Joe,
I have used those little plug in heaters in my home over the years ,the problem is at 1350 watts the wire is border line over heating when you switch heater to the 1500 watt or high side then you are really heating the wire up,if you have 15 amp breakers they will kick off.Now if you have a 20 amp breaker with 12/2/w/g and a 20 amp outlet with nothing else on it then the heater will work ,but I grant you for sure if any thing gets plugged in with it the breaker will trip weather up or down line of the heater.
Either run another circuit at 20 amp breaker 12/2/w/g wire and 20 amp outlet or make sure you run that heater on low
