Mike Dolt Enterprises
Mike Dolt Enterprises
User: Keri_WW, Location: Tennessee
Asked on: Monday, April 18, 2011 at 9:11 pm EDT
Answered on: Tuesday, May 14, 2024 at 4:21 am EDT
Question: I've got a panelboard being served by the utility transformer, which will be a couple hundred feet away from the actual building to be served. This panelboard will feed a gutter and two or three other panels.This is a 240V single phase system. As far as grounding goes, I am providing 4#3/0 (2 current carrying conductors, ground, and a grounded neutral) from the xfmr to the panelboard. I am then providing a #4 ground connected to a 10' ground rod. From this panelboard, I am running 3#250 and 1#4 (upsized for VD) to the gutter. At this gutter I am providing another ground rod, and calling for #4 to the metal water pipe, gas piping (if applicable), and an exothermic weld to building steel.Does this all sound correct? My main areas of confusion are the # and sizes of ground from xfmr to first panel, grounding required at first panel, and grounding required at building gutter.Thanks for the help!!Keri:grin::grin:
Grounding from Transformer to First Panelboard # and Size of Ground
You have provided a 4#3/0 service entrance cable with two current-carrying conductors, a ground, and a grounded neutral. This is correct.
Grounding Required at First Panelboard
At the first panelboard, you need to install a main grounding electrode system (MGE). This MGE consists of: A 10' ground rod A #4 grounding electrode conductor (GEC) connecting the ground rod to the neutral bus of the panelboard
Grounding at Building Gutter Grounding Required
At the building gutter, you need to install a grounding bar or plate that is bonded to the metal gutter.
Connections to Grounding Bar
You need to connect the following to the grounding bar: A #4 GEC from the first panelboard A #4 GEC to the metal water pipe (if present) A #4 GEC to the gas piping (if present) An exothermic weld to the building steel
Summary
Your grounding scheme appears to be correct. You have provided an adequate ground from the transformer to the first panelboard, installed an MGE at the first panelboard, and provided a grounding bar at the building gutter with connections to all appropriate grounding points. Flag for review