GSX14 Service Manual

SERVICING
142
AVPTC/MBVC with ASZC/DSZC Heat Pump and CTK0*
Communicating Themostat
The AVPTC or MBVC air handle/modular blower matched
with an ASZC or DSZC condensing unit and CTK0* commu-
nicating thermostat constitute a network. The three compo-
nents, or subsystems, making up the system communicate
with one another with information passed between all three
components. This leads to a somewhat non-traditional
manner in which the system components receive commands
for system operation. All system commands are routed from
the component through the network to the appropriate des-
tination component.
NOTE: Communicating heat pump systems are designed to
utilize a balance point temperature. The balance point
temperature in part controls heat pump operation. If the
outdoor temperature is below the balance point, the heat
pump is disable and only electric heat is available for heating.
The balance point temperature is set via the CTK0* thermo-
stat in the advanced installer's configuration menu.
The CTK0* thermostat also allows the user to disable the
electric heaters in the air handler/modular blower depending
on the outdoor temperature. The electric heaters are dis-
abled If the outdoor temperature is above the set point. All
heating is supplied by the heat pump.
The outdoor air temperature is aquired from the outdoor air
temperature (OAT) sensor included with the ASZC/DSZC
heat pump models. Faults with the sensor will affect heating
operation.
NOTE: The individual subsystems will cease operation if the
request for operation is NOT refreshed after 5 minutes. This
is a built-in safe guard to prevent the possibility of runaway
operation.
1.0 Cooling Operation - Low and High Stage Cool
1.1 The CTK0* thermostat sends a request for low stage
cooling through the network to the unitary (UC) control
in the heat pump. The UC control receives the command
and processes any compressor and fan delays.
1.2 The UC control sends a request for low stage fan speed
to the air handler/modular blower. The blower energizes
the ECM blower motor at the appropriate speed.
1.3 The heat pump energizes the compressor and con-
denser fan motor at the appropriate low stage speeds.
The reversing valve is also energized.
1.4 The system operates at low stage cooling.
1.5 If the thermostat demand cannot be met on low stage
cooling, the CTK0* thermostat sends a request for high
stage cooling to the heat pump. The heat pump in turn
sends a request for high stage fan speed to the air
handler/modular blower. The AH control increases the
blower speed to the high stage cooling speed.
1.6 The heat pump's unitary control energizes the high stage
compressor solenoid and switches the condenser fan
motor to high speed. The reversing valve remains
energized.
1.7 The system operates at high stage cooling.
1.8 Once the thermostat demand is satisfied, the CTK0*
thermostat commands the UC control to end cooling
operation. The heat pump de-energizes the compressor,
condenser fan motor, and reversing valve. The UC control
continues providing a fan request until any cooling blower
OFF delays have expired.
2.0 Heating Operation
Outdoor Temperature Above the Heat Pump Balance
Point
2.1 The CTK0* thermostat sends a request for the outdoor air
temperature to the heat pump. The heat pump returns an
outdoor air temperature that is above the balance point
temperature. Heat pump heating is enabled.
2.2 The CTK0* thermostat sends a request for low stage heat
pump heating to the unitary (UC) control in the heat
pump. The UC control receives the command and
processes any compressor and fan delays.
2.3 The UC control sends a request for low stage fan speed
to the air handler/modular blower. The blower energizes
the ECM blower motor at the appropriate speed.
2.4 The condenser energizes the compressor and con-
denser fan motor at the appropriate low stage speeds.
2.5 The system operates at low stage heat pump heating.
2.6 If the thermostat demand cannot be met on low stage
heat pump heating, the CTK0* thermostat sends a
request for high stage heat pump heating to the heat
pump. The heat pump in turn sends a request for high
stage fan speed to the air handler/modular blower. The
AH control increases the blower speed to the high stage
heat pump heating speed.
2.7 The heat pump's unitary control energizes the high stage
compressor solenoid and switches the condenser fan
motor to high speed.
2.8 The system operates at high stage heat pump heating.
2.9 If the thermostat demand cannot be met on high stage
heat pump heating, the CTK0* thermostat sends a
request for auxiliary heat to the air handler/modular
blower.
2.10 Upon receiving a demand for auxiliary heat, the air
handler control determines the appropriate airflow for
high stage heat pump + auxiliary heat operation and
operates the ECM blower motor at that airflow demand.
The air handler control determines which airflow demand
is greatest and applies that demand when operating the
ECM blower motor.
2.11 The system operates at high stage heat pump heating
plus auxiliary heat.
2.12 Once the thermostat demand is satisfied, the CTK0*
thermostat commands the heat pump to end heat pump
heating operation. The compressor and outdoor fan
motor are de-energized.