nvent 910 Series Installation, Operating And Maintenance Instructions page 28

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Range: 2°F to 90°F (1°C to 50°C)
Procedure: Adjust the DEADBAND setting to the desired differential from the desired CONTROL
SETPOINT temperature. When the control temperature is above the setpoint + deadband value,
the controller will turn off the output to the tracer. If the control temperature drops down below
the setpoint, the output will be turned back on. Note that the smaller the DEADBAND setting,
the more often the contactor will cycle on and off, decreasing its operational life.
IMPORTANT: See Section 7.2 of this manual for an explanation of Deadband Control. Note
that the MAXIMUM POWER, SWITCH CURRENT RATING, and CIRCUIT BREAKER CURRENT
RATING settings are not available when the HTC is set to Deadband mode (typically when
switching a contactor).
5.2.6 CYCLE TIME SETTING
(For proportional ambient contactor control mode only).
Purpose: This parameter determines the minimum amount of time it will take for a complete
contactor ON-OFF-ON cycle.
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 five 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 minimum controller output duty cycle
is 3%. This results in a minimum contactor ON time of 18 seconds.
5.2.7 SWITCH CURRENT RATING SETTING (SSR ONLY)
Purpose: The SWITCH CURRENT RATING setting defines the current rating of the output
switch. It is used by the controller to limit the maximum average current that will be allowed to
flow to the load before it begins to adjust the output duty cycle, limiting the amount of current
to an acceptable level.
Range: 0.3 to 100.0 Amps
Procedure: Adjust the SWITCH CURRENT RATING setting to the match the current rating of the
output device (i.e. 30.0 Amps).
5.2.8 CIRCUIT BREAKER CURRENT RATING SETTING (SSR ONLY)
Purpose: The CIRCUIT BREAKER CURRENT RATING setting helps prevent in-rush induced
nuisance tripping of the circuit breaker immediately upstream of the controller. The HTC
evaluates the square of the current related to time (I
accordingly, limiting the amount of current to an acceptable level.
Range: 0.3 to 100.0 Amps
Procedure: Adjust the CIRCUIT BREAKER CURRENT RATING setting to the heating circuit
breaker size (i.e. 30.0 Amps).
IMPORTANT: This feature should NOT be used to reduce the size of a circuit breaker or
increase the maximum heating cable length. It can be quite effective in preventing nuisance
trips due to incorrect design or factors outside those considered by the design.
5.2.9 MAXIMUM POWER SETTING (SSR ONLY)
Purpose: This user selectable level limits the maximum amount of power applied to a heat
trace circuit. This is an average power calculated by the controller using the average current
and applied voltage. The HTC switches the output on and off rapidly to limit the average
current to an appropriate level. The MAXIMUM POWER level may be adjusted to eliminate
stepdown transformers, lower the effective output wattage of a cable, or implement energy
management of the heat trace circuit.
t) and adjusts the output duty cycle
2