Date: 202002
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Dusk
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Climb
Airspace: Class B ZZZ
Aircraft component: Air Conditioning and Pressurization Pack
Component problem: Failed
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Reporter qualification: Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Second reporter function: Captain; Pilot Not Flying
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Other / Unknown
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Returned To Departure Airport; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Aircraft; MEL; Procedure
Primary problem: Aircraft

Narrative: Aircraft dispatched with MEL Right Pack Inoperative. I was Pilot Flying climbing to 8000 ft. on departure when the left BLEED TRIP OFF light illuminated around 7000 ft. FO was Pilot Monitoring and ran the checklist in the QRH (Quick Reference Handbook). The trip reset worked. All indications were normal at this point and we received further climb clearance. I initiated the climb as I was considering my options. The one good pack had just hiccupped and I was contemplating continuing versus a return to ZZZ when the same light came on again passing about 11;000 ft. It would not reset a second time and right after the reset attempt the Cabin Altitude warning light and horn came on. My decision was made for me. I disengaged the autopilot and autothrottles and initiated a fairly smooth pushover while directing the FO to tell Center we needed to descend back to 10;000 ft. Center was very accommodating as I suspect they heard the horn in the background. We were now passing about 12000 ft. going to 13;000 ft. before I was able to stop the climb momentum and descend. We barely had time to comply with the QRC (Quick Reference Checklist) before we were back at 10;000 ft. Complied with the rest of the QRC and QRH and asked for and received clearance for lower altitudes as we descended gradually back into ZZZ for an uneventful landing about 2000 lbs. below max landing weight. Cabin altitude did not exceed approximately 13;000 ft. so the passenger masks did not deploy.The only working pack was tripped off at the bleed. Don't dispatch aircraft with one pack.


Second narrative: We were operating a Single Pack aircraft as Right Pack was previously MEL'd by maintenance. On our departure climb out someplace around 8000 ft. we had a LEFT BLEED TRIP OFF Caution indicating a LEFT BLEED Overheat/Overpressure condition.We ran the BLEED TRIP OFF Caution QRH checklist and the BLEED TRIP OFF light extinguished which was considered reset and the end of the procedure. After some time as we continued our climb the LEFT BLEED TRIP OFF Caution light appeared again for the 2nd time.This time as we were re-running the QRH checklist for the 2nd time the BLEED TRIP OFF indication would not reset anymore and stayed illuminated confirming a BLEED Overheat/Overpressure condition. Shortly after we also received a CABIN ALTITUDE Aural Warning indication. We advised ATC; initiated a descent to 10;000 ft. and ran the QRC/QRH CABIN ALTITUDE Warning checklist.After completing the QRH checklist we assessed the situation and due to the multiple BLEED TRIP OFF Overheat/Overpressure indications coupled with the CABIN ALTITUDE Warning indication we decided to divert back to ZZZ for a normal landing. We safely made a normal landing; parked at the gate and handed [the] plane to the ZZZ maintenance team.


Synopsis: B737 Flight Crew reported that the aircraft was dispatched with one air-conditioning pack MEL'd; and the operating pack tripped off after takeoff; causing an air turnback.