250.64 (e)

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chip

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Can someone explain how to size the bonding jumper from 1" EMT containing 3/0 GEC to cold water into the service enclosure. The service is 2000 amp, 277/480 volt the service conductors are 6 sets of 500 kcmil. Also, the size at the cold water end, the 3/0 to the 1" EMT. I was told 12.5% of the total area of the phase conductors, per 250.64 (e) & 250.102 (c)

500 kcmil x 6 = 3000 kcmil x 12.5% = 375 so 400 kcmil

So do I need to use 400 kcmil to bond the EMT to the service enclosure and also the EMT to the 3/0 at the cold water.

please correct me if I'm wrong or any advice. Thank you, Chip
 
Chip,

I dont believe that is correct. If you are asking about 250.64(E) then it simply is saying you need to bond each end on the ferrous raceway. One end should be bonded to the enclosure by the EMT connector and you would simply need to bond the other end of the conduit to the 3/0 CU...they make end connectors for this application.

I believe your references to 12 1/2 percent is for EBJ on the supply side of the service for your raceways and such.
 
Paul, in the 2008 handbook section 250.64 (e) it refers to 250.102 (c) for sizing bonding jumpers to ensure the electrical continuity of ferrous metal enclosures. Thanks for a response and any additional information.

Chip
 
1100205275_2.jpg
 
not sure Chip....I have looked at the revisions for 2008 and I dont see anything other than above. I dont have a 2008 Handbook " handy "....but I do have Mikes 2008 NEC Changes and IAEI's 2008 NEC Changes here and I dont see where 250.64(E) has changed....maybe others know but I dont believe in regards to the GEC bonding that it would need to be larger than the conductor you have already run....would not make sense to increase it and still have only 3/0 going to the electrode.....You are just trying to bonded each end of the ferrous raceway....per 250.64(E)
 
Just keep in mind on that EMT connector at the enclosure you would need a bonding bushing or bonding lock nut as well...but the jumper if you used a bonding bushing would not have to be larger than the GEC within the protective raceway.

lol.....I alwas suggest they use RNC and avoid all the hassle....;)
 
I agree with you Paul, and yes all I'm trying to do is bond each end of the conduit. This is how the inspector is telling us how to size it. I think this is way over kill and just wondering if there are other code sections that state other ways of doing it. Thanks again
 
Not sure what "flash's" Ch# 1 is,.. but why not run the conductor out the end to the electrode and loop through whatever clamp then install a pipe clamp on the emt and end it there.

:confused: I don't see the wording that demands the jumper to be the same size as the electrode conductor. :confused:

Is it the phrase " effectively bonded " in 250.92 (A)(3).

I would think it should be the same size ,....I wonder what was used to determine the size of the jumper in the second photo.. a gut instinct my guess.
 
Look at 2008 handbook 250.64(E), at the end of the section it explains to use 250.102(C) to size the bonding jumper, 12.5% of the area of the largest phase conductors over 1100 kcmil.
 
Thanks ,..I see it now... that makes the second photo a violation under 05 or 08 and most likely 02 .

Hey,.Chip the 05 handbook has an image of the install I suggested on page 217 ,...250.92(A)(3)
 
250.64(E) Enclosures for Grounding Electrode Conductors.
Ferrous metal enclosures for grounding electrode conductors
shall be electrically continuous from the point of attachment to
cabinets or equipment to the grounding electrode and shall be
securely fastened to the ground clamp or fitting. Nonferrous
metal enclosures shall not be required to be electrically continuous.
Ferrous metal enclosures that are not physically continuous
from cabinets or equipment to the grounding electrode
shall be made electrically continuous by bonding each end of
the raceway or enclosure to the grounding electrode conductor.
Bonding shall apply at each end and to all intervening
ferrous raceways, boxes, and enclosures between the service
equipment and the grounding electrode. The bonding jumper
for a grounding electrode conductor raceway or cable armor
shall be the same size as, or larger than, the required enclosed
grounding electrode conductor. Where a raceway is used as
protection for a grounding electrode conductor, the installation
shall comply with the requirements of the appropriate raceway
article.
 
lol...tell that to IAEI....I was trying to show the bushing....or method not the size.....for the life of me I could not find an image of the one like Paul posted....
 
ok....lets post it here and look at it chip.

(C) Size ? Equipment Bonding Jumper on Supply Side
of Service. The bonding jumper shall not be smaller than
the sizes shown in Table 250.66 for grounding electrode
conductors. Where the service-entrance phase conductors
are larger than 1100 kcmil copper or 1750 kcmil aluminum,
the bonding jumper shall have an area not less than 121⁄2
percent of the area of the largest phase conductor except
that, where the phase conductors and the bonding jumper
are of different materials (copper or aluminum), the minimum
size of the bonding jumper shall be based on the
assumed use of phase conductors of the same material as
the bonding jumper and with an ampacity equivalent to that
of the installed phase conductors. Where the service entrance
conductors are paralleled in two or more raceways
or cables, the equipment bonding jumper, where routed
with the raceways or cables, shall be run in parallel. The
size of the bonding jumper for each raceway or cable shall
be based on the size of the service-entrance conductors in
each raceway or cable.

Ok....I read it......but dont see where it applies to the bonding jumper required in 250.64(E)...that bonding jumper being refered to in 250.102(C) is for bonding supply side service raceways....this bonding jumper is designed for a fault current path.....if required.

The 250.64(E) requirement clearly says it the bonding jumper is not required to be larger than the GEC being ran....now if someone wants to run larger then fine but not a requirement of 250.64(E)....sorry i dont see where 250.102(C) applies to 250.64(E)
 
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