Vb1287 Bpp 2-Stage And 2-Stage Split Control; Sequence Of Operation - Daikin Rebel Applied DPSA Installation And Start-Up Manual

VB1287 BPP 2-Stage and 2-Stage Split Control

Sequence of Operation

1. A call for heat is initiated by the rooftop unit control
through a digital Modbus signal. Refrigeration Only
control packages may differ.
2. The VB1287 control will then go through a system check
to ensure that the high temperature limit and rollout
switches are closed, the air pressure switch is open, and
the modulating valve is positioned correctly.
3. The control will then enter the pre-purge cycle, where
the inducer will run at the programmed purge pressure.
During this cycle, the control will look for the air pressure
switch to close and open at the correct settings.
4. Once the system check and pre-purge cycles are
complete, the control will enter the ignition cycle.
a. The inducer will go to its "light off" setting (usually
high speed).
b. The DSI ignition module will be energized and the
spark ignitor will activate.
c. The safety valve will open, allowing gas flow.
d. The burners will ignite and the VB1287 control will
receive a signal from the flame sensor.
e. The spark ignitor will remain active for the duration
of the ignition cycle, regardless of flame status.
5. If flame is not established during the ignition cycle, the
control will repeat the pre-purge and ignition cycles up to
three times. After three failed ignition attempts, the board
will enter a 1 hour lockout.
6. Once flame has been established, the control will enter a
warmup period to ensure flame stabilization and reduce
condensation in the heat exchanger.
7. After the warmup period, the control will enter the run
cycle. During the run cycle, the burner firing rate is
determined by the heat demand received by the control
via a Modbus signal or the analog thermostat. Two firing
stages, High or Low, are available.
NOTE: If the control is paired with a split manifold, steps 1
through 6 pertain to the primary burners. Once the
control exits the warmup period and the firing rate is
dictated by the rooftop control, the control will ignite
the secondary burners and step High or Low the
primary burners based on the demand for heat.
www.DaikinApplied.com
8. The run cycle will continue until any of the following
conditions are met.
a. The call for heat is terminated .Any of the safety
devices (high limit, air pressure, rollout, etc.) are
triggered.
b. The control reaches its maximum run time of 6
hours. If this condition is reached, the control
will terminate the run cycle, continue through
the proper sequence of operations, and then
immediately enter the system check and pre-purge
cycles to prepare for re-ignition.
9. Once the run cycle has terminated, the redundant safety
valve will close, the modulating valve will return to its set
position, and the draft inducer will ramp up to its "light-
off" setting for a 45 second post-purge cycle.
10. After the conclusion of the post-purge, the control
will enter the "OFF" state. All system outputs are
de-energized but all safety devices are still monitored.
99
Unit Maintenance
IM 1287 • REBEL APPLIED ROOFTOP