Protecting the circuits starts by verifying that your power source is wired as the building code requires.
When the customer is depending on you to make sure the new system you are installing works as it is supposed to and can be counted on every time it is needed your first line of CYA is verifying the code is met. The companies I worked for always had a few additional requirements beyond the code regarding power sources.
Every site I was responsible for required an isolated earth grounded circuit for the equipment we were responsible for maintaining. That requirement applied to new installs as well as taking an existing installation under contract.
It was in the contract and had to be verified before the contract was signed. This had a little to do with personnel safety and everything to do with protecting the circuits in our equipment from lightning.
When making a consumer product do not ever call it foolproof but do everything feasible to keep the fool from accessing anything detrimental to the product.
Before you call it 'foolproof' consider what befell the Titanic for having been declared 'unsinkable'.