grounding

[moe1942]

Scenario: Using a Bobcat 225G in the yard, in damp grass. Will grounding to a ground rod reduce/ eliminate shock hazard or none of the above. Not only from the standpoint of welding, but receptacle use and internal faults.

Neutrals are bonded to the frame and the ground lug.

Also, will use of GFCI receptacles increase safety, ie. reduce or eliminate shock hazard or none of the above?

I'll throw this out and run like heck.....


moe1942

[Sberry]

GFCI would be the best protection along with a circuit breaker on it. As for faults they need to be returned to their source which would be to the transformer of the machine generating it just like line power. A rod wont help with this as it does no good to try to send currents to earth. You need to return the current to where it was made from. We need to understand what a rod actually does in a common electric system to start with. It is NOT to return fault currents, the resistance of the earth is way too hi to pass much current. It is to eleminate potential differences between anything such as equipment ant the earth you are standing on as there are all kinds of stray currents floating around from several sources including leaky underground wiring. A rod is also intended to send lightning strikes to ground. Other than that it has no function as a part of the electrical system.

[Sberry]

Here is a little from Bob Keis where he explains ground rods.
The panels in separate buildings are not really subpanels as far as code is concerned. They are the service equipment for the structure. You can have a subpanel from the service equipment in each building if you want. Between buildings, section 250.32 applies and if there are metal interconnections between buildings such as water piping, or air lines, or any metal interconnection at all, then you must install an equipment ground wire so if you have a 120/240 system, you would have four wires. The neutral would be separated in each building and a grounding bar would be installed, just like a subpanel. Then the code requires a grounding electrode conductor (GEC) to a grounding electrode (usually a ground rod). The GEC will be connected to the equipment ground bar at each building. (((((((This is not to clear overcurrent devices, this is for two reasons. One is lightning, the more important one is to put the equipment ground at the same relative potential as the earth. This is for step potential or touch potential voltages so that what you touch in the building is at the same potential as what you are standing on.)))))))) Now the tricky part. If you do not have any interconnecting metal between buildings, the code allows you to install three conductors between buildings. When you do this you bond the neutral and ground the neutral just like a new service. Some inspectors think that every panel in a separate building must be treated as a subpanel, but this is not true. In past codes (1996 and older) these rule were in section 250-24 and Exception 2 addressed the grounding bus.

[Sberry]

"Section 250.4(D) (5) Effective Ground-Fault Current Path. Electrical equipment and wiring and other electrically conductive material likely to become energized shall be installed in a manner that creates a permanent, low-impedance circuit capable of safely carrying the maximum ground-fault current likely to be imposed on it from any point on the wiring system where a ground fault may occur to the electrical supply source. The earth shall not be used as the sole equipment grounding conductor or effective ground-fault current path." This section requires a low impedance fault return path. The only way to achieve this is to have the equipment ground wire in the same cable, or raceway with the circuit conductors. You cannot separate current flow and maintain a low impedance, it is impossible. Notice one more thing in the above statement. The fault return is go back to the electrical supply source, not where else.
Where do we ground equipment? And yes, electronic equipment is equipment under the code and must comply with all the rules. I know some electronic people think they are special, and are exempt from certain aspects of the code, but believe me they are not. They must follow the same rules as the rest of us. Section 250.6(D) contains the following statement: "(D) Limitations to Permissible Alterations. The provisions of this section shall not be considered as permitting electronic equipment from being operated on ac systems or branch circuits that are not grounded as required by this article. Currents that introduce noise or data errors in electronic equipment shall not be considered the objectionable currents addressed in this section."
This next section tells us what we are to ground equipment to. Believe it or not, no equipment goes to a ground rod, and no equipment whatever is ever connected to a ground rod to ground it. (Yes, there is an exception for 'supplemental grounds') Section "250.4(A)( (3) Bonding of Electrical Equipment. Non-current-carrying conductive materials enclosing electrical conductors or equipment, or forming part of such equipment, shall be connected together and to the electrical supply source in a manner that establishes an effective ground-fault current path." The electrical supply source is the system from which the circuit originated, actually the supply neutral.
Remember this statement: When the code requires a piece of equipment to be grounded, it is grounded (bonded really) to the system grounded circuit conductor, the neutral. It is never connected to a ground rod, a water pipe, building steel or anything else. It goes directly to the system grounded circuit conductor. (in the case of delta systems it goes to the grounded service equipment).

[Sberry]

Particular to generators.
That will depend on the type of generator that is to be installed. If the generator is to be permanently installed then the answer is governed by the bonding of the neutral at the generator.

If the neutral is bonded at the generator then you transfer the neutral in the transfer switch. This is done to avoid having two connections to ground on the neutral at both the service equipment and the frame of the generator.

If the neutral is not bonded to the frame of the generator then you do not transfer the neutral so that the generator's neutral will be grounded by the main bonding jumper in the home's service disconnecting means.

A power inlet for a portable generator is done the same way in that a four wire with ground inlet, such as the L14-XX 120/240, is wired to a two pole transfer mechanism. A three wire without ground inlet, such as a L11-XX is wired to a three pole transfer device. In general three pole transfer devices are only available as switches.

[moe1942]

SBerry, I agrre with GFCI's for people protection. Circuit breakers are circuit protectors. They don't react quickly enough for personnel protection. As far as I could tell, the rest of your post dealt with residential wiring.

Here is something from the Miller education site.

Ground Connection - A safety connection from a welding machine frame to the earth. Often used for grounding an engine-driven welding machine where a cable is connected from a ground stud on the welding machine to a metal stake placed in the ground. See Workpiece Connection for the difference between work connection and ground connection.

I started this post to stimulate thought on the subject. Never hear it discussed until after the fact. To ground or not ground is A personal choice.

moe1942