Service Manual

54
CHECK CHARGE
All Two- Stage units must be charged in high stage only.
(See Charging Tables 8 & 10)
Factory charge amount and desired subcooling are shown
on unit rating plate. Charging method is shown on
information plate inside unit. To properly check or adjust
charge, conditions must be favorable for subcooling
charging. Favorable conditions exist when the outdoor
temperature is between 70_F and 100_F (21.11_C and
37.78_C), and the indoor temperature is between 70_F and
80_F (21.11_C and 26.67_C). Follow the procedure below:
Unit is factory charged for 15ft (4.57 m) of lineset. Adjust
charge by adding or removing 0.6 oz/ft of 3/8 liquid line
above or below 15ft (4.57 m) respectively.
For standard refrigerant line lengths (80 ft/24.38 m or less),
allow system to operate in cooling mode at least 15 minutes.
If conditions are favorable, check system charge by
subcooling method. If any adjustment is necessary, adjust
charge slowly and allow system to operate for 15 minutes to
stabilize before declaring a properly charged system.
If indoor temperature is above 80_F (26.67_C), and outdoor
temperature is in the favorable range, adjust system charge
by weight based on line length and allow indoor temperature
to drop to 80_F (26.67_C) before attempting to check
system charge using subcooling method described above.
If the indoor temperature is below 70_F (21.11_C), or the
outdoor temperature is not in the favorable range, adjust
charge for line set length above or below 15ft (4.57 m) only.
Charge level should then be appropriate for the system to
achieve rated capacity. The charge level could then be
checked at another time when the both indoor and outdoor
temperatures are in a more favorable range.
NOTE: If line length is beyond 80 ft (24.38 m) or greater
than 20 ft (6.10 m) vertical separation, see Split System
Long Line Applications Guidelines for special charging
requirements.
Heating Check Chart Procedure
To check system operation during heating cycle, refer to the
Tech Label on outdoor unit. This chart indicates whether a
correct relationship exists between system operating
pressure and air temperature entering indoor and outdoor
units. If pressure and temperature do not match on chart,
system refrigerant charge may not be correct. Do not use
chart to adjust refrigerant charge.
NOTE: When charging is necessary during heating season,
charge must be weighed in accordance with unit rating
plate, ±0.6 oz./ft. of 3/8- in. liquid- line above or below 15 ft.,
respectively.
EXAMPLE:
To calculate additional charge required for a 25- ft. line set:
25 ft. - 15 ft. = 10 ft. X 0.6 oz./ft. = 6 oz. of additional charge.
SYSTEM FUNCTIONS AND SEQUENCE
OF OPERATION
(*CA7, *CA9, *CH6, *CH9)
The outdoor unit control system has special functions. The
following is an overview of the two- stage control functions:
Cooling and Heating Operation
The *CA7, *CA9, *CH6, and *CH9 model utilizes either a
standard 2- stage indoor thermostat or Communication wall
control. With a call for first stage cooling, the outdoor fan,
reversing valve, and low stage compressor are energized. If
low- stage cannot satisfy cooling demand, high- stage
cooling is energized by the second stage of indoor
thermostat or wall control. After second stage is satisfied,
the unit returns to low- stage operation until first stage is
satisfied or until second stage is required again. When both
first stage and second stage cooling are satisfied, the
compressor will shut off. The reversing valve will remain
energized until the control board power is removed or a call
for heating is initiated. With a call for heating, the outdoor
fan and compressor are energized. The compressor will
operate in high or low stage operation, as needed to meet
the heating demand. When the heating demand is satisfied,
the compressor and fan will shut off. The reversing valve is
de- energized in the heating mode.
NOTE: When two- stage unit is operating at low- stage,
system vapor (suction) pressure will be higher than a
standard single- stage system or high- stage operation.
NOTE: Outdoor fan motor will continue to operate for one
minute after compressor shuts off, when outdoor ambient is
greater than or equal to 100°F. This reduces pressure
differential for easier starting on next cycle.
NOTE: If unit has not operated within the past 12 hours, or
following a unit power- up, upon the next thermostat high-
or low- stage demand, unit operates for a minimum of 5
minutes in high- stage.
On models with non- communicating systems, with first
stage of cooling, Y1 and O are powered on; and with
second stage of cooling, Y1, Y2, and O are on. For these
systems, with first stage of heating Y1 is on and for second
stage of heating, Y1 and Y2 are on. When the reversing
valve is energized, O is powered on.
Communication and Status Function Lights
For Communicating Control only, Green
communications (COMM) Light
A green LED (COMM light) on the outdoor board indicates
successful communication with the other system products.
The green LED will remain OFF until communication is
established. Once a valid command is received, the green
LED will turn ON continuously. If no communication is
received within 2 minutes, the LED will be turned OFF until
the next valid communication.
Amber Status
Light
An amber colored STATUS light is used to display the
operation mode and fault codes as specified in the
troubleshooting section. See Table 17 for codes and
definitions.
NOTE: Only one code will be displayed on the outdoor unit
control board (the most recent, with the highest priority).
Compressor Operation
The basic scroll design has been modified, adding an
internal unloading mechanism that opens a bypass port in
the first compression pocket, effectively reducing the
displacement of the scroll. Opening and closing of the
bypass port is controlled by an internal electrical solenoid.
The modulated scroll uses a single step of unloading to go
from full capacity to approximately 67% capacity. A single
speed, high efficiency motor continues to run while the scroll
modulates between the two capacity steps. Modulation is
achieved by venting a portion of the gas in the first suction
pocket back to the low side of the compressor, thereby
reducing the effective displacement of the compressor. Full
capacity is achieved by blocking these ports, thus
increasing the displacement to 100%. A DC solenoid in the
compressor controlled by a rectified 24 volt AC signal in the
external solenoid plug moves the slider ring that covers and
uncovers these ports. The port covers are arranged in such
a manner that the compressor operates at approximately