Operator’s Manual
ASCO Series 300
381333-453
ASCO Power Technologies
Page 9
Features
Bus Optimization
Each load priority is determined by which load
block wiring an ATS is connected to. Priority
wiring is included for priorities 1 to 4 (2-gen
system) or priorities 1 to 8 (3- and 4-gen systems).
To change a priority, an ATS engine start signal
and load shed signal need to be moved to a
different priority block wiring.
Should a Priority Block fail to be added to the bus
while operating in the Emergency Mode, loads
may be added manually by the operator as
described in Block Load Control or automatically
through "Bus Optimization". Bus Optimization is
provided to re-add shed loads one block at a time
based on predetermined kW loading values up
95% (adjustable via OIT) of the capacity of the on-
line power. This percentage value is referred to as
the Bus Optimization KW de-rating value.
With the Bus Optimization switch in the "on"
position during emergency mode and with loads
shed (loads requiring power but are not connected
to the emergency bus), after a stabilization time
delay (Bus Opt stable delay) the optimization
feature is activated and a Bus Optimize Active
light illuminates. The Bus Optimize Active light
flashes through the duration of the stabilization
time delay (default 30 seconds, adjustable via
OIT). At this time, the Bus Optimization loading
control will determine if there is enough room to
add the next load block by checking the pre-set
Load Value (field adjustable, accessible via the
OIT) assigned to the highest priority block that is
shed and compare it to the excess generator bus
capacity (also known as Headroom).
If it is determined that the load can be added
without exceeding the Bus Optimization KW de-
rating value, the load is signaled to add. The real
time kW output of the generator bus is constantly
measured and the next load block priority is
evaluated. Loads are evaluated at a preset time
interval defined via the OIT (Bus Opt Step Time).
When the bus has been loaded to a level such that
the next load would exceed the de-rating value, the
Next Load Exceeds Headroom light (on OIT) will
activate and load adding will pause. The system
will continuously monitor the generator load and
evaluate if the next load step can fit on the bus. If
building load decreases and the next load can fit
(for the duration of the step time delay), the system
will add it and continue the evaluation process
until as many loads as possible are added to the
bus. Refer to (Figure 11).
If the load has already been added, there is no
reason to compare it to see if it will fit; the
program will skip to the next available load.
If the load is not calling for an engine start (load
still fed from normal power), it will be skipped.
If at any time, the online load exceeds 105% of
available rated capacity, the system will remove
the last load block that was added. If the online
load does not decrease to less than 105% of rated
capacity, load blocks will be shed one at a time,
every second in reverse order until the overload is
corrected or until the number of load blocks online
equals the number of generators online. Load
blocks with associated generators online will not
be shed. The Bus Overload light will light to
indicate that the bus is overloaded automatically
reset as the overload is corrected. In this event, the
system will begin a 30 second overload
stabilization delay time (fixed) before evaluating
additional load to be added to the bus.
If a generator fails, it will be removed from the
bus. If the remaining loads online exceed 105% of
the remaining online generator capacity, the load
blocks will step shed as described in the previous
paragraph. If the load does not exceed the online
capacity, no loads will shed. The Bus Overload
light will light to indicate that the bus is
overloaded automatically reset as the overload is
corrected.
