What powers the DC SERV BUS?

• A. DC BUS 2 and APU BATT DIR BUS Through The DC Service Switch
• B. DC BUS 1 And DC BUS 2
• C. External Power
• D. DC BATT BUS

Answer: (A)

The DC SERV bus is powered through a dedicated feed that the DC Service Switch connects to DC BUS 2 and the APU battery direct bus. When the DC Service Switch is in the position that ties these sources to the DC SERV bus, power flows from DC BUS 2 and the APU BATT DIR bus to energize the DC SERV bus, keeping essential service loads powered even if other power sources are unavailable. This arrangement ensures items needed for routine service and maintenance remain energized. External power or other busses aren’t used for this particular feed in this configuration, since the intended source path for the DC SERV bus is through the DC Service Switch from DC BUS 2 and the APU BATT DIR bus.