Scheduling for Known Work Requirements

Our facility has a sign up roster for staff to volunteer to work extra hours. Those who volunteer are allowed to record Compensatory Time for the extra hours worked, but they are not allowed to claim Overtime or Night Differential pay for the hours worked. Is this acceptable?

Comp Time vs. Credit Hours

I would like to better understand the differences between the two types of Premium Hours. What are the rules dictating how credit hours and comp time are earned, accumulated and used? What are the relative advantages and disadvantages for each?