No matter if you choose a negative or positive ground model, you will be getting one that is completely safe, as long as you hook them up properly. Negative grounded models will be grounded by connecting the negative to a metal ground rod or, in the case of an RV, part of the chassis. If you have a positive ground model, then the unit will be grounded correctly by hooking it up to the different electronics the system will power. Make sure you understand which type of system you are getting so that you can install it correctly if you are doing it yourself.