Siemens Energy & Automation, Inc.
Bellefontaine, Ohio 43311 U.S.A.
Installation Instructions
Hazardous Voltage.
Will cause death or severe
injury.
Turn off and lock out all power supplying this
device before removing cover(s) or device
and while cover(s) are removed.
Wire connector shield no. NDTS must be
installed when wire connectors TA2K8750,
TA3P8750, TA4P8500, TA2N8750,
TA3N8750, OR TA4N8500 ARE USED.
Replace all covers and shields before power
supplying this device is turned on.
Page
4 of 6
Continuous Current Switch Ir=%In
Adjustments made to this switch can change the
continuous amps rating of the breaker to 20, 30,
40, 50, 60, 70, 80, 90 or 100% of the maximum
continuous amps rating (In) of the circuit breaker.
The diagram below shows the settings possible on
this switch.
Short Time Delay (optional)
The adjustable short time delay switch allows for
selection from two ranges of short time delays. The
first range of settings enable the breaker to be set
for fixed time delays of .05, .1, .2, .3, or .5 seconds.
The second range of settings enable the breaker
to be set for short time delays based on I
2
t curves
at six times the continuous amps setting. The dia-
gram below illustrates the possible settings for this
switch.
Short Time
Pickup
xIr
Long Time Delay @ 6xIr
The adjustable long time delay switch allows for se-
lection of long time delays based on I
2
t curves at
six time the continuous amps setting (Ir). The dia-
gram below illustrates the possible settings for this
switch.
Continuous Amps
Ir = %In
Long Time Delay
Secs @
6xIr
Short Time Pickup
xIr (optional)
Circuit breakers with the letters “NT” in the catalog
number have adjustments to set the Short Time
Pickup and the Short Time Delay.
The adjustable short time pickup switch allows for
selection of short time pickup in a range from 1.5
to 10 times the setting of the Adjustable Continu-
ous Amps Switch. The OFF position disables the
function. The diagram below illustrates the possible
settings for this switch.
Short Time Delay
I
2
t @
6xIr
Secs.
ELECTRONIC OPERATION
The setting dials on the face of the electonic trip
unit are rotary switches that must be properly set
to mechanical detent (click stop) positions. An
improper switch setting will cause the trip unit to
default (as a fail safe condition) to the lowest
permissive setting and, consequently, may result
in unintentional or nuisance tripping.
8
Released Production, B v1, Dec 18, 1998
Released Production, C v1, Apr 18, 2011
