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DETERMINE VFD SET POINT — The unit of measure for
the Duct Pressure set point at the VFD is output frequency
(Hz), representing the desired DP set point (DPSP) in inches
of water gage (in. wg). To convert desired DPSP into the
VFD set point, refer to Table 13. Locate the pressure value
in the table closest to the desired DPSP for this installation
and use the corresponding VFD set point (Hz) value. If nec-
essary, interpolation between duct static pressure values is
permissible.
ADJUST VFD SET POINT — To adjust the VFD set point,
the VFD must be powered; however, since it is located near
the supply fan and motor, operation of the fan and motor is
not desirable. Either disable the Supply Fan or install the
accessory VFD remote display accessory.
DISABLE SUPPLY FAN MOTOR — To disable the supply
fan motor and change programming of VFD set point:
1. Turn off Indoor Fan Circuit Breaker (IFCB). This will
remove power to the VFD.
2. Wait for the VFD display to go blank and remove VFD
cover without touching any interior components.
3. Ensure that the charge indicator lamp is out which in-
dicates that the VFD is discharged. The lamp is located
on the upper right hand corner of the terminal block. If
still lit, wait until lamp goes completely out. This may
take several minutes.
4. Remove jumper from terminals ST-CC (see Fig. 41) and
replace VFD cover.
5. Turn on IFCB.
6. The drive output will now be disabled but the program-
ming can be changed.
7. Change VFD set point according to Table 14 shown
below.
8. Once the program changes are completed, turn off IFCB.
9. Wait for the VFD display to go blank and remove VFD
cover without touching any interior components.
10. Ensure that the charge indicator lamp is out which in-
dicates that the VFD is discharged. The lamp is located
on the upper right hand corner of the terminal block. If
still lit, wait until lamp goes completely out. This may
take several minutes.
11. Replace jumper to terminals ST-CC.
12. Replace VFD cover.
13. Turn on IFCB to enable the drive.
For additional information on the VFD (including basic
troubleshooting, factory jumper arrangements, and Carrier
factory defaults programming), refer to Troubleshooting, Vari-
able Frequency Drive section (page 52).
IMPORTANT: The Carrier factory default values for
the VFD may be different than the default values of
the manufacturer. Refer to the Service section when
checking default values.
NULL DECREASE
SET POINT
DECREASE
PLANE
SET
POINT
INDICATOR
SET
POINT
ADJUSTMENT
NULL
ADJUSTMENT
COM
N.C.
N.O.
CAPACITOR
LEGEND
COM — Common
N.C. — Normally Closed
N.O. — Normally Open
Fig. 39 — Differential Pressure Switch for Inlet Guide
Vane and Static Pressure Control Option and
Modulating Power Exhaust Option
HZ
PERCENT
SECONDS
KW/AMPS/VOLTS
LOCAL/REMOTE
SPEED CTRL
MANUAL/AUTO
RUN MODE
SETUP
PROGRAM
MONITOR
STOP
RESET
READ
WRITE
RUN
Fig. 40 — Variable Frequency Drive Keypad
P24 RES RR F R S1 S2 S3 S4 RCH P24 LOW LOW
ST FM AMCC CC RX PP IV FP FLC FLB FLA
REMOVE
JUMPER
Fig. 41 — Jumper Removal to Disable Motor
29