My hydro project is at a point where I need to pull 3 #8cu thwn conductors through an underground pvc conduit from the PMA to a GTI in the house. Question: Should I also pull a grounding conductor and connect the frame of the PMA to the house grounding system? If I understand correctly, the 2011 NEC Art. 250-30(B) states that the PMA is a separately derived system with no grounded (neutral) wire and thus should not be connected to the house grounding system, even though the plug and play GTI will be grounded to the house grounding system through the 3-wire plug. The NEC further states that the PMA should be separately grounded to a ground rod to stabilize the voltage, minimize static buildup, lightning, etc. and all equipment related to this system shall be bonded to it. If this is correct, I will pull a grounding conductor from a ground rod installed at the site, through a lug on the frame of the PMA, to the main disconnect at the GTI in the house (since it is part of the separately derived system), and terminate it there. Some how it all makes sense, but doesn't sound right. Does anyone have any thoughts or maybe some guidance on PMA system grounding?