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Manual 2100-538E
Page 16 of 23
SEQUENCE OF OPERATION
MODES OF OPERATION
Cool Only Mode:
• Compressor will modulate from 100% down to 20%.
• Compressor will cycle off if thermostat/controller set-
point is reached.
Heat Only Mode:
•
Electric heat Stage 1 operates at 1
st
-stage heating set-point.
• Electric heat Stage 2 (if equipped) operates on 2
nd
stage (-2F below heating set-point).
Auto Mode:
• Cooling or heating automatically selected based on
building temperature vs. thermostat/controller set-
points and operates as described above.
CCVC (Continuous Compressor Variable Capacity):
• Compressor will modulate from 100% down to 20%.
• Compressor
will not cycle off if thermostat/controller
set-point is reached, and would stay running at the
20% minimum capacity.
• If space temperature drops -2F below cooling set-point
electric heat Stage 1 will then cycle to maintain that
condition.
• If Stage 2 electric heat is installed, and if required, will
cycle at -4F below cooling set-point to maintain that
condition.
• If CCVC is terminated the controller will revert to
Cool or Auto operation.
•
CCVC would be an Operating Mode for all
applications where continuous run of the compressor
is a requirement.
Testing & Troubleshooting Mode CCFC (Continuous
Compressor Fixed Capacity):
• This unit must be controlled with the digital thermostat
controller supplied with the unit. To test or
troubleshoot, change system mode to CCFC. This will
ensure unit runs continuously and in full capacity
mode. AHRI ratings are based on this mode of
operation.
CCFC (Continuous Compressor Fixed Capacity):
• The compressor is turned ON and locked ON as long
as the thermostat/controller is in Test Mode 2.
• When in CCFC the compressor does not modulate but
will be locked ON at 100% capacity.
• If space temperature drops -2F below cooling set-point
electric heat Stage 1 will then cycle to maintain that
condition.
• If Stage 2 electric heat is installed, and if required, will
cycle at -4F below cooling set-point to maintain that
condition.
• If CCFC is terminated the controller will revert to
Cool or Auto operation.
• CCFC would not be considered an Operating Mode
and should only be used for system testing as required.
Indoor Blower Operation
The indoor blower speed will modulate with the
compressor operation from 50% to 100% of operation.
Once compressor operation is at 50 or below, percent
airflow will be at 50% and no further reduction of
airflow will occur. Modulation is accomplished by
modulating a 0-10 volt signal from OUT 7 to the indoor
blower control board which then sends a PWM signal to
the indoor blower motor.
An additional option to maintain airflow at 100% is also
available. This selection is done at the thermostat/
controller under Fan Modes. Default is No for “Always
100%”setting. Change to Yes to disable indoor blower
modulation as described above.
2 LED’s are located on the Blower Control Board. The
Red LED will light anytime 24V is applied to the board
and it is connected to the ECM motor. The Green LED
will flash a series of short and long flashes depending on
the output from the digital thermostat/controller.
Outdoor Fan Motor Operation
The outdoor fan motor speed is varied in response to
outdoor air temperature and pressure. The fan motor
will cycle on and off with the compressor when not in a
CCVC or CCFC. At all times above 122 degrees OAT,
the outdoor fan, OUT 9, will be energized at high speed.
From 122 degrees to 55 degrees the outdoor fan, OUT
9, will be set at normal outdoor airflow. Below 55
degrees the outdoor fan will modulate to maintain a 300
psi head pressure. This will act as a low ambient fan
cycling control. The output may go to zero output to
maintain the 300 PSI. The outdoor ECM motor will be
programmed with a minimum RPM allowed to protect
the bearing system. Any signal that is less than the
percent torque required to maintain the minimum RPM
will cause the motor to shut off. Once head pressure
rises the motor will restart.
These functions are regulated by the digital thermostat/
controller with input from the pressure transducer and
output signal to the Fan Control Board.
2 LED’s are located on the outdoor Fan Control Board.
The Red LED is not active and does not light under any
condition. The Green LED will flash a series of short
and long flashes depending on the output from the digital
thermostat/controller.
Capacity Modulation and High Head Pressure Control
The pressure transducer monitors the high side pressure
providing input to the digital thermostat/controller. It is
powered using a 5Vdc power supply with a digital relay
signaling the compressor unloader solenoid as required.
When the ECU head pressure exceeds 615 PSI based on
outdoor and indoor ambient conditions the compressor
will automatically start to reduce capacity to stay on-line
keeping the pressure at or below 575 PSI. The
thermostat/controller display alternates between OD
temperature and discharge pressure. When compressor
capacity is being reduced due to high pressure conditions
it will also indicate “High Head Pressure Control” mode
on the display. A separate 650 PSI high pressure cutout
switch is also employed as additional safety device. See
Compressor Control Module on following page for more
details.