confusion of neutral bonding

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zyhml

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There are several building in a plant including workshop, office, pumphouse guardhause etc. May i bonding neutral to ground at each building? Is there any constraint?
 
Thanks for your quick response. Yes, but may i consider the feeder to each building as 'service'? Another thought is in one building there is set-down transformer 400v/190v 3 phases, do i need bonding the 190V neutral to ground?
 
zyhml said:
There are several building in a plant including workshop, office, pumphouse guardhause etc. May i bonding neutral to ground at each building? Is there any constraint?
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If your jurisdiction is not yet following the 2008 NEC, you may bond the neutral to the equipment ground conductor at remote buildings from the service. Yes, there are parameters to follow.
See 250.32(B) - (B)(1)&(2).
 
I agree you may bond the neutral providing you have not run an EGC. Once the EGC is run then the neutral and ground must be separate. Also note that ground rods are also necessary as well as a main disconnect at each building. Read art. 250.32 and art. 225.32.
 
Pierre C Belarge said:
If your jurisdiction is not yet following the 2008 NEC, ...
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Does it mean 2008 NEC don't allow bonding neutral in remote building even if the case meet 250.32b?
 
zyhml said:
Does it mean 2008 NEC don't allow bonding neutral in remote building even if the case meet 250.32b?
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He's the 08. Note 32(B)1 and 2 are gone. Also note the exception.

250.32(B) Grounded Systems. For a grounded system at the separate building or structure, an equipment grounding conductor as described in 250.118 shall be run with the supply conductors and be connected to the building or structure disconnecting means and to the grounding electrode(s). The equipment grounding conductor shall be used for grounding or bonding of equipment, structures, or frames required to be grounded or bonded. The equipment grounding conductor shall be sized in accordance with 250.122. Any installed grounded conductor shall not be connected to the equipment grounding conductor or to the grounding electrode(s).
Exception: For existing premises wiring systems only, the grounded conductor run with the supply to the building or structure shall be permitted to 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 where all the requirements of (1), (2), and (3) are met:
(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 each building or structure involved.
(3) Ground-fault protection of equipment has not been installed on the supply side of the feeder(s).
Where the grounded conductor is used for grounding in accordance with the provision of this exception, the size of the grounded conductor shall not be smaller than the larger of either of the following:
(1) That required by 220.61
(2) That required by 250.122
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Dennis Alwon said:
I agree you may bond the neutral providing you have not run an EGC. Once the EGC is run then the neutral and ground must be separate. Also note that ground rods are also necessary as well as a main disconnect at each building. Read art. 250.32 and art. 225.32.
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I think you left out an important part Dennis, 2005 nec 250.32(B)(2) Grounded Conductor .....(2) there are NO continous metallic paths bonded to the grounding system in each building or structure
 
brother said:
I think you left out an important part Dennis, 2005 nec 250.32(B)(2) Grounded Conductor .....(2) there are NO continous metallic paths bonded to the grounding system in each building or structure
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Dennis pointed the OP to the correct article, if the OP went to the article and read it he would see this for himself.

Dennis didn't leave out anything, he said "may", OTOH, your post #2 did leave out some pertainent information didn't it.

Roger
 
roger said:
Dennis pointed the OP to the correct article, if the OP went to the article and read it he would see this for himself.

Dennis didn't leave out anything, he said "may", OTOH, your post #2 did leave out some pertainent information didn't it.

Roger
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Thank you Roger, I was just getting ready to respond when I saw your post.

M.D. said:
Zyhml,...You sure don't sound like an electrical engineer.:confused:
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Was this comment necessary? I think not.
 
Dennis Alwon said:
Thank you Roger, I was just getting ready to respond when I saw your post.



Was this comment necessary? I think not.
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There are a lot of comments made that are not necessary ,.. When I read his profile and then his questions I could not help but to wonder ...if he is in fact an E.E. ,..Perhaps next time I'll wonder to myself ,...sorry if I have offended you or Zyhml.
 
If this is a factory complex, I would bet there are tons of "metallic connections" between the buildings such as piping systems, telephone lines, water pipes...
 
Thanks all you guys, i got clear information now. Actually i am not english background, so i do have problem on many definition and requirements in NEC.
 
I don't mean to sound like a jerk but ,..This seems like a fairly large project,..have you considered hiring a translator with a background in the electrical industry ?? I am concerned with the level of understanding you have of the English language .,,it may effect the safety of those who will occupy these buildings.
I used to know a little french but I cannot imagine trying to understand the french version of the NEC without the help of a well educated translator ,.
 
yes, i know your concern, actually this project is designed in compliance with local code, i just want to know if there is any difference between NEC and local code or i can put higher requirements on design. For example, local code require neutral of UPS has to be bonded to ground, so the bypass of UPS might be a problem if there is no isolate transformer, is it right?
 
You may want to find the IEE Green Book I have no experience with this so I'll take a pass on giving any further advice.

http://ecmweb.com/powerquality/electric_perplexed_pq_issues_7/

Should I install a new ground rod to connect the neutral and ground conductors in the secondary side of the UPS that has a primary (input) voltage of 220V (single-phase, 2-wire) and a secondary (output) voltage of 110/220V (single-phase, 3-wire plus ground)? If yes, does this mean the UPS is considered to be a separately derived system all the time?



McGranaghan, Rick Langley, and Doug Dorr's answer: The IEEE Green Book (IEEE 142-1991) has a section titled, “System Grounding for Uninterruptible Power Systems” that addresses UPS grounding design issues. The book features several illustrative examples to assist the user in better understanding the various guidelines associated with proper grounding techniques. The question of whether to bond the neutral and ground on the output of the UPS depends on several variables, especially the following:

  • The configuration of the UPS bypass circuit.
  • The source supplying power to the UPS.
  • The input/output of the UPS.
According to the Green Book, which uses the NEC as guidance, if the “UPS is considered a separately derived source, the neutral of the UPS output module should be bonded to the equipment grounding conductor, and a local grounding electrode module should be installed, per NEC [1], 250-26.”

Your question doesn't provide us with enough information to supply a specific answer because we don't know if the UPS is really a separately derived source. The best way to make this distinction is to take a multimeter and perform a continuity test from input neutral to output neutral. If the neutral is continuous — there is no isolation transformer in the unit — it isn't a separately derived source. So you can't bond the output neutral to ground.

On the other hand, if the continuity test reveals a break in the neutral circuit, it most likely means the UPS is equipped with an isolation transformer. In this case, the UPS is a separately derived source, and you should bond the neutral and ground conductors. You can also bond this connection to building steel and to the building's grounding electrode system. However, there's generally no need for you to use a new ground. If you do use a ground rod, it should be part of the overall building grounding electrode system, which means it must be bonded to building steel at this location.
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zyhml said:
There are several building in a plant including workshop, office, pumphouse guardhause etc. May i bonding neutral to ground at each building? Is there any constraint?
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The rule is no, see 250.24(A)(5), 250.142(B) & 250.32(B)(1)

The reason is to keep objectionable current off non-current carrying items, inappropriate neutral bonding will cause a parallel path allowing current and dangerous touch voltage where it does not belong.

The exceptions are found in 250.30(A)(1) & 250.32(B)(2)

The change up to 2005 bonding the neutral might be an exception but 2008 it is not allowed

unless it's an existing feeder, and all the criteria of 250.32(B)'s exceptions are met including "there are no continuous metallic paths" between the buildings like metal framing, water, air, phone, coaxial...

Keep the reason in mind while designing or installing.
 
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