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#88864 08/11/04 05:43 AM
Joined: Jun 2004
Posts: 613
S
Member
Iwire...as for the ground rod...the RV would (I guess) be the cord and plugged connected equipment in this case...and the RV power supply that I am installing for suppling power to the RV would be similar to a sub-panel installaton at a remote building, which would require a seperate ground rod if it contained more than one branch circuit as specified in 250.32
It is my understanding that the intention of the groundrod is to help disperse a potential lightning strike.I understand that this is not a remote building, but I think that a ground rod would help divert a lightning strike to earth more effectively than none at all. Does the code prohibit the use of a ground rod for this RV power supply installation anywhere??? I'm just trying to do an installation that is above the requirements of the code.

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#88865 08/15/04 08:03 AM
Joined: Jan 2003
Posts: 4,391
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Shortcircuit first I gave a really short answer to your last question so here goes the long answer. [Linked Image]

The code section requiring the ground rod for a separate structure is this one.

part of 250.32
Quote
250.32 Two or More Buildings or Structures Supplied from a Common Service.
(A) Grounding Electrode. Where two or more buildings or structures are supplied from a common ac service by a feeder(s) or branch circuit(s), the grounding electrode(s) required in Part III of this article at each building or structure shall be connected in the manner specified in 250.32(B) or (C). Where there are no existing grounding electrodes, the grounding electrode(s) required in Part III of this article shall be installed.

Exception: A grounding electrode at separate buildings or structures shall not be required where only one branch circuit supplies the building or structure and the branch circuit includes an equipment grounding conductor for grounding the conductive non–current-carrying parts of all equipment.

The circuit feeding the outlet the trailer plugs in is one branch circuit, so the exception is available to you if you want.

Yes you can add a ground rod any place in an electrical system you want and connect it to the equipment grounding conductor at a place of your choosing.

Quote
250.54 Supplementary Grounding Electrodes.
Supplementary grounding electrodes shall be permitted to be connected to the equipment grounding conductors specified in 250.118 and shall not be required to comply with the electrode bonding requirements of 250.50 or 250.53(C) or the resistance requirements of 250.56, but the earth shall not be used as the sole equipment grounding conductor.

Will it really do anything for lightning protection?

That is beyond my knowledge but it certainly will not hurt anything.


Bob Badger
Construction & Maintenance Electrician
Massachusetts
#88866 08/15/04 09:42 AM
Joined: Mar 2002
Posts: 582
R
Ron Offline
Member
Bob,
Would a circuit going to a RV receptacle be considered a branch circuit (by definition). I think it may be a tough sell. Most RV's have OCPD's within, so the branch circuit would probably be from the OPCD in the RV to the outlet(s) within.
But I can see where it could be gray, since before you plug in the RV, the circuit serving the 30A recept would be the branch circuit, then when you plug in the RV, it becomes a feeder (presto [Linked Image]).


Ron
#88867 08/15/04 10:01 AM
Joined: Jan 2003
Posts: 4,391
I
Moderator
Ron that is a tough one that I did consider. [Linked Image]

Here is my opinion take it for what it is worth [Linked Image] I do not have facts to back it up.

The NEC does not consider those overcurrent devices in the trailer as the whole trailer is one listed, labeled, piece of utilization equipment.

As an example, my home stereo amplifier has a fuse for the incoming power, does that make the wiring to my wall outlet a feeder?

Looking at this from another direction if we do consider this circuit to be a feeder what section of the NEC relives us of the ground rod requirement?

I do not see anyone driving rods on a regular basis for RVs. That means thousands are in violation or there is a code section that relives us from 250.32.

This is how I came up with my opinion, I would be more than happy to hear other opinions. [Linked Image]

Bob

Edit here to hear [Linked Image]

[This message has been edited by iwire (edited 08-15-2004).]


Bob Badger
Construction & Maintenance Electrician
Massachusetts
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