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ACS Marvair VDH2024 Installation And Startup

Scholar 2.0 heat pumps & air conditioners
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INSTALLATION AND
START-UP
Models VDH2024-2036-2040
& VAH2030-2048-2060
2 to 5 Ton Cooling Capacity with
2-Stage Compressors
SAFETY REQUIREMENTS
• If the information in these instructions are not
followed exactly, a fire may result causing
property damage, personal injury or loss of
life.
• Read all instructions carefully prior to
beginning the installation. Do not begin
installation if you do not understand any of
the instructions.
• Improper installation, adjustment, alteration,
service or maintenance can cause property
damage, personal injury or loss of life.
• Installation and service must be performed
by a qualified installer or service agency in
accordance with these instructions and in
compliance with all codes and requirements
of authorities having jurisdiction.
• Follow all safety codes.
MODEL NO.: ______________________ SERIAL NO.: _________________
DATE OF START-UP.: _______________
P.O. Box 400 • Cordele, Georgia 31010 • 156 Seedling Drive • Cordele, Georgia 31015
The most current version of this manual can be found at www.Marvair.com.
WARNING
Marvair, An AirX Climate Solutions Brand
(229) 273-3636 • Fax (229) 273-5154
VDH/VAH Heat Pumps &
VDH/VAH Air Conditioners
Manufactured By:
www.Marvair.com
1
Scholar 2.0
Marvair VDH-VDH Scholar 2.0 I&S Manual
Marvair VDH-VDA Scholar 2.0 I&S Manual
10/2024 Rev.1
10/2024 Rev.1

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  • Page 1 Scholar 2.0 VDH/VAH Heat Pumps & VDH/VAH Air Conditioners INSTALLATION AND START-UP Models VDH2024-2036-2040 & VAH2030-2048-2060 2 to 5 Ton Cooling Capacity with 2-Stage Compressors WARNING SAFETY REQUIREMENTS • If the information in these instructions are not followed exactly, a fire may result causing property damage, personal injury or loss of life.
  • Page 2 How To Use This Manual This manual is intended to be a guide to the Marvair VDH/VAH Scholar 2.0 line of vertical packaged heat ® pumps and air conditioners. This manual covers the installation and start-up of the Scholar 2.0 heat pumps and air conditioners, models VDH/VAH, with two stage compressors.

  • Page 3: Table Of Contents

    Failure to comply will result in death or severe personal injury and/or property damage. DANGER Failure to comply could result in death or severe personal injury and/or property damage. WARNING Failure to comply could result in minor personal injury and/or property damage. CAUTION Used to point out helpful info that will result in improved installation, reliability or IMPORTANT...
  • Page 4 Chapter 6: Scholar 2.0 Startup Start-Up Procedure ....................... 71 Chapter 7: Service and Charging/Recovery Safety Precautions ....................... 74 Leak Detection ......................74 Charging Procedures ....................75 Refrigerant Recovery ....................75 Chapter 8: Decommissioning Decommissioning ......................77 ILLUSTRATIONS Figure 1: General External Component Identification and Access to Scholar 2.0 Heat Pump or Air Conditioner ................

  • Page 5: General Description

    Chapter 1: Description & Specifications GENERAL DESCRIPTION The Next Generation Scholar 2.0 VDH and VAH heat pumps and air conditioners from Marvair are modular HVAC systems designed to provide heating, cooling, and outside fresh air for school classrooms. The units are installed in the classroom against an exterior wall. The vertical configuration minimizes the floor space occupied by the HVAC unit. This unique design makes it ideal for both new schools and for renovation of existing classrooms.

  • Page 6: Model Identification

    MODEL IDENTIFICATION The identification numbering system for the Scholar 2.0 heat pump and air conditioner system is shown below. Example Position 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Unit Designation/Family V = Marvair Scholar Classroom Unit D = Dry Bulb Sensor E = Dry Bulb Sensor w/Dirty Filter A = 11 EER Indoor Air Quality...

  • Page 7: Bottom View

    44.13 [1120] 47.04 NOTE: SUPPLY [1195] 44” X 44” WALL SLEEVE IS AN EXAMPLE OF A COMMON SIZE. ACTUAL DIMENSIONS MAY VARY DEPENDING ON PROJECT SPECIFICATIONS. TOP VIEW 44.13 47.38 34.06 [1120] [1203] [865] 13.00 [330] 44.00 [1118] FRESH AIR FRESH AIR 95.63 [2429]...

  • Page 8: Top View

    32.75 TOP VIEW 48.07 1221 24” x 24” x 2” 24” x 24” x 2” Filter Filter 73.54 1868 INTAKE MOTOR LOCATED BEHIND THIS PANEL 2.08 22.09 2.08 RIGHT VIEW FRONT VIEW CONDENSATE DRAIN GREENCUBE (IF REQUESTED), Note: All overall outside dimensions are given with +/- .250”...

  • Page 9: Standard Controls

    STANDARD CONTROLS A. Programmable Logic Controller (PLC) Microprocessor Scholar 2.0 heat pumps and air conditioners use a factory installed PLC microprocessor to control the operation, the safety switches and function options. LED’s show operational status and provide assistance with diagnosis if troubleshooting is ever required. Various control functions are field selectable. The PLC is also capable of communicating to PLC’s in other Scholar units to allow run time leveling and does not require additional equipment installed in the Scholar 2.0...

  • Page 10: Thermostats And Sub-Bases

    factory to allow simultaneous operation upon a call for electric heat from the system thermostat. Electric heat will only operate: 1. Upon call from thermostat 2. When outdoor thermostat threshold is reached, if installed 3. Or during defrost when set to operate For non-simultaneous operation, navigate to “Option Selection”...

  • Page 11: Optional Controls

    4. MAR8000 thermostat. See Product Data Sheet for complete description.5. The direct digital control (DDC) interfaces with the building automation system (BAS) is to be defined by the specifier, in consultation with the Marvair ® sales representative. Marvair will factory install the DDC sent by the DDC manufacturer, and purchased by the customer. B.

  • Page 12: Chapter 2: Scholar 2.0 Installation

    Chapter 2: Scholar 2.0 Installation TOOLS/FIELD FURNISHED SUPPLIES WARNING TO AVOID PERSONAL INJURY, ADEQUATE PROTECTIVE CLOTHING MUST BE WORN AND PRECAUTIONS IN HANDLING AND INSTALLING THIS EQUIPMENT MUST BE PRACTICED AT ALL TIMES. • Power Drill/Driver & Extension • T25 TORX Bits •...

  • Page 13: Pre Checks

    WARNING DO NOT STACK THE UNIT OR ANY ACCESSORIES ON TOP OF ONE ANOTHER. THE UNITS SHOULD ALWAYS REMAIN IN THE UPRIGHT POSITION WHEN BEING SHIPPED, STORED, HANDLED OR INSTALLED. DO NOT STORE THE UNIT OR ACCESSORIES IN OUTDOOR WEATHER CONDITIONS. WARNING THE SCHOLAR 2.0 UNIT WEIGHS IN EXCESS OF 1,000 LBS.

  • Page 14: Location Selection And Preparation

    2.4 LOCATION SELECTION AND PREPARATION WARNING THE SCHOLAR 2.0 HEAT PUMP AND AIR CONDITIONER MUST BE INSTALLED IN CONFORMANCE WITH ALL APPLICABLE LOCAL AND NATIONAL ELECTRICAL, PLUMBING AND BUILDING CODES. A. The Scholar 2.0 heat pump and air conditioner must be installed on an outside wall for access to outside air.

  • Page 15: Power And Control Wiring (Rough-In)

    Scholar Heat Pumps VDH2024H VAH2030H VDH2036H VDH2040H VAH2048H VAH2060H Minimum Room Size (ft²) 157.1 166.9 196.4 196.4 206.2 216.0 Minimum Supply Height (ft) Scholar Air Conditioners VDH2024A VAH2030A VDH2036A VDH2040A VAH2048A VAH2060A Minimum Room Size (ft²) 157.1 166.9 196.4 196.4 206.2 216.0 Minimum Supply Height (ft)

  • Page 16: Condensate Drain Line (Rough-In)

    through the bottom or rear. The locations of the knockouts for power leads are shown in Figure 3. Depending on the location of the Scholar 2.0 heat pump or air conditioner relative to the outside wall, the exact rough-in location for power lines in the school room can be determined.
  • Page 17 C. To facilitate moving the Scholar through doors, the out door air box can be removed. To remove the outdoor air box, remove the 16 screws - 6 on each side and 4 along the top. Remember to reinstall the outdoor air box before placing the Scholar into its final position in the classroom.

  • Page 18: Assembly/Disassembly Instructions

    I. After measuring for correct locations of power/control wiring entry, condensate drain line, and the appropriate wet heat lines, remove the appropriate knock-out access ports from the cabinet. Be sure they align with the rough-in points for the noted pipes and wires. Be sure electrical, condensate and wet heat piping will not cause interference or be damaged by sliding the Scholar 2.0 heat pump or air conditioner into place.
  • Page 19 REVISIONS ECO# DATE REV. DESCRIPTION C. To remove the external side panel, first remove the 3 sheet metal secure screws located along the bottom edge of each side panel. Note: the securing screws should only be removed after the front doors are removed. MAT'L: -NA- With a firm grip on the edge of the panel, slightly swing the panel away from the unit Last DESCRIPTION ECO # REV DATE while you lift and pull the panel away from the guide flange. This drawing contains confidential information of Marvair, a Division of AIRXC information is not to be disclosed or utilized without the expressed written per Marvair, a Division of AIRXCEL, Inc.
  • Page 20 ALIGN THE THREE SCREWS HOLES AT THE TOP OF THE SIDE PANEL WITH THE THREE SCREW HOLES ON THE TOP PANEL AND SCREW IN PLACE D. Remove the screws securing the electrical panel covers. MATERIAL DRAWN 2020-10-0 TOLERANCES DRAWN BY This drawing contains confidential (EXCEPT AS NOTED) information of Marvair, a Division of...
  • Page 21 E. After removing the interior panel cover, disconnect the wiring to the blower assembly and the four wires to the transformer. Marvair VDH-VDA Scholar 2.0 I&S Manual 10/2024 Rev.1...
  • Page 22 F. Disconnect the condensate drain tube. G. Remove screws to separate upper and lower sections. Marvair VDH-VDA Scholar 2.0 I&S Manual 10/2024 Rev.1...
  • Page 23 H. Using a mechanical lifting device, separate upper and lower sections. I. After installation of the Scholar unit, install the duct flanges and side panel grommets. Scan this QR code to view a brief video demonstration of the Scholar unit separation procedure. Marvair VDH-VDA Scholar 2.0 I&S Manual 10/2024 Rev.1...

  • Page 24: Wall Sleeve Field Assembly Steps

    IMPORTANT TO SEPARATE SYSTEM, THE FRONT DOORS, EXTERNAL SIDE PANELS AND PANEL THAT COVERS THE FORKLIFT AISLES MUST BE REMOVED ON BOTH SIDES. 2.10 WALL SLEEVE FIELD ASSEMBLY STEPS 1. Assemble wall sleeve sides to wall sleeve bottom 2. Assemble wall sleeve top to wall sleeve sides 3.
  • Page 25 STEP 7: MOUNT BLOCKOFF PLATE TO TOP DIVERTER STEP 7: MOUNT BLOCKOFF PLATE TO TOP DIVERTER S/12893 S/12877 S/12893 S/12877 Item # Part # Description SMV15003X WALL SLEEVE BOTTOM C:\Marvair EPDM Vault\Shared\VDA2036-48_Gen2021\Snout Assy\VDA SNOUT ASSY Draw1 SMV15007X WALL SLEEVE LH/RH SIDE C:\Marvair EPDM Vault\Shared\VDA2036-48_Gen2021\Snout Assy\VDA SNOUT ASSY Draw1 SMV15013X...

  • Page 26: Installation Through The Outside Wall

    2.11 INSTALLATION THROUGH THE OUTSIDE WALL A. Slide the Scholar 2.0 heat pump or air conditioner into the wall opening slowly, being careful to clear the appropriate stubouts. The heat pump or air conditioner, when installed properly, should have a clearance between the air box outside edge and the finished outside wall as shown in Figure 4. Proper fit up of the louver/collar assembly to the air box to the outside wall requires the noted recess dimension to be maintained after installing the unit.

  • Page 27: Condensate Float Switch Functional Check

    2.12 CONDENSATE FLOAT SWITCH FUNCTIONAL CHECK A float switch comes standard in all Scholar HVAC units. It is used to manage condensation in both the evaporator and the condenser drain pans. In normal operation, the float switch is closed. In the event condensation levels in drain pan become too high, the float switch opens to terminate the heating, cooling or dehumidification process. After installation of the HVAC unit, a functional check is required to verify that the operation of the float switch was not compromised in transit or installation. “ STEPS TO TEST FLOAT SWITCH: A.
  • Page 28 B. Be sure that the power to the line voltage wiring is off prior to hooking-up the wiring within the Scholar 2.0 cabinet. Remove the lower front panel for access to the disconnect. Figure 5 illustrates the disconnect location with the lower front panel removed.

  • Page 29: Remote Thermostat Installation

    2. Route wires into the terminal strip compartment through the openings provided. Connect wiring to the terminal strip as shown in Figure 9 for a remote, wall mounted thermostat installation. 2.14 REMOTE THERMOSTAT INSTALLATION A. Locate the thermostat about five feet above the floor on an inside wall. Avoid the following: Hot Spots Cold Spots Dead Spots Concealed Pipes or Duct Concealed Pipe or Ducts...

  • Page 30: Figure 6A: Remote Wall Mounted Thermostat Wiring Detail

    Figure 6a. Remote Wall Mounted Figure 6b. Remote Thermostat w/Humidity Thermostat Wiring Detail Controller Wiring Detail C. For Scholar 2.0 heat pump or air conditioner that interfaces with a building automation system (BAS) or energy management system (EMS), detailed instructions for the specific system being installed will be supplied separately by the manufacturer of the BAS/EMS system.

  • Page 31: Figure 7: Ems Wiring Detail

    E. For models with an internal thermostat, no internal control wiring is required. The thermostat is preprogrammed at the factory to maintain a heating mode temperature of 64°F, and a cooling mode temperature of 82°F. To change these settings refer to the directions in installation instructions for the thermostat. F.

  • Page 32: Figure 8: Ventilation Controls Wiring Detail

    EMERGENCY VENTILATION SYSTEM INSTRUCTION FOR CUSTOMER VENTILATION CONTROL EMERGENCY VENTILATION SYSTEM INSTRUCTION FOR CUSTOMER VENTILATION CONTROL CUSTOMER PROVIDED CONTACT FOR EMERGENCY CUSTOMER PROVIDED VENTILATION CONTROL CONTACT FOR EMERGENCY VENTILATION CONTROL CUSTOMER PROVIDED WIRE CUSTOMER PROVIDED WIRE CONNECT 24V R CONNECT 24V R CONNECT TO VENT CONNECT TO VENT TERMINAL BLOCK...

  • Page 33: Figure 9B: Typical Control Center Layout For 3-Phase Scholar 2.0

    ITEM NO. PART NUMBER DESCRIPTION QTY. SMV16001X VDA CONTROL BOX MB03071-ADP BREAKER STAND, 208/230 03198 PLC DISPLAY 28 I/OS EHTERNET M172 MODBUS 70888_A 15 AMP 3PH BREAKER 50040 30AMP 3PHASE CONTACTOR 82015 TERMINAL STRIP VERNITRON W/8 LUG STAB 91092 GROUND LUG 80812A TERMINAL STRIP VERNITRON A1 A2 40VA 50_60 HZ...

  • Page 34: Chapter 3: Scholar 2.0 Calibration, Controls & Hmi Operation

    Chapter 3: Scholar 2.0 Calibration, Controls & HMI Operation VENTILATION SYSTEM CALIBRATION Prior to start-up of the Scholar 2.0 heat pump or air conditioner, the ventilation system requires calibration to ensure the appropriate amount of fresh air is delivered to the classroom. Refer to the appropriate following ventilation system and use the instructions to calibrate the system for correct air delivery.

  • Page 35: Plc Control Adjustments

    Fresh Air Ventilation Points Test # Intake Vent Motor % Airflow Measure (CFM) Airflow Measurement (CFM) vs Intake Vent Motor Setting (%) C. GreenCube® ERV. Using best industry standards and practices, measure the fresh air that is being brought into the classroom. For units with one speed controller (std.), adjust the speed of the intake and exhaust blowers by inserting a slotted screw driver into the opening on the controller.

  • Page 36: Table 3: Led Function And Colors

    The keys can be programmed from the controller application. In the following table are described the keys default setting (keys are configurable through the logic controller. Each control can be adjusted by using the directional buttons. Note: In “Edit Mode”, the cursor flashes under the value that is going to be modified by the user. No. Key Press Once (press and release) • Scroll Up •...
  • Page 37 C. Adjusting Control Speed Parameters Use the right or left arrow key to navigate to the “Control Speed Settings” screen. STEP 1. Use the Up/ Down arrow key to make your selection. STEP 2. Press “OK” key to enter, then use the Up/ Down key to change first the value. STEP 3. Then use the Left/ Right key to go to the next value. STEP 4.
  • Page 38 E. Adjusting Exhaust Motor Timer The exhaust motor timer is to adjust the time it takes to Vent (ventilation) output to energized which will then send 24VAC to the exhaust motor relay coil. The default time is 2 seconds, which can be changed from 2, 5 and 10 seconds. Note: Because the times are preset values, the time cannot be manually changed to a undefined value.
  • Page 39 The PLC inputs are powered only by 24 VAC. The thermostat inputs are: • G - Blower signal from thermostat • Y - Compressor • W2 - Second stage heat (heat pump function only) • O - Reversing valve (energized for cooling) (heat pump function only) •...
  • Page 40 H. PLC Outputs An output is a signal from the PLC to the Scholar 2.0 heat pump or air conditioner or thermostat. All digital outputs on the PLC are 24V. These outputs are: • OAM - Outdoor Air Motor (Fresh air motor for the GreenCube ERV) •...
  • Page 41 ASCT, the Compressor Contactor (CC), Reversing valve (RVS) and Y2 solenoid for full capacity display “on” on the PLC HMI output screen. The Indoor Blower Motor (IBM) and Outdoor Fan Motor (OFM) output speed will display the percentage value for their current speed on the PLC HMI output screen. The Output indicate that the PLC is sending a signal to the devices’...
  • Page 42 When the system has been operating in the heat pump mode for a period of time (set by the Defrost Timer), the system will examine the Defrost Control thermostat Input (DFC). If this input is on (the thermostat is closed), indicated by Output being on, the system will go into Defrost mode based on the defrost time default = 30min (30, 60 &...
  • Page 43 N. OFM Head Pressure Control Modulating Head Pressure Control (ECM Outdoor Motors) – A10K Nominal NTC sensor is secured to the liquid line of the system to monitor the liquid line temperature and is connected to analog input 8 (AI.8). The thermistor value is used as the process variable when controlling the head pressure.
  • Page 44 O. Economizer And Ventilation Control Scholar 2.0 are 2 stage units and Scholars with PLC and economizer option installed should use a 2 stage thermostat, to bring on Y2. If outside conditions are favorable the economizer will run to utilize “free” cooling. If the outside conditions are not favorable 1st stage mechanical cooling will operate.
  • Page 45 P. Outdoor Sensor Type • NTC Sensor used for Dry bulb only • Temp/Hum 4 wire sensor used for Enthalpy sensor only Q. Defrost Timer (DFT) (heat pump function only) Located on the “Preset Timer” screen. The defrost control is based upon both time and temperature.
  • Page 46 T. Troubleshooting The PLC is a microprocessor-based system that has the ability to provide a great amount of information to aid in troubleshooting a malfunctioning system. With the Input and Output screen user can easily diagnose most problem by just seeing what is on and or what is off.
  • Page 47 1. Outdoor Thermostat (heat pump only). Factory set at 40°F, this thermostat determines the outdoor temperature at which the supplemental electric heat or wet heat turns on. This may be field adjusted to the desired temperature setting by changing the settings on the PLC option selection screen. Marvair VDH-VDA Scholar 2.0 I&S Manual 10/2024 Rev.1...

  • Page 48: Chapter 4: Scholar 2.0 Networking And Remote Communication

    Chapter 4: Scholar 2.0 Networking and Remote Communication BACNET INFORMATION This section serves as a reference for the BACnet Information on the VDH units. Below are all the Analog and Boolean points that are Read/ Write and Read only. BACnet device ID & IP address can be configured over BACnet network or locally on the PLC screen to address multiply units over BACnet network.

  • Page 49: Ethernet Port

    3. Architecture Wiring Examples. The following diagram shows an RS-485 (field) architecture wiring example: 4. Communication Settings. Modbus/BACnet ID, PLC address and RS-485 port 1 and port 2 settings. 4.3 ETHERNET PORT 1. Overview. Each TM172P••••• controller is equipped by an RJ45 Ethernet port. To access the RS485-1 and RS485-2 screen, press and hold the right arrow key then press the right arrow key again for the next screen.
  • Page 50 Main Web functionalities: • Web-based access. • Remote reading and support. • Local and remote system control, including alarms management. • Preventive and predictive maintenance. • Email alarm alerts. Care must be taken and provisions made for use of this product as a control device to avoid inadvertent consequences of commanded machine operation, controller state changes, or alteration of data memory or machine operating parameters.
  • Page 51 Status LED. RJ45 Ethernet Status LED Label Signal Color Status Description No Link Ethernet Link Green/Yellow Yellow On Link at 10Mb Green On Link at 100Mb No Activity Ethernet Activity Green Flashing Activity Operation Guide Scan this QR Code for the full PLC Operation Guide Marvair VDH-VDA Scholar 2.0 I&S Manual 10/2024 Rev.1...

  • Page 52: Chapter 5 Optional Electronic Control Board

    Chapter 5 Optional Electronic Control Board Introduction WARNING FAILURE TO OBSERVE THE INSTRUCTIONS CONTAINED IN THIS DOCUMENT MAY RESULT IN PERSONAL INJURY AND/OR PROPERTY DAMAGE AND MAY VOID THE WARRANTY. READ THIS MANUAL BEFORE INSTALLING, REPLACING OR USING THIS PRODUCT. Marvair’s proprietary Printed Circuit Board (PCB) sets the standard for the industry in flexibility, reliability and performance. This UL certified component is engineered to optimize Heating, Cooling and Dehumidification operation while communicating valuable...

  • Page 53: Installation And Replacement

    I/O Table for Control Board Item Description Economizer Actuator Output 2-10 VDC Outdoor Motor Control Output 0-10 VDC or PWM Indoor Motor Control Output 0-10 VDC or PWM Enthalpy Sensor Signal Input 4-20mA Outdoor Sensor Signal 10K NTC (Heat Pumps) / Dry Bulb Sensor Signal Input 10K NTC (Systems Equipped with Dry Bulb Economizer) Supply Air Sensor Signal Input 10K NTC (Systems Equipped with Economizer) Defrost Sensor Signal Input 10k NTC (Heat Pumps Only)
  • Page 54 5.3.1 – Programming Menu Configuration 1. To Enter Programming Mode: • Press and hold the Menu button for 5 seconds until P-01 is displayed. 2. While in Programming Mode main menu: • Press the Menu button to enter the displayed parameter menu. •...
  • Page 55 Configuration Menu Details 1. System Type: This setting allows the PCB to be configured for AC (air-conditioner) or HP (heat-pump). The system type is configured at the factory during production testing for the appropriate system type. The default system type is AC. 2. IBM Select: This setting allows the IBM (Indoor Blower) control signal to be configured for PWM or 0-10vdc control. The default control output signal is PWM. 3. Fan Purge: This setting allows the delay off time of the indoor blower once the call for the indoor blower has been removed.
  • Page 56 11. SCKT Set: The SCKT setting is used to prevent simultaneous operation of the electric heat and compressor. The selections for the SCKT Set are Y (yes) or N (no). When set to N (no, Default) the electric heat will be allowed to operate with the compressor in heat-pump mode upon a call for W2 (auxiliary / emergency heat).

  • Page 57: Operation

    18. Dehum Speed: This is an independent setting for the speed at which the Indoor blower will operate upon a request for HUM (Dehumidification) via Digital Input or MODBUS. The default setting for the Dehum speed is 80% of maximum speed. The speed may be adjusted from 60-100% in 1% increments to meet desired airflow requirements. 19. Pulse Reheat: This setting allows the dehumidification output “RH” to be cycled On and OFF based on the Dehum Supply temperature setpoint. The Options are Y= Yes or N= No and the default is Y.

  • Page 58: Sequence Of Operation

    Communication The Marvair PCB comes equipped the Modbus communications standard. There are 2 adjacent RJ11 Modbus communication ports connected in parallel. That is, both ports transmit the same information. The board allows you to set the Baud Rate at 9600 bits per second or 19200 bits per second.
  • Page 59 7.0 Additional Features Modulating Head pressure Control (ECM Outdoor Motors) Emergency Ventilation Forced Cooling Modbus Communications Low Voltage (Brownout) 8.0 Smoke / Fire Shutdown System Shutdown Contact Wiring Note: Equipment, devices and necessary system components are specified in the respective section. Note: 1. All inputs on the control board go through a 5 seconds Time-On Delay to prevent nuisance request.
  • Page 60 the event that there is a request for all operations or a combination of operations. The controller will NOT energize the compressor outputs and the heater output simultaneously if configured for AC. The controller WILL energize the compressor outputs and the heater output simultaneously if configured for HP. The speed at which the Indoor Fan Operates during Stage 1 (Y1) and Stage 2 (Y2) Cooling Request can be set directly at the board using the configuration menu settings 4 and 5. All requests are interlocked with the Indoor Fan and will run the Fan at the respective speed associated with the operation.
  • Page 61 2.1.2 Y1 and Y2 Cooling (Full Capacity 2nd Stage) – If the space temperature continues to increase pass the defined differential, Stage 2 Cooling (Y2- input) is energized. Under normal operation, this energizes the Compressor 2 Output (CC2). The Indoor Fan motor, will operate at “Y2” speed instead of “Y1”...

  • Page 62: Figure 12: Enthalpy Sensor And Temperature Control Points

    “Y1” speed since Y2 has higher priority. These outputs remain energized until the cooling setpoint is satisfied. Once the setpoint is satisfied, the Compressor and the Outdoor fan outputs are de-energized. The Indoor motor continues to run based on the fan purge timer setpoint (default 90 seconds) selected in setting 3 of the configuration menu of the control board. Note: 2 Stage compressors require a request for Y2 to operate at full capacity in Cooling operation.

  • Page 63: Figure 13: Dry Bulb Sensor

    Enthalpy Operation On a call for cooling from the wall-mounted thermostat, if outdoor conditions are suitable, the sensor will open the damper and admit outside air (i.e., economizer free cooling). If the outdoor ambient is too hot or humid (enthalpy sensor only), the sensor will place the actuator in the closed or minimum open position and activate mechanical cooling.
  • Page 64 3.3 Supply Air Sensor – The supply air sensor is a 10K NTC sensor probe mounted on a bracket in the supply air opening of the system. The probe senses the air temperature entering the structure, and provides a signal to the economizer controller for modulating the position of the damper.
  • Page 65 4.3 Defrost Operation (Heat Pump Systems Only) – The board has an integral accumulation run timer that runs on every request for heat pump heating. The system has a Defrost Sensor (DS) that monitors the outdoor coil circuit for freezing conditions.
  • Page 66 SCKT – Safety Circuit (Heat-Pumps Only) The SCKT is a selectable menu option in the control board configuration menu setting 10. The options for this feature are Y=Yes or N=No. When set to Y=Yes, control board will prevent the compressor and electric heat from operating simultaneously. In this case the compressor will shut off upon a request for “W2” (Electric Heat). The compressor will remain off as long as the request for W2 is active.
  • Page 67 electric heat to allow heat to be introduced into the supply air stream of the system for dehumidification operation. The indoor fan motor will operate at the “Dehum” speed setting on the board or via Modbus. The indoor fan remains on continuously but the outdoor fan modulates based on liquid line temperature. The Fan Cycle Control Sensor (Low Ambient Control Sensor) monitors the liquid line to maintain a 90F liquid line temperature.
  • Page 68 only be active when the Low-Pressure Switch (Normally Closed) opens during a request for Cooling. The first time this fault condition occurs, the system cuts the compressor off WITHOUT locking out. Once the pressure normalizes (rises above 105 PSI), the system will resume operation if the cooling call still exist. If this fault occurs a second time on the same Cooling request, the system locks out.
  • Page 69 6.5 Anti-Short Cycle – This is a built-in protection mechanism that increases the reliability of the compressor by protecting it from excessive short cycling. When the compressor goes off, due to any fault, emergency or if the cooling / heat pump heating setpoint is satisfied, a built-in 3-minute timer locks the compressor for that respective circuit out.
  • Page 70 seconds the control board will de-energize all outputs. This is considered a voltage brownout (low voltage) condition and the display of the control board will show “03” as an indicator of brownout (low voltage). When the voltage rises back to 17 VAC, the control board will allow the system to operate.

  • Page 71: Chapter 6: Scholar 2.0 Startup

    Chapter 6: Scholar 2.0 Startup 6.1 START-UP PROCEDURE CAUTION THIS UNIT CONTAINS A CRANKCASE HEATER (CCH). FAILURE TO FOLLOW INSTRUCTIONS REGARDING THE CCH AND STARTUP WILL VOID THE MANUFACTURER’S WARRANTY. Note for Scholar 2.0 units manufactured after 12/05/2022: Crankcase heaters (CCH) help to prevent refrigerant migration in the off cycle of the compressor, which prevents oil dilution in the compressor.

  • Page 72: Table 4: Voltage Limitations

    2. Set the remote thermostat system switch to “OFF” position. The blower switch should be in “AUTO” position. 3. Check the voltage supply to the disconnect. If voltage readings are appropriate, proceed with start-up. (See Figure 13 for acceptable voltage ranges.) If voltage readings are not appropriate, check the power leads at the disconnect and the main breaker in the mechanical room.
  • Page 73 8. Automatic Changeover For an automatic changeover remote thermostat, the proper functioning of the system can be checked for cooling and heating by using the same sequence as detailed above with the thermostat system switch put in “AUTO” position. 9. Emergency Heat (heat pump version only) This setting on a remote thermostat is to provide electric heat in the event the compressor does not function, and heat is required.

  • Page 74: Chapter 7: Service And Charging/Recovery

    Chapter 7: Service and Charging/Recovery 7.1 SAFETY PRECAUTIONS SERVICE Prior to beginning work on systems containing FLAMMABLE REFRIGERANTS, safety checks are necessary to ensure that the risk of ignition is minimized. For repair to the REFRIGERATING SYSTEM, the following shall be completed prior to conducting work on the system.

  • Page 75: Charging Procedures

    also suitable for use with most refrigerants but the use of detergents containing chlorine shall be avoided as the chlorine may react with the refrigerant and corrode the copper pipework. Note: Examples of leak detection fluids are 1. Bubble method 2. Fluorescent method agents If a leak is suspected, all naked flames shall be removed/extinguished. If a leakage of refrigerant is found which requires brazing, all of the refrigerant shall be recovered from the system, or isolated (by means of shut off valves) in a part of the system remote from the leak.
  • Page 76 5. The REFRIGERANT CHARGE shall be recovered into the correct recovery cylinders. For appliances containing FLAMMABLE REFRIGERANTS other than A2L REFRIGERANTS, the system shall be purged with oxygen-free nitrogen to render the appliance safe for FLAMMABLE REFRIGERANTS. This process may need to be repeated several times.

  • Page 77: Chapter 8: Decommissioning

    Chapter 8: Decommissioning 8.1 DECOMMISSIONING Before carrying out this procedure, it is essential that the technician is completely familiar with the equipment and all its details. It is recommended good practice that all refrigerants are recovered safely. Prior to the task being carried out, an oil and refrigerant sample shall be taken in case analysis is required prior to re-use of recovered refrigerant.

  • Page 78: Appendix A - Wiring Diagrams

    APPENDIX A - WIRING DIAGRAMS Fig 1. Typical Wiring Schematic for 2T-5T A/C | 230V 1-Phase w/PLC Marvair VDH-VDA Scholar 2.0 I&S Manual 10/2024 Rev.1...
  • Page 79 Fig 2. Typical Wiring Schematic for A/C | 230V 3-Ph Power w/PLC Marvair VDH-VDA Scholar 2.0 I&S Manual 10/2024 Rev.1...
  • Page 80 Fig 3. Typical Wiring Schematic for A/C | 460V 3-Phase w/PLC Marvair VDH-VDA Scholar 2.0 I&S Manual 10/2024 Rev.1...
  • Page 81 Fig 4. Typical Wiring Schematic for HP | 230V 1-Phase w/PLC Marvair VDH-VDA Scholar 2.0 I&S Manual 10/2024 Rev.1...
  • Page 82 Fig 5. Typical Wiring Schematic for HP | 230V 3-Phase w/PLC Marvair VDH-VDA Scholar 2.0 I&S Manual 10/2024 Rev.1...
  • Page 83 Fig 6. Typical Wiring Schematic for HP | 460V 3-Phase w/PLC Marvair VDH-VDA Scholar 2.0 I&S Manual 10/2024 Rev.1...
  • Page 84 Fig 7. Typical Wiring Schematic for 2T-5T A/C | 240V 1-Phase w/PCB Marvair VDH-VDA Scholar 2.0 I&S Manual 10/2024 Rev.1...
  • Page 85 Fig 8. Typical Wiring Schematic for 2T-5T A/C | 240V 3-Phase w/PCB Marvair VDH-VDA Scholar 2.0 I&S Manual 10/2024 Rev.1...
  • Page 86 Fig 9. Typical Wiring Schematic for 2T-5T A/C | 460V 3-Phase w/PCB Marvair VDH-VDA Scholar 2.0 I&S Manual 10/2024 Rev.1...
  • Page 87 Fig 10. Typical Wiring Schematic for 2T-5T Heat Pump | 240V 1-Phase w/PCB Marvair VDH-VDA Scholar 2.0 I&S Manual 10/2024 Rev.1...
  • Page 88 Fig 11. Typical Wiring Schematic for 2T-5T Heat Pump | 240V 3-Phase w/PCB Marvair VDH-VDA Scholar 2.0 I&S Manual 10/2024 Rev.1...
  • Page 89 Fig 12. Typical Wiring Schematic for 2T-5T Heat Pump | 460V 3-Phase w/PCB Marvair VDH-VDA Scholar 2.0 I&S Manual 10/2024 Rev.1...

  • Page 90: Appendix B - Ratings And Data

    APPENDIX B - RATINGS AND DATA 1.01 RATINGS / DATA AIR FLOW CFM ESP (WET COIL) BASIC MODEL 0.10 0.15 0.20 0.30 0.40 0.50 VDH2024 ––– ––– VDH2036 1380 1340 1290 1200 ––– ––– VDH2040 1380 1340 1290 1200 ––– –––...

  • Page 91: Appendix C - Base Stand Installation

    APPENDIX C - BASE STAND INSTALLATION 1.01 TOOLS/FIELD FURNISHED SUPPLIES WARNING TO AVOID PERSONAL INJURY, ADEQUATE PROTECTIVE CLOTHING MUST BE WORN AND PRECAUTIONS IN HANDLING AND INSTALLING THIS EQUIPMENT MUST BE PRACTICED AT ALL TIMES. • Power Drill/Driver and Extension •...

  • Page 92: Installation

    HOLES TO SECURE BASE STAND TO FLOOR HOLES TO SECURE SCHOLAR 2.0 STAND TO BASE STAND Figure 1. Top View of Base Stand Also, recheck the locations of the electrical and condensate stub-outs to ensure they are located properly, relative to the cabinet knock-out openings as shown in the Installation and Start-Up Manual, Figures 3 and 4.
  • Page 93 WARNING WHEN MOVING/RAISING THE SCHOLAR 2.0 CABINET, UTILIZE ADEQUATE RESOURCES TO HANDLE THE 1,100 LB. CABINET. THIS IS TO AVOID PERSONAL INJURY OR DAMAGE TO THE EQUIPMENT/FACILITIES. With appropriate resources to lift the Scholar 2.0 unit, place it on the base stand while guiding the air box through the wall opening and maintaining clearance between the plenum (as appropriate) and the ceiling.

  • Page 94: Appendix D - Installation Of The Freeblow Plenum

    APPENDIX D - INSTALLATION OF THE FREEBLOW PLENUM 1.01 TOOLS/FIELD FURNISHED SUPPLIES WARNING TO AVOID PERSONAL INJURY, ADEQUATE PROTECTIVE CLOTHING MUST BE WORN AND PRECAUTIONS IN HANDLING AND INSTALLING THIS EQUIPMENT MUST BE PRACTICED AT ALL TIMES. • Power Drill/Driver and Extension •...

  • Page 95: Plenum Installation

    1.03 PLENUM INSTALLATION 1. Prior to mounting the plenum on top of the Scholar 2.0 unit, remove the front panel from the plenum. Retain the screws (red arrows) for reinstallation after the plenum has been installed. 2. On the top panel of the Scholar 2.0 unit, locate the 6 holes that correspond with the six mounting holes in the plenum.
  • Page 96 The air distribution system which is field supplied and installed downstream of the specified ducted plenum must be engineered to assure sufficient air flow, even under adverse conditions, such as dirty filters. The information provided in Figure 1, Appendix A should be used to design the air distribution system duct size leaving the Scholar 2.0 unit, keeping the external static pressure to a minimum. Applications using duct work should be designed and installed in accordance with the current edition of the National Fire Protection Association codes and standards 90A and 90B. The duct system must be engineered to insure sufficient air flow through the unit to prevent over-heating of the heater element.

  • Page 97: Appendix E - Trim Strip Installation

    APPENDIX E - TRIM STRIP INSTALLATION 1.01 TOOLS/FIELD FURNISHED SUPPLIES WARNING TO AVOID PERSONAL INJURY, ADEQUATE PROTECTIVE CLOTHING MUST BE WORN AND PRECAUTIONS IN HANDLING AND INSTALLING THIS EQUIPMENT MUST BE PRACTICED AT ALL TIMES. • Power Drill/Driver and Extension •...

  • Page 98: Appendix F - Outdoor Louver/Collar Installation

    APPENDIX F - OUTDOOR LOUVER/COLLAR INSTALLATION 1.01 TOOLS/FIELD FURNISHED SUPPLIES WARNING TO AVOID PERSONAL INJURY, ADEQUATE PROTECTIVE CLOTHING MUST BE WORN AND PRECAUTIONS IN HANDLING AND INSTALLING THIS EQUIPMENT MUST BE PRACTICED AT ALL TIMES. • Power Drill/Driver and Extension •...
  • Page 99 The Scholar 2.0 heat pump or air conditioner should be installed following the instructions in this manual. After installation, the Scholar 2.0 air box should be from 1-1/4” to 1-3/8” from the outside surface of the finished wall, as shown in Figure 1. FREEBLOW PLENUM DISTANCE (INCHES) BETWEEN AIR BOX AND OUTSIDE FINISHED WALL LOUVER/COLLAR SCHOLAR V™...
  • Page 100 IMPORTANT BE SURE AIR BOX IS PLACED 1-3/8” TO 1-1/2” INSET FROM OUTSIDE WALL SURFACE. USE LOUVER/COLLAR SCREWS THAT ARE COMPATIBLE WITH THE COLOR OF THE COLLAR. NOTES: 1. The louvers come in three different configurations depending on mounting requirements: (#1) is the louver with collar, (#2) is the louvered grille without collar and (#3) is the collars.

  • Page 101: Appendix G - Startup & Commissioning Checklist

    APPENDIX G - STARTUP & COMMISSIONING CHECKLIST Please complete the information on this form and email to MarvairCustServ@airxcs.com. Date: _____/_____/_______ A. Owner & Location Equipment Owner: _________________________________________________________ Address: _________________________________________________________ City: _________________________________________________________ State: _______ , Zip: ___________ B. Installing Contractor Company: ________________________ Installer: _________________________ Address: ________________________________________________________ City: ________________________________________________________ State: _______ , Zip: ___________...

  • Page 102: Starting Unit

    E. Check Incoming Power at Terminal Block and verify Proper Voltage and Balance BEFORE STARTING UNIT. ❒ 208/230V 1 Phase 60 Hz. ❒ 208/230V 3 Phase 60 Hz. ❒ 460V 3 Phase 60 Hz. ❒ 380V 3 Phase 50Hz. ❒ 575 3 Phase 60 Hz. ❒...
  • Page 103 F. Cooling Mode (Mechanical Cooling) Close the Compressor (Cooling) circuit breaker. Power will be applied to the thermostat / control device. Setup / Configure the control for the desired settings. Adjust the cooling setpoint so there is No demand for cooling. The unit will not be running. Cooling Start If using a standard thermostat, Set the Control to ON, Mode to Cooling, Fan to Auto (other con- trols, set appropriately for cooling mode).
  • Page 104 Cooling (Check and Record Readings) After about 10 minutes of operating in the cooling mode, check and record the following data points. Inside Temperature (IAT) ºF Outside Temperature (OAT) ºF Entering Condenser Air Temperature (Should be same temp as OAT) ºF Leaving Condenser Air Temperature (Acceptable Range 15º...
  • Page 105 Electric Reheat Re-Start While the system is still operating in “Cooling Mode” from the previous test. Re-Start Dehumidification. Do Not change the Humidity Setpoint on the Humidistat. Simply adjust the cooling setpoint to approximately four degrees above the current indoor temperature. After the short delay, the unit will sequence on, start dehumidification. Notice: system did not turn off. The Only change that occurred is “Heater turned on”.
  • Page 106 Economizer Cooling Stop Adjust the cooling setpoint to approximately two degrees above the current indoor temperature. The unit will sequence off.  Is the Economizer Damper Closed? ................ ❒Yes ❒No  Is the indoor blower motor (IBM) Off? ..............❒Yes ❒No Heating Mode (Mechanical Heating Heat Pump) Close the Compressor (Cooling) circuit breaker.
  • Page 107 Auxiliary Heat (ODT) While the system is operating in “Mechanical Heating Mode”. Activate Auxiliary Heat (ODT). * Your unit may be configured with an outdoor thermostat configured as “Auxiliary Heat” or “Mechanical Heat Lockout”, or No outdoor thermostat. * Do Not change the temperature setpoint on the thermostat / control. Simply adjust the ODT set- point to approximately four degrees below the current outdoor temperature.
  • Page 108 Calculate Heater kW Single Phase Units Heater kW = (HCAL1*L1&L2)/1000 = _______________kW. Example: HCAL1 * L1&L2 1000 Measured Voltage: L1&L2 = 241 Volts Measured Amperage: L1 = 20.7 Amps 4988.7 / 1000 = 4.99kW (5kW) Three Phase Units Heater kW = (HCAL1*L1&L2) + (HCAL2*L1&L3) + (HCAL3*L2&L3)/1000 = __________kW. Example: (HCAL1*L1&L2) + (HCAL2*L1&L3) + (HCAL3*L2&L3) 1000 Measured Voltage: L1&L2 = 241 Volts...

  • Page 109: Appendix H: Electronic Control Board Modbus Map

    Appendix H: Electronic Control Board Modbus Map Default Modbus RTU Settings Slave ID Baud = 19200 Data Bits = 8 Stop Bits = 1 Parity = None First Coil 1 , No. of Coils 30 RJ11 Pinout for Communication Discrete Bit/Bool: Read with Function Code 02 multi discrete input read, Write to RW coil with Function Code 05 Single Coil write.
  • Page 110 Registers: Read with Function Code 04 Multi register reads, Write to RW register with Function Code 06 write single register. Attempted Writes to RO registers result in error return. Func 0x10 multiple register writes not supported. MODBUS Human OBI PACKET Register ID REGISTER ZeroBase...
  • Page 111 40020 Current Status of MIN POS 16 bit 20 = MIN, 20-100= OPEN % 40021 Economizer Dry Bulb Temperature setpoint 16 bit 70F=default, 20F-105F 40022 ODS set 16 bit 50 default, 0-70 N= 0, 10-90 SECONDS, 40023 Fan Purge 16 bit 90 SEC IS DEFAULT 40024 Defrost Timer...

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