Siemens SED2 VFD Electronic Bypass Option 125-3208 User Manual

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Siemens Building Technologies, Inc. 

The Interlock feature (also called damper end switch logic) enables the SED2 outputs 
to inhibit motor start until a safety condition (proofing sequence) is confirmed. Any 
call to start the motor from the SED2 or bypass does not directly start the motor, but 
instead initiates the following Interlock procedure: 

•  The Interlock Start Logic Enable indicator is ON. Proofing is required to start 

in VFD or bypass mode. 

•  The Interlock Start Logic Command indicator turns ON and the Proofing 

indicator flashes.  

•  When in VFD mode, the SED2 Relay closes and the Controller board 

Programmable Output closes to initiate the proofing sequence. The 
Programmable Output relay is used to supply power to an external device 
such as a damper actuator.  

•  When not in VFD mode, the Controller board ignores the SED2 Relay.  

•  When in bypass mode, any call to start the motor in bypass (in either hand 

bypass or auto bypass) initiates the proofing sequence. The Programmable 
Output closes and is used to supply power to an external device such as a 
damper actuator.  

•  When control of the external device (such as a damper actuator) is satisfied, 

it must supply a contact closure to the Controller board Interlock Start. The 
Interlock Start Logic Command indicator turns OFF and the Proofing 
indicator turns ON. The motor then starts in the selected mode.  

•  Any call for the motor not to be running requires a new proofing sequence to 

be initiated.  

This feature can only be used with a hardwired start/stop command.  

The Interlock feature requires that Controller board DIP 
Switch 3 is set ON. 

1.  The Interlock Start Logic Enabled indicator is on 

steady.  

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