Carrier 024-036, Service Manual, Page: 27 / 41

: Service Manual
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
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4. Check for even temperature distribution (±5° difference) at outlet of
each circuit of evaporator and for even air distribution over all
evaporator slabs
• If OK proceed to Step 5
5. Move sensing bulb further down suction line.
• If problem not corrected, replace valve
Indoor Airflow and Airflow Adjustments
NOTE: Be sure that all supply- and return-air grilles are open, free from
obstructions, and adjusted properly.
Blower speed tap can be changed by replacing the factory installed blue
low speed tap wire (cooling) with the unused black high speed wire in
unit control box. The red medium speed wire is factory installed to
operate with a call for supplemental electric heat. See unit wiring
diagram.
Be sure new airflow meets the range noted above and minimum electric
heat CFM, if equipped. Refer to Table 5 .
All model sizes are factory wired or rated airflow operation.
Refrigerant Charge
Refrigerant Charge — The refrigerant system is fully charged with
R-410A refrigerant and is tested and factory sealed. Amount of
refrigerant charge is listed on unit’s rating plate. Unit must operate a
minimum of 15 minutes before checking charge.
NOTE: Adjustment of the refrigerant charge is not required unless the
unit is suspected of not having the proper R-410A charge.
NOTE: Units will have either fixed orifice or TXV metering devices
and each style has a different charging procedure. Refer to Table 4 to
find unit specific metering device. See below for correct charging
procedures.
NO CHARGE
Use standard evacuating techniques. After evacuating system, weigh in
the specified amount of refrigerant (refer to unit’s rating plate).
LOW CHARGE COOLING
Fixed Metering Device
1. Operate unit a minimum of 10 minutes before checking charge.
2. Measure suction pressure by attaching an accurate gauge to
compressor suction side service port.
3. Measure suction side temperature by attaching an accurate
thermisitor type or electronic thermometer to suction line about 10
in. from compressor.
4. Measure outdoor air dry-bulb temperature with thermometer.
5. Measure indoor 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 weighed
in. See rating plate for charge quantity.
7. Refer to Required Suction Tube Temp. Table ( Table 6 ). Find
superheat temperature located in Step 6 and suction pressure. At
this intersection note suction line temperature.
8. If unit has a higher suction line temperature than charted
temperature, add refrigerant until charted temperature is reached.
9. If unit has a lower suction line temperature than charted
temperature, reclaim refrigerant until charted temperature is
reached.
10. If outdoor air temperature or pressure at suction port changes,
charge to new suction line temperature indicated on chart.
TXV Metering Device
1. Measure Discharge line pressure by attaching a gauge to the service
port.
2. Measure the Liquid line temperature by attaching a temperature
sensing device to it.
3. Insulate the temperature sensing device so that the Outdoor
Ambient doesn’t affect the reading.
4. Refer to the required Subcooling in Table 7 based on the model size
and the Outdoor Ambient temperature.
5. Interpolate if the Outdoor ambient temperature lies in between the
table values.
6. Find the Pressure Value in the table corresponding to the measured
Pressure of the Compressor Discharge line.
7. Read across from the Pressure reading to obtain the Liquid line
temperature for a required Subcooling.
8. Add Charge if the measured temperature is higher than the table
value.
9. Remove charge if the measured temperature is lower than the table
value.
Heating Mode
NOTE: When charging is necessary during heating season, charge must
be weighed in accordance with unit rating plate.
WARNING
!
UNIT OPERATION HAZARD
Failure to follow this caution may result in equipment damage or
improper operation.
For cooling operation, the recommended airflow is 350 to 450 cfm for
each 12,000 Btuh of rated cooling capacity.
WARNING
!
ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal injury or death.
Disconnect electrical power to the unit and install lockout tag before
changing blower speed.