Date: 202109
Local time of day: 1201-1800
Location: ZZZ1.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: A321
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class C ZZZ
ATC / advisory: Tower ZZZ
Aircraft component: Fuel Distribution System
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Human factors: Communication Breakdown
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Weight And Balance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Fuel Issue
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Overcame Equipment Problem; General Maintenance Action
Contributing factors: Aircraft; Human Factors; MEL; Procedure
Primary problem: MEL

Narrative: On Date; I was the Captain of Aircraft X operating from ZZZ to ZZZ1. The aircraft for this flight was an Airbus A321. The aircraft had NO MEL items and only 1 NEF item - CABIN LT LENSES.The aircraft was properly fuel in ZZZ with our Release FUEL of 43;250 Lbs. Both wings and center tanks were full; and we had the remainder of the fuel in ACT AFT TANK 1.The fuel utilization (burn) was normal with the ACT AFT 1 and the center tank operating normally.After the ACT AFT 1 and center tanks were depleted; the fuel quantity in the RIGHT WING tank started to decrease more than the LEFT WING tank. Both engines showed the same fuel flow and fuel used amounts.The rate in which the RIGHT WING fuel tank was deceasing started to increase over time. When the fuel imbalance exceeded 1;000 Lbs. between wing tanks; First Officer and myself independently preformed the Fuel On Board (FOB) calculation list in the QRH. We both confirmed that we had the correct amount of fuel remaining and there was no fuel leak.At no time did we have any ECAM advisories or alerts.We both came to the same conclusion that somehow fuel was moving from the RIGHT WING tank to supply the left side.The ECAM - Fuel page showed:1) Fuel transfer value in the Closed Position;2) AFT 1 and CTR FUEL TANK empty;3) CRT FUEL TANK PUMPS OFF.Fuel imbalance limitations were check and we well with the limitation.We had an uneventful normal landing at ZZZ1.We arrived at the gate with approximately a 2;400 lb fuel imbalance.After shutdown I called dispatch and talked with Company Maintenance while the dispatcher monitored the phone call. The fuel imbalance / fuel transfer problem was entered into the AML. Maintenance told me on the phone they were going to get one of the fuel computers reset.When the hotel van arrived; the informed the outbound Captain about the fuel problem and informed him at the had called dispatch/maintenance.The outbound flight was delayed while maintenance was working on the aircraft.The next day I was having a conversation with my dispatcher about the routing of our return flight to ZZZ and enroute weather. When I asked if the Dispatched could explain the MEL that was now listed for aircraft X. I explained what had happened the day before with the fuel transferring itself during the flight. The dispatched told me the aircraft had landed that morning in ZZZ with a 3;000 lb fuel imbalance and the crew did a repeat entry in the AML.The aircraft's fuel was checked in ZZZ and the wing tanks did have a 3;000 lb fuel imbalance and it was not just an indication problem. At this time maintenance returned the aircraft to service using MEL 28-XX-X. This MEL has nothing to do with the in-flight problem with the fuel transferring itself. This MEL has to do with refueling the aircraft on the ground. (Indication Problem)The dispatcher called over to maintenance and asked about the issue with aircraft X. He was told that they believe a solenoid that controls the transferring of fuel from ACT AFT 1 tank was at fault. The solenoid was causing the fuel to transfer wing tanks with no indication of the FUEL X FEED valve.The solenoid was replaced the night of DATE1 in ZZZ2.




Synopsis: A321 Captain reported a fuel imbalance during flight. Captain reported an incorrect MEL was applied to the aircraft when it made the return flight to ZZZ with another crew.