I did some work today in a 35 yr old commercial building. The service was a 208Y/120 3-phase. Some of the runs from the main panel were in 3/4 inch emt with #12 thhn. Each conduit had 6 ungrounded conductors, 2 neutrals and 1 ground. I was wondering how they were keeping track of the neutrals so they wouldn't be overloaded. Starting in the first j-box of each run the two neutrals were wired together. I haven't seen this before. Is this an acceptable practice?