bonding rigid pipes

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wireman1

wireman1

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if you run 10runs of ridged pipe for a 4000 amp service using 750 alm. thwn per phase what size ground wire would be required for the bonding bushings to tie them all together? the print shows a 4/0 copper is this the right size or must you use a larger size is there a formula for this or a other way to do this suppose it works out to a 750 you need for the bonding bushings do they have these bushings available
 
Not sure what you mean by ground. Is it supply side bonding jumper or a equipment grounding conductor, check the definitions in the NEC, ground means nothing.
Bushings are available with oversize lugs
 
wireman1 said:
if you run 10runs of ridged pipe for a 4000 amp service using 750 alm. thwn per phase what size ground wire would be required for the bonding bushings to tie them all together? the print shows a 4/0 copper is this the right size or must you use a larger size is there a formula for this or a other way to do this suppose it works out to a 750 you need for the bonding bushings do they have these bushings available
Click to expand...

Tom is pointing out that you are using improper terms that can lead to misunderstandings.
That said, you need to look at 250.102(C)(2). In this size of service you will see that it usually is not practical to daisy chain a supply side bonding jumper. Do the math and let us know the answer for the size needed based on individual or daisy chained at let us know the answer. I am assuming here that you are talking about service raceways here, not the feeder on the load side as it makes a big difference.
In addition, 10X 750 AL for 4000 amp? I don't think so.
 
I agree 10 set of 750 Al is not going to give you 4000 amps. You could use one bonding jumper and connect all of the RMC's together might need to get special order bonding bushings or change the lugs. Is this entering into an open bottom switchboard? If not I would just use bonding locknuts.
 
wireman1 said:
if you run 10runs of ridged pipe for a 4000 amp service using 750 alm. thwn per phase what size ground wire would be required for the bonding bushings to tie them all together? the print shows a 4/0 copper is this the right size or must you use a larger size is there a formula for this or a other way to do this suppose it works out to a 750 you need for the bonding bushings do they have these bushings available
Click to expand...

You mean rigid, right? Ridged is something else.
 
Going from memory, I'm going to say the bonding jumper serving one bushing and conduit, is calculated by the size of the conductors in that conduit. If it daisy chains through all, you have 12.5% of 7500 kcmil. I'll check my book a bit later if no one says yay or nay.

Regarding the conductor size, could be compliant if there is more than one main, but then it would be a 3850 amp service not a 4000 :)
 
I believe you are asking about bonding of the service raceways. Here is what I come up with. Look at Table 250.102(C) especially the notes to the table.

1000 kcmil copper for one conductor connected from conduit to conduit to panel.
750 kcmil x 10 = 7,500,000 cmil x.125 = 937,500 cmil

1/0 awg copper for individual conductors from conduit to panel.
750 kcmil x .125 = 93,750 cmil 1/0 awg conductor is 105,600 cmil according to Chapter 9 Table 8 conductor properties (1 awg is too small)

As others have mentioned, 10-750 kcmil conductors do not equal 4000 amps.
 
reply to bonding of rigid pipes 2 15 18

reply to bonding of rigid pipes 2 15 18

the power company ppl is running the cables from the transformer to the switch gear 4000 amp main breaker .power company will terminate and do all the testing necessary it is a open bottom switch gear .the electrical contractor is required to supply the conduit bonding bushings and bond them together power company requires a 4/0 copper wire for this install can you take a single wire from each of the pipes to a grounding bar and land them on it is a 1/0 wire ok electrical contractor will supply and install the 4 inch conduit
 
texie said:
Tom is pointing out that you are using improper terms that can lead to misunderstandings.
Click to expand...

"What color is it and what does it do?" Mike Holt
Do we need to pull a ground?

It used to be Art 250 was confusing and had mistakes. Lately CMP5 has done a great job of clarifying grounding and bonding terms.
Now if we just could get EGC changed to EBC.

This question by the OP can have two answers depending on if its a supply side bonding jumper or an EGC.
 
wireman1 said:
if you run 10runs of ridged pipe for a 4000 amp service using 750 alm. thwn per phase what size ground wire would be required for the bonding bushings to tie them all together? the print shows a 4/0 copper is this the right size or must you use a larger size is there a formula for this or a other way to do this suppose it works out to a 750 you need for the bonding bushings do they have these bushings available
Click to expand...
If he was correct about it being service raceways then he is asking what size supply side bonding jumper is needed. Though there are some terminology issues in there, I am guessing it is service raceways he is asking about.

If service disconnect is single 4000 amp device he doesn't have large enough conductors. If he has 2-6 service disconnecting means he is fine with those conductors as long as calculated load is not more then 3850 amps.
 
wireman1 said:
if you run 10runs of ridged pipe for a 4000 amp service using 750 alm. thwn per phase what size ground wire would be required for the bonding bushings to tie them all together? the print shows a 4/0 copper is this the right size or must you use a larger size is there a formula for this or a other way to do this suppose it works out to a 750 you need for the bonding bushings do they have these bushings available
Click to expand...

wireman1 said:
the power company ppl is running the cables from the transformer to the switch gear 4000 amp main breaker .power company will terminate and do all the testing necessary it is a open bottom switch gear .the electrical contractor is required to supply the conduit bonding bushings and bond them together power company requires a 4/0 copper wire for this install can you take a single wire from each of the pipes to a grounding bar and land them on it is a 1/0 wire ok electrical contractor will supply and install the 4 inch conduit
Click to expand...

Maybe we could pull both of these post / threads together he said this was a power company installation and they required 4/0
 
wireman1 said:
the power company ppl is running the cables from the transformer to the switch gear 4000 amp main breaker .power company will terminate and do all the testing necessary it is a open bottom switch gear .the electrical contractor is required to supply the conduit bonding bushings and bond them together power company requires a 4/0 copper wire for this install can you take a single wire from each of the pipes to a grounding bar and land them on it is a 1/0 wire ok electrical contractor will supply and install the 4 inch conduit
Click to expand...

If you use one bonding jumper for all of the raceways then it needs to comply with post #8.If using individual bonding jumpers from each raceway then it can be sized according to the conductors within each raceway using Table 250.102(C)(1). For 750 Al that would a minimum size of #3/0 Al or #1/0 copper.
 
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