Adding time values

I have a worksheet that calculated the length of a person's shift according to their time in and time out. I then want to total the hours for my team each day, and each week. I am using the hh:mm format for time...ie: 13:30 = 1:30pm. When I try to add the range of hours together, it automatically starts from zero each time it reaches 24 hours. How can I keep it form doing that? If I have 50 hours scheduled in a day for my team I want it to reflect that.