
oSet the display to Operating Amps (d003). Restart the fans and watch the amps to see if the
amps go above the level set at P033.
oIf F7 occurs, the VFD will shut down, restart, and ramp up again. It will try to restart 5 times.
If it gets F7 fault 5 times in a row, it will fault to F033 and stop restarting.
oCheck the fan rotation direction. A fan spinning backwards will have higher amp draw than
forward rotation. Reverse direction by switching any 2 phase on the output of the VFD. You
can switch the phase at the VFD output terminals or at the motor.
Note that if this is a bypass VFD, check direction both in drive mode and in bypass
mode. Check direction in drive mode first. Correct drive mode if necessary. Then
check bypass mode. If the direction is wrong in bypass mode, switch any two phase
on the input side of the bypass.
oSlow down the fan to get the Operating Amps under the FLA of the motor. Adjust the
pulley on the fan or reduce the maximum speed of the VFD. Use parameter P035 to reduce
the maximum speed of the VFD.
Keep in mind that the minimum operating speed of the VFD should be kept above
18Hz. For example, the minimum speed of Intelli-hood is 40%, then P35 should be
kept above 45 Hz.
oAdjust S-Curve parameter A083.
Typically Melink sets this to 20%. Change to 30 or 40%. This extends the
acceleration time, but makes acceleration smoother and reduces the maximum amp
draw.
oAdjust Start Boost Parameter, A084 or S-Curve parameter A083.
Typically Melink sets this to 1 “30.0 VT”. Change to setting 2 or 3.
F12: Hardware Overcurrent
•Allen-Bradley Explanation:
oCheck Programming. Check for excess load, improper DC boost setting, DC brake volts set
too high or other causes of excess current
•Melink Explanation
oThis is a short on the output side of the VFD.
oUsually we see this when there is a short on the output side of the VFD. There could be a
motor failure. Another common cause is a short in the disconnect switch on the roof.
Check the wiring in the disconnect switch. After a heavy rain or after a hood cleaning
process, water in the disconnect switch can be the root cause.
oF12 can also be a short in the motor.
oDisconnect the output wiring at the VFD. Restart the VFD. If the VFD runs and output
voltage on the terminals is verified to be correct, then the problem is on the output side for
the VFD.
oCheck that VFD is the correct HP for the motor.
oCheck parameter , A089, current limit. It should be 1.5xDrive rated current. See page of the
Quickstart manual for the Drive Rated Current
oAdjust Start Boost Parameter, A084 or S-Curve parameter A083. See F7 Fault