Conair MPW, MPA manual Checking Unloader Valve

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The unloader valve is located between the compressor and the condenser on both air-cooled and water-cooled chillers. It works only during low demand conditions, when loads are up to 24% below normal.

During low-load conditions, the compressor cycles off. To decrease the frequency of cycling, which is harmful to the compressor, the microKool uses an unloader valve to channel some of the hot refrigerant gas from the compressor directly back into the condenser. This increases the temperature within the condenser, simulating an increased load and keeping the compressor running at full capacity.

You can check whether the unloader valve is working properly by observing its behavior while the microKool is running.

1 Clear any alarms and restart the chiller.

2 Watch for the following:

❒The unloader valve light should turn on for 2 seconds when the compressor starts. You should hear the sole- noid activate when the unloader valve light turns on.

❒If the process fluid temperature is below the setpoint, the unloader valve should stay lit until the temperature of the process fluid exceeds the setpoint.

❒If the process fluid temperature is above the setpoint, the unloader valve light should turn off after 2 seconds. You can verify that the unloader valve is inactive by checking the refrigerant line from the solenoid valve to the expansion valve. The line should be cool.

If the line is hot all the way to the expansion valve, then the unloader valve is active. The solenoid valve may be leaking, or the unloader valve may be stuck open with power still supplied to the solenoid.

NOTE: Units with the enhanced PC-2 control have two unloader valves that work together.

CHECKING THE

UNLOADER

VALVE

UGH004/0999

microKool Portable Chillers

TROUBLESHOOTING 6-17

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Contents Page Date Manual Number UGH004/0999 Serial numbers Model numbers Introduction Table of ContentsTroubleshooting Introduction HOW Guide is Organized Purpose User GuideYour Responsibility AS a User Read this SO no ONE Gets Hurt Page Description CHILLER? What is the MicrokoolTypical Applications HOW IT Works Water Cooled HOW IT Works AIR Cooled High Efficiency Compressors FeaturesPsi Pressure Specifications MPW Water CooledMPA-5 Specifications MPA AIR CooledFreeze Protection Requirements Freezing Points of Aqueous Ethylene Glycol SolutionsInstallation Boxes UnpackingMicroKool Portable Chillers come fully assembled Make sure the installation area provides Preparing for InstallationInstall plumbing for process and cooling lines Install pipe to the rear of the chiller Connecting Process Water Supply LinesRemove the shipping pipe plug from the female Coat the pipe threads with thread sealantOpen the unit’s electrical enclosure Connecting Main Power SupplyApply power to the unit Testing the InstallationTurn on the condenser water supply MPW Units and check for leaks. If any leaks appear, stopEntering Setpoint Deviation Parameters Dip switch Configuration Initial SetupOpen the electrical enclosure Change Dip Switch 1 to Changing Temperature UnitsOpen the electrical enclosure Set dip switch 3 to on Disconnect and lock out main power to the unitSelect a new passcode using Setpoint adjustment buttonsOpen the electrical Press the RUN button to save the passcodeFollow Steps 1 through 5 Select a new control point using the Display button Selecting Temperature Control PointPress the RUN button to save the control point Set dip switch 5 toInsert the two power leads from the device Installing Auto Start FeatureWhen Auto Start is enabled Set dip switch 4 to the on positionTo disable Auto Start Activating SPI Communication Apply power to the chiller Enter the passcode, if necessaryConnect the host machine to the chiller Enter the node addressOperation Setpoint display PC-1 Control FeaturesPumpdown On/Off PC-2 Control FeaturesTo raise and swivel the control panel Positioning Control PanelTo lower the control panel To detach the PC-2 control panelPress Setpoint to select the parameter you want to change Entering a PasscodeEnter the passcode Starting the ChillerStopping the Chiller Using Pumpdown FeatureTo shut down the unit Press Stop Press Button to turn on PumpdownPerforming AN Auto Tune Insufficient setpoint/process deviation Page Maintenance Preventative Maintenance Schedule Quarterly every 3 months Inspect power cords, wires and electrical connectionsCleaning Condensers Cleaning EvaporatorsLocate the fill port at Back of the chiller Refilling the TankTo fill the reservoir If the charge is low, recharge the system Checking Refrigerant ChargePerforming System Tests Set dip switches 3Press To shut down the chiller Then open the electrical enclosureKEY/DISPLAY Test Connect all inputs to the system Input TestPress any key to display the first test menus Select the Input Test menuConnect all outputs to the system Output TestSelect the Output Test menu Disabling or Enabling Output Monitors Select the OM Enable/Disable menuSave changes and exit the output menu Release the Setpoint key Calibrating Temperature SensorsPress the up key to begin calibrating Exit Calibration ModeWait until the control displays don or bad Press SelectIndex through test menus to the operating log Logging Operating HoursExit the Operating Hours Log Troubleshooting FEW Words Before BeginningVerify that you have manuals for other equip Messages shown on the control panel. TheseCause of a Problem HOW to IdentifyMotor? Supplied to the pumpIs the required water flow Greater than the pump’sLoose? Is the thermocoupleLevel Switch fuse Has the indicated device Ply wire leads becomeHas one of the main sup Disconnected?Compressor Refrigerant pressure is either too low or too high Shut Down AlarmsAll models Air-cooled unitsInstalled correctly? Is the freezestat settingFreeze Stat Input is open Is there sufficient fluid Flow through he evaporaCable? Is something wrong withSystem Alarms Chiller Will not Power UP If fuses continue to fail Checking Replacing FusesOn the front panel counterclockwise to open Replace the fuse. The fuses are located on the motherCheck the overload Resetting OverloadsLocate the pump overload module attached Replacing the Motherboard Replacing Compressor Contactor Reverse this procedure to install the new conRemove and discard the old contactor Checking Unloader Valve Replacing the Freezestat From outside the United States, call WE’RE Here to HelpAppendix A-2 SPI Command Pairs SPI Commands Supported by Conair MicrokoolStatus, Process SPI Status WordsStatus, Machine Appendix B-4 PARTS/DIAGRAMS PD-2 PD-3 PD-4 PD-5