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4. Adjustments
The AF-600 FP panel has several user settable adjustments which allow it to be tailored specifically for your 3-
phase induction motor. Setting these adjustments appropriately is an important factor in ensuring that
applicable safety codes are met and that your panel, wiring, and motor are adequately protected. The
following list comprises all of the user adjustable devices/components inside the AF-600 FP, Bypass &
Disconnect Drive Panels. The user may wish to have a copy of NFPA 70-2008 (commonly known as the
National Electric Code or simply NEC) available for reference when setting these adjustments.
Input Fuses
Main input fuses are provided standard with your AF-600 FP, Bypass &
Disconnect Drive Panels. In general there are two configurations that utilize
input fuses; 1) input disconnect with load side separately mounted fuses and 2)
input Fused Disconnect where the fuses are an integral part of the disconnect.
If your panel was ordered with the circuit breaker option, the disconnect device
and fuses are replaced by the circuit breaker. The main input fuses provided
with your panel has been closely coordinated to provide short circuit protection
for the inverter.
UL listed Class J time-delay fuses are provided with your panel. These fuses
have been sized in accordance to NEC section 450-52 and Table 450-152. NEC
states fuses of this type are to be sized at 175% of motor full-load amps (FLA).
Due to the fact that actual motor FLA along with starting current requirements
vary between manufacturer and motor types the fuses provided are based on
standard NEC motor data. Verify that the input fuse amp rating is less than or
equal to the actual motor FLA * 1.75. In the case where the actual motor FLA *
1.75 is less than the provided fuses amp rating then smaller fuses may need to
be installed to be in compliance with NEC section 430-52 and Table 430-152.
Please note exception 1 to NEC 430-52, which states that where the calculated
fuse amp rating does not correspond to a standard fuse size the next higher
standard fuse size may be used. In cases where the fuses provided is not
sufficient for the starting current requirements of the motor, please note
exception 2-b to NEC 430-52. Exception 2-b states the rating of a time-delay
fuse may be increased but shall not exceed 225% of the motor FLA in any case.
In the case where a larger or smaller fuse is required, a limiting factor in the
panel may be the fuse holder. The appendices provide a table for the
maximum fuses size permitted in the existing fuse holder. If these fuses shall
ever need to be replaced, refer for rating label located on the back of panel
cover.
Circuit Breaker Trip Level
The optional circuit breaker in the AF-600 FP HVAC panel is a solid state
Spectra
RMS
TM
molded case circuit breaker from GE. The purpose of the circuit breaker
is to provide short circuit protection and over current for the panel components,
field wiring and the motor. The breaker uses a solid state sensing element
which calculates the true RMS
TM
value of the current every cycle, resulting in a
tripping action which is very fast. For this reason the NEC allows the trip level to
be set at 700% of the motor FLA to allow for the high locked rotor current which
the motor draws during across-the-line starts (see NEC section 430-52 and
Table 430-152 of the NEC).
EH40608
– Page 8
AN 11-2021 Rev 05, 12/15/2011
