Trane RTXC-XE Series Installation, Operation And Maintenance Manual page 66

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Table 16. Layout of STO Board Terminals
Port Signal
STO1+ Positive input of the first security signal
STO1- Negative input of the first security signal
STO1+ Positive input of the second security signal
STO2- Negative input of the second security signal
DNS+ Positive output of external detection signal
DNS- Negative output of external detection signal
Figure 31. External 24V Power Supply for STO Board
STO1+ and STO2+ are connected by NC contacts to the positive pole of the 24 V power supply.
STO1- and STO2- are directly connected to the negative pole. When contacts are closed, the AC
drive runs properly with 24 V input. When contacts are open, the AC drive executes an emergency
stop.
Function Remarks
Vin1: Voltage difference between
STO1+ and STO1-
Vin2: Voltage difference between
STO2+ and STO2-
DNS: Voltage difference between
DNS+ and DNS-; OC door output
RTXC-SVX003D-EN