has been operating in this mode for at least 20 minutes. This alarm will occur after a Load or Stop Unit Warning.