User manual

A-2
Load Shedding
The UTS includes an algorithm (software) for intelligent load management, defined by APC as adaptive
load management (ALM), that maximizes the capabilities of backup sources. The algorithm sheds (drops)
loads when the generator is in danger of being overloaded, and reconnects them when adequate power is
available. It also adaptively selects the most suitable loads to drop or reconnect at any given time, which
minimizes load disruptions.
When load shedding is turned off, the UTS will not drop any loads. During overload conditions the
generator may stop running, a circuit breaker may trip, or the loads may momentarily experience severe
under voltage conditions.
Press the
System Setup button to display the next message.
Voltage Sensitivity
It is recommended that you only use
HIGH when the loads are very sensitive to small, brief power
fluctuations.
LOW can be used if you have frequent power fluctuations that do not require the attention of
the UTS. More detailed specifications are provided in Appendix A of the Universal Transfer Switch Site
Preparation and Installation Guide (Document No. 990-2992A).
Press the
System Setup button to display the next message.
Time Management
The two key time management components are
MAXIMUM OFF time, and MINIMUM ON time. They can be
individually set for each circuit. When this feature is
ON, time management works in the background to
ensure that each circuit is not shed (power is not removed) for more than the
MAXIMUM OFF time.
Conversely, the
MINIMUM ON time ensures that the circuit will be powered for at least the minimum time
setting before it can be shed (dropped) again. More detailed information is provided later in this chapter in
the Delayable Circuits description.
Load shedding can be turned ON or OFF, as shown in this
example, to shed (drop) a load or loads. The factory
default setting is ON.
Note When ALM is on it can increase the perceived power output of a typical generator
by about 20%. This allows you to add more loads without overloading or stalling
the generator.
The level the voltage sensitivity is set to (
LOW, MEDIUM or
HIGH) determines how the UTS reacts to momentary power
fluctuations. The factory default setting is MEDIUM, which is
suitable for most situations.
Time management is used with load shedding to ensure that
your loads receive the power they need over extended periods
of time.
When time management is set to OFF, the
MAXIMUM OFF
time and
MINIMUM ON time settings are disabled.
LOAD SHEDDING:
ON/OFF
!
VOLTAGE SENSITIVITY:
LOW/MEDIUM/HIGH
TIME MANAGEMENT:
ON/OFF