We had an unexplained trip out of this circuitbreaker when we turn off both center boost pumps. All 3 control relays were OK (tank 1 fwd boost pump relay, tank 2 aft boost pump relay and right center boost pump relay), they are behind copilot CB panel. At the end we found a defective “scavenge fuel shut off valve” who is energized across a 20 minute timer in engine accessory unit module from this same CB! Thanks to Viktor for this input.