I have add. would it be effective at work if i set a timer for 20/30 min for hard work and let myself distract for a couple and repeating the cycle?

Can be helpful: Anyone, ADD or not, can often benefit from pacing their study or work projects. Doing so has been shown to increase focus and productivity for the work interval. It is important to reward yourself for efforts completed and this does help. Be sure you don't get caught up in your "break". You might also set a timer for 5 min for the break.

Try it out: Try it out and see. In fact most people benefit from breaks throughout the work day. If I might make a suggestion, pair a certain cue with the activity to condition your mind to focus in the presence of that cue - this might be sound (music or certain frequency sound such as that used in meditation), tactile/kinesio (such as meditation balls), taste (gum or candy), etc. Best wishes.

Time management-ADHD: With adult ADHD, it's important that you have good time management. Setting a timer for work and for 5-10 min breaks is vital for your best performance. Also placing yourself in a quiet area away from your co-workers, wearing headphones, and taking notes as reminders of have-to's is helpful. You do have a right to 504 accommodations thru your employer. Read Lynne Weiss' book on adult ADHD, also.

Reasonable: If this schedule is consistent with your work environment and you can get all of your responsibilities covered, this type of schedule is reasonable for a person who does not want to take medication. If this does not work out, see your doctor about a trial of medication or referral to a neurologist or psychiatrist.