Operating Instructions

Troubleshooting
Siemens Building Technologies, Inc. 49
Troubleshooting
Description of Problem Possible Cause
Commanding the SED2 to start
closes the bypass contactor.
SED2 required programming for bypass operation has not
been programmed in the VFD. Make appropriate VFD
programming changes. See Required SED2 Parameter
Setting.
Contactors do not close.
• Main input short circuit protection has opened.
• Control power fuse has opened.
• Safety circuit is open.
• Motor overload needs to be reset.
• Loose control wire connection.
Drive does not start on closing of
bypass control terminals 1 and 2.
• Drive–Off–Bypass switch is not in the Drive position.
• Drive output contactor is not closed.
• Remote contact is not really closing, replace with a wire
jumper or use drive parameters to verify this contact
closure.
• Run relay has failed.
• Loose control wire connection.
• Drives digital input 1 is not programmed appropriately.
Main input fuses clear when
motor is run in bypass
The short circuit protection supplied by the factory is
approximately 1.5 times NEC listed motor current rating.
Some applications and motor characteristics may require
up sizing this protection. If this is required in the field,
ensure that there is an appropriate match between the
fuses type and rating with fuse holder.