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10 Operating information
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Installation & Operation Manual
If the water temperature at the system supply sensor is less
than the set point + the turn-off offset - the off-on differential,
then the control will initiate a call for heat on the Cascade (see
the SYNC Service Manual for an explanation of the offset and
differential). The Leader will energize the lead boiler on the
Cascade. For a new startup this will be the Leader boiler.
The boiler will fire at its ignition speed and will then modulate
its firing rate to maintain the set point. If the first boiler
reaches 100% of its firing rate, the Leader will calculate at what
point the second boiler could fire at 10% of its firing rate. At
this point, the Leader will fire the second boiler on the
Cascade. For a new startup, this would be the first Member
boiler. The boiler will fire at its ignition speed and will then
modulate its firing rate to maintain the set point.
If the set point still cannot be met, the Leader will continue
firing more Members until either the heat demand is met or all
boilers on the Cascade are firing. As the heat demand
decreases, the last boiler on will modulate down to 10% of its
firing rate. Once the demand for that boiler is zero, it will shut
down. As the heat demand decreases further, the second to last
boiler will modulate down and shut off. This will continue
until the demand is satisfied and all boilers are shut off.
HW operation with cascade
For HW operation any boiler(s) in the Cascade can be selected
to provide heat for a HW call. Select a boiler to be designated
as the HW boiler. Connect the HW thermostat or sensor to
the terminals on the Low Voltage Connection Board marked
for the HW Thermostat or sensor. When the boiler receives a
HW call, the Leader control will take that boiler out of the
Cascade sequence. If another boiler is available, the Leader will
start it up to take its place.
The HW boiler will adjust its set point to the programmed
HW set point and will adjust its firing rate to maintain this.
Once the HW call has been satisfied, the Leader control will
place that boiler back into the Cascade sequence.
Night Setback operation with cascade
Night Setback operation of the boilers within the Cascade is
available. Programming of the Night Setback will be done
through the Leader boiler. Refer to the SYNC Service Manual
for information regarding Night Setback.
Sequence of the cascade
To equalize the run time of all boilers on the Cascade, the
firing sequence will automatically be changed at set intervals.
For the first 24 hours after initializing the Cascade, the
sequence will be changed every hour. After that the sequence
will be changed once every 24 hours. The switching on/off
sequence will be as follows:
DAY SWITCHING ON SEQUENCE
Day 1 L-M1-M2-M3-M4-M5-M6-M7
Day 1 + 1 hour M2-M3-M4-M5-M6-M7-L-M1
Day 1 + 2 hours M4-M5-M6-M7-L-M1-M2-M3