Carrier 38AU appendix Appendix C, Low Ambient Option Factory Installed, Operation, Troubleshooting

Page 47

APPENDIX C

Low Ambient Option — Factory Installed

Units with the factory installed low ambient option are equipped with a MotormasterR solid-state head pressure control which regulates fan speed. A temperature sensor, mounted on circuit 1 of the outdoor coil (see Figs. 44 and

45)controls the speed of approved outdoor fan motors in order to maintain a constant head pressure in the outdoor coil. The control maintains the appropriate head pressure at low ambient temperatures down to -20_F (-28_C).

Wind baffles are required to prevent wind cross currents from causing abnormally low condensing temperatures.

SUse 20-gauge sheet metal to fabricate wind baffles (see Fig. 46 and Table 14) and mounting brackets (see Fig. 47).

NOTE: Mounting brackets are for use on 15 ton model units only.

S Install the wind baffles as show in Fig. 48, for 15 ton units and Fig. 49, for 20 ton units .

Operation —

Fan on/off control in cooling-only units (38AUZ, 38AUD) is provided by an outdoor fan relay (OFR).

In cooling mode, fan motor speed of outdoor motors OFM1 and OFM3 is regulated by the speed control temperature sensor on outdoor coil 1 for a minimum coil condensing temperature of approximately 100_F (38_C) at higher outdoor ambient temperature and 80_F (27_C) at lower ambient. Additionally, outdoor fan motor OFM2 and OFM4 are turned on/off by the low ambient temperature switch, LAS, operating the low ambient relay (LAR). The LAS control temperatures are open 42_F +/- 5_F, close 57_F +/- 5_F (open 5.5_C +/- 2.8_C, close 13.9_C +/- 2.8_C).

To override the speed control for full fan speed operation during service or maintenance, either:

a.remove sensor and place in hot water >120_F (>49_C), or

b.rewire to bypass control by connecting speed control input and output power wires.

Troubleshooting —

OBSERVATION

POSSIBLE REMEDY

Fans won’t start

All fans:

 

Check power & wiring

 

Check outdoor fan relay (OFR)

 

OFM1, OFM3 only:

 

Check speed control sensor location

 

Check speed sensor resistance

 

OFM2, OFM4 only:

 

Check low ambient switch (LAS)

 

Check low ambient relay (LAR)

 

 

Cooling --- Center outdoor

Normal operation

fans (OFM2, OFM4) off

 

below approximately 60_F

 

(16_C) outdoor ambient.

 

 

 

Cooling --- Center outdoor

Check low ambient switch (LAS)

fans (OFM2, OFM4) not on

Check low ambient relay (LAR)

above approximately 60_F

 

(16_C) outdoor ambient

 

 

 

Cooling --- Slow fan speed

Normal operation

for outer fans (OFM1,

 

OFM3) at start or during

 

low outdoor ambient

 

 

 

Cooling --- Slow fan speed

Check speed control sensor location

for outer fans (OFM1,

Check speed control sensor

OFM3) above 85_F (29_F)

resistance

outdoor ambient (should

Check fan motor capacitor

be full speed)

 

 

 

Cooling --- motor current

Normal operation

into speed control is

Up to 30% higher A at partial speed

greater than motor name-

at low ambient

plate FLA

 

 

 

Speed Control Sensor Resistance —

TEMPERATURE

RESISTANCE

_F +/---2_F

_C +/---1_C

Ohms, nominal

 

 

 

--- 22

--- 30

88350

 

 

 

--- 4

--- 20

48485

 

 

 

14

--- 10

27650

 

 

 

32

0

16325

 

 

 

50

10

9950

 

 

 

68

20

6245

 

 

 

77

25

5000

 

 

 

86

30

4028

 

 

 

104

40

2663

 

 

 

122

50

1801

 

 

 

140

60

1244

 

 

 

158

70

876

38AU

47

Image 47
Contents Contents Installation, Start---Up Service InstructionsReplacement/Retrofit R-22 to PuronR Safety ConsiderationsInstallation Guideline Unit Damage Hazard InstallationRtpf UnitMchx 38AUD*25 38AUZ*25Condenser Fans Unit Size 38AURefrigerant TYPE‡ CompressorScroll Pressurestat Settings kPa High CutoutNominal Capacity kW Rtpf Shipping Charge kgFace Area sq ft total Rows/Fins per inch FPI Rtpf Shipping Charge A/B lbOil Charge A/B oz Qty...r/s Motor Hp Nema Diameter mm Operating Weight kg Novation Coil Al TubeRtpf Shipping Charge A/B kg Oil Charge A/B LU Z a 2 5 a 0 G 6 a 0 a 0 a Do not Bury Refrigeration Lines InstallationMatching 38AU Model To Evaporator Coil Jobsite SurveyCheck 38AU Model with Evaporator Coil Connections Provide Safety ReliefSlab Mount Equivalent Lengths for Common Fittings ft38AUZ 16-25 Piping Recommendations Single-Circuit Unit Liquid LiftSuction Riser Hot Gas Bypass 38AUD 16-25 Piping Recommendations Two-Circuit UnitVertical Separation outdoor unit above indoor unit Insulate Suction LinesRefrigerant Specialties Part Numbers Install Filter Driers and Moisture IndicatorsMake Piping Connections Install Liquid Line Solenoid ValveCapacity Control Liquid Line Solenoid Valve Selecting an AccumulatorPreliminary Charge Evacuation/DehydrationAll Units Field Power SupplyUnits with Factory-Installed Disconnect Fire HazardElectrical Operation Hazard Convenience OutletsConvenience Outlet Utilization Notice Label Field Control WiringThermostat Control Transformer WiringUnbalanced 3-Phase Supply Voltage Unit Wire/Fuse or Hacr Breaker Sizing DataPreliminary Checks PRE-START-UPSTART-UP System CheckStart Unit Advanced Scroll Temperature Protection AstpAdjust Refrigerant Charge Using plotted operating pointFinal Checks 38AUZ*25 Check Compressor Oil Level38AUD*16 Charging Chart Novation 38AUZ*16 Charging Chart Rtpf 38AUD*16 Charging Chart Rtpf 38AUD*25 Charging Chart Rtpf Typical 38AUZ Wiring Diagram 15 Ton 230V Tandem Unit Shown Typical 38AUD Wiring Diagram 15 Ton 230V Dual Unit Shown Base Unit Controls Operating SequenceEquipment Damage Hazard Routine System MaintenanceService Refrigeration SystemLiquid Line Filter Drier Field Refrigerant Access PortsFactory High-Flow Access Ports Input Terminal Voltage Comfort Alert Diagnostic ModuleLockout LED Status CodesCompressor Protection 38AUD Size 16 Cabinet LPS 38AUZ,D Size 25 Cabinet 38AUZ*25 Compressor Assembly Rear View NOVATIONt Type Novation Coil Cleaning and MaintenanceRepairing Novation Condenser Tube Leaks Coil Type IdentificationUnit Reliability Hazard Routine Cleaning of Round-Tube Plate Fin Rtpf CoilsReplacing NOVATIONt Condenser Coil Fastener Torque Values TroubleshootingProblem Solution Compressor does not RUN Compressor Stops on HIGH-PRESSURE SwitchSystem is Noisy Problem Solution Compressor Cycles on LOW-PRESSURE SwitchCompressor Running but Cooling Insufficient Unit Operates TOO Long or ContinuouslyAppendix B Wiring Diagram ListAppendix a Operation Low Ambient Option Factory InstalledTroubleshooting Appendix C38AUZ*16 & 38AUD*16 Novation 38AUZ*16/25 & 38AUD*16/25 Rtpf Motormaster Sensor LocationDimensions --- MM Unit Baffle Wind Baffle DimensionDimensions --- Inches Unit Baffle Wind Baffles Fabrication 15 Ton Wind Baffle Brackets Fabrication Front Front Back Left Right Catalog No 38AU---09SI II. PRE-START-UP Outdoor Unit START-UP ChecklistCheck Voltage Imbalance