DET-653C
EntelliGuard
®
G Circuit Breaker Application Guide
24-May-12
Section 6. Application Data
©2012 General Electric All Rights Reserved
77
EntelliGuard G circuit breaker is used with cables directly
connected, contact your GE application engineer for
information to ensure proper cabling information. Cable
with insulation ratings above 75°C may be used, providing
it is sized to 75°C ampacity per the NEC or other applicable
codes.
Ambient Temperature – Factor B
Ambient temperatures have a wide effect on the rating of
the breaker-cable system. While the internal sensing and
tripping circuitry in EntelliGuard TU trip units are ambient
insensitive, high-ambient temperatures may cause
internal components to exceed operating temperature
limits. Low temperatures substantially increase the
current-carrying capabilities of the breaker-cable system
until other limiting factors occur (e.g., lubrication problems
or mechanical binding of internal parts due to differential
contraction). The ambient temperature around an
EntelliGuard G breaker should not be less than -20°C nor
exceed 70°C.
Ambient temperature always refers to the temperature of
the air immediately surrounding the breaker and not the
temperature of the air outside the breaker’s enclosure.
Room or outside air temperatures only establish the
thermal floor to which all other heating is added.
To convert breaker ambient from room ambient, it is
necessary to know the temperature rise within the
equipment housing the breaker. Temperature rise is a
function of several variables, including heating caused by
other equipment, ventilation, solar heating, factors relating
to group mounting and the free surface area of the
breaker’s enclosure. Once the device’s ambient
temperature is determined, select Factor B from Table 6.7.
Table 6.7. Ambient Temperature Rating - Factor B
Ambient
Temperature, °C
1
Maximum Wire
Insulating Rating °C
2
Factor B
25
75
1
40
90
1
50
105
1
60
125
1.1
70
125
1.15
1 Average air temperature over a 24-hour period outside the breaker’s
insulated case, but inside the enclosure.
2 Cable (wire) must be based on 75°C current rating per Table 3 10-16,
current National Electrical Code.
Operating Frequency – Factor C
All UL EntelliGuard circuit breakers may be applied at their
published ratings on 50Hz and 60Hz power systems. At
nominal system frequencies less than 50Hz but above
direct current, digital solid-state trip may become
inaccurate. On direct current systems, digital solid-state
trip units are completely inoperative. EntelliGuard G circuit
breakers may be used on DC applications, but EntelliGuard
TU trip units may not.
System operating frequencies above 60Hz may change
the performance and ratings of circuit breakers by heating
metallic parts and significantly reducing interrupting
capacity. EntelliGuard TU trip units are not suitable for
applications at 400Hz.
For operating frequencies of both 50Hz and 60Hz, the
operating frequency rating Factor C = 1.00. For operating
frequencies other than 50Hz and 60Hz, contact your GE
applications engineer.
Altitude – Factor “D”
EntelliGuard G UL circuit breakers are designed for
operation at altitudes from sea level to 6000ft (1800m).
Reduced air densities at altitudes above 6000ft affect the
ability of the circuit breaker to both transfer heat and
interrupt short circuits. Determine the altitude of the
breaker’s installation, and select the altitude rating - factor
D from Table 6.8.
Table 6.8. Altitude Rating – Factor D
Altitude
Factor D
Feet
Meters
100 - 6,000
30 - 1,800
1
6,001 - 10,000
1,801 - 3,000
1.04
>10,001
>3,001
1.08
Load Class Rating – Factor E
The type of load and its duty cycle must be considered in
the application of EntelliGuard G circuit breakers. Loads
such as capacitors and electromagnets require a
substantial and continuous de-rating factor if the breaker
is normally used to switch the load. With loads such as
resistance welders, the breaker’s continuous current rating
must be no less than 125% of the welder’s 100% duty-
cycle rating.
In general, circuit breakers are intended for the protection
of insulated cable. Where a circuit breaker is intended to
protect load equipment, prudent engineering practices call
for obtaining factory review and concurrence with the
selection of a specific protective device. Load class
selection Factor E for typical applications are listed in
Table 6.9.
