B737-800 Captain reported refusing an aircraft after the previous Captain had also refused the aircraft. The aircraft had a deferred air conditioning pack and required repair. Ground temperatures were very high.

Narrative

Refused aircraft. Just prior to push back; Dispatch notified me that my aircraft was needed for a different flight because the Captain had refused the plane; which was parked a few gates from me. I called dispatch to ask to discuss and was told the plane had an inoperative pack that had been written up previously; and the Captain couldn't cool the plane. I walked over to check the plane. The Captain was still there. I discussed the situation with him. The same pack had repeat write ups and had been MELed for the same problem previously. Neither the APU nor external air cooled the plane where it could be boarded or operated in ZZZ summertime heat. The cabin was about 85 F in front and about 92 F in the back and never cooled beyond that. I was informed that maintenance could not repair the pack at ZZZ. In interest of the safety and health of passengers and crew; I elected to refuse the plane. Too hot to board passengers or for cabin crew to work. Once the doors close; it's worse. It's ZZZ in summertime. The inoperative pack is a category X repair; so it can be flown 10 days before it's fixed. This pack had been written up more than once. In the summertime; especially; this isn't reasonable. Furthermore; when a pilot refuses a plane; it's not appropriate to assign the plane to another flight in hopes that a different pilot will accept it.