Scholar III™ Heat Pumps & Air Conditioners (CSI 15740)
Contents
1. Scholar III M amp S 8 09 1 15700 28 HVAC Equipment Troubleshooting Chart DISCONNECT ALL POWER TO UNIT BEFORE SERVICING CONTACTOR MAY BREAK ONLY ONE SIDE FAILURE TO SHUT OFF POWER CAN CAUSE ELECTRICAL SHOCK RESULTING IN PERSONAL INJURY OR DEATH Problem Symptom Likely Cause s Correction Unit will not ER Power off or loose electrical connection 1 Check for correct voltage at unit discon nect Check for correct voltage at contac tor in unit system 2 Thermostat out of calibration 2 Reset set too high 3 Defective contactor 3 Checkfor24 volts at contactor replace if contacts are open 4 Blown fuse tripped breaker 4 Replace fuses reset breaker 5 Transformer defective 5 Check wiring replace transformer 6 High pressure control open 6 Reset 7 Low pressure control open 7 Reset Outdoor fan runs 1 Rum capacitor defective 1 Replace compressor doesn t 2 Loose connection 2 Check for correct voltage at compressor check and tighten all connections 3 Compressor stuck grounded 3 Wait at least 2 hours for overload to or open motor winding open reset If still open replace the internal overload compressor 4 Low voltage condition 4 Add start kit components Insufficient cooling 1 Improperly sized unit 1 Recalculate load 2 Improper indoor air flow 2 Check should be2. gn 9 HVAC Equipment 15700 10 Scholar M amp S 8 09 1 Figure 7b Typical Wiring Schematic for Air Conditioner Model VAIA SCHEMATIC DIAGRA 7 D he SEM REM Des por Scholar M amp S 8 09 1 Single Phase Power te p E i i 2 i E E EN 15700 11 HVAC Equipment Figure 8a Typical Wiring Schematic for Heat Pump Model VAIA Three Phase Power a dele ia T ELECTRICAL LEGEND ou bd com LES Dr HE TESI o dme Se Ree ME bog Wr asian emo EER MTIR CONTROL Qo TERMINAL Le BREN Ee RE SR i44 5 t oct a tee bs soer o t eum D y B cue gr So oo PON at uw Scholar M amp S 8 09 1 15700 12 HVAC Equipment Figure 9 Remote Wall Mounted Thermostat Wiring Detail THE INTERNAL TRANSFORMER IS NOT DESIGNED TO POWER OTHER EXTERNAL DEVICES Figure 9b Humidity Controller Wiring Detail Scholar III M amp S 8 09 1 15700 13 HVAC Equipment 4 1 MAINTENANCE BEFORE PERFORMING MAINTENANCE ON THE SCHOLAR III SWITCH ELECTRIC POWER OFF AT THE DISCONNECT LOCATED BEHIND THE RIGHT FRONT DOOR FAILURE TO DO THIS COULD RESULT IN PROPERTY DAMAGE BODILY INJURY OR DEATH
3. OAM Outdoor Air Motor PROGRAM Fresh air motor for the GreenWheel ERV IBM Indoor Blower Motor Relay Note On early models this was IFM e GW GreenWheel ERV Drive Motor RHS Reheat Solenoid The next five outputs are 24 VAC These outputs are CC Compressor Contactor HTR Heat Contactor RVS Reversing Valve heat pump only A Lock Out Indicator A blinking LED indicates that a pressure switch has opened A flash rate of once per second indicates a low pressure switch lockout A flash rate of twice per second indicates a high pressure lockout OFM Outdoor Fan Motor Relay On the left side beneath the Marvair logo are three LED s that indicate the operational status of the PLC SF System fault indicates an internal fault in the PLC The fault can be found using the Microwin Programming System and an external PCI cable Run Normal operation The PLC is on operational When the micro switch is in the RUN position this LED should be lit Stop The PLC is off non operational When the micro switch is in the STOP position this LED should be lit Scholar III M amp S 8 09 1 15700 22 HVAC Equipment Operation Guide Cooling Mode During normal operation of the system the thermostat calls for cooling by turning on the Y and inputs to the system This request will be indicated on the Y and O indicators at
4. cooling Check to see that when the heat pump comes on that the air coming out the discharge grille is cooling Let unit run for five minutes in this mode If heat pump continues to run and provide cooling this verifies that the indoor blower compressor and outdoor blower are all running Scholar M amp S 8 09 1 15700 5 HVAC Equipment f Now slowly raise the cooling set point up toward room temperature until the pump compressor and outdoor blower motor turn off This will be audible The indoor blower will continue to run and turn off after 90 seconds 5a Heating heat pump version only a Put the thermostat system switch to HEAT mode Wait five minutes after testing on cooling before testing in heating mode b Slowly raise the heating set point above room temperature until the heat pump comes on The indoor blowers will start and the heat pump will provide warm air from the air supply grille Let run for five minutes Slowly lower the set point temperature until the heat pump compressor and outdoor blower turn off The indoor blower will turn off 90 seconds later 5b Heating air conditioner version only Set the heating set point below room temperature and put the thermostat system switch on HT b Raise the set point slowly and the indoor blower and the electric supplemental heat will turn on at the same time Lowering the set point slowly should turn the electric heat off The indoor blower wi
5. Air filters on the Scholar III model VATA require scheduled inspection and maintenance They should be inspected and cleaned or replaced twice a year as a minimum before the heating and cooling season They should be inspected more often as necessary Please refer to Chapter 7 1 for instructions on accessing the return air filters The GreenWheel Media can be checked visually for excessive dirt build up If there is residue build up on the GreenWheel media it can be vacuum cleaned in place as necessary See Chapter 7F for access to the GreenWheel for cleaning Check it and Vacuum clean as necessary Also check to see that the rubber drive belt is properly engaged on the GreenWheel and drive motor pulley B Cabinet Panels Indoor Grilles may be cleaned with a sponge and warm soapy water or a mild detergent Do not use bleach abrasive chemicals or harmful solvents C Ifthe Indoor Coils becomes clogged or dirty it may be cleaned by careful vacuuming or with a commercial evaporator cleaning spray DO NOT use a solvent containing bleach acetone or flammable substances Turn off power before Cleaning Be careful not to wet any of the electrical components Be sure the unit has dried before restarting See Chapter 7 3 for instructions on cleaning the indoor coils D Outdoor Coils Periodically inspect the outdoor condenser coil and the cabinet air reliefs for dirt or obstructions Remove foreign objects such as leaves paper etc
6. ON OFF OFF orr OFF OFF ON oF orr on ON OFF ON OFF on on OFF on on on on on on ON on on on orr ON Defrost Mode heat pump only 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 the LED being on the system will go into Defrost mode At this point the Outdoor Fan Motor relay OFM is de energized and the reversing valve is energized In this mode heat is being applied to the outdoor coil to remove any possible buildup of ice on the coil The Defrost Control Switch DFC comes on at roughly 28 F and goes off at approximately 56 F During the Defrost Cycle the unit will continuously examine the DFC input and when it switches off OR the system has been in defrost for 10 Scholar M amp S 8 09 1 15700 23 HVAC Equipment minutes the system will revert back to normal heating mode By having maximum time for the Defrost Cycle to operate the system will not go into Defrost and remain in Defrost made if a Defrost Switch malfunctions If the Electric Heat During Defrost EHDD function has been selected the Heat Contactor HTR will come on to supply
7. 29 AIRXCEL Inc 150 8001 2000 REGISTERED COMPANY Scholar Heat Pumps amp Air Conditioners CSI 15740 MAINTENANCE amp SERVICE Model VAIA 2 2 5 3 3 54 amp 5 Tons CAUTION Read all instructions before use Retain this manual for future reference This equipment should be installed and serviced only by a trained professional HVAC service person Due to continuous product improvement use only the current issue of this manual The latest version can be downloaded from the Scholar Marvair website www marvair com 60 Manufactured By Marvair Division of AIRXCEL Inc Box 400 Cordele Georgia 31010 156 Seedling Drive Cordele Georgia 31015 229 273 3636 Fax 229 273 5154 E mail marvairtech airxcel com Internet www marvair com M amp S 8 09 1 SECTION 15700 HEATING VENTILATING AND AIR CONDITIONING EQUIPMENT MAINTENANCE amp SERVICE MANUAL FOR SCHOLAR III HEAT PUMP amp AIR CONDITIONER MODEL CSI 15740 TABLE OF CONTENTS Chapter Description Page 11 General Description 3 12 Model Identification 4 24 Start up Instructions 5 22 Ventilation System Calibration e 34 Electrical 9 41 Maintenance 51 Function amp Description of Primary Components 6 1 Troubleshooting 71 Service 84 Filing a Service Warranty Claim 9 1 Warranty Statement 10 1 Exploded V
8. High head pressure 1 Non condensibles air Unusual head and 1 Wrong refrigerant suction readings Foreign matter 1 Copper tubing cuttings d dn mh ed copper recover refrigerant Add filter drier evacuate and recharge Copper oxide 1 Dirty copper piping Welding scale 1 Nitrogen not used Soldering flux 1 Adding flux before seating copper part way Excess soft solder 1 Wrong solder material Loss of Lubrication Low suction pressure 1 Low charge 1 Check system charge 2 Refrigerant leaks 2 Repair and recharge Cold noisy compressor Dilution of oil with refrigerant 1 Observe piping guidelines slugging Noisy compressor 1 Migration 1 Check crankcase heater Cold sweating 1 Flooding 1 Check system charge compressor Low load 1 Reduced air flow 1 Dirty filter 2 Thermostat setting Dirty Wrong duct size Restricted duct 2 Advise customer Short cycling of 1 Faul pressure control 1 Replace control compressor Loose wiring 2 Check all control wires 3 Thermostat 3 In supply air stream out of calibration Customer misuse Flooding Poor system control 1 Loose sensing bulb 1 Secure the bulb and insulate using a TXV 2 Bulbin wrong position 2 Relocate bulb 3 Wrong size 3 Use correct replacement 4 Improper superheater setting 4 Adjust if possible replace if not Scholar III M amp S 8 09 1 15700 33 HVAC Equipment Flo
9. Remove the eighteen screws that hold the door and carefully remove the door Scholar III M amp S 8 09 1 15700 47 HVAC Equipment 3 Disconnect the flexible duct by removing the screws at the top and bottom of the duct 4 Remove the six bolts that hold the fan motor assembly It is necessary to hold the nut on the backside of the flange when unscrewing the bolts Scholar III M amp S 8 09 1 18700 48 HVAC Equipment 5 Carefully rotate the fan motor assembly 90 and pull the assembly out of the machine Use care not to damage the coil or a refrigerant line when removing the fan motor assembly 1 Removalofthe Outdoor Fan Motor Assembly 4 amp ST Units Only Tools Required 7016 socket 5 16 nut driver 1 Remove the two screws that hold the condensate line to the middle front door Note Do not remove or disconnect the condensate tubing Remove the eighteen screws that hold the door and carefully remove the door 3 Disconnect the flexible duct by removing the screws at the top and bottom of the duct 4 The two blowers can be removed individually Disconnect the two electrical plugs to the blower assembly s that is to be removed 5 Remove the three screws on each side of the assembly and pull the assembly out of the unit Use care not to damage the coil or a refrigerant line when removing the fan motor assembly Note See photo on following page Scholar M amp S 8 09 1 18700 49 HVA
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11. odo 5 I ne Ws Ws EER KER Mount tot Mar Em Em En 2 Reversing valve ETE EEN MEN EN EN EN C terae EEEN sonse sana EN Tak DE pz 0055 REET 708 ER Fier Revers Lg Lg EEJ 7886 Tug Fan 245 Opn 40 Goa Em Em En En EE Seis Pressure 610 Open 420 Cose EH En Tot Suits ss of Charge 80 Open 80 Cose En En En KEH EEH Tran Quet iner E EZ ass Duc Fee EEI EE Cl mso esn osm sme vahe Water Ze Waa aun Em Em aun aun aun Thermostat Outi Tan Tan EE EH EH Kab rero EEH EEH JS 705 Thermostat Mourning Bader EE EE EE esos Damper ertsen opens 57 0107 007 0107 owes Supply Ar Paver EBM OAM ET ET ETA Capote Ar Move 4 TO Ex Ex ET Soi continued on following page Scholar III M amp S 8 09 1 15700 57 HVAC Equipment PARTE vane ae ne var ar vaar ENEN NE Em ET Ex Dare ein EEEN E DE S SE En Reaver Wind Wear EN EEn prj sux as Gretel
12. If the condenser coil is dirty it may be washed off with a commercial solvent intended for this purpose TURN OFF POWER BEFORE CLEANING Be sure that all electrical components are thoroughly dry before restoring power See Chapter 7 4 for information on cleaning the outdoor coils D Condensate Lines Each Scholar air conditioner or heat pump has condensate line The condensate line for the indoor and outdoor drain pans are tied together and the condensate is discharged either through the base of the unit into a floor drain or out of the back of the unit at the bottom of the unit 5 1 FUNCTION AND DESCRIPTION OF PRIMARY COMPONENTS A Compressor All Scholar units use a fully hermetic scroll compressor to minimize sound levels and maximize efficiency Scroll compressors like several other types of compressors will only compress in one rotational direction The direction of Scholar III M amp S 8 09 1 15700 14 HVAC Equipment rotation is not issue with single phase compressors since they will always start and run in the proper direction However three phase compressors will rotate in either direction depending upon phasing of power Since there is a 50 50 chance of connecting power in such a way as to cause rotation in the reverse direction it is imperative to confirm that the compressor is rotating in the proper direction at the initial field start up of the system Verification of proper rotation is made by obser
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14. approximately 400 per ton 3 Incorrect refrigerant charge 3 Charge per procedure 4 Air non condensibles or mois 4 Recover refrigerant evacuate and ture in system recharge add filter drier Compressor short cycles 1 Incorrect voltage 1 Atcompressor terminals voltage must 1096 of nameplate marking when unit is operating 2 Defective overload protector 2 Replace check for correct voltage 3 Refrigerant undercharging 3 Add refrigerant Registers sweat 1 Low indoor air flow 1 Increase speed of blower or reduce restriction replace air filter Highhead lowvapor 1 Restriction in liquid line expan 1 Remove or replace defective pressures sion device filter drier component 2 Flow check piston size too small 2 Change to correct size piston 3 Incorrect capillary tubes 3 Change assembly High head high or 1 Dirty outdoor coil 1 Clean coil normal vapor 2 Refrigerant overcharge 2 Correct system charge pressures cooling 3 Outdoor fan not running 3 Repair or replace mode 4 Air or non condensibles in 4 Recover refrigerant evacuate and recharge Scholar III M amp S 8 09 1 15700 30 HVAC Equipment Troubleshooting Chart cont d Problem Symptom Likely Cause s Correction Low head high vapor 1 Flow check piston size too large 1 Change to correct size piston pressures 2 Defective compressor va
15. are closed the system will shutdown Location The PLC is located in the unit control center The control center is located behind a panel in the lower right portion of the cabinet an En Scholar M amp S 8 09 1 18700 19 HVAC Equipment On the right side of the PLC there is small door Behind the door is a three position micro switch and two control adjustments an anti short cycle timer and a defrost timer Each control can be adjusted by turning the knob with a small flat head screwdriver The indicator the Ri knob is the gap between the two protrusions with the hollow centers on the knob See drawing below For both control timers turning the knob clockwise increases js the time period NOTE Scholar III air conditioners do not je have the defrost function 5 ASCT DFT The micro switch has three positions RUN TERM amp STOP The switch should be in the RUN position during normal operation Term is for operation from a remote terminal Stop is no output non operational The Anti short Cycle Timer ASCT is located to the far left of the switch The anti short cycle timer prevents the compressor from destructive short cycling by allowing the compressor to restart only after a selected time interval has passed from compressor shutdown The timer begins when the compressor turns off Th
16. decrease the air flow Read the setting by watching the LAMP flashes The LAMP continuously flashes out the current setting After a pause the LAMP flashes out the tens digit then the units digit of a number percent between 1 and 99 If the lamp stays on the setting is 100 Long flashes represent the tens digit and short flashes represent the units digit A setting of 23 will flash two longs and three shorts The LAMP feature can be used to record an air balance setting or to precisely set the signal to the ECM motor without using a meter The outdoor coils filter drier high pressure switch loss of charge switch outdoor orifice defrost sensor are located behind the middle front door HIGH PRESSURE SWITCH OUTDOOR ORIFICES LOSS OF CHARGE SWITCH VENTILATION DEFROST FILTER DRIER OUTDOOR COIL Scholar III M amp S 8 09 1 15700 16 HVAC Equipment D Indoor Outdoor Coils The coils are constructed of lanced aluminum fins mechanically bonded to rifled seamless copper tubes E Filter Drier The filter drier performs two functions in the refrigerant circuit First it removes foreign particulate matter e g dirt scale solder particles from the refrigerant to protect the compressor and other components in the refrigerant system with small openings or close tolerances Second it absorbs any moisture in the refrigerant with desiccant granules High and Low Refrigerant Pressure Air Conditioner
17. motor 7 While lifting up on the horizontal divider panel that rests on the ventilation module pull the ventilation module out of the unit Access to 460v transformer and to fresh air exhaust motor is behind this panel Scholar M amp S 8 09 1 18700 44 HVAC Equipment G Removal of the Indoor Blower Motor Tools Required 5 16 Nut Driver Clippers to Cut Wire Tie 1 Remove the top cover fifteen screws 2 Disconnect the two electrical harnesses on the blower motor Scholar III M amp S 8 09 1 15700 45 HVAC Equipment 3 the tie wrap that holds the wires to the blower housing 4 Remove the six screws two on the left two in the front and two on the right that hold the blower motor to the top panel These screws penetrate the blower motor flange vertically into the top panel 5 Pull forward on the blower Use caution when removing the blower it is heavy Note when reinstalling the blower motor the rear flange of the blower motor must engage the three clips in the top panel Photo 3343 Scholar III M amp S 8 09 1 15700 46 HVAC Equipment Removal of the Outdoor Fan Motor Assembly 2 2 1 2 3 amp 3 1 2 Units Only Tools Required 7 16 Socket 5 16 Nut Driver 1 Remove the two screws that hold the condensate line to the middle front door Note Do not remove or disconnect the condensate tubing 2
18. the bottom of the unit If the compressor has been off for a least the amount of time interval set on the ASCT the Compressor Contactor Indoor Blower IBM Reversing Valve RVS and the Outdoor Fan Motor OFM LED s should be on This indicates that the controller is sending an output to turn those devices on Heating Mode When the thermostat calls for first stage heating it turns on the G and Y inputs The indicators will come on to indicate the thermostat is calling for heat If the compressor has been powered off for at least the time set on the ASCT the Compressor Contactor CC Indoor Blower Motor IBM and Outdoor Fan Motor OFM LED s will be on The LED s indicate that the PLC is sending an output to the devices controls 1f the thermostat calls for second stage heating heat pump only the W2 indicator will be lit If the W2 LED is on indicating that the thermostat is calling for second stage heat and the ODS indicator is not and the outside temperature is not below the ODS set point the second stage heat HTR will not come on If the W2 indicator is on and the ODS indicator is on then in addition to the CC IBM and OFM indicators the HTR indicator will be on indicating the call for second stage heat If the SCKT LED is on indicating that the S Circuit function is selected the CC and OFM indicators will be off and the HTR indicator will be on Refer to table below v w2 ops sckr IBM cc OFM
19. to the disconnect If voltage readings are appropriate proceed with start up See Figure 2 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 Take appropriate corrective action to supply sufficient voltage to the Scholar disconnect Figure 2 Voltage Limitations Electrical Voltage Designations A c D Nominal Voltage 208 230 208 230 460 Phase 1 3 3 Minimum Voltage 197 197 414 Maximum Voltage 253 253 506 Letters refer to model number code designations Example VAIA 36 HP _ voltage 3 Turn the Scholar III disconnect to ON position 4 Cooling a Setthe remote thermostat system switch to OFF position The blower Switch should be in AUTO position b Atthe remote thermostat raise the cooling set point several degrees above room temperature Lower the heating set point several degrees below room temperature c Move the blower switch on the remote thermostat from AUTO to ON position The indoor blower should come on as evidenced by sound and air blowing out of the air supply grille d Move the blower switch on the remote thermostat from to AUTO and the indoor blower will stop 90 seconds later e Move the system switch on the remote thermostat from OFF to COOL Slowly lower the cooling set point to just below room temperature and bring
20. C Equipment Three Screws on Each Side Electrical Plugs J Removal of the Fresh Air Exhaust Fan Motor Tools Required 5 16 Nut Driver No 2 Phillips Head Screwdriver 1 Remove the 18 screws that hold the middle door Scholar III M amp S 8 09 1 15700 50 HVAC Equipment 2 Remove the lower plenum front cover eight screws 5 Disconnect wires to the fan motor 6 Remove fan motor two Phillips head screws Scholar M amp S 8 09 1 18700 51 HVAC Equipment K Access to Electrical Box Tools Required 5 16 Nut Driver 1 Remove the eight screws that hold the control box cover panel Location of major components 1 Compressor reversing valve and coil Schrader fittings and condensate drain hose SCHRADER Wines COMPRESSOR ENSATE TUB Scholar III M amp S 8 09 1 15700 52 HVAC Equipment Outdoor Coil Filter drier High pressure switch Loss of charge switch Outdoor orifice Defrost sensor Flexible duct for ventilation air HIGH PRESSURE SWITCH OUTDOOR ORIFICES LOSS OF CHARGE SWITCH VENTILATION DUCT DEFROST FILTER DRIER AREA COIL 3 Indoor Coil Indoor blower motor assembly and Thermal Expansion Valve THERMAL EXPANSION VALVES INDOOR ASSEMBLY Scholar III M amp S 8 09 1 15700 53 HVAC Equipment 4 Outdoor thermostat reheat valve and solenoid coil for reheat valve SOLENOID VALVE
21. N MIE apicis UK V bie 351370 7407370 45 7370 45 370 70 40 40 370 zw NECS En En Emm Em En muc NU HPCIHPD 19013 19013 19013 19013 19013 19013 nn EE 7604 7604 7608 Tuer E Compressor 2082 E 2005 Thermal Expansion Vive ndr wa xeu men men ma 30 mo mo xs 850 and Retainer T En an een Sms Nahe ay Divering 6 3957 3957 El El ST Selenald 3 Way Dering G Optra 200 007 2s EE 20028 Check valve TE sider Option 200 2002 EZ E EJ nir ol mea en sen Susp seri Troe Wheel Hausa me 3 EE Tee soo E aer s s xm ns En 3s HE ms ms os 79 Cone Un TET LES Erg 701 anual onl Unt En En En En zx gj 0 Cale ezen Sisi sisi ssi ws weno esn Power Cable hse DEH DEH usu 0520 0520 oss condos olet Sue 0032 0031 0 036 0 041 0 045 0051 moa sen sn meg weg zene zone aem ome zone mens eres mes mams 36 55 352265 Ra FT IN GEN EIG 3566 EX m css EEn EHH EE Ouidius Motor 7 480 8491440 wa En ss 358 Outdoor Blower heel Housing xoa te
22. Scholar III M amp S 8 09 1 15700 54 HVAC Equipment 8 1 PROCEDURE FOR FILING A WARRANTY CLAIM ZMarvair 156 Seedling Drive Cordele GA 31015 P O Box 400 Cordele GA 31010 0400 Phone 800 841 7854 229 273 3636 Fax 229 276 1479 Svc Pager 800 204 8210 MARVAIR SERVICE REQUEST PURCHASE ORDER FOR SERVICE DATE DATE TIME RECEIVED nonien oisparcheo oispaTcHen service po Person requesting service requesting service Phone Fax Point of Contact Company Phone Alt Name amp Phone Site Address Site Bldg Name City ST Zip Site Access Information Equipment Repair Information MODEL SERIAL NUMBER NATURE OF PROBLEM Marvair Use Service Company Information Service Company Contact Phone s Fax Address Labor Rate City ST Zip included here please review and sign our service centers Warranty Policy Information Agreement then fax back to 229 273 5154 Invoices wil bo paid in accordance with Labor Allowance Guidelines included with this PO Failure to follow these guidelines and labor allowances may result in delayed payment All over ime work must be approved in advance AIl imes Slowed for entry into the refrgerant grau include evacuation recharge and der change Serves centers are to natt
23. Supplemental heat during the Defrost Cycle Low Pressure Lockout The Low Pressure air conditioner or Loss of Charge heat pump is designed to guard against the operation of the system in the event of a loss of refrigerant If the Low Pressure Switch stays open for more than eight minutes the system will turn off and a Low Pressure Lockout fault will be indicated by a slow flashing on the A LED The interval for the flash is once per second The loss of charge and low pressure switch open at 40 psig and close at 60 psig In cold weather the pressure in the refrigerant system is low prior to operation When the Scholar III unit starts in the heat pump mode during cold weather low pressure could cause the system to lock out To guard against nuisance lockouts the Scholar III unit will not shut off if the Loss of Charge Switch LPS opens during the first eight minutes of operation and the switch has not cycled more than three times in hour In other words the compressor will start and operate for eight minutes even with the LPS switch open three times before causing a lockout on low pressure High Pressure Switch The system has a High Pressure Switch HPS that indicates a high system pressure When this occurs the system will run for five seconds then set a High Pressure Lockout This lockout condition shuts the system off and flashes the A indicator quickly at a rate of twice per second The high pressure switch opens at 610 psi
24. amp S 8 09 1 15700 39 HVAC Equipment 4 With the door removed carefully spray the coils with the cleaning solution E Removal of Fresh Air Intake Blower Motor Tools Required 5 16 Nut Driver Slotted Screw Driver Clippers to Cut Wire Tie 1 Remove the two screws that hold the blower in place Scholar M amp S 8 09 1 15700 40 HVAC Equipment 2 Remove the eight screws that hold the lower plenum front cover 3 tie wrap that hold wires 4 Disconnect the four wires at the butt splice 5 Slide the blower motor out Scholar III M amp S 8 09 1 15700 41 HVAC Equipment Access to the GreenWheel Drive Motor and the GreenWheel and the Damper Motor for the B Ventilation Option and access to 460v transformer and to fresh air exhaust motor Tools Required 5 16 Nut Driver 5 16 Socket Wrench or Open End Wrench Clippers to Cut Wire Tie Remove ventilation filters Remove ventilation fresh air intake blower motor See instructions for removing this blower motor Remove the filter cover holder seven screws Scholar III M amp S 8 09 1 15700 42 HVAC Equipment 4 Remove the filter rack assembly thirteen screws 5 Remove the two GreenWheel dividers one on the left and one on the right Each divider has two screws Scholar III M amp S 8 09 1 15700 43 HVAC Equipment 6 Disconnect wires to the GreenWheel drive motor or the damper
25. ctor contactor contacts 3 Power company problem trans 3 Have problem corrected before diagnosis former continues 4 Undersized wire feeding unit 4 Correct and complete diagnosis High voltage 1 Power company problem 1 Have problem corrected Scholar III M amp S 8 09 1 15700 31 HVAC Equipment Compressor Overheating cont d Faulty or wrong size heat pump fan motor Faulty outdoor blower Recirculation of air 6 Additional heat source 7 Non condensibles Problem Symptom Likely Cause s Correction High head pressure 1 Overcharge 1 Check system charge 2 Dirty heat pump coll 2 Clean 3 3 Replace fan motor 4 Replace blower Replace with correct rotation motor 5 Correct installation 6 Check for recirculating from other equip ment 7 Recover refrigerant evacuate and recharge system Short cycling of compressor 1 Faulty pressure control 2 Loose wiring 3 Thermostat 5 Capillary Tube 6 Low charge 7 Low evaporator air flow B Faulty run capacitor 9 Faulty internal overload Replace pressure control Check unit wiring 3 Located in supply air stream Differential setting too close Customer mis use 4 Internal foreign matter Power element failure Valve too small Distributor tube tubes restricted 5 Restricted with foreign matter Kinked 1 0 reduced from previous compressor failure 6 Check system c
26. ds too much Moisture causing valve to stick 1 Recover refrigerant replace filter drier refrigerant with low open evacuate system and then recharge superheat and higher than 2 Dirt or foreign material causing 2 Recover refrigerant replace filter drier normal suction pressure valve to stick open evacuate system and recharge seat leak a gurgling or hiss 3 Replace the ing sound is heard at the during the off cycle if this is the cause Not applicable to bleed port valves 4 Oversized Install correct 5 Incorrect sensing bulb 5 Install bulb with two mounting straps location in 2 00 or 4 00 position on suction line with insulation 6 Low superheat adjustment only 6 Turn superheat adjustment clockwise applicable to with adjust able superheat setting 7 Incorrectly installed or restricted 7 Remove restriction or relocate exter equalizer Scholar III M amp S 8 09 1 15700 34 HVAC Equipment Thermostatic Expansion Valves cont d Problem Symptom Likely Cause s Correction Compressor flood back 1 Any of the causes listed under 1 Any of the solutions listed under upon start up symptoms of prablem 2 solutions of problem 2 Superheat is low to normal with low suction pressure 1 Unequal evaporator circuit loading 2 Low load or air flow entering evaporator 1 Ensure air flow is equally distributed thr
27. e U S A Canada and Mexico This warranty does not cover damage caused by improper installation misuse of equipment or negligent servicing THIS WARRANTY CONSTITUTES THE EXCLUSIVE REMEDY OF ANY PURCHASER OF A Marvair amp HEAT PUMP OR AIR CONDITIONER AND IS IN LIEU OF ALL OTHER WARRANTIES EXPRESSED OR IMPLIED INCLUDING WITHOUT LIMITATION ANY IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR USE TO THE FULLEST EXTENT PERMITTED BY LAW IN NO EVENT SHALL ANY IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR USE EXCEED THE TERMS OF THE APPLICABLE WARRANTY STATED ABOVE AND Marvair SHALL HAVE NO OTHER OBLIGATION OR LIABILITY IN NO EVENT SHALL Marvair BE LIABLE FOR INCIDENTAL OR CONSEQUENTIAL DAMAGES OR MONETARY DAMAGES THIS WARRANTY GIVES YOU SPECIFIC LEGAL RIGHTS AND YOU MAY ALSO HAVE OTHER RIGHTS WHICH VARY FROM STATE TO STATE Some states do not allow limitations or exclusions so the above limitations and exclusions may not apply to you Scholar M amp S 8 09 1 15700 56 HVAC Equipment 10 1 PARTS LIST Scholar II Heat Pump Parts List TATUS AIRES VAUGUHF MC VAIMSEHE LLL Sew unns nume Ex 10352 EE pm Compressor we 1075 1050 10353 Em Tons CNN Er EEN 1358 Em 1015 E sons EEN EEN E
28. e time interval is frm 3 seconds to eight minutes in one minute increments The three second setting is used only for factory testing and should NEVER be used when installed in a classroom Select the desired time interval by rotating the knob to the desired setting The factory set point is 3 minutes The Defrost Timer DFT heat pump function only is located next to the three position micro switch The defrost control is based upon both time and temperature The DFT initiates a defrost cycle whenever the outdoor coil temperature is 28 F or below and the selected time interval from the previous defrost cycle has been exceeded Select the desired time interval by turning the DFT knob When turned completely to the left counterclockwise the time interval between defrost cycles is 30 minutes When turned completely to the right clockwise the time interval is 90 minutes The knob allows setting the defrost time anywhere between 30 and 90 minutes i e mid way between the 30 and 90 minutes is 60 minutes The Marvair factory set point is 30 minutes PLC Inputs amp Outputs The PLC has inputs located along the bottom of the controller and outputs along the top of erga the controller An input is a signal to the PLC S from either the thermostat sensors in the Scholar III heat pump or air conditioner or a customer supplied input e g DDC An output is a signal from the PLC to the heat pu
29. e between saturated temperature and suction line temperature is the superheat Superheat normal range 12 to 18 Air Conditioning System Troubleshooting Tips Indicators System Problem Discharge Suction Super Sub Compressor Pressure Pressure heat cooling Amps Overcharge High High Low High High Undercharge Low Low High Low Low Liquid Restriction Drier Low Low High High Low Low Evaporator Airflow Low Low Low Lo Low Dirty Heat Pump High High Low Low High Low Outside Ambient Temp Low Low High High Low Inefficient Compressor Low High High High Low TXV Feeler Bulb Charge Lost Low Low High High Low Poorly Insulated Sensing Bulb High High Low Low High Temperature Pressure Chart Temp R 22 R 410A Temp R 22 410 Temp R 22 R 410A er PSIG PSIG er PSIG PSIG er PSIG PSIG 40 05 10 25 487 860 90 168 4 2730 35 25 142 30 549 955 95 1818 2941 30 49 178 35 615 1057 100 1959 3164 25 74 218 40 685 1166 105 2107 3399 20 101 261 45 760 1283 2263 3646 132 so 840 140 8 115 242 7 3905 10 165 359 ss 925 1541 120 2599 4177 5 200 415 60 1016 1682 125 2779 4463 239 475 65 111 2 1832 130 296 8 4763 282 541 70 121 4 1992 135 316 5 5076 10 328 612 75 1322 2161 140 337 2 540 5 15 377 688 80 143 6 2340 145 258 8 5748 20 430 771 85 1557 2530 150 381 5 610 6
30. e two return filters in the upper indoor section of the unit A filter is located behind each of the return grilles To remove the filters open both doors and slide the filters out as shown below 1 5 2 x 1 x RETURN AIR FILTERS B Changing the Ventilation Air Filters Tools Required Slotted screw driver The ventilation filter s are located in the left section of the bottom compartment behind a panel Scholar III M amp S 8 09 1 15700 36 HVAC Equipment 1 Remove the two screws at the top and bottom of each panel to access the filters 2 Slide the filters out to inspect replace After inspecting replacing of the filters replace filter access panel Scholar M amp S 8 09 1 15700 37 HVAC Equipment C Access to the Indoor Coils for Cleaning Tools Required 5 16 Nut Driver 1 Remove the top cover fifteen screws 3 Carefully spray the coils with the cleaning solution Use care NOT to spray the electrical connections for the indoor motor 2 Remove the filters Scholar III M amp S 8 09 1 15700 38 HVAC Equipment D Access to Outdoor Coils for Cleaning Tools Required 5 16 Nut Driver 1 Remove the two screws that hold the condensate line to the middle front door Note Do not remove or disconnect the condensate tubing 2 Remove the eighteen screws that hold the door n 3 Carefully remove the door Scholar III M
31. echnician s thinking Through a series of yes and no answers follow the logical path to a likely conclusion A novice technician should use these charts like a road map Remember that the chart should clarify a logical path to th Electrical Checks Flow Chart ee problem s solutions Unit Running NO YES Thermostat Problem YES Repair and Recheck NO Transformer Problem YES Repair and Recheck NO Voltage on Compressor Side of Contactor YES NO Capacitor Voltage on Line Side of Contactor Compressor Internal NO m Overload Open Compressor Winding Circuit Breakers or compressor Contactor 60 to Mechanical Check Open Fuses Open for Cooling or Heating Unit Wiring and High Pressure Cut Out YES Connections Compressor Winding Low Pressure Cut Out Grounded Outdoor Fan Motor Compressor Time Grounded Delay Grounded Capacitor Unit Wiring and Replace Fuses or Connections Reset Breakers and Recheck System Scholar M amp S 8 09 1 15700 26 HVAC Equipment Cooling Mechanical Checks Flow Chart Unit Running Outdoor Air Closed YES NO Pressure Problems High Head Low Head Low Suction Pressure Pressure Pressure Dirty Outdoor Coil Low on Charge Dirty Filters Inoperative Outdoor Low Ambient Dirty Indoor Coil Fan Temperature Overcharge Inoperative Inadequate Indoor Air Compressor Valves R
32. ecirculation of Outdoor Check Valve Inoperative Indoor Blower Non condensibles Restricted Indoor Metering Device Low on Charge High Ambient Air Restricted Filter Restricted Indoor Entering Outdoor Coil Drier Metering Device Wrong Outdoor Fan Reversing Valve Restriction in System Rotation Failure Recirculation of Indoor Air Wrong Indoor Blower Rotation Inadequate Ducts Outdoor Check Valve Closed Restricted Filter Drier Go to Electrical Checks Flow Chart Scholar III M amp S 8 09 1 15700 27 HVAC Equipment Heating Mechanical Checks Flow Chart Unit Running Compressor Valves YES NO Pressure Problems High Head Low Head Low Suction Pressure Pressure Pressure Dirty Filters Low on Charge Dirty Outdoor Coil Dirty Indoor Coil Low Indoor Inadequate Air Flow Temperature Over Outdoor Coil Inoperative Indoor Closed Indoor Check Inoperative OD Fan Blower Valve Overcharge Inoperative Low on Charge Go to Electrical Inadequate Indoor Air Flow Restricted Outdoor Metering Device Restricted Outdoor Metering Device Non condensibles Restricted Filter Drier Restriction in System Wrong Indoor Blower Rotation Inadequate Ducts Reversing Valve Failure Closed Indoor Check Valve Recirculation of Out door Air Restricted Filter Drier Checks Flow Chart Defrost Mechanical Ch
33. ecks Flow Chart Defrost System No Defrost Incomplete Defrost Excessive Defrost Reversing Valve Stuck Poor Sensor Location Wrong Defrost Control Timer Setting No Defrost Timer Control Power Setting Wrong Defrost Control Timer Poor Sensor Location Failed Defrost Control stop O D Fan Failed Defrost Relay doesn t Low System Charge Failed Defrost Relay Loose Default Sensor Defrost Thermostat Satisfies During Wind Affecting in Defrost Scholar III M amp S 8 09 1 15700 28 HVAC Equipment Subcooling Calculation Measure the liquid pressure at the liquid line service valve Convert the liquid line pressure to saturated temperature See tables below Measure the liquid line temperature at the liquid line service valve Compare the liquid line temperature to the saturated temperature The difference between saturated temperature and liquid line temperature is the subcooling Subcooling normal range 12 to 20 Superheat Calculation Measure the suction pressure at the suction line service valve z Convert the suction line pressure to saturated temperature See tables below 3 Measure the suction line temperature approximately 6 to 8 from the compressor 4 Compare the suction line temperature to the saturated temperature 5 The differenc
34. es on during the first eight minutes of operation and the switch has not cycled more than three times in an hour In other words the compressor will start and operate for eight minutes even with the LPS switch open three times before causing a lockout on low pressure Both switches open at 40 psig and close at 60 psig The high and low pressure switches are resettable at the wall thermostat or by turning power off and then on to the Scholar II unit A fault LED located on the PLC indicates that a lockout has occurred and whether it is due to high or low refrigerant pressure or indoor coil freeze up The LED will flash once per second for low pressure or indoor coil freeze up lockout and twice per second for high pressure lockout G Metering Devices The Scholar III uses a thermal expansion valve on the indoor cooling circuit and a fixed orifice on the outdoor heating circuit Scholar M amp S 8 09 1 15700 17 HVAC Equipment Reversing Valve The reversing valve reverses the refrigerant s direction of flow heat pump allowing the heat pump to switch from cooling to heating or heating to cooling Exhaust Air Ventilation Blower is used to exhaust classroom in the GreenWheel ERV and Power Vent ventilation options The blower can exhaust up to 450 CFM of air from the classroom In the standard configuration both the exhaust and the intake ventilation blowers are controlled by a single speed controller This speed contr
35. for design requirements Should the modulator need adjustment use the following procedure On the face of the modulator there is an adjustment dial with a slot in the middle Using a slotted screw driver gently turn the dial clockwise to increase the air flow and counterclockwise to decrease the air flow While rotating the adjuster a numerical flow index is locked on the display After adjustment the display shows fan RPM Scholar M amp S 8 09 1 15700 15 HVAC Equipment C Outdoor Air Mover The outdoor air mover is an axial fan with an asynchronous external rotor motor on the 2 2 3 amp heat pumps and all air conditioners Scholar heat pumps models VAIA amp 48 amp 60 use two blowers with electronically commutated motors ECM One of the blowers operates a full speed anytime the compressor is on A fan cycle switch on the second blower cycles the blower on amp off to maintain proper refrigerant pressures The switch closes at 400 psig and opens at 245 psig Each blower motor is controlled by a pulse width modulator identified in the control box by OFM 1 and OFM 2 The modulators are factory set for proper air flow for design requirements Should the modulator need adjustment use the following procedure 1 Inthe middle of each modulator there is a blue dial with a slot in the middle 2 Using a slotted screw driver gently turn the dial clockwise to increase the air flow and counterclockwise to
36. g and resets at 420 psig O Ventilation Blower Fan Speed Control The ventilation blower speed control is located in the upper left corner of the electrical control box Factory setting for the indoor blower speed is full speed If a lower speed setting is required the blower motor speed control may be adjusted with a slotted screwdriver rotating the speed control as shown in Figure 12 Reference unit label for minimum required air flow settings for specific unit model Figure 12 Ventilation Blower Speed Control Adjustment Instructions e SERIES 706 VARI SPEED MOTOR CONTROL LO O HI o Scholar M amp S 8 09 1 18700 24 HVAC Equipment P Standard Ventilation Control The motorized fresh air damper with PowerVent and GreenWheel ERV ventilation options are equipped with a fresh air fan speed control The fresh air fan speed control operates both the ventilation intake and exhaust blowers together Optional Ventilation Controls The unit control system is factory wired to energize the ventilation package anytime the indoor fan blower is energized If additional control of the ventilation package is desired it may be accomplished by the following The controls contractor must remove the factory installed jumper between terminals V1 and V2 then provide a set of contacts 24 VAC pilot duty between terminals V1 and V2 When the field supplied contacts between V1 and V2 are dosed the ventilation package will operate whe
37. harge 7 Dirty coil Dirty filter Duct too small or restricted 8 Replace 9 Replace compressor Faulty compressor valves Fast equalization low pressure difference Replace compressor and examine system to locate reason Electrical Voltage present on load side of compressor con actor and compressor won t 1 Run capacitor Internal overload 3 Compressor windings Check with ohmmeter Allow time to reset 3 Check for current ohms Voltage present on line side of compressor contactor only 1 Thermostat 2 Compressor control circuit 1 Check for control voltage to compressor contactor coil 2 High pressure switch Low pressure switch Compressor tumed off on control or interlock Scholar III M amp S 8 09 1 15700 32 HVAC Equipment Electrical cont d Problem Symptom kely Cause s Correction No voltage on line side Blown fuses or tripped circuit breaker 1 Check for short in wiring or unit Li d 2 Improper wiring 1 2 of compressor contactor 2 Recheck wiring diagram Improper voltage High voltage 1 Power supply problem Low voltage 2 Power supply problem Wiring undersized Loose connections 3 Single phasing 3 phase 3 Check incoming power and fusing Contamination Moisture 1 Poor evacuation on installation or during service
38. harge EXW Cordele Georgia the required replacement part Any related service labor diagnosis calls filter driers and refrigerant are not included Marvair will pay for non priority shipping costs of the compressor during the first twelve months of the warranty period After the first twelve months of the warranty period all costs of shipment and risk of loss during the shipment of the compressor shall be the responsibility of the owner The owner of the product may ship the allegedly defective or malfunctioning product or part to Marvair at such owner s expense and Marvair will diagnose the defect and if the defect is covered under this warranty Marvair will honor its warranty and furnish the required replacement part All costs for shipment and risk of loss during shipment of the product to Marvair and back to the owner shall be the responsibility and liability of the owner Upon written request by an owner Marvair may arrange for remote diagnosis of the allegedly defective or malfunctioning product or part but all costs for transportation lodging and related expenses with regard to such diagnostic services shall be the responsibility and liability of the owner An owner requesting performance under this Warranty shall provide reasonable access to the allegedly defective or malfunctioning product or part to Marvair and its authorized agents and employees This warranty applies only to products purchased and retained for use within th
39. iews and Parts List Scholar III M amp S 8 09 1 15700 2 HVAC Equipment SECTION 15700 HEATING VENTILATING AND AIR CONDITIONING EQUIPMENT The purpose of this manual is to provide instructions for maintenance and service for the Marvair Scholar series of heat pumps and air conditioners In addition to this manual there are other pieces of literature available from Marvair The Engineering and Design Manual details the design and selection of HVAC systems using the Scholar III series The Installation and Start Up manual covers the installation of the unit and various accessories and the initial start up of the unit An overview of the product line can be found in the Heat Pump and Air Conditioner Product Data Sheets The current version of this literature can be found and down loaded from the Marvair website at www marvair com To minimize sound levels within the classroom certain options should be selected These op tions are designated by throughout the guideline 1 1 GENERAL OPERATION A Scholar III heat pumps and air conditioners are designed to provide quiet comfort to the classroom cooling mode the compressor will cycle on to provide the cooling required The system provides cooling dehumidification and air circulation In heating mode the compressor heat pump only will cycle on to provide the heating required The system provides heating and air circulation At lower outdoor temperatures additio
40. ll turn off 90 seconds later 6 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 7 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 In emergency heat mode the compressor is de energized and electric heat supplies all heating controlled by the thermostat To check this out set the heating set point below room temperature and put the thermostat system switch on EM HT Raise the set point slowly and the indoor blower and the electric supplemental heat will turn on at the same time Lowering the set point slowly should turn the electric heat off The indoor blower will turn off 90 seconds later Scholar M amp S 8 09 1 15700 6 HVAC Equipment 2 2 VENTILATION SYSTEM CALIBRATION 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 A Manual Fresh Air System Fresh air ventilation by means of a damper with pressure relief opening to outside but no exhaust blower a ventilation intake blower and a fan speed controlle
41. lves Replace compressor 3 Incorrect capillary tubes 2 Replace coil assembly Low vapor cool com 1 Low indoor air flow 1 Increase speed of blower or reduce pressor iced indoor restriction replace air filter 2 Operating below 55 F outdoors 2 Add low ambient kit 3 Moisture in system 3 Recover refrigerant evacuate and recharge add filter drier High vapor pressure 1 Excessive load 1 Recheck load calculation 2 Defective compressor 2 Replace Fluctuating head and 1 hunting 1 Check TXV bulb clamp check air distribu vapor pressures 2 Air or non condensibles in sys tion on coil replace TXV tem 2 Recover refrigerant evacuate and recharge Gurgle or pulsing noise 1 Airornon condensibles in sys 1 Recover refrigerant evacuate and at expansion device tem recharge liquid line Service Analyzer Charts Compressor Overheating Problem Symptom Likely Cause s Correction High superheat 1 Low charge 1 Check system charge 2 Fauly metering device 2 Restricted cap tube TXV Power element superheat adjustment Foreign matter stopping flow 3 High internal load Hot air attic entering room Heat source on miswired or faulty control 4 Restriction in liquid line 4 Drier plugged Line kinked 5 Low head pressure 5 Low charge Operating in low ambient temperatures Low voltage 1 Loose wire connections 1 Check wiring Dirty or pitted compressor 2 Replace conta
42. mp air conditioner or to the thermostat stili IL Scholar M amp S 8 09 1 15700 20 HVAC Equipment PLC Inputs 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 The PLC has indicator LED s that show the status of all thermostat inputs and sensors For example if the G LED is on this means that voltage is present from the G terminal on the thermostat Scholar III heat pump and air condi sensor or control inputs HPS High Refrigerant Pressure Switch The HPS is ON during normal operation No light indicates an open switch See lockout indicator A under Outputs LPS Low Refrigerant Pressure Switch The LPS is ON during normal operation No light indicates an open switch See lockout indicator A under Outputs HUM Humidity Controller Used when an external humidity controller operates the Scholar to control the humidity in the classroom EHDD Electric Heat During Defrost Allows the user to select whether electric heat operates when the heat pump enters into the defrost mode The units are wired at the factory to prevent the electric heaters from operating during the defrost mode For operation during defrost a wire is moved from one terminal to an
43. mperature switches The first is an auto reset type that turns power off to the heater if it senses a temperature of 145 F When the temperature drops to approximately 105 F power is restored to the heaters This auto reset switch is in the low voltage circuit The second type of switch is a one time limit switch If it senses a temperature of 3009 power is turned off to the elements This switch does NOT reset when the temperature drops and must be replaced when it activates The number and location of both switches is determined by the power supply and the KW of the heaters Hot Water is installed above the indoor blower outlet as shown in the hot water plenum A diverter valve is a factory installed option with the hot water coil only Hot water heat is factory installed in the freeblow or the ducted plenums and is plumbed from the top right side of the plenum As a standard safety feature each hot water coil has a protective 24 volt freezestat embedded within it to trigger at 35 F and to turn the unit off Scholar M amp S 8 09 1 15700 18 HVAC Equipment Programmable Logic Controller PLC Microprocessor The Scholar III heat pump uses 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 comm
44. n the indoor fan blower is energized The motorized fresh air damper with PowerVent and GreenWheel ERV ventilation options can be equipped with an exhaust fan air speed control which controls the ventilation exhaust blower independently of the fresh air intake blower Demand Control Ventilation A field or factory installed carbon dioxide sensor controls the ventilation damper and only opens the damper when CO levels exceed a specified level Demand control ventilation saves energy and utility costs by ventilating the classroom based upon occupancy Note Not available on manual fresh air damper B configuration P Outdoor Thermostat 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 rotating the adjustment knob the control box Please note that when the outdoor thermostat activates wet heat the compressor does not operate The outdoor thermostat is located above the hinged control box behind the middle front door OUTDOOR THERMOSTAT REHEAT VALVE amp Pom SOLENOID VALVE Scholar III M amp S 8 09 1 15700 25 HVAC Equipment 6 1 TROUBLESHOOTING In diagnosing common faults the heat pump system develop logical thought pattern as used by experienced technicians The charts which follow are not intended to be an answer to all problems but only to guide the t
45. nal heating capacity may be provided by an optional electric resistance heater or a hot water steam coil Ventilation air may be provided by the manual or motorized fresh air vent power vent or GreenWheel ERV These ventilation systems operate when there is a call for cooling or heating or independently to provide fresh air Note that with the manual motorized fresh air vent and the power vent options if the compressor is not operating and the indoor blower is running unconditioned outside air is being introduced into the classroom The GreenWheel ERV provides tempered outside air Control systems are either a remote external thermostat internal thermostat or a direct digital control interfacing with the building automation system BAS Hot Gas Reheat HGR Dehumidification Option To provide on demand dehumidification the Scholar III heat pump or air conditioner can have a factory installed hot gas reheat coil to allow dehumidification through continued cooling with discharge air reheated to avoid over cooling the classroom The hot gas dehumidification option can be used with electric steam or hot water heat The operation of the HGR is controlled by a three way heat reclaim valve The HGR is sized to provide a heating capacity approximately equal to the sensible capacity of the unit When the demand for cooling is satisfied and the humidity controller calls for dehumidification hot gas is directed to a reheat coil downstream f
46. oding cont d Problem Symptom Likely Cause s Correction Poor system control 1 Overcharge 1 Check system charge using capillary tubes 2 High head pressures 2 Dirty heat pump Restricted air flow Recirculation of air 3 Evaporator air flow too low 3 Adjustair to 400 CFM Ton Thermostatic Expansion Valves external equalizer line High superheat low 1 Moisture freezing and blocking 1 Recover charge install filter drier suction pressure valve evacuate system recharge 2 Dirt or foreign material blocking 2 Recover charge install filter drier valve evacuate system recharge 3 Low refrigerant charge 3 Correct the charge 4 Vapor bubbles in liquid line 4 Remove restriction in liquid line Correct the refrigerant charge Remove non condensible gases 5 Misapplication of internally equal 5 Use correct ized valve 6 Plugged external equalizer line 6 Remove external equalizer line restriction 7 Undersized 7 Replace with correct valve 8 Loss of charge power head 8 Replace power head or complete sensing bulb 9 Charge migration from sensing 9 Ensure is warmer than sensing bulb to power head warm power bulb head with warm wet cloth Does valve operate correctly now 10 Improper superheat adjustment only applicable to with ad 10 Adjust superheat setting counter justable superheat settings dockwise Valve fee
47. oller permits the motor speed to be adjusted for the correct cfm of ventilation air As an option a second motor controller may be factory installed to allow independent control of the intake and exhaust air blowers This allows pressurization of the classroom All ventilation options have an intake air blower Intake Ventilation Air Blower is used to introduce outside air into the classroom In the standard configuration both the exhaust GreenWheel ERV and PowerVent only and the intake ventilation blowers are controlled by a single speed controller This speed controller permits the motor speed to be adjusted for the correct cfm of ventilation air As an option a second motor controller may be factory installed to allow independent control of the intake and exhaust air blowers This allows pressurization of the classroom Electric Resistance Heat is installed above the indoor blower outlet Electric heat is field installed on all Scholar III units Electric heat can be used with the freeblow plenum or with ducted air distribution options The heaters are available in nominal KW of 5 10 amp 15 KW for operation on 208 230v 10 208 230 v 30 and 460v 30 The model number of the heat pump or air conditioner indicates the power supply and kW Electric Resistance Heat Controls Included with the electric heat assembly temperature switches designed to turn power off to the heaters if the temperature is too high There are two types of te
48. or Loss of Charge Heat Pump Switches amp Optional Heat Pump Only Indoor Coil Freeze Stat These switches render the compressor and outdoor fan motor inoperative whenever the limits of the high or low pressure switches are exceeded or indoor freeze up In the event of high pressure the Scholar IIT unit will turn off and lockout The high pressure switch opens at 610 psig and resets at 420 psig The system has a High Pressure Switch HPS that indicates a high system pressure When this occurs the system will run for five seconds then set a High Pressure Lockout This lockout condition shuts the system off and flashes the A indicator on the PLC quickly at a rate of twice per second The Low Pressure air conditioner or Loss of Charge heat pump switches are designed is designed to guard against the operation of the system in the event of a loss of refrigerant If the Pressure air conditioner or Loss of Charge heat pump switch opens for more than eight minutes the system will turn off and a Low Pressure Lockout fault will be indicated by a slow flashing on the A LED The interval for the flash is once per second In cold weather the pressure in the refrigerant system is low prior to operation When the Scholar III unit starts in the heat pump mode during cold weather low pressure could cause the system to lock out To guard against nuisance lockouts the Scholar III unit will not shut off if the Low Pressure Switch LPS com
49. other in the control box NOTE for operation of the electric heat during defrost the electric heat control must be configured to allow simultaneous operation of the electric heat and the compressor heat pump only SCKT S Circuit Signal that indicates the electric heat and the compressor can never operate simultaneously This function is controlled by the electric heat control toggle switch in the control center The LED should be ON if Y is ON the electric heat is on and the toggle switch is in the S circuit position heat pump only ODS Outdoor Thermostat Determines at what outdoor temperature factory set at 40 F the supplemental heat turns on The LED should be ON if the outdoor temperature is below the ODS set point heat pump only EMS Energy Management System A shutdown input from an external source GWR GreenWheel ERV Relay When this LED is lit the GreenWheel ERV is operating DFC Defrost Control Thermostat Indicates whether the defrost thermostat is closed The defrost cycle is based upon both time see defrost timer and outdoor coil temperature heat pump only Scholar M amp S 8 09 1 18700 21 HVAC Equipment PLC Outputs An output is a signal from the PLC to the Scholar heat pump or thermostat The first four outputs from left to right are connected to a 230 RT VAC supply and thus provide 230 VAC when energized apen These outputs are 9m
50. ough evaporator Ensure proper piston Check for blocked distributor tubes 2 Ensure blower is moving proper air Remove correct any air flow restriction Superheat and suction pressure fluctuate valve is hunting 1 Expansion valve is oversized 2 Sensing bulb is affected by liq uid refrigerant or refrigerant oil flowing through suction line 3 Unequal refrigerant flow through evaporator circuits 4 Improper superheat adjust ment only possible with TXV having superheat adjustment 5 Moisture freezing and partially blocking TXV Install correct TXV Relocate sensing bulb in another position around the circumference of the suction line 3 Ensure proper distributor piston is inserted Ensure sensing bulb is located properly Check for block distributor tubes 4 Replace or adjust superheat 5 Recover refrigerant change filter drier evacuate system and recharge Valve does not regulate 1 External equalizer line not con nected or line plugged in 2 Sensing bulb lost its operating charge 3 Valve body damaged during soldering by improper instal lation 1 Connect equalizer line in proper location remove any blockage 2 Replace TXV 3 Replace TXV Scholar M amp S 8 09 1 15700 35 HVAC Equipment 7 1 SERVICE A Changing the Return Air Filters Tools Required Slotted screw driver or key for opening front doors There ar
51. r provides up to 450 cfm of outside air The damper can be manually adjusted at installation to provide the required ventilation airflow The fresh air door should be set in accordance with the amount of fresh air flow required up to a maximum of 450 CFM Figure 3 illustrates the fresh air door settings and air flow rates Follow the directions in Figure 3 to ensure proper air flow rate settings B Motorized Fresh Air Configuration B This ventilation option includes a motorized damper a fresh air intake blower and motor and a blower motor speed controller This ventilation option can provide up to 450 CFM of outside air but not to exceed 4096 of rated airflow and includes pressure relief opening to outside but no exhaust blower The motorized damper and blowers are controlled by a Programmable Logic Controller PLC The PLC will operate the damper and ventilation motors ONLY when the Indoor Evaporator blower is operating The PLC is factory wired for this operation by a 24 VAC signal to an input terminal on the PLC The damper is adjusted after installation for the required rate of ventilation An optional 24 VAC 120 VAC or 240 VAC coil relay may be factory installed to control the damper and motor from an external signal e g an EMS or BAS system A filter on the incoming outside air is standard PowerVent Configuration J Optional This ventilation option includes a motorized damper a fresh air intake blower and motor an exhaus
52. rom the evaporator to add heat to the dehumidified chilled air supplied to the classroom Hot gas Scholar M amp S 8 09 1 15700 3 HVAC Equipment reheat is available with motorized fresh air PowerVent and GreenWheel ventilation systems Marvair recommends that for optimum performance hot gas reheat be used in conjunction with the GreenWheel heat recovery ventilator When used with other ventilation options hot gas reheat may not maintain satisfactory control of the humidity in the classroom over all outdoor conditions Figure 1 Conditioned Air Flow and Fresh Air Flow 1 2 MODEL IDENTIFICATION The Scholar heat pump and air conditioner identification numbering system is shown below The model identification number is on the data label The data label is at the bottom of the of left side panel s A E i WHEN SCHOLAR III SYSTEMS ARE INSTALLED MODEL NUMBER AND SERIAL NUMBERS ARE TO BE RECORDED AND MAINTAINED IN A LOCATION FOR IMMEDIATE ACCESS WHEN REQUESTING FURTHER INFORMATION Scholar M amp S 8 09 1 15700 4 HVAC Equipment 2 1 START UP PROCEDURE A This start up procedure applies to Scholar models equipped with a remote wall mounted thermostat and electric supplemental heat i Tum the disconnect in the Scholar unit to OFF position and double check all electrical connections before applying power 2 Check the voltage supply
53. t air blower and motor and one blower motor speed controller The blower speed controller operates both blowers in tandem An optional blower speed control for the exhaust air blower can be factory installed to provide independent control of the exhaust air blower motor and allow pressurization of the classroom The PowerVent can provide up to 450 CFM of outside air but not to exceed 40 of rated airflow and includes active pressure relief The motorized damper and blowers are controlled by Programmable Logic Controller PLC The PLC will operate the damper and ventilation motors ONLY when the Indoor Evaporator blower is operating The PLC is factory wired for this operation by a 24 VAC signal to an input terminal on the PLC The damper is adjusted after installation for the required rate of ventilation An optional 24 VAC 120 VAC or 240 VAC coil relay may be factory installed to control the damper and motor from an external signal e g an EMS or BAS system A filter on the incoming outside air is standard The fresh air door is opened and closed by the motorized drive Calibration as shown in Figure 4 will ensure the required amount of air up to a maximum of 450 CFM is delivered to the classroom Scholar M amp S 8 09 1 15700 7 HVAC Equipment Follow the directions in Figure 4 to ensure the proper air flow rate setting After calibrating the ventilation system replace the lower front cabinet panel Figure 3 Manual Fresh Air Sys
54. t the speed of the blowers Repeat as necessary to meet the fresh air requirements For units with the optional variable fan speed controller for the exhaust blower on the GreenWheel ERV first measure the air being introduced into the classroom using best industry standards and practices Adjust the speed of the intake air blower until the required outside air is being brought into the classroom Now measure the exhaust air from the classroom Adjust the speed of the exhaust air blower until the required air is being exhausted from the classroom The exhaust air controller is in the control box It is usual practice to pressurize the classroom by exhausting slightly less air than is being brought into the classroom Scholar III M amp S 8 09 1 15700 8 HVAC Equipment 3 1 ELECTRICAL Scholar Ill heat pumps and air conditioners are built in a wide variety of configurations and options The illustrations of the control center and the electrical schematics shown here are typi cal but probably are not identical to your units Please refer to the electrical schematic in each unit for the specific construction of that unit Figure 5 Typical Control Center Layout for Models VAIA24 30 36 40 Scholar M amp S 8 09 1 15700 9 HVAC Equipment Figure 7 Typical Wiring Schematic for Heat Pump Model VAIA Single Phase Power il Bun ien pr ie EEN En B P pre s of
55. tem Calibration Procedure Inside the lower section locate the circular calibration plates asnotedin the drawing Ais fixed movable Remove the screw shown by the arrow from Manual Settings escent Rotate plate B in a clockwise direction until the hole from asc which the screw was removed aligns with the hole adjacent to the desired air flow rate in Reinsert the screw into the hole in plate B and firmly drive the screw through the appropriate airflow rate hole plate Bis securely fastened at the desired opening ot reece enal ata crane 14 cien gera e Figure 4 Motorized and PowerVent System Calibration Procedure Inside the lower section locate the circular calibration plates as noted aboveinthe drawing A is fixed B is movable Remove the screw shown by the arrow from motorized settings Reinsert the screw into the hole in plate B adjacent to the desired air flow rate in CFM and firmly drive the screw in until focal seine it bottoms out at the screw head pd Waregem C GreenWheel 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 The speed controller is located the control box Measure the intake air again and adjus
56. unicating to other Scholar III unit PLC s to allow run time leveling and does not require additional equipment installed in the Scholar III unit The PLC microprocessor provides improved reliability because of the reduction of components the components utilized are more durable and the control box wiring has been simplified Pertinent statistical data about the of the refrigeration system can be accessed through the PLC The PLC microprocessor provides for the following control and operation functions Anti Short Cycle Timer Prevents the compressor from destructive short cycling due to momentary power interruptions One of three time intervals can be field selected Defrost Timer heat pump only Adjustable defrost control that is based upon both time and temperature The time interval is adjustable from 30 to 90 minutes BAS Control Provides 24 VAC coil to control operation from Building Automation System BAS Note an additional BAS control relay can be added when 120 or 240 VAC coils are required The unit control system is factory wired to operate upon an input signal from any appropriate 24 VAC control thermostat or DDC control system If unit shutdown is desired during unoccupied periods of the temperature controlled space it may be accomplished by the following the controls contractor must provide a set of contacts 24 VAC pilot duty between terminals E1 and E2 When the field supplied contacts between E1 and E2
57. ving that the suction pressure drops and the discharge pressure rises when the compressor is energized An alternate method of verification for self contained system with small critical refrigerant charges where the installation of gauges may be objectionable can be made by monitoring the temperature of the refrigerant lines at the compressor The temperature should rise on the discharge line while the suction line temperature decreases Reverse rotation also results in a substantially reduced current draw when compared to tabulated values There is no negative impact on durability caused by operating three phase compressors in the reversed direction for a short duration of time usually defined as less than one hour However after several minutes of operation the compressor s internal protector will trip The compressor will then cycle on the protector until the phasing is corrected Reverse operation for longer than one hour may have a negative impact on the bearings The compressor reversing valve and coil and the Schrader fittings are located behind the hinged control box See figure below SCHRADER 22 a CONDENSATE TUBING Indoor Blower and Motor All Scholar air conditioners and heat pumps use an electronically commutated EC blower motor and a single blower The motor speed is controlled by pulse width modulator located in the electrical box and identified as IBM The modulators are factory set for proper air flow
58. y Marva T sie Travel wil exceed T hour each way additional rave me must be approved in advance Detaled invoices or service lech cal shectwork orders are required a be submited wih invoices for payment Service Tech s should document work in detail and include vary model and serial number s of the equipment and include Marvairs PO on all documentation Marvair wil provide contractors with warranty replacement parts for service calls please contact us at 800 Scholar III M amp S 8 09 1 15700 55 HVAC Equipment 9 1 WARRANTY If any part of your Marvair Air Conditioner Heat Pump or Unit Ventilator fails because of a manufacturing defect within fifteen months from the date of original shipment from Marvair or within twelve months from the date of original start up whichever is the earlier date Marvair will furnish without charge EXW Cordele Georgia the required replacement part Any transportation related service labor diagnosis calls filter driers and refrigerant are not included The owner must provide proof of the date of the original start up The owner s registration card filed with Marvair the contractor s invoice the certificate of occupancy or similar document are examples of proof of the date of the original start up In addition if the hermetic compressor fails because of a manufacturing defect within sixty months from the date of original shipment from Marvair Marvair will furnish without c
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