Defrost Control - Carrier 50JZ024 Installation, Start-Up And Service Instructions Manual

1. Place room thermostat SYSTEM switch or MODE control in
OFF position. Observe that blower motor starts when FAN
mode is placed in FAN ON position and shuts down within 60
sec (030-060 size) or 30 sec (024 size) when FAN MODE
switch is placed in AUTO position.
2. Place SYSTEM switch or MODE control in COOL position
and FAN mode in AUTO position. Set control below room
temperature. Observe that cooling cycle shuts down when
control setting is satisfied.
3. Place SYSTEM switch or MODE control in HEAT position.
Set control above room temperature. Observe that compressor,
outdoor fan, and indoor blower motors start. Observe that
heating cycle shuts down when control setting is satisfied.
4. When using an automatic changeover room thermostat, place
both SYSTEM or MODE control and FAN mode switches in
AUTO positions. Observe that unit operates in Cooling mode
when temperature control is set to ''call for Cooling'' (below
room temperature), and unit operates in Heating mode when
temperature control is set to "call for Heating" (above room
temperature).
IMPORTANT: Three-phase, scroll compressors are direction ori-
ented. Unit must be checked to ensure proper compressor 3-phase
power lead orientation. If not corrected within 5 minutes, the
internal protector may shut off the compressor. The 3-phase power
leads to the unit must be reversed to correct rotation. When turning
backwards, the difference between compressor suction and dis-
charge pressures may be dramatically lower than normal.
CHECKING AND ADJUSTING REFRIGERANT CHARGE
— The refrigerant system is fully charged with R-410A refriger-
ant and is tested and factory sealed.
NOTE: Adjustment of the refrigerant charge is not required
unless the unit is suspected of not having the proper R-410A
charge. The charging label and the tables shown refer to system
temperatures and pressures in cooling mode only. A refrigerant
charging label is attached to the outside of the service access door.
If charge level is suspect in Heating mode, reclaim all refrigerant
and charge to nameplate amount. (This information may be
obtained from the physical data table also.)
IMPORTANT: When evaluating the refrigerant charge, an indi-
cated adjustment to the specified factory charge must always be
very minimal. If a substantial adjustment is indicated, an abnormal
condition exists somewhere in the cooling system, such as insuf-
ficient airflow across either coil or both coils.
REFRIGERANT CHARGE — The amount of refrigerant charge
is listed on the unit nameplate and /or the physical data table. Refer
to Carrier Refrigeration Service Techniques Manual, Refrigerants
Section.
NO CHARGE — Check for leak. Use standard evacuating tech-
niques. After evacuating system, weigh in the specified amount of
refrigerant (refer to system data plate).
LOW CHARGE COOLING — Use Cooling Charging Charts
(Fig. 23-28). Vary refrigerant until the conditions of the chart are
met. Note that charging charts are different from type normally
used. Charts are based on charging the units to correct superheat
for the various operating conditions. Accurate pressure gauge and
temperature sensing devices are required. Connect the pressure
gauge to the service port on the suction line. Mount the tempera-
ture sensing device on the suction line and insulate it so that the
outdoor ambient does not effect the reading. Indoor air CFM must
be within the normal operating range of the unit.
TO USE COOLING CHARGING CHARTS — Take the outdoor
ambient temperature and read the suction pressure gauge. Refer to
the chart to determine what the suction temperature should be.
NOTE: If the problem causing the inaccurate readings is a
refrigerant leak, refer to Check for Refrigerant Leaks section.
INDOOR AIRFLOW AND AIRFLOW ADJUSTMENTS
For heating and cooling operation, the recommended airflow
is 350 to 450 cfm for each 12,000 Btuh of rated cooling
capacity. for units with optional electric heat, the airflow must
not be reduced below the levels stated in Table 2.
Table 4 shows both heating and cooling airflows at various
external static pressures. Refer to these tables to determine the
airflow for the system being installed.
NOTE: Be sure that all supply-and return-air grilles are open, free
from obstructions, and adjusted properly.
Airflow can be changed by changing the lead connection of the
blower motor.
Unit 50JZ three-speed motors (except size 030 and 048) are
factory wired for low speed operation. Unit 50JZ 030 and 048 are
factory wired for medium speed.
For 208/230v Motors:—The motor leads are color-coded as
follows:
3-SPEED
Black = high speed
Blue = medium speed
Red = low speed
To change the speed of the blower motor (BM), remove the fan
motor speed leg lead from the blower relay (BR). This wire is
attached to IGC terminal BM for single-phase and 3-phase units.
To change the speed, remove and replace with lead for desired
blower motor speed. Insulate the removed lead to avoid contact
with chassis parts.
For 460v GE Motors—The motor leads are color coded as follows:
3-SPEED
Black = high
Violet = jumper
Orange = medium
Red = low
To change the speed of the blower motor (BM), remove fan motor
speed lead from the blower relay (BR) and replace with the lead
for the desired blower motor speed. The motor speed lead is
attached to terminal BM. For low and medium speeds black must
be connected to the jumper wire. Insulate removed lead end to
avoid contact with chassis parts. To select high speed on 460v GE
motors, separate the black female quick connect (QC) from the
jumper lead male quick connect (QC) and connect the black lead
to the BR. Insulate the jumper to avoid contact with any chassis
parts.
Step 3—Defrost Control
QUIET SHIFT — Quiet Shift is a field-selectable defrost mode,
which will eliminate occasional noise that could be heard at the
start of defrost cycle and restarting of heating cycle. It is selected
by placing DIP switch 3 (on defrost board) in ON position.
When Quiet Shift switch is placed in ON position, and a defrost is
initiated, the following sequence of operation will occur. Revers-
ing valve will energize, outdoor fan will turn off, compressor will
turn off for 30 sec and then turn back on to complete defrost. At
the start of heating after conclusion of defrost reversing valve will
de-energize, compressor will turn off for another 30 sec, and the
outdoor fan will stay off for 40 sec, before starting in the heating
mode.
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