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Joined: Sep 2002
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MJR Offline
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Is there ever an occasion where a ground rod should be installed at a sub panel in a remote building (and attached to the ground wire from the main panel)? I haven't found any reference to it (yet) and I would think it should be done only because of ground potential differences between where the two panels are mounted.
Thanks-Michael

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Sean WB Offline OP
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was not attached to ground from main panel. There was no ground to the sub panel in barn. with all the welding/compressor loads, its a good idea.:O)


I did not get as think so badly as you shocked I did.
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MJR,
250.32(A) requires a grounding electrode at the second building any time there is more than a single branch circuit feeding the second building.
Don


Don(resqcapt19)
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MJR Offline
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Thanks, Don - got it!

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Not to open any worms but... you may be able to use your bonding screw depending on what type of panel you use. For example, GE has a true split neutral buss which allows you remove the MBJ with two bolts. Thus splitting the bus into a isolated neutral and ground bus. Then you could use the pretty green screw on the ground side (the left hand bus)

Do not confuse this with the short bus, which is what I rode to school in.

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arseegee, yep... I've only removed the bar once in an installation, the rest of the time I've always installed a bus.

But you are indeed correct, especially with GE (and I consider myself somewhat of an expert with GE since that's what I use the most often!).

The important thing is to bond the EGC and GC only once and to provide a bond to the EGC to all metal enclosures, and to use an approved means to do so.


-Virgil
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(quote)"If you are feeding a subpanel(50-125 amp) from a main service panel(200 amp) , do you need to have 4 wires to the sub panel?"

Correct me if this is wrong here guys, but my continuing ed instructor often illistrates a sub-panel in a seperate building (garage) using a 3-wire feed from the main panel(no equipment ground). The heading under this illistration reads "permitted but not recommended".

The illistration clearly shows the feeder wires originating at a 2-pole breaker inside the main panel, not from a meter socket. It also shows the main bonding jumper installed in the sub. I'd like to clear this up.

Can anyone quote an article number where it states that "all" sub-panels must be fed with a 4-wire feed? Can anyone quote an article where the code even uses the term "sub-panel"? Matt

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Wow... In fact, 250.32(B)1 & 2 elude to the option as well... (if it is to a seperate structure...)


Hmmm... My bad, Matt... Jeez, back to the books I go!

Now how come y'all didn't catch that!

[This message has been edited by sparky66wv (edited 09-24-2002).]


-Virgil
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Sean WB Offline OP
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I was talking to someone again Today about this [Linked Image] he swears you Do run a ground back from main and DO NOT bond at sub for the simple fact that your GFCI protection will function more accurately .
Thats the best reson so far [Linked Image]


I did not get as think so badly as you shocked I did.
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Quote
I was talking to someone again Today about this he swears you Do run a ground back from main and DO NOT bond at sub for the simple fact that your GFCI protection will function more accurately .
Thats the best reson so far


The only ground fault protection that will function more accurately is the ground fault protection of equipment and that is already covered by condition three of section 250.32 (B) (2).

(2) Grounded Conductor. Where (1) an equipment grounding conductor is not run with the supply to the building or structure, (2) there are no continuous metallic paths bonded to the grounding system in both buildings or structures involved, and (3) ground-fault protection of equipment has not been installed on the common ac service, the grounded circuit conductor run with the supply to the building or structure shall be connected to the building or structure disconnecting means and to the grounding electrode(s) and shall be used for grounding or bonding of equipment, structures, or frames required to be grounded or bonded. The size of the grounded conductor shall not be smaller than the larger of
(1) That required by 220.22
(2) That required by 250.122

If ground fault protection of equipment is installed the building disconnecting means and panels must be wired as if they are in the same building as the service supplying them. This is because a bonding connection to the neutral at the second building will cause some current to flow through the earth back to the service and transformer grounding electrodes. This can cause nuisance tripping of the ground fault protection.
--
Tom


Tom Horne

"This alternating current stuff is just a fad. It is much too dangerous for general use" Thomas Alva Edison
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