For our friend in Bristol, 15 hours is usually 5 courses, for 3 credit hours each. The usual is that classes are either scheduled in one-hour blocks on M,W,&F, or in 1.5 hour blocks on Tu & Th. One spends 3 clock hours in the classroom for each course each week, therefore each course is said to be a 3-hr. course. 15 credit hours = 5 courses.
As someone has already noted, one-credit-hour courses are kind of unusual, as they only meet for one hour per week. Usually these are peripheral sorts of things, like the one I used to teach, "Introduction to Books and Libraries", or as it was colloquially known, "Books n' Berries." It was a required class for Freshmen, we taught them how to use the university libraries' resources. In our case, since it was a 10 week semester, we taught it over the course of 5 days, for 2 hours each day during the first week of classes.