B737-800 DIVERTS TO AN ENROUTE ARPT WHEN A FAILED PACK REQUIRES FLT AT AN ALT THAT PRECLUDES CONTINUING TO DESTINATION.

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WX WAS CAVOK. WE HAD A BLEED TRIP OFF LIGHT LEADING TO A PRESSURIZATION ISSUE. LEAVING ZZZ WE WERE CLBING THROUGH FL250 WHEN WE ENCOUNTERED A 'BLEED TRIP OFF' LIGHT ON THE R ENG. WE LEVELED OFF AT FL270 AND RAN THE QRH CHKLIST FOR BLEED TRIP OFF LIGHT. THE CHKLIST ACTIONS FAILED TO CORRECT THE PROB. PRESSURIZATION WAS PROVIDED BY ONLY THE L PACK FROM THE L ENG BLEED. UPON CONFERRING WITH THE COMPANY DISPATCHER AND MAINT COORDINATOR WE DECIDED THE BEST COURSE OF ACTION GIVEN THE NON-NORMAL PRESSURIZATION CONFIGN WAS TO DIVERT TO ZZZ1 FOR AN EQUIP SWAP. WE DID NOT HAVE ENOUGH FUEL TO REACH ZZZ2 AT FL250 AND I WAS CONCERNED ABOUT CONTINUING ON TO DEST AT FLT PLANNED ALT HAVING ONLY THE L ENG BLEED TO SUPPLY ALL OF THE PRESSURIZATION REQUIREMENTS FOR THE FLT. FOR SAFETY OF FLT REASONS I DECIDED TO CONTINUE THE FLT AT FL250 TO PRECLUDE ANY FURTHER PROBS (IE; RAPID DEPRESSURIZATION) SHOULD THE L BLEED FAIL. AFTER CONSULTING THE MANUAL FOR THE LNDG DISTANCE AND BRAKE COOLING REQUIREMENTS I DECIDED AN OVERWT LNDG IN ZZZ1 WAS THE BEST COURSE OF ACTION. THE MANUAL SHOWED WE WERE WELL WITHIN LIMITS FOR THE LNDG AT ZZZ1. MAINT APPROVAL FOR AN OVERWT LNDG WAS RECEIVED. WE DSNDED TO FL250 AND PROCEEDED TO ZZZ1. THE LNDG WAS UNEVENTFUL. ACFT WT AT TOUCHDOWN WAS 160000 LBS AND VVI WAS APPROX 100 FPM. AN 'OVERWT LNDG' WRITE UP WAS ENTERED INTO THE ACFT LOGBOOK TO INCLUDE THE GROSS WT AND THE VVI AT TOUCHDOWN.