There are four electric fans hanging over us/our heads.
Does the above sound right? And do both us and our heads fit in it?
Quite definitely: OUR heads.
Ah, I understand your question now! I thought you were asking whether you should say 'us heads' or 'our heads'.
'Fans hanging over us' is perfectly OK.
(Believe it or not, some people here do mistakenly say 'us heads' - I think in olden days it may have been a corruption of 'ours heads' when even English adjectives had to agree with the noun.)
Dave