a question about grounding.

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Fulthrotl

Fulthrotl

~Autocorrect is My Worst Enema.~
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E
a question was asked of me at lunch, and i knew where to find the answer....
:D

in a commercial occupancy, with an emt raceway feeding a motor, is it legal
to place a ground wire OUTSIDE the raceway? the motor in question is being
fed by a VFD, and the person doing the work want's to know if it is permissable
under the code to do something like this....

i'm saying yes, based on past practices. it used to be common for sealtite
to have a bond wire wrapped on the outside of the sealtite, depending on
the voltage, and the size of the sealtite.

so, it's been done, in the past. is is still legal to do it?

thanks for any feedback....


randy
 
ibew441dc

ibew441dc

Senior Member
infinity said:
How would you connect the bonding jumper on each end?
Click to expand...

liquid2.jpg


Here's one way....
 
ibew441dc

ibew441dc

Senior Member
ibew441dc said:
BJ-100.jpg


Here's another way....this ones good for EMT, Rigid, or a copper water pipe...
Click to expand...


Why would you use a strap like that to bond EMT on the outside (some might be wondering)? Maybe you are using an expansion fitting like this
EC-075.jpg

and you didn't install an EGC of the wire type.
 
ibew441dc

ibew441dc

Senior Member
Expansion Fitting Scenario

Expansion Fitting Scenario

infinity said:
If he's using EMT why would he need one of those? The EMT is already an EGC.
Click to expand...

Agreed...EMT is already an EGC.
I think we are getting off track as to the original question, but, a strap similar to
BJ-100.jpg
may be required to comply with 250.98.

250.98 Bonding Loosely Jointed Metal Raceways. Expansion
fittings and telescoping sections of metal raceways
shall be made electrically continuous by equipment bonding
jumpers or other means.
Click to expand...

If there were no EGC installed inside the raceway, the only way to comply would be to put a jumper on the out side.
 
tom baker

tom baker

First Chief Moderator
Staff member
Location
Bremerton, Washington
300.5 requires all the circuit conductors be be physically close together.
250.4 (5) states
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 low-impedance circuit facilitating the operation of the overcurrent device or ground detector for high-impedance grounded systems. It shall be 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 considered as an effective ground-fault current path.

250.102 (E)
(E) Installation. The equipment bonding jumper shall be permitted to be installed inside or outside of a raceway or enclosure. Where installed on the outside, the length of the equipment bonding jumper shall not exceed 1.8 m (6 ft) and shall be routed with the raceway or enclosure. Where installed inside a raceway, the equipment bonding jumper shall comply with the requirements of 250.119 and 250.148.

A bonding jumper can be installed on the exterior of a racway up to 6 ft. Longer than 6 ft increases the impedance of the EG path such that a fault may not be cleared.
If you install a long bonding jumper on the exterior its a waste of time and money.

The NEC assumes you understand electrical theorey and why running a bonding jumper won't work on the outside or a raceway. I find the why makes the how easier.
 
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