I run a mobile coffee cart and have had the same problem over time with different equipment, amperage, 10, 15, 20 amp etc.... The main thing to consider is when each piece of equipment is warming up ( machine, Fridge etc... ) it draws a lot of power on start up. It pays to turn one device on, let it power up fully before turning the next item on and so on. Electricians have given me the best advice of adding up the power requirements of all your appliances together and double it for the required gene then your covered in the most extreme circumstances, you don't want your grinder to stop working because the machine and fridge have maxed out your gene! for the sake of adding an additional 1/2kva! to be safe.
hope this helps, feel free to contact me if you want to chat
Hart's Coffee Cart