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When configured, SETPOINT 2 is used as the STANDBY WATER setpoint. Although commanded
to remain off by the master, each slave is to maintain the STANDBY WATER setpoint which is typi-
cally the 'warm' state. When commanded to be on by the master boiler, the slave's SETPOINT 2 set-
point values are ignored because its operation and firing rate is controlled by the master boiler. While
in STANBY WATER, the slave will modulate according to its own PID.
The master boiler has to be operational and controlling the system in order for the master to assume
control. The slave boiler state is initially in the “STANDBY” state when the master is not calling for
any additional support to maintain the system. If the slave boiler is in any other initial state, then the
slave must be commanded to go to the “STANDBY” state until the master determines that a state
change is needed.
SLAVE ON RATE (1-100%)
This value determines the firing rate of the master boiler at which the first and all subsequent slave
boilers come on. Slaves are brought on line according to the priority order previously discussed. The
master and the last slave on will modulate in unison controlled by the master.
SLAVE 1 ON DELAY (0-255 minutes)
SLAVE 2 ON DELAY (0-255 minutes)
SLAVE 3 ON DELAY (0-255 minutes)
The timer to command a slave on begins when the modulation rate exceeds the SLAVE ON RATE.
While the time set above is expiring and the boiler load falls below the slave ON RATE, the com-
mand to begin to bring on the slave will be cancelled. After the first slave is commanded on and
reaches AUTO and the master's modulation rate is still above the SLAVE ON RATE (expected), the
timer to bring on the next slave is initiated. A value of 0 will initiate the next slave to turn on as soon
as the slave ON RATE is exceeded.
SLAVE OFF RATE (1-100%)
When the master boiler and last slave boiler on modulate below this rate and exceed the time value
set in SLAVE OFF DELAY, the last slave commanded on will be turned off. At this point, the master
and the previous (if any) commanded on slave will begin to modulate in unison until they together
are below this setting. This will continue until only the master boiler remains on.
The slave OFF RATE can never be equal to or larger than the slave ON RATE.
SLAVE OFF DELAY (0-255 minutes)
This option sets the time delay when the modulation rate is at or below the value set in SLAVE OFF
RATE and the last slave turned on being turned off. This also sets the time delay between successive
slaves being turned off should the modulation rate stay below the SLAVE OFF RATE setting. The
slave off delay is common to all slaves.
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