TP-7070 8/2024 Section 2 Operation
2.6 Load Shed
The manual key switch/ load shed module is available as
a
n optional kit.
The load shed function drives outputs to four Form C dry
contacts to remove non-critical loads. If the generator
set load reaches or exceeds the level set in power
threshold #9, loads are shed until the total load drops
below the threshold level.
Loads are added again when the total load drops below
the level in threshold #9. Factory-set time delays ensure
that the load is stable before loads are shed or added.
Load 1 is shed first and added last. Load 4 is shed last
and added first.
The load shed level is set in Power Threshold 9 on the
APM802 controller. The factory default setting for
threshold 9 is 90%. The threshold setting can be
changed in Screen 1.2 after logging in with the
operator’s password. See Sections 2.8 and 2.12.1.
Do not connect critical loads to the load shed outputs.
Only connect low-priority loads that can be
disconnected when necessary.
Connection
Controllers with load shed capability are equipped with a
Manual Key Switch/Load Shed digital I/O Module, which
is factory-installed in the first position. Connect up to
four non-critical loads to Load Shed Outputs 1 through 4
on the Manual Key Switch/Load Shed Module. See
Figure 2-4. The load shed outputs are Form C contacts.
Connect to the normally open (NO) or normally closed
(NC) contacts as required for the application.
Load
Power
Threshold *
Load Shed
(Disconnect)
Time Delay
Load Add
(Reconnect)
Time Delay
Displayed
as
1 #9 5 seconds 60 seconds O #0
2 #9 5 seconds 45 seconds O #1
3 #9 5 seconds 30 seconds O #2
4 #9 5 seconds 15 seconds O #3
* Default setting = 90%. Power threshold setting can be
changed by the technician.
Figure 2-3 Load Shed Settings
Operation
The outputs are activated and loads are shed when the
total generator set load reaches the level set in power
threshold #9. Load 1 (output #0) is shed first . Additional
outputs are activated every 5 seconds as shown in
Figure 2-3 until the total load drops to the threshold
value or all four non-critical loads are shed. Messages
on the main screen will indicate that load shed outputs 1
through 4 are active.
If all four loads are shed, the generator set will continue
to run if the load remains at or below 100% of the rated
load.
When the generator set load drops below the level in
threshold 9, the outputs are deactivated one at a time
starting with Load 4 (output #3), reconnecting the loads.
Adjust the loads, if necessary to avoid cyclic adding and
shedding around the threshold #9 level.
GM103061
Load Shed
Customer
Connections
Key switch
f
actory
connections
MANUAL KEY SWITCH/
LOAD SHED I/O MODULE
Figure 2-4 Load Shed Output Connections