vacuum and continuum
Well, there's probably more than three. Right now I could only think of "balloon" and raccoon though, assuming that you meant those double letters have to be next to each other.
These letters can be unscrambled to spell the word tundra.The next longest word has five letters and is the word daunt.
The letters 'anlcopmi' unscramble to spell the word complain.The next possible longest word is campion.
The letters 'ehcealrihw' unscramble to spell the word wheelchair.The next longest possible word at eight letters is leachier.
ballon embarrass coffee raccoon tennessee mississippi football
bellhop
"a" & "b".
quizmaster
quizmaster
bellhop
bellhop
quizmaster
bellhop
From the official Scrabble dictionary:AllhealBellhopFulhamsKolhozyOilholeWoolhat
240
RR
There is none in English, not counting compound words.