Pentair 920 Series - Page 21

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EN- Raychem920series-IM-H5687405/15
INDUSTRIAL HEAT TRACING SOLUTIONS
3.5.5 DEADBAND SETTING
(Deadband control mode only or if a point controls an INHIBIT output signal)
Purpose: When an HTC equipped with a contactor is used to control a trace circuit, it is necessary
to use deadband rather than proportional control. This is done to prevent the contactor from
switching on and off rapidly and being worn out prematurely. This deadband acts as an on/
off control where the decision to turn the output off or on is based upon a window of difference
between the measured control temperature and the desired CONTROL SETPOINT temperature.
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 tem-perature 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5.2onpage50foranexplanationofdeadbandcontrol.NotethattheMAXIMUM
POWER, SWITCH CURRENT RATING, and CIR-CUIT BREAKER CURRENT RATING settings are
not available when the HTC is set to deadband mode (typically when switching a contactor).
• TheDEADBANDparameterisalsoavailableforPointAwhentheEXTERNALOUTPUTis
configured for use as an INHIBIT output. See section 3.6.4 on page 30 for additional details.
3.5.6 CYCLE TIME SETTING (V3.11 AND UP)
(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.
3.5.7 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
(CURRENT TURNS RATIO = 1.00)
Procedure: Adjust the SWITCH CURRENT RATING setting to match the current rating of the
output device (i.e. 30.0 amps). Note that the SWITCH CURRENT RATING setting is affected by
the CURRENT TURNS RATIO setting. The absolute maximum adjusted SWITCH CURRENT RATING
setting is 300.0 amps. The absolute minimum adjusted SWITCH CURRENT RATING setting is 0.1
amps. See section 3.5.22 on page 26 for more information regarding the CURRENT TURNS RATIO
function.
3.5.8 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 (I2T) and adjusts the output duty cycle accordingly,
limiting the amount of current to an acceptable level.