Unit installation

Page 14
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GENERAL
Operation of the unit heating and cooling cycles is automatic for
HEAT and COOL functions. (The optional automatic changeover
thermostat, when in the AUTO position, automatically changes to
heat or cool with sufficient room temperature change.) The fan
switch can be placed in either the ON position, causing continuous
indoor fan operation on low speed, or the AUTO position causing fan
operation to coincide with heating or cooling run cycles.
COOLING CYCLE
Thermostat call for cool ( 2-stage thermostat)
Call for 1st stage only:
With the room thermostat system switch in the “COOLING” position
and the fan switch in the “AUTO” position,power is supplied from
the indoor thermostat “O” terminal to the switchover valve coil
(SOV) and the "O" terminals on the Control and ICMC boards. This
energizes the switch-over valve (SOV) and places it in the cooling
position (it is in the heating position when de-energized). The Y1
thermostat contact closes to the Control board,
(the Control will wait
3 seconds to check if Y2 may also be calling)
the Control will
energize the compressor contactor (CC1) and RLY-1 the outdoor
fan relay for low speed operation and the G thermostat terminal to
G on the ICMC is energized for low speed (ICM) indoor fan motor
operation . (The status light is flashing and the Y1 light is on.)
The energized compressor contactor (CC1) completes the circuit to
the compressor (CPR1), If the compressor safety controls are
closed, the compressor (CPR1) will operate with the outdoor fan
motor (ODM) on low speed. The (ICM) indoor fan motor will operate
on low speed. The thermostat will continue to cycle the compressor
and fans to maintain the desired temperature.
With the thermostat fan switch in the “ON” position, the G thermo-
stat contact is closed to G on the ICMC board and the the (ICM)
indoor fan motor will continue to run on low speed regardless of
compressor and condenser fan operation.
Call for 2nd stage after 1st stage:
The Y2 thermostat contact closes to the Control board. For 1 minute
both compressors are off, (all lights are flashing for 1 minute), then
the board will energize the (CC2) compressor contactor,and the
RLY-2 outdoor fan relay for high speed and Y from the Control board
to Y on the ICMC board is energized for indoor high speed fan
operation.
(The status light is flashing and the Y1 and Y2 lights are
on.)
2nd stage satisfied, 1st stage still called:
The Y2 thermostat contact opens to the control board. For 1 minute
both compressors are off,
(the status and Y1 light are flashing for 1
minute),
then the Control board will energize the (CC1) low
compressor contactor, and the outdoor fan relay RLY-1 for low
speed and the indoor fan for low speed.
(The status light is flashing
and the Y1 light is on.)
HEATING MODE
Thermostat call for heat ( 2-stage thermostat)
Call for 1st stage only:
the Y1 thermostat contact closes to the control board,
(the board will
wait 3 seconds to check if the Y2 may also be calling) the board will
energize (CC1) and the RLY-1 outdoor fan relay for low speed
operation and the G thermostat contact to G on the ICMC is
energized for low speed (ICM) indoor fan motor operation . (The
status light is flashing and the Y1 light is on.)
SEQUENCE OF OPERATION
Call for 2nd stage after 1st stage:
The Y2 thermostat contact closes to the control board. For 1 minute
both compressors are off, (all lights are flashing for 1 minute), then
the Control board will energize the (CC2) compressor contactor,and
the RLY-2 outdoor fan relay for high speed and Y on the ICMC board
is energized for indoor high speed fan operation.
(The status light
is flashing and the Y1 and Y2 lights are on.)
2nd stage satisfied, 1st stage still called:
The Y2 thermostat contact opens to the Control board. For 1 minute
both compressors are off,
(the status and Y1 and Y2 lights are
flashing for 1 minute),
then the Control board will energize (CC1)
low compressor contactor,and the RLY-1 outdoor fan relay for low
speed and the indoor fan for low speed. (The status light is flashing
and the Y1 light is on.)
SUPPLEMENTARY HEAT
The supplementary electric heat is brought on when the indoor
temperature drops below the thermostat setting. providing power to
the “W” terminal on the indoor thermostat to "W" terminals on the
Control and ICMC boards and to the supplementary heater first
stage control circuit. NOTE: The indoor fan must be on. An outdoor
thermostat may have been added to disallow the second stage (if
provided) of electric heat above a selected outdoor temperature. If
the outdoor temperature falls below the setting on the outdoor
thermostat, this additional heater stage will come on. When the
outdoor air temperature rises, and the outdoor T-stat setpoint is
reached, the system will revert back to first stage electric heating.
When the indoor temperature is satisfied, W contacts will open and
the unit will revert back to the compressor only heating mode and
then off. For emergency heat (use of supplementary electric heat
only), an emergency (EMERG) heat switch is provided on the
thermostat. When placed in the emergency heat position, it will
disable the compressors, bypass the outdoor thermostats, if pro-
vided, and engage the supplementary electric heaters and indoor
fan.
DEMAND DEFROST OPERATION OF THE CONTROL BOARD
During the heating cycle, the outdoor coil may require a defrost
cycle which is determined by the demand defrost control (DFC).
This control continuously measures the outdoor coil temperature
(CBS) and the outdoor ambient temperature (ODS-B) and calcu-
lates the difference or delta-T measurement. When the calculated
delta-T is met, the demand defrost control (DFC) opens the circuit
to the outdoor fan motor (ODM) and energizes the switch-over valve
(SOV), placing the unit in the second stage high cooling mode to
defrost the outdoor coil. The outdoor coil temperature sensor (CBS)
terminates the defrost cycle, or times off after fifteen minutes in
defrost, the (DFC) energizes the outdoor fan motor (ODM) and
twelve seconds later de-energizes the (SOV), which returns the unit
to the heating mode. Supplementary electric heat, if provided, is
brought on to control indoor temperature during the defrost cycle.
ICM FAN MOTOR ADJUSTMENTS
If the airflow needs to be increased or decreased, see the Indoor
Blower Performance Table in the Service Facts. Information on
changing the dip switch settings for speed control of the blower
motor is in this table.
Blower speed changes are made on the ICMC Fan Control mounted
in the control box. The ICMC Fan Control controls the variable
speed motor.
There is a bank of 8 dip switches, (See Figure below), located at the