B737-800
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 169
Aircraft Equipment Problem Less Severe; Flight Deck / Cabin / Aircraft Event Other / Unknown
Flight Crew Returned To Departure Airport; General Maintenance Action
Aircraft
During taxi; we had the left pack light illuminate during annunciator recall on the Before Takeoff Checklist.  The light extinguished during Master Caution recall; indicating a single controller failure or a fault in the SRADA.  I contacted Maintenance and we deferred the malfunction under MEL 21-32-01.  We then proceeded to take off.Shortly after takeoff; hot air started entering the cockpit from the cockpit vents.  The ZONE TEMP warning light for the CONT CAB zone illuminated.  We ran the QRH for ZONE TEMP.  The supply duct temperature for the CONT CAB zone was pegged hot off scale at 200 degrees F.  Running the QRH procedure for ZONE TEMP did not stop the hot air from entering the cockpit.  The cockpit temperature rose quickly and was very; very hot.  The FO's iPad shut down from overheating.  The cabin temperature was normal as were the supply duct temperature readings for the FWD and AFT cabin zones.  After coordination with Maintenance and Dispatch via the radio; we returned back to land at MDW underweight and uneventfully.  The pack light never illuminated again on its own after we deferred it on the ground.Because the QRH procedure for ZONE TEMP did not solve this problem; I want to highlight this situation for analysis and consideration for modifying the QRH.  I believe an additional step(s) that could be considered is/are shutting off packs one at a time to see if this alleviates the problem; similar to the PACK light QRH procedure.  If that doesn't work; then shutting off a bleed(s) to cut out the hot air source (and using the isolation valve in conjunction).  I have not heard from Maintenance yet.  (I called them a few hours post-flight to see if the problem was identified; and they said that they suspected a failure somewhere in the left pack; but had not made a definitive repair or conclusion yet.)   I suspect the problem was the left pack not conditioning the air properly and just emitting out very hot air that eventually went to the cockpit.The pack light never illuminated independently on its own again during our situation.  Had that happened in-flight; the QRH for pack light would have eventually directed us to shut down the affected pack; and perhaps this would have solved our problem. But; I'm not sure in our situation if the pack would have ever overheated at the sensor location to turn on the pack light.  Nor am I sure of the final Maintenance analysis of what really happened.While we were close to a suitable field for landing; if this happens in an ETOPS or Class II situation the cockpit could get unbearable hot before landing.  While I understand not every situation can be covered in the QRH; perhaps this one can be covered depending on the outcome of the Maintenance analysis of our problem.  Beyond shutting off pack(s) and bleed(s); I was also considering simply opening the cockpit door to vent the hot air out of the cockpit; (after coordination with FAs to guard the door properly).I have also contacted the EFB Team for them to look into what temperatures the iPads overheat and auto-shutdown; as my FO's EFB did.  We were approaching a dual EFB failure scenario.  Perhaps we could give guidance to the Pilot Group to take actions to protect the EFBs in this high-cockpit-temperature scenario; such as putting the EFB away in a protected location (like a flight bag) to lessen heat exposure until needed for navigation/landing.  Or; give an EFB to the FAs to keep cooler in the cabin until needed.
Climbing out of 3000 feet; the temperature in the cockpit was extremely hot and the duct pressure was 200+F. It was hot enough to warp my iPad case that I stuck in front of the side vent and eventually shut my iPad down. I could not use it because of its temperature limits. We then got the Temp Light and Air Cond annunciator on the overhead panel.
B737-800 flight crew reported very high cockpit temperatures apparently caused by a pack issue. Flight returned to departure airport for maintenance attention.