Some of the other techs on this thread are correct if you agreed to do installs before working there than yes, they do have a rite not to compensate you. but then even if they didn't tell you they can change up in an instant and declare it in your daily agenda, although they haven't yet. if you stop doing installs I believe they will find a reason to tell you later that you have to do them. I could be wrong but with companies I have worked for its always about them. Good luck.
