bonding

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johneymac

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i am installing a 1200 amp three phase service how do i calculate the size of the service equipment bonding jumper, thank you all johneymac.:-?
 

SPARKYNSJ

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Bonding x0

Bonding x0

This is actually a similar question. How/what do i size gec for the x0 to the ground rod? Xfrm is 277/480 primary:120/208 400amp secondary.
 

augie47

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i am installing a 1200 amp three phase service how do i calculate the size of the service equipment bonding jumper, thank you all johneymac.:-?

If this is your main bonding jumper you best take a look at 250.28, you most likely are looking at the 12-1/2% rule.
 

infinity

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i am installing a 1200 amp three phase service how do i calculate the size of the service equipment bonding jumper, thank you all johneymac.:-?

If the total area of your parallel conductors are larger than 1100 kcmil Table 250.66 won't work. You'll need to use the size outlined in 250.28(D)(1) which is 12.5% of the size of the phase conductors.

This is actually a similar question. How/what do i size gec for the x0 to the ground rod? Xfrm is 277/480 primary:120/208 400amp secondary.


250.66, need not be larger than #6 AWG.

Welcome to the forum. :)
 

iwire

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This is actually a similar question. How/what do i size gec for the x0 to the ground rod? Xfrm is 277/480 primary:120/208 400amp secondary.

To a just a ground rod?

To a ground rod 6 AWG copper or 4 AWG AL is the largest required for any size transformer.

250.66(A).
 

augie47

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State Electrical Inspector (Retired) DINOSAUR
This is actually a similar question. How/what do i size gec for the x0 to the ground rod? Xfrm is 277/480 primary:120/208 400amp secondary.

similar, yet not. johnnymac was speaking of an equipment bonding jumper which in his case, as a service, is determined by 250.28. You are speaking of an SDS where 250.30 does reference us back to 250.28, but when you mention ground rod, we are now talking about grounding electrode conductors and not system bonding jumpers.
The grounding electrode conductor would be sized per 250.66, but if you have to fall back to a 250.52 electrode, I would think the #6 referenced in 250.66(A) would apply.

(woops a lot of folks answered while I was still looking up Code reference.. us old men can't remember so well)
 
It doesn't have to be any larger than 6 cu or 4alum as long as its the only connection to a grounding electrode. If it is also hitting a ground ring, building steel, etc, then it must be sized according to table 250.66
 

iwire

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It doesn't have to be any larger than 6 cu or 4alum as long as its the only connection to a grounding electrode. If it is also hitting a ground ring,

If its hitting a ground rod and ground ring it would never have to larger than the conductor used as the ground ring. 250.66(C)

250.66(A), (B) & (C) can all remove table 250.66 from the answer.

Really the only full size GECs are the going to the water line and building steel.
 
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