What does the BUS TIES Selector Knob OVRD position do?

What does the BUS TIES Selector Knob OVRD position do?

• A. The BTCs are kept closed regardless of EDL, provided that no overcurrent is detected
• B. The BTCs open when EDL is active
• C. The BTCs are left in whatever state EDL dictates
• D. The BTCs close automatically if APU is online

Answer: (A)

Putting the bus-ties in override locks the bus tie contactors closed, bypassing the normal automatic logic that would decide their state. They stay closed regardless of what the Electrical Distribution Logic would normally do, as long as there’s no overcurrent detected. In other words, you’re guaranteeing a connected path between the two essential buses, which can be important during certain power configurations or tests. If an overcurrent or fault occurs, protection still trips the BTCs open to safeguard the system. This is why the override is about forcing closure versus the automatic behavior where the EDL would decide to open or leave the ties as is, or respond to another condition like the APU state.

Putting the bus-ties in override locks the bus tie contactors closed, bypassing the normal automatic logic that would decide their state. They stay closed regardless of what the Electrical Distribution Logic would normally do, as long as there’s no overcurrent detected. In other words, you’re guaranteeing a connected path between the two essential buses, which can be important during certain power configurations or tests. If an overcurrent or fault occurs, protection still trips the BTCs open to safeguard the system. This is why the override is about forcing closure versus the automatic behavior where the EDL would decide to open or leave the ties as is, or respond to another condition like the APU state.