Super Systems 9120 - Manual (Page 26)

4574 - SSi 9120 Manual Rev A Page 26 Super Systems Inc
Clicking on the value will allow the user to change the value. The range for the proportional band value is 0 – 999.0.
Reset
This is the reset field. This represents the I in PID. I = Integral. This is the actual temperature being monitored over a
period of time and then averaged to keep within the Proportional band. The reset is in repeats per minute. This helps to
eliminate offset. Clicking on the value will allow the user to change the value. The reset range 0 – 100.00
Rate
This is the rate field. This represents the D in PID. D = Derivative. This is the sudden change or rate in the temperature.
This rate is in minutes. This affects the controller output which is proportional to the rate of change of the measurement
and will control the amount of output by time restraints. Thus derivative takes action to inhibit more rapid changes of the
measurement than proportional action. Derivative is often used to avoid overshoot. Clicking on the value will allow the
user to change the value. The range for the rate is 0 – 100.00. The rate is not typically used for heating/carbon
Mode
This is the mode of the loop. Clicking on the value will allow the user to change the value.
The following is an explanation of the dual/single and direct/reverse properties:
Dual – This has two output relays which can increase and decrease to achieve your SP.
Single – This has one relay which works in only one direction to achieve your SP.
Direct - If the PV - SP is a positive number and the output would bring the PV down toward setpoint that is direct.
Reverse – If the PV - SP is a negative number and the output would bring the PV up toward setpoint then that is reverse
Example: If a 12 mA output drives a 0 degree F temp. (PV) up to a 1200 degree F temp. (SP) this would be REVERSE
and since this would take a SINGLE output from the controller the Mode for the Temperature Loop is Single Reverse.
The mode values can be:
Dual Reverse; gas/air or heat/cool
Single Reverse; heat
Dual Direct; Dewpoint gas/air
Single Direct; cool
Integral Preset
This field provides an offset for the starting point for PID control, also referred to as “Load Line” or “Manual Reset”.
Clicking on the value will allow the user to change the value. The range for the integral preset is –100 to 100.
Cycle Time
Clicking on the value will allow the user to change the value. This field is typically set to the valve travel time multiplied
by 1.5. The cycle time range can be 0 – 300.
Setpoint Change Limit
This is a smart time feature that allows the Process Loop to use PB only without Reset until the Process Variable drops
below the percent output set under this category.
It is used to eliminate overshoot.
The Output percentage selected under this category
must be above the normal operating output percentage of the
furnace at heat.
Clicking on the value will allow the user to change the value.
Example – if the furnace runs at 40% output at heat for the maximum load, the setpoint change limit should be set to
60%
.
The value can be:
OFF
80 %
70 %
60 %