u/External-Response829

I am updating my kitchen and just bought a stovetop to replace a previous one. My neighbor who is a licensed plumber offered to help me with connecting the stovetop. I assumed a plumber would know at least a little electrical...well I think I was wrong. He wired up 120/240v stovetop to a junction box with the incoming feed coming from a Type nm-b 6/2 wire which previosuly powered a 240v only cooktop and comes directly from the panel. In doing this, it appears my plumber/handyman tied the neutral and ground from the stovetop to a bare ground wire from the incoming feed. It looked funny to a DIYer, so I began googling. My google says this is against code and a safety issue. My question would be how big of a safety issue? As in my house is burning down if I use it once and I should keep the breaker off untill I can get an electrician out to run new 6/3? Or can I use the stovetop and get an electrician to replace when time permits (end of the month)? Thanks!