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proportional valve. The more the valve is open, the more gas passes through, and the more
heat is applied to the process. Feedback is provided to the control algorithm by subtracting
the thermocouple measurement (the Process Temperature) from the desired temperature
(the Process Setpoint).
PID Controller (Menu 1)
To perform temperature control with a proportional valve, the PF2100 uses a PID Controller
with temperature as its input. The PID Controller uses three parameters to specify how
it performs its control: PID–Proportional Band, PID–Integral, PID–Derivative. The default
parameters are sufficient for most common heater applications, but they can be tuned for
faster control if necessary. See Appendix A for the recommended tuning procedure for the
PID Controller.
RESTART SETTINGS
The PF2100 can be configured to automatically restart after certain alarm conditions clear. The number of
restart attempts is configurable. There are three settings that affect restart behavior: Auto Restart, Level
Event Restart, and Restart Attempts.
The number of restart attempts the system will make differs depending on the mode and the reason that
the burner is being re-lit.
MODE PROCESS CONTROL FLAME OUT
Manual 3 0
Auto 3 User Configurable
Auto Restart (Menu 4)
If this setting is enabled, the following conditions will cause the system to enter the
“Waiting” state instead of shutting down. In addition, the system will automatically restart
once these and all other enabled restart conditions have cleared.
1. System Input Voltage too low (including power cycle)
2. System Input Voltage too high
Level Event Restart (Menu 4)
If this setting is enabled, the system will restart automatically once all alarm conditions are
cleared and if the reason that the system stopped running was any of the following:
1. Level Contact open
2. 4-20mA Level Input below Low Setpoint
Pressure Restart
If this setting is set to “Enabled”, the following conditions will cause the system to enter the
“Waiting” state instead of shutting down. In addition, the system will automatically restart
once these and all other enabled restart conditions have cleared.
1. Low Pressure Contact open
2. 4-20mA Pressure Input below Low Setpoint
If this setting is set to “Main Control”, the following conditions will cause the system to close
the Main Valve instead of shutting down. In addition, the system will automatically reopen
the Main Valve once these conditions have cleared and if the temperature control algorithm is
also satisfied.
1. Low Pressure Contact open
2. 4-20mA Pressure Input below Low Setpoint
The main valve opening will always occur 7 seconds after the Low Pressure Contact Closes
and the 4-20mA Pressure Input rises above the Pressure Low Setpoint. This 7 second delay
is comprised of 2 seconds for the pressure measurement to stabilize (to prevent oscillation)
plus a 5 second countdown on the screen: “Main on in 5…4…3…2…1...0”.
The timing of the main valve closing is determined by the Pressure/Level Delay Setting.
Refer to the Pressure Delay Table for details.
Note that the PF2100 always enforces a minimum 30 second delay between any state
transition and this situation is no exception. If this delay is unacceptable, the PF3100 system
can be used to achieve this same behavior but without this delay.
Restart Attempts (Menu 4)
A restart attempt is an attempt by the system to light the burner. These can occur under two
types of circumstances:
1. As a result of normal process control. Examples Include:
The system is started by a user by switching to Auto Mode.
The system is started remotely via the Start Contact.
The Pilot Turns off as a result of process control and then is
automatically turned back on after the temperature drops
below the Pilot Off Setpoint.
The system automatically restarts after recovering from one
of the situations described in the Auto Restart or Level Restart
sections.
2. As a result of the pilot flame unexpectedly going out.
Examples Include:
The gas supply is cut off.
Excessive wind blows out the burner flame.
Insufficient oxygen supply snuffs out the burner flame.
The flame detection rod becomes dirty and unable to detect
flame.
TIMING DELAY SETTINGS
There are four time delay settings that can be adjusted to match the needs of various applications.
Purge Time (Menu 4)
This setting is used to set the minimum amount of time that must elapse between when all
valves are known to be closed and the next time that the pilot is lit. This will be the minimum
elapsed time between relights and also the minimum amount of time before lighting the
burner after a loss of power. The purge time ensures that dangerous amounts of gas are not
present in the fire tube before the pilot is lit thus reducing the risk of an explosion. Generally,
the larger the burner, the larger the purge time should be. Local codes may dictate the
amount of purge time required for a given application. This setting can be set to a minimum
of 10s and a maximum of 900s.
Pilot-To-Main Delay (Menu 4)
This setting is used to set the minimum amount of time that must elapse between the pilot
successfully lighting and the main (or low fire) valve opening. The Pilot-to-Main Delay is used
to ensure that enough draft is established before opening the main valve. If this is not done,
the volume of gas flowing through the main valve can snuff out the flame due to insufficient
oxygen supply. Generally, the larger the burner, the larger the delay should be. This setting
can be set to a minimum of 5s and a maximum of 600s.
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