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Trane HORIZON ABDA Manual

Single and two-stage steam and two-stage direct-fired absorption chiller with microprocessor control panel
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HORIZON
Single and Two-Stage Steam and
Two-Stage Direct-Fired
Absorption Chiller
With Microprocessor Control Panel
Unit Models
ABDA, ABTF, ABSD
April 2004
®
ABS-CTR-3B

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Summary of Contents for Trane HORIZON ABDA

  • Page 1 Controls ® HORIZON Single and Two-Stage Steam and Two-Stage Direct-Fired Absorption Chiller With Microprocessor Control Panel Unit Models ABDA, ABTF, ABSD ABS-CTR-3B April 2004...

  • Page 2: Table Of Contents

    Table of Contents (11) Control System Proportional, Integral, and (1) Introduction - 3 Derivative (PID) Control - 69 (2) Absorption Cycle - 4 (12) Control System Limits - 70 (3) Sequence of Operation - 11 (13) Crystallization Sensing Detection and Recovery (SDR) - 71 (4) Control Panel Identification - 16 (14) Absorber Entering or Low Condensing...

  • Page 3: Introduction

    (1) Introduction Manual Layout The following information describes the Trane microprocessor based absorption control panel (UCP = The table of contents outline the topics covered. Unit Control Panel). This section details the control The following are the major sections: strategies designed to ensure a more reliable and efficient Absorption Cycle (Section 2) - This section covers the chiller operation.
  • Page 4 (2) Absorption In the case of ABDA machines, a burner provides heat When the intermediate lithium bromide solution is sprayed energy input while the ABTF is a regulated supply of 115- onto the absorber tubes, the solution is cooled from the psig steam or 350°F hot water supplied to the high cooling tower water flowing through the tubes.
  • Page 5 Hot Water Heating ABDA only (Figure 1) Condensate Heat Exchanger ABTF only Heating only or simultaneous heating with cooling is The condensate heat exchanger is used to recover heat from the steam condensate, after it has passed through the accomplished utilizing a heat exchanger. As system heating high temperature generator.
  • Page 7 Table 1. ABTF machine cooling cycle (See Figure 1) Lithium Bromide Solution Point Concentration Temperature Temperature or Refrigerant Water (°F) (°C) Absorber Dilute Solution Absorber Dilute Solution Entering the Low Temperature Generator (LTG) Solution Leaving the Low Temperature Generator (LTG) Solution Entering the High Temperature Generator (HTG) Solution Leaving the High Temperature Generator (HTG) 65.5...
  • Page 8 Figure 2. ABDA fluid cycle - (Reference Table 2) Direct - Fired Absorption Unit Purifier Hot Water Heater Purge Low Temperature Generator Condenser Evaporator High Temperature Generator Pump Direct-Fired Generator High Temperature Temperature Heat Heat Exchanger Exchanger Absorber Refrigerant (HXER) (HXER) Storage Absorber...
  • Page 9 Table 2. ABDA machine cooling cycle (See Figure 2) Point Lithium Bromide Solution Concentration Temperature Temperature or Refrigerant Water (°F) (°C) ilute Solution Absorber D Absorber Dilute Solution Entering the Low Temperature Generator (LTG) Intermediate Solution Leaving the Low Temperature Generator (LTG) Intermediate Solution Entering the Low Temperature Generator (LTG)
  • Page 10 Machine Solution Cycle The machine solution cycle is discussed in this section. Refer to the cooling cycle schematic, Figure 3, during the cycle explanation and reference Table 3. Figure 3. Single-stage absorption refrigeration cycle Table 3. Machine cooling cycle (Ref. Figure 3) (Typical Temperatures) Concentration Temperature Temperature Point LiBr Solution or Refrigerant Water...

  • Page 11: Sequence Of Operation

    (3) Sequence of Operation restart diagnostic where the chiller will start once the The sequence of operation illustrates time and events that chilled water flow switch logic is satisfied. occur at initial power-up, at startup when auto is selected, or auto off cycle, or manual stop operation. The time line Failure to receive condenser water flow or ventilator fan sequence of operation follows the events that are confirmation within the time period’s results in an MMR-...
  • Page 12 Sequence of Operation (Continued on Next Page) Sequence of Events from a Stop or Auto condition through Start (No intervening Power Ups or Software Resets.). Standard Mode Stop Auto Starting Absorber or Condenser Pumps Display: Wait for Condenser Water Flows, Wait for Chilled Water Flow, Wait for a If flow not established...
  • Page 13 Sequence of Operation (Notes - Reference Next Page) Sequence of Events: From Running through Dilution Cycle (No intervening Diagnostics or Software Resets.). Local or Remote Stop Standard Mode Display: Unit is Running Chilled Water Dilution Cycle Pump off delay Go to (See Note 1 and 6) (See Note 7) Time...
  • Page 14 Startup/Shutdown Sequence of Operation Time Line Referenced Notes (See pages 11 & 12) Startup Pre-heat 1) See “Using the Control Panel” for a listing of valid Solution pumps are started before energy is input. modes that may occur during “Unit is Running.” The controls execute a pre-heat sequence upon startup to 2) Upon power up, refrigerant dilution valve 1 (RDV1) establish an adequate concentration level before releasing...
  • Page 15 opened when the dilution cycle started, remains open until During the dilution cycle Refrigerant Dump Valve 1 (RDV1) the machine is restarted. The CLD displays stop with the opens. Once opened, RDV1 remains open until the dilution completion of the dilution cycle. cycle is completed, or the machine is restarted after power failure, or Panic Stop...

  • Page 16: Control Panel Identification

    (4) Control Panel Identification The following information explains the details of chiller The inner control panel components are illustrated in control. The details include hardware identification and Figure 4. Modules are stacked in a top, bottom or middle location, control strategies, limits and operating sequences. configuration.
  • Page 17 Figure 4. Panel layout Bot- Bot- Bot- or Less Panel Layout Legend 1S1 - Line Voltage Fused Disconnect 1U1 - Starter Module Switch * 1U2 - Circuit Module 1K1 - Refrigerant Pump Abnormal Relay 1U3 - Chiller Module 1K2 - High Temperature Solution Pump Abnormal 1U4 - Purge Module Relay 1U5 - Stepper Module...
  • Page 18 Control Modules Microprocessor control modules are mounted on the left- hand and right-hand side of the main unit control panel and in the burner control panel. Figure 5. Location of microprocessor control modules within the main unit control panel and burner panel Left Hand Side of Unit Control Panel Right Hand Side of Unit Control Panel Class II Wiring...
  • Page 19 Signal Block Diagram pumps are electrically controlled and interlocked to the unit The following block diagram illustrates the interrelationship control panel. This interlocking arrangement provides of the interprocessor communications (IPC) link. These protection from improper system water pump control or connections allow the individual microprocessors to loss of flow conditions, which can damage the machine.
  • Page 20 available to the chiller module via an interprocessor 1U8, 9,10 Optional External Communications Modules communications link This module also provides output • IPC Buffer Module - Used to communicate to contact closures for control devices. external devices. • Printer Communications Interface - required for 1U4_ Purge Module printer compatibility.
  • Page 21 Main Power Termination Point Total Motor Current Monitoring The connection point in the power section for customer Current transformers are used to monitor total unit three phase power. currents. See Table 3 to select CT Rating. In many cases • 1TB1 Main terminal block (standard).

  • Page 22: Using The Control Panel

    (5) Using the Control Panel Table 4 - Current gain settings as a function of CT factor for UCP2 starter module CT Factor Current Gain Setting The operator interface or local clear language display (LCLD) is used to communicate with the chiller. The machine operator can select information displayed from group menus that have predetermined information.

  • Page 23: Operator Interface

    The panel controls the backlight current based on the Functional Keys equipment room ambient temperature. The Next and Previous keys allow the operator to step through the various menus within a group. The report Menus group will sequence around to the top or bottom of that The display has access to the current operation status, group when the end or beginning is reached, respectively.
  • Page 24 If required, contact the local key to backup. To quickly go to the last menu item, press Trane service agency for assistance. the Previous key at the display header. 6. The chiller will restart if “auto” operation was To Create the Custom Report: interrupted and the differential to start set point is satisfied.

  • Page 25: Report Menus

    1. Press Operator Settings key. The custom reports are easily programmed by the following sequence: 2. Press Next to advance to the “Purge Operating Mode” display. To create a custom report when the desired report is being displayed from one of the other report menus, press the (+) 3.
  • Page 26 Typical “Chiller Operation Mode Displays” are Continued from Column 1 provided in the following table. Unit is Running: Run: Low Cooling Water Temperature Limit Low Absorber or Condenser Temperature Limit (This is not an all-inclusive listing) Machine Displayed Message Run: Evaporator Limit Unit is Running: Condition (First Line/Second Line)
  • Page 27 The following displays appear as the next key is pressed to 6. Hot Water Setpoint or Evaporator Leaving Water advance through the menu. Temperature (unless Cool Only). Hot Water Setpoint (Source): xxx.xf/c The displays are self explanatory except as noted. Some Hot Water Leaving Temperature: xxx.xf/c displays are present only when the option is selected.
  • Page 28 14. Absorber Leaving Water Temperature: xxx.xf/c Condenser Leaving Water Temperature: xxx.xf/c Custom Chiller Cycle Pump/Purge Report Report Report Report 15. Solution Pump speed Reported Command: If the solution pump AFD Speed is set to Auto/[manual] Control Solution Pump AFD Auto or [manual] Speed Cycle Report Command: xxx.x Press (Next)(Previous) To Continue...
  • Page 29 Collection (Condensing Unit is On, Vac Pump is on) startup group. This feature is set at the factory. If operator Enabled password is desired contact your local Trane service (Temperature initiated pumpout) Pumping company. •...
  • Page 30 Custom Chiller Cycle Report Report Report Solution Pump AFD Auto Speed Command: Cycle Report User Defined Custom Report xxx.x Press (Next) (Previous) to Continue Press Next or Previous to Continue Press (Next) (Previous) to Continue Solution Temperature Leaving Heating: xxx.x F/C Solution Pump AFD Auto Speed Command: Chiller Status Interstage Vapor Temperature:...
  • Page 31 Purge/Pump Report Pump/Purge Hours, Starts and Amps Press (Next) (Previous) to Continue Purge Operating Mode: (Mode) Purge Status: (status) Purge Refrigerant Suction Temperature: xxx.x F/C Press (Next) (Previous) to Continue Purge Pumpout Rate: xxx.x Minutes/24 Hours Purge Maximum Pumpout Rate: xxx.x Minutes/24 Hours Purge Total Pumpout Time: xx,xxx.x Minutes...

  • Page 32: Operator Settings

    6. Chilled Water Setpoint Source (applicable with External Settings Menu Chilled Water Setpoint Only). If the Tracer Option is installed, the word “Default” will appear in front of the setpoint source. Diagnostics Operator Service Service Settings Settings Tests (Default) Chilled Water Setpoint Source: (Source) Possible values of (source) are Front Panel Default or External.
  • Page 33 13. Heat/Cool Priority Setpoint Source is available only if 18. Heat/Cool Priority Select the Auxiliary Heating and the Ext Priority Setpoint options Displayed when the Auxiliary Heating Option is installed. are installed). Heat/Cool Priority: (Status) Press (+) (-) to Change Setting If a Tracer is installed, the word “Default”...
  • Page 34 Operator Settings Chilled Water Reset Type: Chilled Water Setpoints and Purge Control Unit Function: (Cool/heat) (type) Press (Next) (Previous) to Continue Press (+) (-) to Change Setting Press (+) (-) to Change Setting Settings in this Menu are (Status) (Type) Reset Ratio: xxx% (Default) Priority Setpoint Source: Press (+) (-) to Change Setting (Password Message)
  • Page 35 5. Decimal Places Displayed: (Status) Press (+) (-) to Change Setting Diagnostics Operator Service Service Settings Settings Tests The choices for Status are: XXX.X- Default or, XXX 6. Display Menu Headings: (d/e) Press (+) (-) to Change Setting The Service Settings menu has three submenus within it. Default is Enabled.

  • Page 36: Service Settings

    Service Settings Service Settings: BASIC SETUPS Press (Next) (Previous) to Continue If Keypad lock password featured Next enabled ***Display and Keypad Are Locked*** Press (Enter) to Lock Display and If Keypad lock password If press Keypad ***Enter Password to Unlock*** feature disabled enter Password will be required to Unlock...

  • Page 37: Field Startup Group

    When the keypad lock feature is Disabled, the keypad lock personnel. Call your local Trane service company for display disappears and the non-password-protected area of assistance. the Service Settings menu and the Keypad/Display are 12.
  • Page 38 5. ICS Address 10. Softloading Time Setpoint ICS address is used only with Trane BAS systems for Soft load time (control response) is the time that the control machine ID during communications. will use to ramp to a new target set point. This setpoint is Range of Values is 1 to 127 in increments of 1.
  • Page 39 Range of Values is 40 to 90°F (4.4 to 32.2°C) in increments See Table 5A for initial settings for items 20, 21, 22, & 25. of 1 or 0.1°F or C depending on the Service Setup Screen Table 5A. Concentration control setpoints xxx or xxx.x.
  • Page 40 27. Solution Pump AFD Maximum Frequency Setpoint Solution Flow Control This setpoint will set the UCP2 maximum flow output Solution Pump Speed Setup signal in hertz for the Low Generator Temperature Solution The solution pump AFD’s are factory programmed. Pump (LTSP). However, the actual minimum and maximum speed of the Selectable Range is 20 to 65 Hz in increments of 1.
  • Page 41 In-Direct Fired Energy Input Adaptive Mode 35. Hot Water Control Gain The maximum energy input is typically set to 110%. The This menu is displayed only on Direct Fired units with the control system reads the steam pressure to the valve and Auxiliary Heating option installed.
  • Page 42 50. Evaporator Fluid Coefficient 42. Purge Pumpout Interval Setpoint This setpoint sets the interval between absorber purge This input identifies the proper fluid characteristics. Water is 100. (This number is found by multiplying the specific chamber pumpout cycles. gravity times the specific heat times 100.) Range 10-250 minutes.
  • Page 43 For linear energy input characteristics they are as follows: 56. Energy Linearization Coefficient Number 0 B0=0, B1=100, B2=0, B3=0. To enter these first set all Energy Coefficient 0: xxx E-1 individually using the (+) (-) and use Next key. When at the Press (+)(-) to Change Setting load display press enter.
  • Page 44 The following figures illustrate three various energy input coefficient configurations. Figure 9 - Linear coefficients Used with Modulating Head burners or anytime straight line control is desired. Command Signal Figure 10 - Butterfly valve coefficients Used on fixed head burners with butterfly valve gas control. Command Signal Figure 11 - Adaptive coefficients As determined by Control System.
  • Page 45 Service Settings: Field Start Up EV Maximum Travel Setpoint: xx,xxx Steps Press (+)(-) to change setting Group (++—++) OVERVIEW Energy input closed stop: xxx% Press (+)(-) to change setting [Shaded is sales order specified] Energy input open stop: xxx% Press (+)(-) to change setting Password required to access field start up group Minimum alternate fuel firing rate: xxx% (++—++)

  • Page 46: Machine Configuration Group

    (Service Settings continued) 1. Machine Configuration Group Heading This header is not suppressed if the headers in the Service Energy Coefficients Settings menu are not revealed. Press (Enter) To View 2. Unit Frequency Energy Coefficients Possible values of Frequency are: 60 Hz; module default, 50 Press (Enter) To Edit Energy Coefficients Energy Coefficient 0: xxx E-1...
  • Page 47 10. High Pressure Cutout Setpoint Sales Order Specified Features When the concentrator pressure as determined by the 17. Line Voltage Sensing Option interstage transducer output equals this setting, machine Only to be installed if voltage potential transformers and shutdown will occur. Manual reset is then required (MMR). fuses and wiring are present.
  • Page 48 Service Settings: Machine 23. Alternate Fuel Option – Direct-Fired Only When installed creates another minimum fire rate stop for Configuration Group (+ - + - + -) alternate fuel setpoint within field startup group. Possible values for statuses are installed, or not installed-module In all cases the second line would be default.
  • Page 49 8. Water Flow Sensing. The following will be displayed if 1. Service Tools Group Password Request the differential water pressure sensor is installed and Pswd Reqd to Access Service Tools Group selected from the machine configuration menu. Please Enter Password Absorber or Condenser Differential Pressure: xxPsid The Password is ++—++ followed by enter.
  • Page 50 Values for [message] are Press (+) (-) to Change Setting. 19.2. If the heat valve control status is “Manual” the This setpoint will return to auto on any transition from following is displayed. running to stop When the heat valve control status is transitioned from 16.1.

  • Page 51: Service Tests

    Service Tests Note: When in the manual Normal operation does not require use of Solution pump AFD (status) mode the “Alarm” LED Service Tests. Password access only. speed Command: xxx Password required to access service tools group illuminates to indicate that the Service Tests should only be performed by (Message) manual mode has been...
  • Page 52 2.1 If there are any diagnostics present, the following 3 screens are displayed sequentially when the Next key is pressed. The first screen is: Service Service Diagnostics Operator Settings Tests Settings “Diagnostics Report Follows” Press (Next) for More 2.2. The second screen is Press (Next) to Display Operating Mode Diagnostics Menu At Time of Last Diagnostic...
  • Page 53 The definitions of diagnostic and sequence number are the If the enter key is depressed, the following message is same as for the active diagnostic messages. If Next is displayed for two-seconds: pressed, the second historic diagnostic screen is displayed. IFW Diagnostics Have Been Cleared Diagnostics Report is Being Reset 4.2.

  • Page 54: Diagnostics

    Diagnostics Press Diagnostic Key Diagnostic Occurs Header Screens New Diagnostic One Time Display Operating Mode at Last Diagnostic Set of Screens for First Active Diagnostic Up to If More Active 20 Sets Total Set of Screens for First Historic Diagnostic Up to If More Historic 20 Sets...

  • Page 55: Sensors And Controls

    (6) Sensors and Controls ABDA Control Locations Machine controls are factory mounted and wired. External controls are connected with field wiring, and are controlled by the chiller or used by the chiller system. Figure 12. Location of electrical components See View C Burner Control Panel (BCP)
  • Page 56 Machine Sensors Figure 12. Machine Sensor Locations (Continued) Left Hand End Right Hand End Front View Figure 13. Sensor locations of the absorption fluid cycle – see table 7 Direct-Fired Absorption Unit Optional Hot Water Heater Low Temperature Generator Condenser Evaporator High Temperature...
  • Page 57 Table 7 identifies unit sensors, primary function control or monitor, connection points and the normal operation temperature range of the sensors located in the fluid cycle. Table 7 Figure 13 Usable Sensor Primary Sensor Range in °F Function Reference Module Evaporator Leaving Water Temperature 28 - 70 LCWT Control...
  • Page 58 ABTF Control Locations Machine controls are factory mounted and wired. External controls are connected with field wiring, and are controlled by the chiller or used by the chiller system. Figure 14. Machine sensor locations (Other Sensors on Next Page) Left Hand View Left Hand End Detail A - A (Rear View)
  • Page 59 Figure 14. Machine Sensor Locations (Continued) Left Hand Right Hand Front View To Control Panel Detail B - B Right Hand View...
  • Page 60 Figure 15. ABTF absorption fluid cycle sensor locations See Table 8 Steam-Fired Absorption Unit Purifier Purge Low Temperature Generator Condenser Steam-Fired Generator Evaporator High Temperature Generator Pump Absorber Refrigerant Storage High Tem- Temperature Condenser perature HXER HXER HXER Absorber Spray Pump Evaporator Spray Pump Eductor...
  • Page 61 Table 8. Provides machine sensors, primary function control or monitor, connection points, and normal operation temperature range Figure 13 Sensor Usable Sensor Primary Range in °F Reference Function Module Evaporator Leaving Water Temperature 28 - 70 LCWT Control Chiller Design 44 Evaporator Entering Water Temperature 28 - 80 LCWT Control...
  • Page 62 Figure 15. ABTF absorption fluid cycle sensor locations See Table 8 28 29 23 & 24 25 & 26 10 Across the Absorber Table 3. Sensing points for single stage Horizon Chiller Evaporator Entering Water Temperature Evaporator Leaving Water Temperature Condenser Leaving Water Temperature Absorber Leaving Water Temperature Absorber Entering Water Temperature...

  • Page 63: Control Strategy

    (7) Machine Control 2. Concentration Control The concentration control adjusts the energy input for Strategy optimum solution efficiency. The strong solution concentration is typically maintained at 15 degrees F from the theoretical crystallization point. This is called the low The unit control panel is designed to reliably achieve and temperature heat exchanger (LTHX) temperature margin.
  • Page 64 Horizon’s Adaptive Cycle Management The Equilibrium chart below illustrates the Generator Temperature Limit, the Interstage Pressure Limit and the Low Refrigerant Temperature Limit areas with respect to the normal cycle operation. These three limits along with PID Concentration and Solution Controls provide complete cycle management.

  • Page 65: Leaving Chilled Water Temperature Control

    (8) Leaving Chilled Water Temperature Control The solution concentration is changed by adjusting the The unit control maintains leaving water temperature speed of the LTSP using an AFD. Solution flows and setpoint by varying the refrigerant vapor pressure in the concentrations are adjusted any time the demand for evaporator.

  • Page 66: Low Leaving Water Temperature Cutout

    (9) Low Leaving Water Control Band The control band is a region “around” setpoint within Temperature Cutout which the leaving water temperature is allowed to drift. The control band is the setpoint + or - 1.0 degrees F. The control (LCWTC) algorithms are active within this band to maintain control.

  • Page 67: Concentration Control

    (10) Concentration Control (4) When no limit conditions take precedence and with The concentration control algorithm adjusts the energy solution flows within the set AFD operating range, the input to deliver concentrated solution for optimum solution mixed concentration is controlled to a preset number of cycle efficiency.
  • Page 68 Low Temperature Heat Exchanger (LTHX) Margin Vs Capacity Control Signal The microprocessor will control the generator concentrations to maintain the selected Low Temperature Heat Exchanger (LTHX) service setting setpoint. The Low Temperature Heat Exchanger (LTHX) margin setpoint is located in the service settings field startup group menu. The standard set point is 15°F which is the solution margin at nominal design conditions.
  • Page 69 (11) Control System’s Gain, Reset and derivative settings are available at the CLD in the service setting (service level inputs). Factory tested PID Control settings are intended to provide satisfactory performance under most site conditions, however, these inputs are accessible for those occasions when it is necessary to make The simplified control (Figure 19) illustrates how the field adjustments.

  • Page 70: Control System Limits

    (12) Control System Limits The microprocessor control continuously monitors for When the limit or safety takes over the priority control, the unsafe or unreliable operating conditions known as control clear language display will indicate the active limit mode. A limits and safeties. If such a condition is detected the limit limit mode does not necessarily mean that a problem control system can override Leaving Water Temperature exists.

  • Page 71: Crystallization Sensing Detection And Recovery (Sdr)

    (13) Crystallization Sensing Detection and Recovery (SDR) SDR is a control system strategy that through continuous The SDR system feature provides a secondary line of sensing will detect unusual solution flow patterns, and defense against crystallization over and above the routine upon detection, a recovery cycle is executed and operating Low Temperature Heat Exchanger (LTHX) concentration adjustments are made to correct the condition.
  • Page 72 The SDR uses temperature sensors to detect reverse flow 4. System will restart normal chiller operation (unless the from the high temperature generator. Under normal system has been commanded to Stop or there are operation solution from the high temperature generator pending diagnostics).
  • Page 73 Diagram Illustration of an SDR Occurrence • Figure 23 illustrates a typical SDR trip temperature (center dotted line) and crystallization sensing detection sensor temperature (solid). • The left arrow point indicates where the solid line crosses the dotted line. This is where the SDR trip criteria is met and recovery mode is initiated.
  • Page 74 Soft Loading Time [Control Response] Summary Horizon chiller control (soft loading feature) ramps setpoint changes. This provides a controlled transition during machine startup and when setpoint changes are entered during operation. Soft Loading along with solution pre- heating are used to bring the chiller solution concentrations and temperatures up to normal operating levels in a controlled manner.

  • Page 75: Absorber Entering Or Low Condensing Temperature Limit

    (14) Absorber (Abs) Entering and Low Condensing Temperature Limit The purpose of this limit is to provide reliable machine operation with variations in entering absorber water temperatures. • Fluctuations in entering saturated condensing temperatures above 90°F (100°F ABSD) will have an affect on the energy input because of the built in feed- forward gain function.
  • Page 76 (15) Chilled and Refrigerant Temperature Cutouts, Limit and Differential to Start or Stop Low Chilled Water Temperature Cutout (LCWTC) The low chilled water temperature cutout (LCWTC) will shut the machine down when the leaving water temperature (Leaving Water Temperature) reaches the chilled water cutout setpoint.
  • Page 77 To restore service, the diagnostic must be manually reset. Low Refrigerant Temperature Cutout (LRTC) The factory setting of 36°F should not be changed, however and Limit it is accessible from within the service settings: field startup The low refrigerant temperature cutout (LRTC) limit is used group menu if the chiller selection requires a new setpoint to prevent a chiller shutdown when the evaporator for stable operation.
  • Page 78 Differential to Start/Stop With the chiller in Auto mode waiting for a need to cool and the leaving water temperature (Leaving Water Temperature) reaches the Differential-to-Start setpoint, the chiller start sequence is initiated as the Leaving Water Temperature reaches the Differential-to-Stop setpoint. The chiller returns to the AUTO mode waiting for a need to cool mode after completing a solution dilution cycle (Reference Figure 28).
  • Page 79 Filtered Setpoint Feature The filtered setpoint feature allows the operator to change the chilled water set point without a chiller shutdown. The micro utilizes a filtered chilled water setpoint feature. Figure 29 illustrates a typical front panel setpoint change The micro response to a loss of chilled waterload does not from 44 to 50°F.
  • Page 80 Leaving Water Temperature Control Figure 30 is a composite of all the settings regarding leaving water temperature (LWT) control. Depending on Setpoints where the actual leaving water temperature falls within the Table 9 identifies the maximum differential-to-stop and start figure below, will indicate the active UCP2 control functions. settings recommended for the leaving water temperature (Leaving Water Temperature) setpoints, without violating the LCWTC or LRTC factory settings.

  • Page 81: Interstage Pressure Limit

    (16) Inter-Stage Pressure The limit is a proportional control that limits loading as the Interstage Vapor Pressure approaches the UCP2 high- Limit pressure cutout setpoint. See the illustration below for an understanding of the allowed loading verses interstage pressures. High Interstage Pressure A pressure transducer monitors the inter-stage vapor Low Interstage Pressure Limit pressure generated by first stage generator.

  • Page 82: Generator Solution Temperature Limit

    (17) Generator Solution Temperature Limit Control As the solution temperature increases, the control system will limit machine energy input attempting to keep the chiller operational. Limited energy input to the first-stage generator begins when the strong solution leaving the temperature exceeds 315°F. The control system will enter limit loading from 315 to 325°F;...

  • Page 83: High Exhaust And Gas Temperature Limit

    (18) High Exhaust Gas High Exhaust Gas Temperature Limit This limit function reduces the burner fire rate or turns off Temperature Limit and the burner lowering the overall generator temperature when the temperature zone is violated. Figure 33 illustrates Cutout the associated temperatures.
  • Page 84 High Exhaust Gas Temperature Cutout - HEGTC (Direct Fire Only) The High Exhaust Gas Temperature Cutout (HEGTC) provides machine shutdown when an unusual operating condition causes excessive flue gas temperature. The exhaust gas temperature limit and high temperature cutout are two active sensors located in the stack that continually monitor flue gas temperature during normal operation.
  • Page 85 Figure 35. The following diagram indicates a typical HTC circuit Circuit Module Located in Power Side of Machine Control Panel HTC Input Flame 120 vac Optical Safeguard (FSG) Burner Safety String HTC Stack A and B Temperature represent the Burner Module FSG pins that Located in the must be tied...

  • Page 86: Steam Control

    (19) Adaptive Steam Field set-up of the unit is simplified because energy valve end stops are automatically set by the inputs in the Control machine configuration menu: unit size in tons, valve size in inches, and valve type (V-ball or butterfly). Steam flow control is possible because of the addition of two factory Horizon steam-fired chillers have added adaptive steam mounted pressure transducers on the steam line.

  • Page 87: Generator Entering Hot Water Limit Control

    (20) Generator Entering Hot Water Limit Control (Hot Water Only) Generator Entering Hot Water Temperature Limits apply to both single and two stage absorption units. The purpose is to limit the heat energy to the generator to prevent tube expansion damage within the generator. See Figure 36. This is a proportional limit control that will limit loading as the hot water temperature approaches the temperature limit value.

  • Page 88: Purge System

    (21) Purge System Figure 37. Horizon Purifier Purge The primary purge tank is connected to the Horizon condenser by supply and return lines Pump out compressor through which refrigerant may freely flow. The Horizon purge refrigeration system has its evaporator Condenser located inside this tank.
  • Page 89 Figure 38 is a plot of the purge pump-out schedule as a Purge Service Log Reset function of saturated condenser temperature. The purge service log reset is used to reset the Service Log data in the Pump/Purge Report menu. This can be used to track the pumpout time after the unit has been serviced.
  • Page 90 Liquid Level Sensor Alarm Relay The liquid level sensor is a binary input used to indicate the This relay will be energized in the presence of latching presence of a high level of liquid refrigerant in the primary purge diagnostics. It will be de-energized at all other times. purge tank.
  • Page 91 The outputs should have the following states unless in Ready to Pumpout Service Pumpout mode: In running status, the purge refrigerant system is running Purge refrigerant compressor relay and the pumpout is disabled. The purge outputs shall have Purge pumpout compressor relay the following status: Exhaust valve relay Purge refrigerant compressor relay...
  • Page 92 A business of American Standard Companies www.trane.com Trane has a policy of continuous product and product data improvement and reserves the right to change For more information contact your local sales office or design and specifications without notice. Only qualified technicians should perform the installation and servicing of equipment referred to in this publication.

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