System information

17
Checking cooling and heating control operation
Start and check the unit for proper control operation as follows:
1. Place room thermostat SYSTEM switch or MODE control
in OFF position. Observe that fan motor starts when FAN
mode is placed in FAN ON position and shuts down after
proper fan off delay, when FAN MODE switch is placed
in AUTO position.
2. Place system switch or MODE control in HEAT position.
Set control above room temperature. Observe that
compressor, outdoor fan, and indoor fan motors start.
Observe that heating cycle shuts down when control
setting is satisfied.
3. 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
oriented. Unit must be checked to ensure proper compressor
3-phase power lead orientation. If not corrected within the
phase monitor (Fig. 23) will not provide the unit with power.
A red light on the phase monitor will blink. The 3-phase
power leads to the unit must be reversed to correct rotation.
Checking and adjusting refrigerant charge
The refrigerant system is fully charged with R-410A refrigerant
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 (see the physical data table).
IMPORTANT: When evaluating the refrigerant charge, an
indicated 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 insufficient air flow across either coil
or both coils.
Refrigerant charge
The amount of refrigerant charge is listed on the unit nameplate
and/or in the physical data table. Refer to the Refrigeration
Service Techniques Manual, Refrigerants Section.
No charge
Check for leak. Use standard evacuating techniques. After
evacuating system, weigh in the specified amount of refrigerant
(refer to system data plate).
Low charge cooling
Use cooling charging table. Vary refrigerant until the conditions
of the table are met. Note that charging tables are different
from the type normally used. Tables 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 temperature sensing device on the
suction line and insulate it so that the outdoor ambient does not
affect the reading. Indoor air flow must be within the normal
operating range of the unit.
Heating mode charge
Do not attempt to adjust charge by cooling methods while in
heating mode. When charging is necessary in heating mode,
recover refrigerant and weigh in according to unit data plate
refrigeration data.
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 air flow and air flow adjustments
CAUTION: For heating and cooling operation, the recom-
mended air flow is 165 l/s to 212 l/s for each 3.5 kW of rated
cooling capacity. For units with optional electric heat, the air
flow must not be reduced below the levels stated in Table 2.
Table 4 shows both heating and cooling air flows at various
external static pressures. Refer to this table to determine the air
flow for the system being installed.
NOTE: Be sure that all supply- and return-air grilles are
open, free from obstructions, and adjusted properly.
Air flow can be changed by changing the lead connection of
the fan motor. To change the speed of the indoor fan motor
(IFM), remove the fan motor speed leg lead from the indoor
fan contactor (IFC). To change the speed, remove and replace
with lead for desired fan motor speed. Insulate the removed
lead to avoid contact with chassis parts.
For 400-V motors: The motor leads are color coded as follows:
3-speed 2–speed
Black = high Black = high
White = common Red = low
Blue = medium Yellow = common
Red = low
To change the speed of the indoor fan motor (IFM), remove fan
motor speed lead from the indoor fan contactor (IFC) and
replace with the lead for the desired fan motor speed. The
motor speed lead is attached to terminal BM. Insulate removed
lead end to avoid contact with chassis parts.