14
I.B. 8926-1A
Part 6
OVERCURRENT PROTECTION DEVICES
DEVICE SELECTION
Articles 240 and 430 of the NEC contain the rules for
selecting fuses, circuit breakers and overload relays
by type and by voltage and ampere rating. Follow
these rules for feeder circuits, and the instructions
attached to the inside of the left-most vertical
wireway door, for motor branch circuits. Select and
install overload relay current elements (heaters)
based on the motor service factor and full-load
current. Ambient compensated overload relays are
used in motor control centers (MCC’s) to offset the
temperature gradient which occurs from top to
bottom in a loaded vertical section.
HEATERS MUST BE INSTALLED IN THE
STARTER OVERLOAD RELAY ASSEMBLIES
BEFORE THE STARTER IS ENERGIZED.
C306 THERMAL OVERLOAD RELAYS (FIG.24)
C306 Overload Relays are provided on Freedom
Starters. Four sizes are available for overload
protection up to 114 amperes. Features include:
•
Selectable Manual or Automatic Reset operation.
•
Interchangeable Heater Packs adjustable
±
24%
to match motor FLA and calibrated for use with
1.0 and 1.15 service factor motors.
Heater packs for 32 ampere overload relay will
mount in 75 ampere overload relay – useful in de-
rating applications such as jogging.
•
Class 10 or 20 heater packs. (Fig. 24) Use Class
10 heaters with fusible or thermal magnetic
breaker disconnects only.
•
Bimetallic, ambient compensated operated. Trip
free mechanism.
•
Electrically isolated NO – NC contacts (pull
RESET button to test).
•
Overload trip indication.
•
Single phase protection.
•
UL listed, CSA certified and NEMA compliance.
Fig. 23 Overload Relay Settings
Fig. 24 C306 Thermal Overload Relay and Heater
Pack.
C306 OVERLOAD RELAY SETTING
FLA DIAL ADJUSTMENT – For motors having a
1.15 service factor, rotate the FLA adjustment dial to
correspond to the motor’s FLA rating. Estimate the
dial position when the motor FLA falls between two
letter values as shown in Fig. 23.
For motors having a 1.0 service factor, rotate the
FLA dial one-half position counterclockwise (CCW).
MANUAL/AUTOMATIC RESET – The overload relay
is factory set “M” for manual reset operation as
shown in Fig. 23. For automatic reset operation, turn
the reset adjustment dial to the “A” position.
Automatic reset is not intended to two-wire devices.
TEST FOR TRIP INDICATION – To test overload
relay for trip indication when in manual reset, pull out
the blue reset button. An orange flag will appear
indicating that the device has tripped. Push reset
button to reset.
WARNING – To provide continued protection
against fire or shock hazard, the complete overload
relay must be replaced if burnout of the heater
element occurs.
