sum cells ignoring ones with blanks

i have a time sheet that calulates the hours worked per day and i want to add them up to give a total hours worked in a week.

The Cells in Column AO need to add up the cells in column (H,M,R,W,AB,AG,AL) but i keep having the issue that if one of those cells is blank (and i need it blank not 0) from the formula in that cell, then it returns # value or blank depending on the formula used. ( i have a couple of different ones in the cells that i have been testing)

copy attached.

Cheers