An isolated equipment grounding receptacle is installed using a rigid nonmetallic conduit and a metal device box. two 12 awg conductors enter the box and are spliced to two 12 awg conductors leaving the box and to two pigtails, which feed the receptacle. the 12 awg isolated equipment ground has a pigtail splice for the receptacle and continues through the box. a bare 12 awg equipment grounding conductor enters the box, connects to the box grounding screw, and continues on through the box. determine the minimum size metal device box for this installation.