Desert Aire LW Installation And Operation Manual
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Desert Aire LW Installation And Operation Manual

Wide temperature range dehumidifiers
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• Designed for low
ambient temperatures,
35° to 80°F
• Defrost cycle uses hot
gas defrost to quickly
eliminate frost from
evaporator coils
• Timed defrost cycle
initiated automatically
only when required
• Heat of rejection can
be delivered to the
space or optional
remote condenser
Installation and Operation Manual
LW System

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  • Page 1 35° to 80°F • Defrost cycle uses hot gas defrost to quickly eliminate frost from evaporator coils • Timed defrost cycle initiated automatically only when required • Heat of rejection can be delivered to the space or optional remote condenser LW System...
  • Page 3 TERMS Desert Aire warrants all components (except as noted) for a period of two (2) years from the date of shipment. This warranty shall be limited to the supply of new or rebuilt parts for the part which has failed because of defects in workmanship or material, and does not include the cost for labor, transportation or other costs not herein provided for.
  • Page 4 PH: (262) 946-7400 TOLL FREE: (800) 443-5276 FAX: (262) 946-7401 E-MAIL: service@desert-aire.com Additional copies of this manual can be purchased for a nominal fee from Desert Aire. Submit requests to the contact information listed above. Desert Aire - LW Manual...
  • Page 5 Indicates a potentially hazardous situation which, if not avoided, could result in minor or moderate injury. Caution used without the safety alert symbol indicates a potentially hazardous situation which, if not avoided, could result in property damage. Desert Aire - LW Manual...
  • Page 6 Desert Aire - LW Manual...

  • Page 7: Table Of Contents

    3.2.5 Blower Operation ..................3.3 Refrigeration Testing ....................3.4 General Testing ....................... 3.5 Routine Maintenance Schedule ................3.5.1 Service Every Month ................... 3.5.2 Service Every Six Months ................Troubleshooting ......................4.1 Supply Blower Will Not Run ..................4.2 Compressor Will Not Run ..................4.3 Evaporator Coil Does Not Fully Defrost ..............4.4 Head Pressure is Too High ..................4.5 Unit Runs but Excess Condensate Forms ............4.6 Frost Build-up on the Compressor or Suction Line ..........Desert Aire - LW Manual...
  • Page 8 Appendix ........................... 5.1 Compressor Failure ....................5.1.1 Compressor Replacement ................5.2 Recommended Duct Design .................. 5.3 System Guidelines ....................5.3.1 Unit Airflow ....................5.3.1.1 Determining System Airflow ............5.3.1.2 Blower Adjustment Procedure ............5.3.2 Unit Operation ....................5.3.2.1 Controller Set-Points ..............5.3.2.2 Refrigeration System Pressures ........... 5.4 Component Replacement, Charge, Evacuation, & Leak Instructions ....5.5 Rating Plate ......................5.6 System Start-Up Report ..................Service Bulletin 027 ....................LW Series Start-Up Report ..................LW Series Compressor Replacement Form ............Desert Aire - LW Manual...

  • Page 9: Introduction

    Read these instructions carefully before you install the dehumidifier. Inspection Desert Aire inspects and tests each dehumidifier before it leaves the factory so that you receive a quality piece of equipment. Unfortunately, equipment may become damaged in transit. Inspect the dehumidifier carefully before signing the receiving papers.

  • Page 10: Rigging The Remote Condenser

    Do not tip the dehumidifier on its side. Avoid dropping the unit down stairways or subjecting it to severe mechanical shock. 1.3.2 Rigging the Remote Condenser Refer to separate Remote Condenser Manual for specifications regarding rigging. Desert Aire - LW Manual...

  • Page 11: Installation

    Do not attempt to conserve installation space by fabricating restrictive ductwork with abrupt bends. You may reduce the operating efficiency and the moisture removal capacity of the dehumidifier. See section 2.2 for detailed duct installation instructions. Figure 1 - Typical Floor Installation Desert Aire - LW Manual...
  • Page 12 (see Figure 3 for layout). If you must install the dehumidifier outside, you must use an outdoor-rated dehumidifier. Desert Aire seals and weatherproofs outdoor dehumidifiers to help prevent water infiltration. You can determine whether your dehumidifier is outdoor-rated by inspecting the unit rating plate (see section 5.5 for details).

  • Page 13: Duct Installation

    Select the grilles, registers and diffusers for low static pressure loss, required throw distance and the specified CFM rating. You can find this information in most grille manufacturers’ catalogs. If you are installing the grilles in a corrosive environment, such as an indoor Desert Aire - LW Manual...

  • Page 14: Condensate Drain Piping

    5 feet. A cleanout tee or plug may also be required near the trap to facilitate cleanout. When gravity disposal is not possible, you may use a condensate pump. Follow the pump manufacturer’s installation instructions. Desert Aire - LW Manual...
  • Page 15 2.0” of water. If your return air static exceeds this specification, consult Desert Aire for help in resizing the P-trap. You may also need to install a cleanout tee or plug near the trap. Note that the drain opening in the drain pan is off-center to simplify its cleaning and servicing.

  • Page 16: High Voltage Wiring

    On three phase units the power supply must have 4 connections (3 power, 1 ground). Connect the power supply wires to the main power block located in the upper section of the electrical compartment. Figure 7 - Single-Phase and Three-Phase System Power Connection Desert Aire - LW Manual...

  • Page 17: Wire And Fuse Sizing

    2.5 Controls and Wiring The standard Desert Aire LW Series dehumidifiers are controlled by the CM3540 microprocessor controller. This controller is designed for precise monitoring and control of air temperature and relative humidity (RH) within a conditioned environment. A separate controls manual has been provided.
  • Page 18 0 < 25 1-1/8 33.0 47.5 25 < 50 1-1/8 40.1 54.6 50 < 75 1-3/8 52.4 75 < 100 1-3/8 Figure 9 - Additional Refrigerant Charge (R-407C) and Line Size Required - Quiet Series Desert Aire - LW Manual...

  • Page 19: Start-Up Procedures

    3.1 Preliminary Inspection Verify that all contractors have completed their work. Find the Desert Aire “LW Start-Up Report,” which is normally placed inside this manual within the electrical compartment of the dehumidifier. You must fill out the start-up report to validate the dehumidifier warranty. Check the following items: •...

  • Page 20: System Operation Modes

    3.2 System Operation Modes OPTIONAL O/A Box with 2-Position Damper OPTIONAL Temperature Sensor Humidity Sensor COMPRESSOR Evaporator Coil Hot Gas Reheat Coil Condensate Drain OPTIONAL Remote Condenser Figure 12 - LW Options that Impact System Operation Modes Desert Aire - LW Manual...

  • Page 21: Dehumidification / Air Reheat / Optional Outdoor Air

    See Low Voltage E1 Exhaust Blower Schematic for Details E2 Exhaust Blower Figure 13 - LW Outdoor Operation Mode 3.2.1 Dehumidification / Air Reheat / Optional Outdoor Air When the room air requires dehumidification, the dehumidifier runs in the “reheat” mode. Entering air is dehumidified as it passes over the evaporator coil. The energy absorbed at the evaporator is rejected at the reheat condenser, which warms the dehumidified air.

  • Page 22: Evaporator Defrost Mode

    3.2.3.1 Defrost Cycle Settings The LW series dehumidifier is factory set to run a defrost cycle at 15 timed cycles that are initiated with an evaporating temperature below 30°F. The delay between cycles is set at 30 minutes. The cycle terminated upon temperature rise to 40°F.

  • Page 23: Refrigeration Testing

    This is a critical component to the longevity of the system. Some Desert Aire systems are shipped in sections to allow for installation of some of the sections in a location much different than another. An example is a unit with a remote condenser ready circuit.

  • Page 24: General Testing

    “occupied” signal from the dehumidifier. If you have installed an exhaust blower, make sure that it is interlocked with the “occupied” signal or with an end switch on the outdoor air damper actuator. Desert Aire - LW Manual...

  • Page 25: Routine Maintenance Schedule

    Make sure that the fans cycling switches, which are mounted on the condenser, are correctly piped and have been set according to the Desert Aire condenser wiring diagram. Verify that the fans are blowing air vertically upward when they run.
  • Page 26 Desert Aire - LW Manual...

  • Page 27: Troubleshooting

    Troubleshooting Although Desert Aire dehumidifiers have been designed for reliable and trouble-free operation, you may occasionally encounter a service-related problem. If you cannot immediately diagnose and fix the problem, do not be intimidated by the apparent complexity of the dehumidifier. Your common sense and experience can help you solve the majority of these problems.

  • Page 28: Compressor Will Not Run

    C) Replace compressor. D) Incorrect rotation (reverse phasing) Heat conditioned air to minimum 35°F. NOTE: THE LW SERIES DEHUMIDIFIER IS DESIGNED FOR A MINIMUM Note that heating air will also reduce RETURN AIR TEMPERATURE OF 35°F. If return air temperature drops below relative humidity.

  • Page 29: Evaporator Coil Does Not Fully Defrost

    1) Check coil for kinks in tubing. 2) Evaluate debris in distributor. NOTE: The LW series dehumidifier is NOT intended for use below 32° F ambient air temperatures. Running the system below 32° F will cause safety devices to shut down the unit.

  • Page 30: Head Pressure Is Too High

    Excessive pressure drop in line sets B) Re-evaluate remote condenser installation. NOTE: When the remote condenser is active and the outdoor temperature is above 95°F, normal head pressure can be as high as 300 psig. Desert Aire - LW Manual...

  • Page 31: Unit Runs But Excess Condensate Forms

    Evaluate charge 4.6 Frost Build-up on the Compressor or Suction Line NOTE: Thermal expansion valves on LW series dehumidifiers must be set to maintain a proper superheat at the evaporator. Frost build-up on the suction lines or the compressor can indicate lack of superheat. Lack of superheat will create the damaging possibility of liquid flood back to the compressor which will accelerate failure.
  • Page 32 Desert Aire - LW Manual...

  • Page 33: Appendix

    You must clean the system thoroughly to prevent repeated compressor burnouts. 5.1.1 Compressor Replacement Desert Aire dehumidifiers are designed with scroll compressors. Scroll compressors are known for operating more reliably than other compressors in air conditioning and dehumidification applications due to their ability to cope with occasional periods of liquid refrigerant return.
  • Page 34 A new filter dryer must be installed when the system has been opened. If there is no acid or particulates indicated, the new compressor can be installed and run. Proceed to Testing and Final Diagnosis. Desert Aire - LW Manual...
  • Page 35 Particulate Indicated • Install a replaceable core liquid line filter shell. Note that larger Desert Aire systems will have replaceable core liquid filter shells installed from the factory. The pressure drop levels will be monitored and several core changes may be required.
  • Page 36 Testing and Final Diagnosis It is of critical importance to ensure that the system is operating as expected before unit is returned to normal service. Complete a LW Series Compressor Replacement Form located in the back of this manual. Validation of this report allows for the continued coverage of the compressor under the original warranty.

  • Page 37: Recommended Duct Design

    Undersized or restrictive ducts reduce the system airflow, which can cause premature compressor failure. Use the following diagrams as a guide when you design the duct system. Figure 15 - Recommended Duct Designs for Desert Aire Dehumidifiers Desert Aire - LW Manual...

  • Page 38: System Guidelines

    System Guidelines 5.3.1 Unit Airflow Desert Aire dehumidifiers are designed to operate at a specified airflow rate. System airflow must be checked prior to troubleshooting the refrigeration circuit to assure that such problems are not actually caused by improper unit airflow. Problems with excessive airflow: •...
  • Page 39 UNIT AIRFLOW GUIDELINES Each Desert Aire Dehumidifier is designed to operate at a specified airflow rate. Airflow must be set prior to starting the refrigeration circuit to assure that problems are not caused by improper unit airflow.

  • Page 40: Unit Operation

    • OPERATING PARAMETERS – LW series dehumidifiers are designed to operate in ambient temperatures between 32° and 70°F. Running the system beyond this envelope can lead to a host of problems and possible system failure.

  • Page 41: Component Replacement, Charge, Evacuation, & Leak Instructions

    Desert Aire dehumidifiers have different receiver sizes depending on the model and size. Condenser sizes and configurations may also vary. In general, larger receivers will come equipped with isolation valves that will allow for a portion of the charge to be contained in the receiver during servicing.
  • Page 42 • After completion of all repairs, pressure test system using nitrogen pressure decay test or nitrogen with tracer gas and appropriate leak detector. Desert Aire - LW Manual...
  • Page 43 1000 microns in 10 minutes timeframe. If successful, continue evacuation or check for leaks. It is anticipated that the system was clean and tight from the original process and refrigerant only is Desert Aire - LW Manual...
  • Page 44 Thoroughly test systems to ensure repeat failures do not occur. Note: Compressors supplied with an oil sight glass should be viewed and filled to 75% capacity. Desert Aire - LW Manual...

  • Page 45: Rating Plate

    A copy of the system “Start-Up Report” can be found inside this manual. This report needs to be filled out thoroughly by a qualified service technician and returned to Desert Aire for warranty validation. Please ensure that the model and serial number of the unit are noted on this form. The model and serial number can be found on the system’s rating plate located on or near the electrical compartment...

  • Page 46: Service Bulletin 027

    A CST Start-Up is performed by a local Certified Service Technician who has been trained by Desert Aire. The CST performs all duties of commissioning and also trains responsible parties on the proper maintenance and operation of the unit.
  • Page 47 SERVICE BULLETIN 027 QS / QM / QH / QV / LT / TOTAL AIRE FACTORY START-UP SUPERVISION Desert Aire Corporation • N120 W18485 Freistadt Road • Germantown, WI 53022 • (262) 946-7400 • Fax (262) 946-7401 Please complete and sign this one page document and return it to Desert Aire for start-up scheduling. Dates will be scheduled after this form is received. Please type or print clearly. Unit Information Model # ___________________________________________________________ Serial # ___________________________________________________________...

  • Page 48: Lw Series Start-Up Report

     Before continuing, read the Installation and Operations manual. If you do not fully understand the manual contact the Desert Aire Service Department. Please be prepared with the model and serial numbers located on the rating plate of the unit.
  • Page 49 I/O Manual Additional R407C Added Additional Oil Added Flush Cycle Enabled Fan Cycle Controller Settings – Refer to Air Cooled-Condenser manual for instructions SENS SN-1 SN-2 SN-3 OUTR SENS OUTR SENS OUTR SENS OUTR SENS Desert Aire - LW Manual...
  • Page 50 Suction Pressure Psig Refrigerant Sight Glass Clear Suction Temp at Compressor °F Superheat °F Subcooling °F Compressor Oil Level Sight Glass ½ ¾ (level should be at least 3/4 full at completion of the start up) Desert Aire - LW Manual...
  • Page 51 °F Building Management System Information* Communication Type BACnet MS/TP BACnet Ethernet - Modbus (circle one) Device Instance BACnet MS/TP MAC Address Baud Rate IP Address BACnet Ethernet Netmask Gateway Modbus Baud Rate Address Additional Comments: Desert Aire - LW Manual...

  • Page 52: Lw Series Compressor Replacement Form

      Compressor drawing locked rotor current    (3 phase units)      Runs without pumping: Pressures:  _____  / _____  Other (describe):   Continuity (0 resistance) to Ground on one or more legs    Compressor drawing higher current than design    Continuity (0 resistance) between two or more legs     Compressor drawing locked rotor current    (3 phase units)      Runs without pumping: Pressures:  _____  / _____  Other (describe):   Final Determination of Failure Liquid Floodback    Low Superheat Debris Defective Expansion Valve Low Sump Oil Insufficient Motor Cooling Other (Describe): Diagnostic/Corrective Action Summary Describe what corrective action was taken to prevent a repeat failure.  _________________________________________________________________________________________________ _________________________________________________________________________________________________ _________________________________________________________________________________________________ ________________________________________________________________________________________________ Desert Aire - LW Manual...
  • Page 53 PSIG  PSIG (At access fitting nearest TXV)  Suction Pressure  PSIG PSIG PSIG  PSIG (At compressor)  Liquid Line Temperature  °F °F °F  °F (At access fitting nearest TXV)  Suction Temperature  °F °F °F  °F (At Compressor)  Refrigerant Sight Glass Condition             (Clear, Intermittent Vapor, Flashing) Comp. Oil Level Sight Glass  ½       ¾       F  ½       ¾       F  ½       ¾       F  ½       ¾       F  (Shut down comps., wait 5 minutes)    Desert Aire - LW Manual...
  • Page 54 Optimizing Solutions Through Superior Dehumidification Technology N120 W18485 Freistadt Road • Germantown, WI 53022 • E-mail: info@desert-aire.com Ph: (262) 946-7400 • Fax: (262) 946-7401 • Website: www.desert-aire.com 340 2017/09...

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