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Carrier 024-036 Service Manual Download Page 11

: Service Manual

Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.

11

Check Defrost Thermostat

There is a liquid header with a brass distributor and feeder tubes going

into outdoor coil. At the end of 1 of the feeder tubes, there is a 3/8-in.

OD  stub  tube  approximately  3  in.  long.  (See 

Fig. 13

.)  The  defrost

thermostat should be located on stub tube. Note that there is only 1 stub

tube used with a liquid header, and on most units it is the bottom circuit.

(See 

Fig. 15

 and 

Fig. 16

 for DFT Sensor Location.)

A97517

Fig. 13 – Defrost Thermostat Location

NOTE: 

The defrost thermostat must be located on the liquid side of the

outdoor coil on the bottom circuit and as close to the coil as possible.

Defrost Control Board

Troubleshooting  defrost  control  involves  a  series  of  simple  steps  that

indicate whether or not board is defective.

NOTE: 

This procedure allows the  service technician to check control

board and defrost thermostat for defects. First, troubleshoot to make sure

unit  operates  properly  in  heating  and  cooling  modes.    This  ensures

operational problems are not attributed to the defrost control board.

Defrost Control

The demand defrost control is used in all Mobile Home series heat pump

models. Its features include a selectable initial defrost interval of either

30, 60, 90 or 120 minutes and an automatic interval adjustment that is

based  off  the  previous  defrost  cycles.  This  section  describes  the

sequence of operation and troubleshooting methods for this control.

Cooling Sequence of Operation

On a call for cooling, thermostat makes R-O, R-Y, and R-G. Circuit R-O

energizes reversing valve switching it to cooling position. Circuit R-Y

sends  low  voltage  through  the  safeties  and  energizes  the  contactor,

which starts the compressor and energizes the T1 terminal on the circuit

board. This will energize the OF2 fan relay which starts the outdoor fan

motor. 
When  the  cycle  is  complete,  R-Y  is  turned  off  and  compressor  and

outdoor  fan  should  stop.  With  corporate  thermostats,  the  O  terminal

remains energized in the cooling mode. If the mode is switched to heat

or Off, the valve is de-energized.  There is no compressor delay built into

this control. 

A05332

Fig. 14 – Defrost Control

Heating Sequence of Operation

On a call for heating, thermostat makes R-Y, and R-G.  Circuit R-Y sends

low voltage through the safeties and energizes the contactor, which starts

the compressor and energizes the T1 terminal on the circuit board. The

T1 terminal energizes the defrost logic. This will energize the OF2 fan

relay start the outdoor  motor.  The T1 terminal must  be energized for

defrost to function.
When the cycle is complete, R-Y is turned off and the compressor and

outdoor  fan  should  stop. There  is  no  compressor  delay  built  into  this

control.

Defrost Sequence

The defrost mode is factory set to an initial 60-minute time interval. It

may also be adjusted to an initial interval of 30, 60, 90 or 120 minutes.

During  operation, the  control  may  vary  based  on  the previous  defrost

interval and previous defrost period. If the previous defrost period is less

than  2  minutes  for  two  consecutive  defrost  cycles  the  control  will

lengthen the defrost interval by 15 minutes, up to a maximum of 120

minutes  or  30  minutes  greater  than  the  original  setpoint,  whichever

comes first. If the previous defrost period is more than 5 minutes for two

consecutive defrost cycles the control will shorten the defrost interval by

15 minutes, down to a minimum of 30 minutes or 30 minutes from the

original setpoint, whichever is first.
The defrost  thermostat senses coil temperature throughout the  heating

cycle.  When the coil temperature reaches the defrost thermostat setting,

it will close, which energizes the DFT terminal and begins the defrost

timing  sequence.  When  the  DTF  has  been  energized  for  the  selected

time, the defrost cycle begins, and the control shifts the reversing valve

into cooling position, and turns the outdoor fan off. This shifts hot gas

flow  into  the  outdoor  coil  which  melts  the  frost  from  the  coil.  The

defrost  cycle  is  terminated  when  defrost  thermostat  opens,  or

automatically after 10 minutes. 

FEEDER TUBE

DEFROST
THERMOSTAT

A97517

STUB TUBE

COIL

OUTDOOR FAN

RELAY

Y OUTPUT TO PRESSURE

SWITCHES AND CONTACTOR

THERMOSTAT INPUTS

T1 - ENABLES DEFROST  
       TIMER.MUST BE  
       ENERGIZED FOR  
       DEFROST TIMER  
       TO START 

C - COMMON

O - REVERSING VALVE

SPEEDUP

DEFROST  THERMOSTAT

MUST BE CLOSED BEFORE

DEFROST TIMER BEGINS

Summary of Contents for 024-036

Page 1: ...ns Rotating fan blades can cause personal injury Appropriate safety considerations are posted throughout this manual where potentially dangerous techniques are addressed Follow all safety codes Wear safety glasses protective clothing and work gloves Have a fire extinguisher available Read these instructions thoroughly and follow all warnings or cautions included in literature and attached to the u...

Page 2: ... low ambient cooling applications Suggested in all commercial applications 2 Evaporator Freeze Thermostat An SPST temperature actuated switch that stops unit operation when evaporator reaches freeze up conditions Usage Guideline Required when low ambient kit has been added 3 Isolation Relay An SPDT relay which switches the low ambient controller out of the outdoor fan motor circuit when the heat p...

Page 3: ...ls must meet the original equipment specifications Insulation must meet NFPA 90A requirements for flame spread and smoke generation Foam gaskets that are in the conditioned air stream must meet the requirements of UL 94 5VA for flammability Instructions for insulation installation 1 Apply adhesive on non foil side of the insulation 2 Align insulation to the panel 3 Care must be taken while applyin...

Page 4: ... reserves the right to change at any time specifications and designs without notice and without obligations 4 A220851 Fig 3 Unit Base Dimensions Small Medium Cabinet with Full Louver 13 4 SEER2 HEAT PUMP 13 4 SEER2 AIR CONDITIONER ...

Page 5: ... the right to change at any time specifications and designs without notice and without obligations 5 A220853 Fig 4 Unit Base Dimensions Heat Pump Air Conditioner Large Cabinet with Full Slots 13 4 SEER2 HEAT PUMP 13 4 SEER2 AIR CONDITIONER ...

Page 6: ...acturer reserves the right to change at any time specifications and designs without notice and without obligations 6 A220854 Fig 5 13 4 SEER2 Air Conditioner Medium and Large Cabinet with Louvers 13 4 SEER2 Air Conditioner ...

Page 7: ... panel to access components above See Fig 7 3 Access or removal of the condenser coil a Removal of the top the control compressor panel the front left side louver panel b Screws from the compressor compartment and either the side of the unit or below the condenser fan depending on the shape of coil will need to be removed to remove condenser coil See Fig 8 4 Access or removal of the evaporator coi...

Page 8: ...ons 8 Labeling The wiring schematic sub cooling charging tables with instructions and warning labels Refer to Fig 10 for label location A10163 Fig 10 Label Location FIELD CONNECTIONS BLOWER PANEL WIRING DIAGRAM ON BACKSIDE OF CONTROL FRONT OF CONTROL COMPRESSOR PANEL WARNING ADVERTISSMENT WARNING ADVERTISSMENT WARNING ADVERTISSMENT ...

Page 9: ...0k scale Using an analog ohmmeter check each terminal to ground use capacitor case Discard any capacitor which measures 1 2 scale deflection or less Place ohmmeter leads across capacitor and place on R X 10k scale Meter should jump to a low resistance value and slowly climb to higher value Failure of meter to do this indicates an open capacitor If resistance stays at 0 or a low value capacitor is ...

Page 10: ...s or heat pumps R 410A pressure switches are identified by a pink stripe down each wire Low Pressure Switch Neither of the air conditioner or heat pump units have a low pressure switch The heat pump models have a loss of charge switch located downstream of the liquid line filter drier See loss of charge for more details High Pressure Switch AC HP The high pressure switch is located in the discharg...

Page 11: ...at or Off the valve is de energized There is no compressor delay built into this control A05332 Fig 14 Defrost Control Heating Sequence of Operation On a call for heating thermostat makes R Y and R G Circuit R Y sends low voltage through the safeties and energizes the contactor which starts the compressor and energizes the T1 terminal on the circuit board The T1 terminal energizes the defrost logi...

Page 12: ...gations 12 A220832 Fig 15 DFT Sensor Location 024 048 SEE DETAIL B DETAIL SEE DETAIL D DETAIL D SEE DETAIL F DETAIL SEE DETAIL H DETAIL H HIURVW WKHUPRVWDW FDQ HLWKHU EH ORFDWHG RQ WKH ERWWRP RI WXEH DV VKRZQ RU RQ WKH WRS DQG PXVW QRW LQWHUIHUH ZLWK DQ RWKHU WXELQJ 030 036 13 4 SEER2 042 13 4 SEER2 048 13 4 SEER2 024 13 4 SEER2 ...

Page 13: ...Whether the unit is in heating or cooling mode it will run a defrost cycle for 10 minutes each time the compressor has been energized for the selected time interval The board will terminate automatically after 10 minutes of defrost time regardless of defrost thermostat position If defrost thermostat is stuck open The unit will not defrost If unit will not defrost 1 Perform the speedup function as ...

Page 14: ...0 F 10ºC to 70 F 21 1ºC Resistance goes from zero to when contacts are open 8 If either opening or closing temperature does not fall within above ranges or thermostat sticks in 1 position replace thermostat to ensure proper defrost operation NOTE With timing cycle set at 90 minutes unit initiates defrost within approximately 21 sec When you hear the reversing valve changing position remove screwdr...

Page 15: ... manufacturer s performance data 4 A whistling or squealing noise during operation may indicate a partial blockage of the refrigerant charge 5 A whistle on shut down could indicate a partial leak path as refrigerant is equalizing from high to low side On occasion an in line discharge check valve has prevented this sound 6 If a compressor hums but won t start it could indicate either a voltage or a...

Page 16: ... sources of problems have been eliminated compressor must be replaced Because compressor is a sealed unit it is impossible to determine exact mechanical failure However complete system should be checked for abnormalities such as incorrect refrigerant charge restrictions insufficient airflow across indoor or outdoor coil etc which could be contributing to the failure Runs Does Not Pump In this type...

Page 17: ...not run although external electrical and mechanical systems appear normal Compressor must be checked electrically for abnormalities Before troubleshooting compressor motor review this description of compressor motor terminal identification Single Phase Motors To identify terminals C S and R 1 Turn off all unit power 2 Short the run and start capacitors to prevent shock 3 Remove all wires from moto...

Page 18: ...mpressor Removal and Replacement Once it is determined that compressor has failed and the reason established compressor must be replaced 1 Shut off all power to unit 2 Remove and recover all refrigerant from system until pressure gages read zero psig Use all service ports 3 Disconnect electrical plug from compressor Disconnect or remove crankcase heater if equipped and remove compressor holddown n...

Page 19: ...ing or first stage heating for heat pumps O Energizes reversing valve on heat pumps C Common side of transformer G Indoor Fan Ground Circuit To determine if a wire has broken or come in direct contact with shell causing a direct short to ground follow these steps 1 Recover all refrigerant charge 2 Using an ohmmeter on R X 10 000 ohm scale or megohmmeter follow manufacturer s instructions 3 Be sure...

Page 20: ...checked such as frost or condensate water on refrigerant tubes The sound made by a reversing valve as it begins or ends defrost is a whooshing sound as the valve reverses and pressures in system equalize An experienced service technician detects this sound and uses it as a valuable troubleshooting tool Using a remote measuring device check inlet and outlet line temperatures DO NOT touch lines If r...

Page 21: ...tor with liquid refrigerant The bleed hole allows a small amount of oil and refrigerant to enter the return line where velocity of refrigerant returns it to compressor If bleed hole plugs oil is trapped in accumulator and compressor will eventually fail from lack of Table 3 Compressor Information 13 4 SEER2 AC Unit Size 24 30 36 42 48 60 Type Emerson Scroll Emerson Scroll Emerson Scroll LG Scroll ...

Page 22: ...tdown TXVs are specifically designed to operate with R 410A refrigerant use only factory authorized TXV s Do not interchange R 410A and R 22 TXVs TXV Operation The TXV is a metering device that is used in air conditioning and heat pump systems to adjust to changing load conditions by maintaining a preset superheat temperature at the outlet of the evaporator coil The volume of refrigerant metered t...

Page 23: ...ston TXV Number Outdoor Heating Piston Number 13 4 SEER2 24 57 30 63 36 67 42 76 48 80 60 TXV Heat Pump Unit Size ton Indoor Cooling Piston TXV Number Outdoor Heating Piston Number 13 4 SEER2 24 57 30 63 55 36 67 57 42 76 59 48 TXV 60 TXV 70 WARNING PERSONAL INJURYAND ENVIRONMENTAL HAZARD Failure to relieve system pressure could result in personal injury and or death 1 Relieve pressure and recover...

Page 24: ...power to unit 2 Recover refrigerant from system through high flow service valves 3 Break vacuum with nitrogen 4 Remove top cover See Access Compressor or other internal cabinet component Fig 6 Fig 8 5 Remove screws in coil panels 6 Use midget tubing cutter to cut liquid and vapor lines at both sides of coil Cut in convenient location for easy reassembly with copper slip couplings 7 Lift coil verti...

Page 25: ...and assure a tight dry system before charging The 2 methods used to evacuate a system are the deep vacuum method and the triple evacuation method Deep Vacuum Method The deep vacuum method requires a vacuum pump capable of pulling a vacuum of 500 microns and a vacuum gauge capable of accurately measuring this vacuum depth The deep vacuum method is the most positive way of assuring a system is free ...

Page 26: ...ely not controlling properly i e stuck open REPLACE VALVE If superheat is higher than 15 F proceed to Step 3 3 Perform TXV function check With system running place sensing bulb in ice bath for 1 minute superheat should increase If no response Replace Valve If OK proceed to Step 4 4 Check for even temperature distribution at outlet of each circuit of evaporator If greater than 15 F between circuits...

Page 27: ...air return air wet bulb temperature with a sling psychrometer or electronic equivalent 6 Using Superheat Charging Table Table 6 find outdoor temperature and indoor air wet bulb temperature At this intersection note superheat Where a dash appears on table do not attempt to charge unit under these conditions or refrigerant slugging may occur In this situation refrigerant must be evacuated and weighe...

Page 28: ... for Safe Electric Heater Operation Air Conditioner AC Unit Size Minimum Airflow CFM 5 kW 7 5 kW 10 kW 15 kW 20 kW 24 600 750 750 X X 30 600 750 750 X X 36 600 750 750 1050 X 42 600 750 750 1050 X 48 600 750 750 1050 1400 60 600 750 750 1050 1400 Heat Pump HP Unit Size Minimum Airflow CFM 5 kW 7 5 kW 10 kW 15 kW 20 kW 24 750 800 800 X X 30 750 800 800 X X 36 750 800 800 1200 X 42 750 800 800 1200 ...

Page 29: ...12 107 102 97 92 2785 45 42 39 36 33 414 114 109 104 99 94 2854 46 43 40 37 34 424 116 111 106 101 96 2923 47 44 41 38 35 434 118 113 108 103 98 2992 48 45 42 39 36 444 119 114 109 104 99 3061 48 46 43 40 37 454 121 116 111 106 101 3130 49 47 44 41 38 464 123 118 113 108 103 3199 50 48 45 42 39 474 124 119 114 109 104 3268 51 48 46 43 40 484 126 121 116 111 106 3337 52 49 47 44 41 494 127 122 117 ...

Page 30: ...ower off to the unit Disconnect the two plugs going into the motor One plug is the high voltage supply and the other is the low voltage control Cycle power back on and measure the high voltage supply plug to determine if there is voltage at plug If there is no voltage at plug determine if there is power to the unit The easiest place to measure the voltage is on the line side of the contactor If th...

Page 31: ...ntrol panel will expose most of the unit s components Both the air conditioner and heat pump control boxes will be in the upper right corner of the unit There will be a contactor that cycles components off and on The capacitor will assist the outdoor fan and compressor to operate The heat pump models will have a circuit board to control the defrost cycle Always replace these devices with the Facto...

Page 32: ...lectric Heat wiring interconnection electric heater controls removed for clarity Electric Heat Control Box shown uninstalled Electric Heat wiring interconnection electric heater controls removed for clarity Electric Heat Control Box shown uninstalled Air Conditioning Control Box Wiring Heat Pump Control Box Wiring A10030 A10031 HIGH VOLTAGE POWER WIRING ENTRY HOLE LOW VOLTAGE WIRING ENTRY HOLE gro...

Page 33: ...ual Manufacturer reserves the right to change at any time specifications and designs without notice and without obligations 33 A210120 Fig 33 Typical Air Conditioning Single Phase Unit Connection Electrical Diagram ...

Page 34: ...anual Manufacturer reserves the right to change at any time specifications and designs without notice and without obligations 34 A210121 Fig 34 Typical Air Conditioning Single Phase Unit Ladder Electrical Diagram ...

Page 35: ...ervice Manual Manufacturer reserves the right to change at any time specifications and designs without notice and without obligations 35 A210797 Fig 35 Typical Heat Pump Unit Connection Electrical Diagram ...

Page 36: ... Service Manual Manufacturer reserves the right to change at any time specifications and designs without notice and without obligations 36 A210799 Fig 36 Typical Heat Pump Unit Ladder Electrical Diagram ...

Page 37: ...d basepan 5 Reinstall side panel 6 Reconnect electrical power and check for proper operation Cleaning Outdoor Fan Motor and Blade 1 Remove grille fan motor and blade Be careful not to bend or dent fan blade 2 Clean motor and blade with soft brush or cloth Be careful not to disturb balance weights on fan blade 3 Check fan blade setscrew for tightness 4 Reinstall fan motor and blade to grille and ch...

Page 38: ...3 53 5 592 147 9 64 4 58 7 3 13 7 160 56 2 13 4 262 86 9 30 5 364 110 0 43 3 466 128 7 53 7 596 148 4 64 7 60 8 6 13 0 162 57 0 13 9 264 87 4 30 8 366 110 4 43 6 468 129 0 53 9 600 149 0 65 0 62 10 0 12 2 164 57 7 14 3 266 87 9 31 1 368 110 8 43 8 470 129 3 54 1 604 149 5 65 3 64 11 3 11 5 166 58 4 14 7 268 88 4 31 3 370 111 2 44 0 472 129 7 53 2 608 150 1 65 6 66 12 6 10 8 168 59 0 15 0 270 88 9 ...

Page 39: ...TIVE RUN CAPACITOR OUTDOOR FAN STOPPED OR CYCLING ON OVERLOAD OUTDOOR AIR RESTRICTED OR RECIRCULATING RESTRICTED DISCHARGE TUBE OVERCHARGE OR NON CONDENSABLES IN SYSTEM LOW REFRIGERANT CHARGE LINE VOLTAGE TOO HIGH OR LOW DEFECTIVE RUN CAPACITOR COMPRESSOR BEARINGS HIGH SUPERHEAT LOOSE LEAD AT FAN MOTOR MOTOR DEFECTIVE LOW SUCTION PRESSURE DIRTY AIR FILTERS DUCT RESTRICTED DAMPERS PARTLY CLOSED COM...

Page 40: ...OAD CONDITION REVERSING VALVE JAMMED IN MIDPOSITION HIGH SUPERHEAT DEFECTIVE FAN MOTOR CAPACITOR LOOSE LEADS AT FAN MOTOR FAN MOTOR BURNED OUT LOW SUCTION LOW HEAD OUTDOOR FAN STOPPED LOOSE LEADS AT OUTDOOR FAN MOTOR INTERNAL FAN MOTOR KLIXON OPEN FAN MOTOR BURNED OUT DEFROST RELAY N C CONTACTS OPEN ON CIRCUIT BOARD REVERSING VALVE DID NOT SHIFT UNIT NOT PROPERLY CHARGED OUTDOOR FAN RUNNING REVERS...

Page 41: ...R OUTDOOR FAN STOPPED OR CYCLING ON OVERLOAD OUTDOOR AIR RESTRICTED OR RECIRCULATING DAMAGED OR STUCK REVERSING VALVE RESTRICTED DISCHARGE TUBE OVERCHARGE OR NON CONDENSABLES IN SYSTEM LOW REFRIGERANT CHARGE LINE VOLTAGE TOO HIGH OR LOW DEFECTIVE RUN CAPACITOR COMPRESSOR BEARINGS HIGH SUPERHEAT LOOSE LEAD AT FAN MOTOR DEFROST RELAY N C CONTACTS OPEN MOTOR DEFECTIVE LOW SUCTION PRESSURE DIRTY AIR F...

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