how can I turn off the setting that disconnects me from poor wifi

I have the Motorola G second gen. (2014) and ive looked everywhere for the setting that makes your phone avoid poor wifi, and I can't find it. on my old phone, I found the option and that old phone was running KitKat 4.4.? I forget the last number, but I've recently updated my phone to the newest version of lollipop and I can't find this setting anywhere. Please help.