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Outdoor Refrigerant Temperature
(DPS 003–015 only)
Only Rebel Heat Pumps units will have an Outdoor Refrigerant
Temperature Sensor (ORT). This sensor is used in Cooling
Mode when ClgEVOmethod is set to control subcooling. This
sensor is attached to the refrigerant piping upstream (Cooling
Mode) of the Outdoor Expansion Valve (EVO).
Figure 33: Outdoor Expansion Valve
Defrost Temperature Sensor
Only Rebel Heat Pump, DPH, units will have a Defrost
Temperature Sensor (DFT). This sensor is used in Heating
Mode and Defrost Mode to determine the amount of frost
accumulated on the Outdoor Coil.
Heating
The unit’s heating mode of operation is determined by the
control temperature and the heating setpoint temperature. The
unit enters the heating mode of operation by comparing the
control temperature to the heating setpoint.
The control temperature can be either the return temperature
or the space temperature.
The return temperature is typically used for VAV units and the
space temperature is typically used for CAV units.
The unit goes into the heating mode of operation when the
control temperature (return or space temperature) is below the
heating setpoint by more than ½ the deadband.
For example, a standard air conditioning unit with supplemental
gas, electric, or hot water heat with a heating setpoint of 68.0ºF
and a deadband of 1.0ºF would enter heating mode if the
control temperature reached 67.4ºF. When this takes place,
the heating mode of operation will begin and the 1st Stage of
heating operation will start.
Heat Pump (DPS 003–015 only)
The heating mode of operations will be slightly different for heat
pump units. It is the manufacturer’s recommendation that all
Rebel heat pump units be purchased with supplemental gas,
electric, or hot water heat. When the control temperature drops
below the heating setpoint by half the deadband the unit will
energize the four way valve and initiate mechanical heating.
On heat pumps mechanical heating is the primary source of
heat and will always be the unit’s first attempt to meet the
application’s load. After start-up the variable compressor will
ramp up to meet the DAT Setpoint. If the mechanical heating
capacity at the ambient conditions is capable of meeting the
building load the variable speed compressor will stabilize at
some value. If the heat pump’s capacity is insufficient at the
ambient conditions the supplemental (gas, electric, hot water)
heat will be enabled and gradually ramp/stage on to make up
the capacity shortage. If the combined capacity of the heat
pump’s mechanical and supplemental heating is greater than
the building load the supplemental supply will ramp/stage
down. The unit will always seek to operate with mechanical
heating as much as possible.
Periodically during heating operations the unit will need to
enter defrost to remove frost build up from the outdoor coil.
During defrost mechanical heating will be unavailable and the
supplemental heat will ramp/stage up to meet the DAT set-point.
Outdoor
Outdoor
Refrigerant
Refrigerant
Temperature
Temperature
Sensor (ORT)
Sensor (ORT)
Outdoor Expansion
Outdoor Expansion
Valve (EVI)
Valve (EVI)
IM-1125-13 • REBEL ROOFTOPS
30
www.DaikinApplied.com
Refrigeration System