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High Output Limiting - Honeywell 900 User Manual

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High Output Limiting

On PID loops this feature prevents potentially damaging the product or the process by exposing material to
excessive thermal shock caused by applying the maximum PID output during initial startup or product
changeover. High output limiting is enabled by the Track digital input, and when active, limits the PID
output to a value present on the Track analog input for a user specified time period. After the time period
expires, the output limit ramps up at a user specified rate to the normal (non-override) high PID output
limit. The operator interface will indicate an OVERRIDE status at the bottom of the loop displays when
the High Output Limit is active.
The Output limiting feature is also available for Carbon Potential loops but the output limiting action is
only active after the process temperature limit has exceeded the user specified Low Temperature Limit,
which forces the output to 0% or 50% for duplex outputs.
Item
Loop type
High Output Limit Override Enable
High Output Limit Override Status
Current High Output Limit %
Time In Override
Delay Time (Mins)
Ramp Rate (%/Min)
Revision 9
May 2014
Loop type is PID or CARBON
YES: Changes the operation of track command and track value to output
limit enable and output limit value.
NO: Normal output high limit is used.
ON: Digital input controlling output limiting is ON.
OFF: Digital input controlling output limiting is OFF.
Current output high limit. When in override status, this changes
according to loop's tracking value and ramp rate. It will never exceed the
loop's normal (non-override) high output limit.
Elapsed time that High Output Limit Override Status is ON and High
Output Limit Override Enable is YES. It will continue counting even after
the loop's normal output high limit is reached. It resets to zero when the
Override Status changes to NO (i.e., when loop's discrete Output Track
Command turns off).
Enter number of minutes. When override status is ON, the delay time
elapses before the override output limit begins to ramp up at the
specified rate. Delay time of zero causes the override high output limit to
track the loop's tracking value until override status is OFF.
Enter %/minute rate at which the output limit will (after delay time) ramp
up to the normal non-override high limit. Rate of zero causes override
limit to track the loop's tracking value during the delay time, after which
high output limit steps without ramping to the normal output high limit.
900 Control Station User Guide
Description
Loops
Loop Setup
157

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