QUANTUM™ HD COMPRESSOR CONTROL PANEL
OPERATION
090.040-O (MAR 12)
Page 45
[Step Down Deadband]
and
[Step Down Delay]
– When the System Discharge Pressure stays
below the difference of the values for Condenser
Control Setpoint minus the Step Down Deadband
for the amount of time as set in the Step Up De-
lay, the next module in the Step Order will turn
off.
[High Pressure Override]
and
[High Pressure
Override Delay]
- When the System Discharge
Pressure goes and stays at or above the High
Pressure Override value for the amount of time
as set in the High Pressure Override Delay, all
modules will turn on.
WET BULB CONTROL
The Quantum™ HD control panel provides a Wet
Bulb control strategy which has the ability to run
a condenser based on current atmospheric con-
ditions by sensing the outdoor air temperature
and humidity. This technique, also referred to as
fl
oating head pressure, provides the ability to run
a refrigeration system at the lowest permissible
head pressure. Traditional condenser control
uses a
fi
xed head pressure that does not change
with weather conditions or system load. However
studies have found that allowing the condenser/
head pressure to
fl
oat will result in energy sav-
ings. These savings result from the compressor
not working as hard. While the condenser may
use more energy to achieve a lower head pres-
sure, the reduction in energy consumption by the
compressor is signi
fi
cantly greater, providing an
overall savings.
The Wet Bulb control utilizes a humidity sensor
along with a standard (dry bulb) temperature
sensor. These values are combined to produce a
Wet Bulb temperature. The Wet Bulb Approach
temperature is then added to the calculated Wet
Bulb temperature. The Approach temperature
sets how close the condenser will run to the
Web Bulb temperature and will be determined
by the condenser and system design. Finally, the
Control temperature (which is the sum of the
Wet Bulb Temperature and the Approach Tem-
perature) is converted to the saturated vapor
pressure which in turn becomes the condenser
control pressure. A minimum condensing pres-
sure setpoint speci
fi
es the lowest permissible
condenser control pressure.
The following selections are provided:
•
Disabled
- The Wet Bulb feature is ig-
nored.
•
Enabled
- The Wet Bulb feature will be
utilized.
The following setpoint is available (if Wet Bulb
is enabled):
[Wet Bulb Approach]
- This is a value to be
entered by the facilities refrigeration engi-
neer, which will be added to the Wet Bulb
Temperature to determine the Control Tem-
perature.
The following information is provided (if Wet
Bulb is enabled):
Minimum Condensing Pressure
- This
value speci
fi
es the lowest condenser con-
trol pressure that is permitted while the wet
bulb control strategy is in use.
Refrigerant
- The type of refrigerant being
used is shown.
Outside Air Temperature
- The actual out-
side air temperature is shown.
Outside Relative Humidity
- The actual
outside relative humidity is shown.
Wetbulb Temperature
- The value shown
here is the calculation of Outside Air Tem-
perature and Outside Relative Humidity to
arrive at a Wet Bulb Temperature.
Saturated Control Temperature
- This is
the calculated control Saturated Condens-
ing Temperature. This value is converted to
the associated pressure which serves as the
control pressure setpoint.
