Daikin ComfortNet DX18TC Service Instructions Manual page 75

SERVICING
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 in-
creases 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.
The air handler/modular blower is commanded to end
auxiliary heat operation. The air handler control de-
energizes the electric heat sequencer outputs. The ECM
blower motor remains energized until any blower OFF
delay timing has expired.
Outdoor Temperature Below 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 below the balance point
temperature. Heat pump heating is disabled.
2.2 The CTK0*** thermostat sends a request for auxiliary
heat to the air handler/modular blower.
2.2 The air handler control energizes the ECM blower motor
at the auxiliary heat speed. The electric heat sequencer
outputs are also energized, thus energizing the electric
heaters.
2.3 The system operates at auxiliary heat.
2.4 Once the thermostat demand is satisfied, the CTK0*
thermostat commands the air handler/modular blower to
end auxiliary heat operation. The air handler control de-
energizes the electric heat sequencer outputs. The ECM
blower motor remains energized until any blower OFF
delay timing has expired.
3.0 Continuous Fan Operation
3.1 With a demand for continuous fan operation, the CTK0*
thermostat sends a fan request to the integrated air
handler control along with a fan demand.
controladjustable via the CTK0* thermostat. The com-
pressor delay is intended to eliminate compressor noise
during the reversing valve shift.) The compressor will
energized (or re-energized) at high stage.
3.2 If the thermostat demand for continuous fan is removed,
the CTK0* thermostat commands the integrated air
handler control to end continuous fan operation. The
integrated AH control immediately de-energizes the
ECM blower motor.
4.0 Defrost Operation
4.1 While the system is operating in heat pump heating (see
2.0 Heating Operation), the control in the outdoor unit
may determines that a defrost cycle is needed. Upon
determing that a defrost cycle is needed, the UC control
de-energizes the condensor fan motor and energizes the
reversing valve.
4.2 The compressor may be de-energized for a short delay
during the reversing valve shift. (The delay period is
adjustable via the CTK0* thermostat. The compressor
delay is intended to eliminate compressor noise during
the reversing valve shift.) The compressor will energize
(or re-energize) at high stage.
4.3 The UC control sends a request for defrost operation to
the integrated air handler control. The air handler control
energizes the electric heat sequencer outputs and oper-
ates the ECM blower model at the electric heat speed.
4.4 Once the defrost cycle is terminated, the heat pump
commands the air handler/modular blower to end defrost
operation.
4.5 The system returns to heat pump heating operation that
was in effect prior to the defrost cycle.
5.0 Emergency Heat Operation
5.1 The CTK0* thermostat sends a request for emergency
heat to the air handler/modular blower.
5.2 The air handler control energizes the ECM blower motor
at the emergency heat speed. The electric heat se-
quencer outputs are also energized, thus energizing the
electric heaters.
The
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