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• When using series-type, constant wattage, or self-regulating tracers in an ambient
temperature control application, significant energy savings may be realized versus traditional
ambient control algorithms. Heat Tracing design is normally done assuming worst-case
conditions, where 100% of the design output power (less an appropriate safety factor) is
required to maintain the desired minimum temperature. When the ambient temperature is
above the design minimum, but some heat is still required, adjusting the PROPORTIONAL
BAND width accordingly will allow only the amount of power required by the application to
be consumed, while maintaining the minimum required temperature.
Example: A water line must be protected from freezing when the ambient temperature falls
below 50°F (10°C). Either the proportional ambient SSR or proportional ambient contactor
mode is selected as the control method (depending on the type of switch being used). The
heater and insulation combination are chosen to impart enough heat to the line to keep it from
freezing at a worst-case ambient temperature of –40°F (–40°C). At 50°F (10°C), the heater
should be completely off, since no heat is required at this temperature to guarantee that the
water will not freeze. It follows that the amount of heat required by the water line decreases
as the ambient temperature increases from –40°F (–40°C) to 50°F (10°C) (theoretically, at 5°F
(–15°C) the heater output should be approximately 50%). Setting the CONTROL SETPOINT
temperature to 50°F (10°C), and the PROPORTIONAL BAND to 122°F (50°C), will force the
control module’s output to be 100% on at –40°F (–40°C), 50% on at 5°F (–15°C), and off at
50°F (10°C).
3.4.7 CYCLE TIME SETTING (CM 2000+ ONLY)
(For proportional ambient contactor control mode only when not configured as an ATC SLAVE).
Purpose: This parameter determines the minimum amount of time it will take for a complete
contactor on-off-on cycle when using proportional ambient contactor control.
Range: 10 to 255 Minutes
Procedure: Adjust the CYCLE TIME setting to yield the desired contactor on+off time for a
particular duty cycle. For instance, if the contactor should remain on for 5 minutes with a 50%
duty cycle, then the CYCLE TIME should be 10 minutes. A new duty cycle (based on measured
control temperature, PROPORTIONAL BAND and CONTROL SETPOINT) is calculated every time
the contactor is required to change state.
IMPORTANT:
• If the calculated duty cycle is 0% or 100%, then the contactor will not change state and the
duty cycle will not be calculated again for a time period = CYCLE TIME/30.
• The minimum cycle time setting is 10 minutes, and the control module’s minimum output
duty cycle is 3%. This results in a minimum contactor on time of 18 seconds.
3.4.8 SWITCH CURRENT RATING SETTING (SSR ONLY)
Purpose: If a control module is not configured as an ATC SLAVE, the SWITCH CURRENT
RATING setting defines the current rating of the output switch. This parameter is used by
the control module soft start feature to limit the maximum average current that will be
allowed to flow to the load during overcurrent conditions. This will minimize the potential for
SSR damage.
Range: 0.3 to 50.0 A for CM 2000
0.3 to 60.0 A for CM 2000+
Procedure: Adjust the SWITCH CURRENT RATING setting to match the current rating of the
output device (i.e. 30.0 A).
3.4.9 CIRCUIT BREAKER CURRENT RATING SETTING (SSR ONLY)
Purpose:IfacontrolmoduleisnotconfiguredasanATCSLAVE,theCIRCUITBREAKER
CURRENT RATING setting helps prevent in-rush induced nuisance tripping of the circuit breaker
immediately upstream of the control module. The control module evaluates the square of the
current related to time (I2t) and adjusts the output duty cycle accordingly, limiting the amount
of current to an acceptable level.
Range: 0.3 to 60.0 A for CM 2000+
0.3 to 120% of SWITCH CURRENT
RATING for CM 2000
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