CleaverBrooks CFC-500 Operation, Service And Parts Manual page 201

Parameter
LL - Slave priority sequence order 0-255
LL - Demand-to-firing delay
LL - Base load rate
LL - Fan during off-cycle rate
LL Master Operation and Setup
LL master operation is subdivided into the following functions:
Overall control - The LL master has parameters that enable
and disable its operation.
Periodic data polling - The LL master uses polling to discover
new slave Falcon devices and to periodically refresh the
information it has about known slave devices.
Slave control - The LL master sends each active slave a
command and also performs a slave status read for each
known slave device at a high rate. It also sends a Master
status broadcast that is heard by all slaves.
Slave status manager - The LL master operates a state
machine that keeps track of slave status for each Falcon that is
enabled as a slave device.
Demand and priority - Different sources of demand can
cause the LL master to operate in different ways. These
sources have a priority relationship.
Parameter
LL master enable
LL master Modbus port
LL operation switch
Table 34. Slave Data Supporting Lead Lag Parameters. (Continued)
Slave sequence order is used to determine the order in which the slaves will be used (staged
on) for those Falcons with the same Slave mode setting. Numbers may be skipped, that is 3
will be first if there is no 1 or 2.
Note: For Equalize Runtime purposes, 1 does not mean the unit will be used first every time;
that will vary over time based on the master's run time equalization scheme. In this case the
sequence number determines the relative order in which Falcon controls will be used in a
round-robin scheme.
If the slave sequence number value is zero, then the slave unit's modbus address will be
used instead.
If two Falcons are set to the same mode and both have the same sequence number then an
alert will occur and the order in which they are used will be arbitrary and is not guaranteed to
be repeatable.
mm:ss or None
This delay time is needed by the LL master to determine the length of time to wait between
requesting a slave to fire and detecting that it has failed to start. It should be set to the total
time normally needed for the burner to transition from Standby to Run, including such things
as transition to purge rate, prepurge time, transition to lightoff rate, all ignition timings, and
include some extra margin.
rpm or %
This specifies the preferred firing rate of a burner, which is used for some types of control.
rpm or % (0=disable)
This determines if or where the fan is to be operating during the standby period.
Table 35. Overall Control Parameters.
Disable, Enable
MB1, MB2
The LL master may be disabled, enabled. If Disable is selected then all LL master functions
are inactive. If Enable is selected then it acts as the active bus master at all times on the
modbus port it is assigned to use by the LL Master Modbus port parameter.
Off, On
This controls the LL master in the same way that the Burner switch controls a stand-alone
Falcon. If "On" then the LL master is enabled to operate. If this parameter is "Off" then the LL
master turns off all slaves and enters an idle condition.
Comment
Rate control - Each demand source has one or more
setpoints that may be active and an operation sensor. These
are used to detect turn-on and turn-off conditions. The
difference between operating point and setpoint is sent to a
PID block to determines the LL master's firing rate.
Rate allocation - The PID block's output is used to determine
the firing rate of each slave using various rate allocation
techniques.
Stager - The stager determines when slaves should turn on as
the need for heat increases, and when they should turn off as it
decreases.
Add-stage methods - Various methods can be used to
determine when a new stage should be added.
Drop-stage methods - Various methods can be used to
determine when a stage should be dropped
Sequencer - The sequencer determines which Falcon will be
the next one to turn on or turn off.
Comment
77
CB FALCON
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