O/T Electrical Question

I am going to install a 60 amp sub-panel in my barn.My question is do I have to run the ground wire back to the main panel or can I run it to a grounding rod at the barn? Or do I do both.?

Al

you should have to only run it to the grounding rod at the barn

The ground rod alone at the barn will not project you from shock. You need that fourth wire. The ground rod at the barn is then optional, but not required.

Gerald J.

You can run 2 commons & a neutral from main panel to barn . Then drive 2 ground rods at barn . Run a single piece of #6 bare from one rod to the other & then to the grd bar in the panel . It needs to be a condinuous ground . Then for more protection at the barn , if you have a water line in the barn , run a piece of #6 bare from the metal water line to the grd bar in panel also . That's how I wired many barns & other out building for farmers & it was according to the electrical code at that time . Never had any inspections denied .But make sure a 60amp is large enough for expected usage . God bless, Ken

Code now requires 4 wires. Bonding the water line can (will) create a parallel path if the neutral fails and it is bonded at both ends.

As previously stated, four wires and the grounding system.
Open the bond between the remote panel's neutral and ground buses.

There are two separate issues here, which get confused and intertwined.

Every building served by more than one branch circuit requires a grounding electrode system. This can be driven ground rods, metal water pipes, "Ufer grounds" (rebar in footings), etc. For safety, metal parts like pipes and ducts should be BONDED to the grounding electrode system. The building disconnect means (typically the remote sub-panel) is to be bonded to the grounding electrode system.

So, no matter what, you must provide "ground rods" or some equivalent at the remote building.

The independent issue is provision of the equipment grounding conductor. The preferred solution for safety is a 4 wire feeder. Two hots, a neutral, and an equipment grounding conductor run between the two buildings. The sub-panel DOES NOT bond the neutral and equipment grounding conductor. The sub-panel DOES NOT bond the neutral and the building's grounding electrode system. The sub panel DOES BOND the equipment grounding conductor to the building's grounding electrode system. This is the only solution allowed by the 2008 National Electrical Code.

THe 2005 and older NEC allowed for the use of a 3 wire feeder in certain circumstances. (In particular, there must not be other metallic paths between the buildings, such as water pipes or phone lines). Two hots, and a neutral are run. The building's grounding electrode system is bonded to the NEUTRAL at the sub-panel. The ground bar in the subpanel is bonded to the neutral in the sub-panel. This saves the cost of the equipment grounding conductor, but is an inferior solution especially in a livestock environment.

The 2005 NEC is still in effect in many (most?) jurisdictions. It takes a while for local codes to fully reflect code changes. So you may be able to do the three wire solution for a little longer.
But it is going away eventually, and good riddance to it.

Driven ground rods are there to provide lightning protection. They do little or nothing to provide a fault current path, as the resistance of the typical driven ground rod is 30 ohms or more.

If a tool gets a short from line to case and that case is only grounded by the local ground rod the current will not be great enough to trip a breaker, yet the voltage to ground will be enough to kill the tool user. I've investigated several such deaths. Don't do without that fourth wire unless you want to buried younger than your time.

Gerald J.

I'm not an electrician and I don't plan to be, but these electrical discussions are interesting.
Here's something I don't understand.
If if you run four wires and don't bond the neutral and equipment ground at the branch panel, how can a breaker in the branch panel trip, if the ground becomes energized?

TnT,

The neutral and ground are tied together at one place: The main panel or disconnect. Which is why the ground conductor must be able to handle enough current to fault the circuit breaker.