CleaverBrooks CFC-500 Operation, Service And Parts Manual page 211

• If this parameter is "Measured run time" then they are
ordered according to their reported run time. If two have the
same measured run time, then either may be selected.
• Last are any Available slaves that have a mode of Use Last.
These will have the highest numbers. If two or more Use
Last boilers exist, they are numbered according to their
assigned LL - Slave sequence order or Modbus address if
this value is zero, as described above.
Voluntary Lead Rotation
The current lead boiler is identified by the LeadBoilerSeqNum
value. This value will change when the stager has asked the
sequencer for a boiler to add and either:
• the boiler identified by LeadBoilerSeqNum is neither
Available nor Firing (i.e. it has a fault or is OnLeave), or
• the LeadBoilerRunTime value exceeds LL - Lead rotation
time.
In either of these cases, the algorithm performed is:
If the LL - Lead selection method is "Rotate in sequence
order", then
LeadBoilerSeqNum is incremented, and then new lead boiler
is the one that is a slave in Equalize Runtime mode that is
responding to the LL master (i.e. not OnLeave or Recovering,
but it might be Firing), and:
• has a sequence number equal to
LeadBoilerSeqNum, or
• If no boiler has this then the closest one with a
sequence number greater than this number is used,
or
• If no boiler has a greater sequence number, then the
one that has the smallest sequence number is used
(wrap around).
Otherwise when the LL - Lead selection method is "Measured
run time", then the lead boiler is the one having the lowest
Measured run time value. If two have the same measured run
time, then either may be selected.
The LeadBoilerRunTime value is then set to zero to give the
new lead boiler a fresh allotment.
NOTE: if the old lead boiler is the only one, then this process
may end up redesignating this as the "new" lead with
a fresh time allotment.
Forced Lead Rotation
When the boiler identified by LeadBoilerSeqNum is firing and
also LeadBoilerRunTime reaches the LL - Force lead rotation
time parameter time then:
1. The current lead boiler is noted.
2. Lead rotation occurs as described above under Volun-
tary Lead Rotation (this changes the designation, but
does not change the actual firing status).
SLAVE WRITE: DATA
This allows the slave to accept command messages from a
Falcon master.
SLAVE READ: DATA
This provides the slave status message to be read by a master.
It includes all of the data that is read from a slave.
SLAVE MODE: USE FIRST, EQUALIZE RUNTIME, USE
LAST
• If set to Use First, then this slave will be used prior to using
other slave slaves with other values.
• If this parameter is set to Equalize Runtime, then this slave
will be staged according to a run time equalization. (Any
slaves set to Use First will precede any that are set to
Equalize Runtime.)
• If this parameter is set to Use Last, then this slave will be
used only after all Use First and Equalize Runtime slaves
have been brought online.
SLAVE PRIORITY SEQUENCE ORDER: 0-255
Slave sequence order is used to determine the order in which
the slaves will be used (staged on) for those slaves 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
slave 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 deter-
mines the relative order in which slave controls will be
used in a round-robin scheme.
If the slave sequence number value is zero, then the slave's
Modbus address will be used instead.
If two slaves 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.
Sequencer Ordering Function
Part of the sequencer is called by the stager just before the
stager runs, to give the sequencer a chance to assign order
numbers to stages that very recently turned on, and to
maintain these in a sequence. It uses the StagingOrder item in
the Slave Status table for this purpose.
The sequencer ordering function examines all slaves and sets
to zero the StagingOrder of any stage that is not Firing.
This ensures that any stage that has left the Firing condition
recently is no longer in the number sequence.
Next, skipping all of those that have 0 values in StagingOrder it
finds the lowest numbered StagingOrder and gives it the value
1, the next receive 2, etc.
Thus if gaps have developed due to a slave dropping out these
are filled in.
Finally, the ordering function continues on, giving the next
numbers to and Firing stages which have a 0 StagingOrder
values (i.e. they recently were added, or they recently returned
from OnLeave).
Example:
Before
Notfiring 3 0
Notfiring 0 0
Firing 2
Firing 5
Firing 0
Firing 4
87
CB FALCON
After
750-265