replace H3 with M3......or if your feed uses 3H then use 3M.
Some time the rollover with volume changing. Some use the 5min chart to see gaps...then they switch.
Some just switch tomorrow morning.
If you use e-signal then they have a perpetual symbol for the SP e-mini with the symbol ES #F then no change is necessary. However for that symbol they observe the rollover to be the 2nd day before the last trading day of the expiring contract.
Michael B.