ProFire PF3100 Product Manual page 75

12.4.3 4-20mA OUTPUT BEHAVIOR – PID CONTROL
Controller State
Any stopped state
Any running state
12.4.4 4-20mA OUTPUT BEHAVIOR – FARC ACTUATOR
Post Purge
Controller State
Mode
Purge
Any stopped state – post purging
Hold Last
Any stopped state – not post purging
Waiting or Startup Checks
Request Purge or Prove Airflow or Pre-Purge
Request Pilot Position
Pilot
Any
Pilot - Request Light Off
Low Fire
Process Control
1 FARC channel output positions are specified separately for each channel.
Channel output positions are displayed on the UI in % in accordance with the configured channel position settings and the
2
FARC table, but the corresponding mA output values are dependent on the configured Output Inversion setting as follows:
Disabled: 0% corresponds to 4mA, 100% corresponds to 20mA; Output = (Displayed output reading x 16mA) + 4mA
Enabled: 0% corresponds to 20mA, 100% corresponds to 4mA; Output = ((100% - Displayed output reading) x 16mA) + 4mA
Example: A channel output of 75% corresponds to a 4-20mA output of:
- 16mA when direction setting is Disabled ((75% x 16mA) + 4mA).
- 8mA when direction setting is Enabled (((100% - 75%) x 16mA) + 4mA)).
3 Cross limiting is applied to all leading FARC channels when the actual position of a lagging channel exceeds its expected
position from the FARC table by ignoring the current firing rate and driving the leading channel outputs to their FARC table
values corresponding to the actual position of the lagging channel.
Cross limiting is applied to all lagging FARC channels when the actual position of a leading channel is less than its expected
4
position from the FARC table by ignoring the current firing rate and driving the lagging channel outputs to their FARC table
values corresponding to the actual position of the leading channel.
Example: Current firing rate = 50%, Expected fuel Position = 32%, Actual Fuel Position =
Firing Rate
Fuel (lagging)
Air (leading)
In the example above, the firing rate remains at 50%, the fuel channel output remains at 32% and the air channel output is
increased to 48% (the FARC Table value corresponding to a fuel output of 35%).
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30 35 40
20 23 26
23 28 33
System Behavior
PID is stopped – output is held at the configured System Stop
Output position
PID is operating – output is changed within the configured Low
Output Limit and High Output Limit in accordance with
configured PID parameters
Output Signal 1, 2
Purge Position
Last position before purge event
Off Position
Off Position
Purge Position
Pilot Position
Pilot Position
Light Off Position
Light Off Position
Normal conditions: FARC table position corresponding to the
current firing rate.
Cross limiting conditions: FARC table position corresponding to
Cross Limiting scheme 3 4
35%
45 50 55
29 32 35
38 43 48
PF3100 Product Manual
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