I am a new lecturer (non-tenure track) at an American engineering university (lecturer=teaching track professor, in my case). I am on a 9 month rolling contract and am contracted to work between Sep-May of a year. I am really young in my career and will embark on my first teaching assignment as a lecturer this Summer (2015).
Our university does offer graduate and undergraduate courses in the summer and needs instructors (teaching track lecturers or research/tenure track professors) to teach them. Usually, research/tenure track professors supervise Masters or PHD students in the summer and trade teaching for that. It is incumbent on lecturers to teach summer courses.
I volunteered to teach one course in the summer (June 2015-Aug 2015) and my department chair, who is responsible for course load distribution asked if I "would be willing to teach" a second course during the same months. I politely declined and offered to teach the second course in the following Fall semester if the need arose.
June-Aug is really "off-contract" season for me and teaching a course "off-contract" is compensated on an hourly or a per-course fashion ($xx/hr or $xxxx per course).
I am unsure of whether I was tactless in my handling of this situation. How does one manage such a request from the department chair? Did I shoot my career really early in the foot by declining such a request (however offering to teach the course in a later semester) or is declining a request OK in academia? How do I improve my approach to manage such a situation for course negotiation or teaching load distribution in the future so that I am not perceived as being a slouch "who dodged extra responsibility"?