Re: To ground or not to ground. attn:--=9BMr. Tom H. Group: alt.engineering.electrical Date: Tue, Mar 29, 2005, 10:34pm (EST+5) From: daestrom@NO_SPAM_HEREtwcny.rr.com (daestrom) wrote in message news: snipped-for-privacy@news3.newsguy.com... On Tue, 29 Mar 2005 13:39:58 -0500 Roy Q.T. wrote: | I already Stated the code that Prohibits Grounding the Neutral at a | Subpanel of a System that is already Neutral/Grounded at the Service | Disconnect, You guys may be talking about 2 different things. Absent a specific example, I can't say who's statement is more right than the other. Still, I've seen cases where neutral and ground are double bonded and everyone insists it is right (bonding at the meter and at the service entrance), and it drives me nuts to see it that way. The *original* question wasn't about 'double-bonding' though. To me, that is connecting the neutral to the *same* ground system in two different panels. And that is generally bad. The *original* question was a service panel feeding a separate building. The feed to the separate building consists of two hots and the neutral (only a 3-wire feed). The feed to the separate building does *not* include the ground (EGC). The separate building has *no* conductor (not even pipes) that connect to the first service panel. So it is two
*separate* ground systems. Bonding one grounding system to neutral at the service entrance is okay. And so is bonding a
*separate* ground system to the neutral in the separate building. In this circumstance the code
*clearly* allows for bonding the EGC of the separate building to the neutral
*and* installing two grounding rods for the separate building's EGC. In this type of installation it is safe to bond the EGC to the Grounded Current-carrying Conductor ('neutral') in the sub-panel because the grounding system in the separate building is
*separated* from the grounding system at the main service entrance, there will be very little current flow diverted from the neutral conductor between the buildings. Diverting neutral current in a sub-panel, into a single grounding system that re-connects to the neutral in the main service is what needs to be avoided. But with no interconnection between the separate building and the service panel, this isn't a problem. The purpose of the EGC system is to help maintain the frame/exposed parts of portable equipment and appliances at a potential as close to the
*local* earth potential as possible. This minimizes the hazards to people standing on 'earth' and touching said appliances. This is why it is preferable to have the EGC connected to local grounding rods if it is an electrically separate grounding system. If bonding the neutral to the EGC in a sub-panel can create multiple pathways for neutral current to return to the main service, then it must be avoided by
*not* bonding neutral and ground locally in the sub-panel. In that situation, the sub-panel's EGC bus-bar can have a significant potential above the earth where the grounding system actually contacts earth. And that can be a hazard to people standing on earth and touching an appliance's frame connected to the sub-panel's EGC. But that wasn't the case in the
*original* question. daestrom
------------------------ let me see if i got understood you,
we agree the systems are seperate but for the 3wire underground conductors, you say, since no bonding conductor was transfered over from the service disconnect it is Ok to bond the Neutral & EGC {{{but with Seperate Grouding Rods}}} =3D[do i have you right this far?] not useing the jumper tag inside the panel, Right? I think the bonded Neutral that runs from the Cabin to the Meter/Service Disconnect at the Pole is a pretty strong path for current ( wouldn't you say) If He were to Bond That Neutral conductor from the Cabin to Earth to The EGC Buss via the supplied jumper as others suggest in my book would create a hazard.
the *original* question was to ground bond with EGC to the EGC Buss in His Cabins Panel with an Isolated Neutral from the Pole., somehow he is lead to believe He must bond the Neutral Bar as well as the Cabinet EGC Bar, My Point is He should Bond the EGC Buss to Earth with A groudning Electrode and not to the Neutral which is apparently bonded at the service entrance.
I am witholding my opinion on the Neutral/EGC Buss being bonded [commentaries] in light of them being grounded WITH SEPERATE GROUNDING ELECTRODES as Daestrom pointed out.
- This technique is beyond me, since I have never seen this done.
=AEoy