McQuay AWS Operating Manual
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McQuay AWS Operating Manual

Air-cooled screw chillers 50 hertz r-134a
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Control Panel
Air-Cooled Screw Chillers
AWS
50 Hertz
R-134a
Operating Manual
KOMAC00607-09EN
Date: July 2009
Supercedes: None

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  • Page 1 Operating Manual KOMAC00607-09EN Date: July 2009 Supercedes: None Control Panel Air-Cooled Screw Chillers 50 Hertz R-134a...

  • Page 2: Table Of Contents

    Manufactured in an ISO Certified facility ©2009 McQuay International. Information covers the McQuay International products at the time of publication and we reserve the right to make changes in design and construction at anytime without notice. ®™ The following are trademarks or registered trademarks of their respective companies: BACnet from ASHRAE;...

  • Page 3: Introduction

    Operation of this equipment in a residential area can cause harmful interference, in which case the user will be required to correct the interference at the user’s own expense. McQuay International Corporation disclaims any liability resulting from any interference or for the correction thereof.

  • Page 4: Operating Limits

    Test mode allows the service technician to manually control the controllers’ outputs and can be useful for system checkout. Building Automation System (BAS) communication capability via LonTalk®, Modbus®, or BACnet® standard protocols for all BAS manufacturers-simplified with McQuay’s Open Choices™ feature. Pressure transducers for direct reading of system pressures. Preemptive control of low evaporator pressure conditions and high discharge temperature and pressure to take corrective action prior to a fault trip.

  • Page 5: General Description

    General Description The control panel is located on the front of the unit at the compressor end. There are three doors. The control panel is behind to left-hand door. The power panel is behind the middle and right-hand doors. General Description The MicroTech III control system consists of a microprocessor-based controller and a number of extension modules, which vary depending on the unit size and conformation.

  • Page 6: Panel Layout

    Power Panel Layout The power panel is at the front of the unit, behind the two doors to the right Figure 2, Power Panel, Left Side Figure 3, Power Panel, Right Side KOMAC00607-09EN...

  • Page 7: Components

    Economizer Components The chiller may or may not have economizers depending on design capacity requirements. An economizer is a well-proven device to increase a refrigerant circuit’s capacity and to a lesser extent, its efficiency. Figure 4, Economizer Components Brazed-plate Heat Gas to Comp.
  • Page 8 Figure 5, Piping Schematic with Economizer Circuit, One Circuit KOMAC00607-09EN...

  • Page 9: Controller Description

    Controller Description Hardware Structure The MicroTech III control system for AWS chillers consists of a main unit controller with a number of extension I/O modules attached depending on the chiller size and configuration. One of the optional BAS communication modules may be included.
  • Page 10 System Architecture The overall controls architecture uses the following: • One Microtech III main controller • I/O extension modules (sometimes referred to as “controllers”) as needed depending on the configuration of the unit • Optional BAS interface as selected Figure 6, System Architecture BAS Interface (Bacnet, Lon, Microtech III Main Controller...

  • Page 11: Sequence Of Operation

    Sequence of Operation Figure 7, Unit Sequence of Operation (see Figure 9 for circuit sequence of operation) AWS Chiller Sequence of Operation in Cool Mode Unit power up Unit in Off state The chiller may be disabled via the unit switch, the remote switch, the keypad enable setting, or the BAS network.
  • Page 12 KOMAC00607-09EN...
  • Page 13 Figure 8, Circuit Sequence of Operation AWS Sequence of Operation - Circuits Unit power up When the circuit is in the Off state the EXV is closed, compressor is off, and all fans Circuit is in Off state are off.

  • Page 14: Controller Operation

    Controller Operation MicroTech III Inputs/Outputs I/O for the unit control and for circuits one and two are found on CP1. The chiller may be equipped with two or three compressors. Analog Inputs Description Signal Source Expected Range Evaporator Entering Water Temp NTC Thermister (10K@25°C) -50°C –...

  • Page 15: Ircuit #1 To #3

    Extension I/O Compressor #1 to #3 Analog Inputs Description Signal Source Expected Range Discharge Temperature NTC Thermister (10K@25°C) -50°C – 120°C Evaporator Pressure Ratiometric (0,5-4,5 Vdc) 0 to 5 Vdc Oil Pressure Ratiometric (0,5-4,5 Vdc) 0 to 5 Vdc Condenser Pressure Ratiometric (0,5-4,5 Vdc) 0 to 5 Vdc Motor Protection...

  • Page 16: (Pol)

    Extension I/O Fan Module Circuit #1 & 2 Digital Inputs Description Output Off Output On PVM/GFP Circuit #1 Fault No fault PVM/GFP Circuit #2 Fault No fault Digital Outputs Description Output Off Output On Circuit #1 Fan Step #5 Fan Off Fan On Circuit #1 Fan Step #6 Fan Off...
  • Page 17 Setpoints The following parameters are remembered during power off, are factory set to the Default value, and can be adjusted to any value in the Range column. Read and write access to these set points is determined by the Global HMI (Human Machine Interface) Standard Specification.
  • Page 18 Description Default Range Unit Ft/Lb Clear Ice Timer No,Yes SSS Communication No, Yes Multi Point Single Point, Multi Point , None(SSS) Noise Reduction Disabled Disabled, Enabled Noise Reduction Start Time 21:00 18:00 – 23:59 Noise Reduction End Time 6:00 5:00 – 9:59 10.0 °F 0.0 to 25.0 °F Noise Reduction Condenser...
  • Page 19 Description Default Range Unit Ft/Lb Oil Press Differential 35 PSI 250 kPa 0-60 PSI / 0 to 415 kPa Low Oil Level Delay 120 sec 10 to 180 sec 230 °F High Discharge Temperat. 110 °C 150 to 230 °F / 65 to 110 °C High Lift Pressure Delay 5 sec 0 to 30 sec...
  • Page 20 Auto Adjusted Ranges Some settings have different ranges of adjustment based on other settings. Cool LWT 1 and Cool LWT 2 Available Mode Selection Range Imp. Range SI Without Glycol 40 to 60 4 to 15 °C With Glycol 25 to 60 -4 to 15 °C Evaporator Water Freeze Available Mode Selection...

  • Page 21: Unit Functions

    Unit Functions Calculations LWT Slope LWT slope is calculated such that the slope represents the change in LWT over a time frame of one minute with at least five samples per minute. Pulldown Rate The slope value calculated above will be a negative value as the water temperature is dropping.

  • Page 22: Ontrol States

    The Available Modes Set Point must only be changed when the unit switch is off. This is to avoid changing modes of operation inadvertently while the chiller is running. Unit Mode is set according to the following table. NOTE: An “x” indicates that the value is ignored. Control Source Mode Available Modes...

  • Page 23: Tatus

    Unit Status The displayed unit status is determined by the conditions in the following table: Enum Status Conditions Auto Unit State = Auto Unit State = Off, Unit Mode = Ice, and Ice Delay = Off:Ice Mode Timer Active Off:OAT Lockout Unit State = Off and Low OAT Lockout is active Off:All Cir Disabled Unit State = Off and all compressors unavailable...

  • Page 24: Eduction

    • EWT is less than the Evap Freeze set point minus 0.6 °C and EWT sensor fault isn’t active The control state is Run when the flow switch input has been closed for a time greater than the Evaporator Recirculate set point. Pump Selection The pump output used is determined by the Evap Pump Control set point.
  • Page 25 Leaving Water Temperature (LWT) Reset The base LWT target may be reset if the unit is in Cool mode and it is configured for a reset. The type of reset to be used is determined by the LWT Reset Type set point. When the active reset increases, the Active LWT Target is changed at a rate of 0.1 degrees F every 10 seconds.

  • Page 26: Unit Capacity Control

    Outside Air Temperature (OAT) Reset The Active Leaving Water variable is reset based on the outdoor ambient temperature. Parameters used: 1. Cool LWT set point 2. Max Reset set point 3. OAT Reset is 0 if the outdoor ambient temperature is greater than Start Reset OAT set point. From Start Reset OAT set point down to Max Reset OAT the reset varies linearly from no reset to the max reset at Max Reset OAT set point.
  • Page 27 Maximum Circuits Running If the number of compressors running is equal to the Max Circuits Running set point, no additional compressors will be started. When multiple compressors are running, one will shut down if the number of compressors running is more than the Max Circuits Running set point. Compressor Staging in Ice Mode The first compressor will start when evaporator LWT is higher than the target plus the Startup Delta T set point.

  • Page 28: Unit Capacity Overrides

    The compressor capacities are adjusted one at a time while maintaining a capacity imbalance that does not exceed 12.5%. Load/Unload Sequence This section defines which compressor is the next one to load or unload. Next To Load The next compressor to load meets the following requirements: Lowest capacity of the running compressors that can load up •...
  • Page 29 As the signal varies from 4 mA up to 20 mA, the maximum unit capacity changes by steps of 1% from 100% to 0%. The unit capacity is adjusted as needed to meet this limit, except that the last running compressor cannot be turned off to meet a limit lower than the minimum unit capacity.

  • Page 30: Circuit Functions

    Circuit Functions Calculations Refrigerant Saturated Temperature Refrigerant saturated temperature is calculated from the pressure sensor readings for each circuit. A function provides the converted value of temperature to match values published data for R134a -within 0.1 C for pressure inputs from 0 kPa to 2070kPa, -within 0.2 C for pressure inputs from -80 kPa to 0 kPa.
  • Page 31 • Circuit switch is closed • No circuit alarms are active • Circuit Mode set point is set to Enable • BAS Circuit Mode set point is set to Auto • No cycle timers are active • Discharge Temperature is at least 5°C higher than Oil Saturated Temperature Starting The circuit will start if all these conditions are true: •...

  • Page 32: Circuit Status

    Rapid Shutdown A rapid shutdown requires the compressor to stop and the circuit to go to the Off state immediately. The circuit will do a rapid shutdown if either of these conditions occurs at any time: • Unit State is Off •...
  • Page 33 Capacity will not be increased above 25% until discharge superheat has been at least 22 degrees F for a time of at least 30 seconds. Manual capacity control The capacity of the compressor can be controlled manually. Manual capacity control is enabled via a set point with choices of auto or manual.

  • Page 34: Condenser Fan Control

    Condenser Fan Control The compressor must be running in order to stage fans on. All running fans will turn off when compressor goes to the off state. Saturated Condenser Temperature Target The condenser fan control logic attempts to control the saturated condenser temperature to a calculated target.

  • Page 35: Exv Control

    When one fan is running, a fixed point is used in place of a deadband. When the Saturated Condenser temperature drops below 70°F, stage down error is accumulated. When a stage down occurs or the saturated temperature rises back within the Stage Down dead band the Stage Down Error Accumulator is reset to zero.

  • Page 36: Economizer Control

    The target value is adjusted as needed to maintain discharge superheat within a range from 27 degrees F to 45 degrees F. As the discharge superheat approaches 27 degrees F, the suction superheat target is adjusted up. As the discharge superheat approaches 45 degrees F, the suction superheat target is adjusted down.

  • Page 37: Alarms And Events

    Alarms and Events Situations may arise that require some action from the chiller or that should be logged for future reference. A condition that requires a shutdown and/or lockout is an alarm. Alarms may cause a normal stop (with pumpdown) or a rapid stop. Most alarms require manual reset, but some reset automatically when the alarm condition is corrected.
  • Page 38 2: Evaporator Pump State = Start for time greater than Recirc Timeout Set Point and all pumps have been tried Action Taken: Rapid stop all circuits Reset: This alarm can be cleared at any time manually via the keypad or via the BAS clear alarm signal.

  • Page 39: Unit Events

    Trigger: Sensor shorted or open Action Taken: Rapid stop all circuits Reset: This alarm can be cleared manually via the keypad, but only if the sensor is back in range. Leaving Evaporator Water Temperature Sensor Fault #1 Alarm description (as shown on screen): Evap LWT Sens#1 Fault Trigger: Sensor shorted or open Action Taken: Rapid stop of circuits 1 and 2 Reset: This alarm can be cleared manually via the keypad, but only if the sensor is...

  • Page 40: Circuit Stop Alarms

    Reset: Auto reset when sensor is back in range. Unit Power Restore Event description (as shown on screen): Unit Power Restore Trigger: Unit controller is powered up. Action Taken: none Reset: none External Event Alarm description (as shown on screen): External Event Trigger: External Alarm/Event input is open for at least 5 seconds and external fault is configured as an event.
  • Page 41 Reset: This alarm can be cleared manually if the evaporator pressure is above –10 psi. Low Pressure Start Fail Alarm description (as shown on screen): LowPressStartFail N Trigger: Circuit state = start for time greater than Startup Time set point. Action Taken: Rapid stop circuit Reset: This alarm can be cleared manually via the Unit Controller keypad Mechanical Low Pressure Switch...
  • Page 42 Oil Level Switch Alarm description (as shown on screen): Oil Level Low N Trigger: Oil level switch open for a time greater than Oil level switch Delay while compressor is in the Run state. Action Taken: Rapid stop circuit Reset: This alarm can be cleared manually via the Unit Controller keypad. Compressor Starter Fault Alarm description (as shown on screen): Starter Fault N Trigger:...
  • Page 43 Trigger: [Circuit 1 or Circuit 2 Number of Fans > 6 OR PVM Config = Multi Point] and communication with the I/O extension module has failed. Section 3.1 indicates the expected type of module and the address for each module. Action Taken: Rapid stop of circuit 1 and 2 Reset: This alarm can be cleared manually via the keypad when communication between main controller and the extension module is working for 5 seconds.

  • Page 44: Circuit Events

    Reset: This alarm can be cleared manually via the keypad, but only if the sensor is back in range. Oil Pressure Sensor Fault Alarm description (as shown on screen): OilPressSensFault N Trigger: Sensor shorted or open Action Taken: Normal shutdown of circuit Reset: This alarm can be cleared manually via the keypad, but only if the sensor is back in range.

  • Page 45: Alarm Logging

    Action Taken: Action Taken: Unload the compressor by decreasing the capacity by one step every 5 seconds until the evaporator pressure rises above the Low Evaporator Pressure Unload set point. Reset: While still running, the event will be reset if evaporator pressure > (Low Evaporator Pressure Hold SP + 2psi).

  • Page 46: Using The Controller

    Using the Controller The Unit Controller Operation Figure 9, Unit Controller Alarm Button Menu Button Navigation Wheel Back Button Display The keypad/display consists of a 5-line by 22 character display, three buttons (keys) and a “push and roll” navigation wheel. There is an Alarm Button, Menu (Home) Button, and a Back Button.

  • Page 47: Navigating

    Continue W/O Password, which links to the Main Menu and allows access to a Figure 13 limited number of parameters (with asterisks) as shown in on page49. Password Menu Figure 11, McQuay AWS > Enter Password > Continue W/O Password Figure 12,...
  • Page 48 previous line (up) on the page. The faster the wheel is turned the faster the cursor moves. Pushing the wheel acts as an “Enter” button. Three types of lines exist: • Figure 12 Menu title, displayed in the first line as in •...
  • Page 49 Figure 13, Home Page, Main Menu Parameters and Links Home Page View/Set Unit > Status/Settings > Enter Password Set-Up > Continue W/O Password Temperatures > Date/Time/Schedules > Power Conservation LON Setup Main Menu BACnet IP Setup BACnet MSTP Setup > View/Set - Unit Modbus Setup >...
  • Page 50 Figure 14, Navigation, Part A View/Set Unit Status/Settings (view/set unit) > Status/Settings Unit Status > Set-Up Chiller Enable > Temperatures Control Source > Date/Time/Schedules Next Circuit On > Power Conservation Chiller Enable Setpoint - > LON Setup Chiller Mode Setpoint - Network >...
  • Page 51 Figure 15, Navigation, Part B View/Set Unit Power Conservation (view/set > Status/Settings Unit Capacity > Set-Up Unit Current > Temperatures Demand Limit Enable > Date/Time/Schedules Demand Limit Value > Power Conservation Current @ 20mA > LON Setup Current Limit Setpoint >...
  • Page 52 Figure 16, Navigation, Part C View/Set Unit AWM Setup (view/set unit) > Status/Settings Apply Changes > Set-Up DHCP > Temperatures Actual IP Address > Date/Time/Schedules Actual Mask > Power Conservation Actual Gateway > LON Setup Given IP Address > BACnet IP Setup Given Mask >...

  • Page 53: Optional Remote User Interface

    The optional remote user interface is a remote control panel that mimics operation of the controller located on the unit. Up to eight AWS units can be connected to it and selected on the screen. It provides HMI (Human Machine Interface) within a building, the building engineer’s office for example, without going outdoors to the unit.
  • Page 54 KOMAC00607-09EN...

  • Page 55: Start-Up And Shutdown

    Start-up and Shutdown NOTICE McQuay service personnel or factory authorized service agency must perform initial start-up in order to activate warranty. CAUTION Most relays and terminals in the unit control center are powered when S1 is closed and the control circuit disconnect is on. Therefore, do not close S1 until ready for start-up or the unit may start unintentionally and possibly cause equipment damage.

  • Page 56: Extended (Seasonal) Shutdown

    CAUTION If all power to the unit is turned off, the compressor heaters will become inoperable. Once power is resumed to the unit, the compressor and oil separator heaters must be energized a minimum of 12 hours before attempting to start the unit.
  • Page 57 disconnect switches to "on." This will energize the crankcase heaters. Wait a minimum of 12 hours before starting up unit. Turn compressor circuit breakers to "off" position until ready to start unit. 6. Open the optional compressor suction butterfly as well as the liquid line shutoff valves, compressor discharge valves.

  • Page 58: Field Wiring Diagram

    Field Wiring Diagram Figure 17, Typical Field Wiring Diagram, Sheet 1 NOTE: 1 Compressor Alarm No. 3 applies to future product releases. 2 The compressor alarms will not be energized by a unit fault, only the unit alarm will do so. Using the unit alarm and the circuit alarms will include all faults and also designate which compressor has an alarm.
  • Page 59 Figure 17, Typical Field Wiring Diagram, Sheet 1 Note: The BAS interface modules and the remote display shown above are available as options. KOMAC00607-09EN...

  • Page 60: System Maintenance

    The initial vibration analyzer test provides a benchmark of the compressor, and when performed routinely, can give a warning of impending problems. Lubrication No routine lubrication is required on AWS units. The fan motor bearings are permanently lubricated. No further lubrication is required.
  • Page 61 Sealing Spigot Oil Filter - 250mm Oil Filter Housing Cover O-Ring – 89.5x3 O-Ring – 76.1x3.4 M8 Bolts • Unscrew and remove two hex head side cover bolts 180° apart. Insert M8 guide studs into the vacant holes. • Remove remaining bolts, remove oil filter housing cover. •...
  • Page 62 No maintenance is ordinarily required except the routine removal of dirt and debris from the outside surface of the fins. McQuay recommends the use of non-caustic, non-acidic, foaming coil cleaners available at most air conditioning supply outlets.
  • Page 63 Lead-Lag A feature on all McQuay AWS air-cooled chillers is a system for alternating the sequence in which the compressors start to balance the number of starts and run hours. Lead-Lag of the refrigerant circuits is accomplished automatically through the MicroTech III controller. When in the auto mode, the circuit with the fewest number of starts will be started first.

  • Page 64: Appendix

    Appendix Definitions Active Setpoint The active setpoint is the setting in effect at any given moment. This variation occurs on setpoints that can be altered during normal operation. Resetting the chilled water leaving temperature setpoint by one of several methods, such as return water temperature, is an example.
  • Page 65 High Saturated Condenser – Unload Value High Cond Unload Value = Max Saturated Condenser Value – 3 degrees F This function unloads the compressor whenever the pressure approaches within 3 degrees of the maximum discharge pressure. The purpose is to keep the compressor online during periods of possibly temporary elevated pressures.
  • Page 66 Setpoint Solid state starter as used on McQuay screw compressors. Suction Superheat Suction superheat is calculated for each circuit using the following equation: Suction Superheat = Suction Temperature – Evaporator Saturated Temperature See page 38 for details.
  • Page 68 “The present publication is drawn up by of information only and does not constitute an offer binding upon McQuay. McQuay has compiled the content of this publication to the best of its knowledge. No express or implied warranty is given for the completeness, accuracy, reliability or fitness for particular purpose of its content, and the products and services presented therein.

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