Power Failure; Refrigerant Charge; Thermostatic Expansion Valve (Txv) - Carrier WeatherMaker 48A2020 Controls, Start-Up, Operation, Service And Troubleshooting Instructions

Power Failure

The economizer damper motor is a spring return design. In
event of power failure, dampers will return to fully closed posi-
tion until power is restored.

Refrigerant Charge

Amount of refrigerant charge is listed on unit nameplate. Refer
to Carrier GTAC II; Module 5; Charging, Recovery, Recycling,
and Reclamation section for charging methods and procedures.
Unit panels must be in place when unit is operating during
charging procedure.
NOTE: Do not use recycled refrigerant as it may contain
contaminants.
NO CHARGE
Use standard evacuating techniques. After evacuating system,
weigh in the specified amount of refrigerant from the unit
nameplate.
LOW CHARGE COOLING
All Units with Round Tube-Plate Fin Condenser Coils
Connect the gage set and a temperature-measuring device to the
liquid line. Ensure that all condenser fans are operating. It may
be necessary to block part of the coil on cold days to ensure that
condensing pressures are high enough to turn on the fans. Adjust
the refrigerant charge in each circuit to obtain state point liquid
subcooling for specific models as listed in Table 110.
NOTE: Indoor-air cfm must be within normal operating range of
unit.
Table 110 — Round Tube, Plate Fin Unit Charge
UNIT REFRIGERANT
48/50 TYPE
A R-410A
48/50A Units with MCHX Condenser
Due to the compact, all aluminum design, microchannel heat
exchangers will reduce refrigerant charge and overall operating
weight. As a result, charging procedures for MCHX units re-
quire more accurate measurement techniques. Charge should
be added in small increments. Using cooling charging charts
provided (Fig. 49-55), add or remove refrigerant until
conditions of the chart are met. As conditions get close to the
point on the chart, add or remove charge in
LIQUID
SIZE
SUBCOOLING
020, 027, 040,
15°F ± 2°F
050, 060
030, 035 20°F ± 2°F
025 12°F ± 2°F
1 / lb increments
4
until complete. Ensure that all fans are on and all compressors
are running when using charging charts.
To Use the Cooling Charging Chart
Use the outdoor air temperature, saturated suction temperature
and saturated condensing temperature (available on the Com-
fortLink display), and find the intersection point on the cooling
charging chart. If intersection point is above the line, carefully
recover some of the refrigerant. If intersection point is below
the line, carefully add refrigerant.
NOTE: Indoor-air cfm must be within normal operating range of
unit.
Units with Humidi-MiZer Adaptive Dehumidification System
All circuits must be running in normal cooling mode. Indoor
airflow must be within specified air quantity limits for cooling.
All outdoor fans must be on and running at normal speed.
Use the following procedure to adjust charge on Circuit B of
Humidi-MiZer equipped units:
1. Start all compressors and outdoor fans. Allow unit to run for
5 minutes.
2. Switch system to run in a Dehumidification mode for 5 min-
utes by switching RHV to ON through the Service Test func-

tion (Service Test
3. At the end of the 5-minute period, switch back into Cooling
mode through the Service Test function (Service Test

COOL RHV) by switching RHV to OFF.
4. Using the cooling charging charts provided (Fig. 49-55), add
or remove refrigerant until conditions of the chart are met.
As conditions get close to the point on the chart, add or re-
move charge in 1 /
graph "To Use the Cooling Charging Chart" for additional
instructions.
5. If a charge adjustment was necessary in Step 4, then repeat
the steps in this paragraph (starting with Step 2) until no
charge adjustment is necessary. When no more charge ad-
justment is necessary after switching from a Dehumidifica-
tion Mode to a Cooling Mode (Steps 2 and 3), then the
charge adjustment procedure is complete.

Thermostatic Expansion Valve (TXV)

Each circuit has a TXV. The TXV is adjustable and is factory
set to maintain 8 to 12°F superheat leaving the evaporator coil.
The TXV controls flow of liquid refrigerant to the evaporator
coils. Adjusting the TXV is not recommended.
142

COOL RHV).
lb increments until complete. See para-
4
 