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Raychem-AR-H58692-ACS30UIT2Programming-EN-1805
The Temp Control window allows you to select the temperature control mode to Ambient Control,
Line Control or PASC. This option depends on where the controlling RTD inputs are situated and
utilized: either measuring the temperature of the environment surrounding the pipe (ambient), or
directly on the pipe itself (line). Tap PASC
Fig. 3.39
Setup|Pipe Freeze PASC Control window
PASC (Proportional Ambient Sensing Control):
PASC takes advantage of the fact that the heat loss
from a pipe is proportional to the temperature difference between the pipe and the ambient air. This
is true regardless of heater type, insulation type, or pipe size. Once the heat tracing and insulation on
a pipe has been designed to balance heat input with heat loss for maintaining a 40°F (4°C) pipe, the
main variable in controlling the pipe temperature becomes the ambient air temperature.
The ACS-30 system has a control algorithm that uses the measured ambient temperature, the
desired 40°F maintain temperature, minimum ambient temperature assumption used during design,
and size of the smallest pipe diameter to calculate how long the heater should be on or off to
maintain a near-constant pipe temperature.
Maintain Temperature Setpoint:
Fixed design setpoint: 40°F (4°C)
Minimum Ambient:
ENTER THE MINIMUM AMBIENT TEMPERATURE FOR YOUR INSTALLATION:
Range:
-40°F (-40°C)–40°F (4°C)
Default: 30°F (-1°C)
Min Pipe Size:
Min. Pipe Size is the diameter of the smallest heat-traced pipe in the group controlled
by this circuit. Small diameter pipes heat up and cool down more rapidly than larger diameter pipe.
Therefore, the PASC duty cycle is calculated over a shorter time base. Larger diameter pipes heat and
cool less rapidly, so the on/off periods for the heater system can be stretched over a longer period. If
electromechanical contactors are being used to control the heater circuit, the longer time base reduces
the number of contactor on/off cycles and extends the contactor life.
Select:
0.5, 1,
≥
2 inches
Default:
0.5 inches
Power Adjust:
THIS ALLOWS THE PASC CONTROL TO BE ADJUSTED WHEN THE HEATING CABLE
OUTPUT IS GREATER THAN THE DESIGN ASSUMPTION, OR IF THE PIPE INSULATION PROVES TO
BE MORE EFFICIENT THAN ASSUMED. PIPE TEMPERATURE MAY RUN HIGHER OR LOWER THAN
DESIRED IF THE HEATING CABLE HAS A DIFFERENT OUTPUT THAN REQUIRED TO OFFSET THE
HEAT LOSS. THE POWER ADJUST PARAMETER ENABLES A REDUCTION OR AN INCREASE IN
THE HEATING EFFECTIVE POWER BY ENTERING A VALUE LESS OR GREATER THAN 100%
Range: 10–200%
Default: 100%
