Bell & Gossett 10-001-275 XLS Integrated Pump Controller - Manual (Page 21)

21
Combo Up (After XL Start):
This setting controls the speed the VFD running
the main pump will be forced to when a fixed
speed lag pump starts. This helps prevent
overpressuring by reducing the capacity of the
VFD Pump, which is then being provided by the
fixed speed pump after it starts. Generally set to
1/3 the value between min speed and 32767.
This speed will be held for “Hold Sec”, which is
generally set to 1 (may need to increase for
systems using soft-starters for fixed speed lag
pumps).
Combo Down (After XL Stop):
This setting controls the speed the VFD running
the main pump will be forced to when a fixed
speed lag pump stops. This helps replace the
capacity provided by the fixed speed pump and
eliminate pressure dips when these pumps are
shut off. Generally set to 2/3 the value between
min speed and 32767. This speed will be held
for “Hold Sec”, which is generally set to 1.
Speed at 0 psi Startup:
This setting controls the speed the VFD of the
Jockey OR main will start if pressure is very low
when the pump starts (see deadband below).
This setting should be adjusted to be the point the
pump just begins to flow water at 0 psi discharge.
The actual starting speed will be calculated
between this speed and “Combo Down (After XL
Stop)” speed setting, depending on the actual
pressure at the time of start. A function is used to
calculate the speed between these points.
Threshold Deadband (psi):
This setting determines the pressure below
setpoint for determining starting speed. If set
to “20”, the threshold function is used to
calculate starting speed when pressure is
equal to or less than 20 psi below setpoint.
The VFD 1start factor corresponds to the starting
speed of the first main or Jockey pump starting on
VFD. A high value causes the VFD to start running at
a higher speed, creating more pressure. This helps
the system to reach the setpoint faster, but at the
same time the system may overshoot the setpoint
very quickly since the PID does not have enough
time to react to the fast occurring changes. A very
low value will make the system take a lot of time to
reach the setpoint.
Tap [Next] to move to the next Field Setup screen
Supplemental Control
Figure 5 0 : Supplemental Control Home Screen
OPA Enable
This is a method used to shut down lag pumps
operating across-the-line in a system that uses both
VFD and XL (across-the-line) pumps. Check this box
to enable.
The overpressure accumulator measures the
overpressure, and calculates a value to add to the
Overpressure Accumulator depending on this error
on each program scan. The system will shut off a lag
pump when “Trip Preset” is reached.
Min combo:
Combo # on which, OPA is not desired because it is
preferred that the last pump stop in speed test.
Line Fill Mode
This configures how the XLS controller will respond
to powering up, or being put in “Auto”, under very low
pressure conditions. Under these conditions, air may
be in the system and it can be dangerous to the
piping to immediately start pumps and run full out to
attempt to bring pressure back too setpoint too
quickly.
The line fill system works by starting one main pump
at a fixed frequency (calculated from Speed @ 0 psi
startup) under PID control). The system will hold this
speed until pressure and flow are considered
“Steady” for a period of time. Then the system will
increase the speed. The process continues, possibly
starting additional pumps, until the max line fill
pressure is reached, at which time the system
switches over to “Ramp up” mode and continues.