120/208/240 4 wire delta - Bonding sub panels

[Jamespcboyd]

I have read the NEC and it says that bonding a sub panel is a not done today because it creates multiple paths back to the transformer.. Some of these existing Sub Panels.. might as well be called sub service entances.. will be well over 100ft, 200ft, and into the 300's.. is there any situation in which I would bond the neutral? I've been told bonding is proper.. EKM UL listed meters will be installed at each buildings panels?

 

[ActionDave]

Your going to have to be more clear about what you are asking. There is no such thing as a 120/208/240 Delta. Do you mean 240/120 Delta which has a 208V high leg?

I have read the NEC and it says that bonding a sub panel is a not done today because it creates multiple paths back to the transformer.. Some of these existing Sub Panels.. might as well be called sub service entances.. will be well over 100ft, 200ft, and into the 300's.. is there any situation in which I would bond the neutral? I've been told bonding is proper.. EKM UL listed meters will be installed at each buildings panels?

Do you have multiple transformers with the secondary feeding one panel or one transformer feeding several panels or just a one three phase service from the utility feeding the whole building?

 

[augie47]

Your post is a bit confusing with some of the terminology.
Any panel fed directly from a Power Co. transformer will be a service panel and the neutrals are bonded at service panels.
Any panel fed from (by) a service panel is often refered to as a sub panel and the neutrals are not bonded there (an equipment ground is required)

 

[Little Bill]

If there are meters at each panel, that (normally) means each panel is a separate service and bonding would need to be done.

 

[Jamespcboyd]

Yes eventually I'll get the lingo down.. these panels will be sub panels. I was confused why I was told to bond the sub panels.. I figured it was because the buildings are separated or there was something I missed... I appreciate the input..

 

[Jamespcboyd]

If there are meters at each panel, that (normally) means each panel is a separate service and bonding would need to be done.

They are ekm sub meters.. beautiful setup.. monitor usage and print bills online like a separate power company.. but technically that still makes it a sub panel.. because it is not directly fed from the transformer..

 

[tortuga]

but technically that still makes it a sub panel.. because it is not directly fed from the transformer..

James being fed from a transformer has nothing to do with distinguishing a service from a feeder (sub panel).
Do you have a code book? Check out article 100 definition of feeder and service.

 

[Jamespcboyd]

James being fed from a transformer has nothing to do with distinguishing a service from a feeder (sub panel).
Do you have a code book? Check out article 100 definition of feeder and service.

I do not have the code book here at the moment.. but was able to obtain an explanation yet another section of the nec states that the main service panel or first disconnect at the service entrance should only be bonded.. so now im still confused.. any panel that branches off the main shouldn't be bonded?

Let's say I had 14 sub panels (branches?) 60 amps 3 phase each in separate buildings.. all fed off a 42 space panel the neutral or ground as far as I read should not be bonded.. while they will be metered but not by the poco.. picture me like a monkey learning to talk.. lol when explained..

 

[LarryFine]

There is no situation where bonding neutral to ground is proper in a feeder or sub-panel in any new work.

 

[Jamespcboyd]

Branch is not the proper terminology thank you for the 100 article reference!

 

[augie47]

Every panel should be bonded ! I inferred from your question (perhaps wrongly) that we were talking about a neutral bonded to the panel. That only happens as service panels. Downstream panels are bonded to the EGC>

 

[ActionDave]

Yes eventually I'll get the lingo down.. these panels will be sub panels. I was confused why I was told to bond the sub panels.. I figured it was because the buildings are separated or there was something I missed... I appreciate the input..

I do not have the code book here at the moment.. but was able to obtain an explanation yet another section of the nec states that the main service panel or first disconnect at the service entrance should only be bonded.. so now im still confused.. any panel that branches off the main shouldn't be bonded?

Let's say I had 14 sub panels (branches?) 60 amps 3 phase each in separate buildings.. all fed off a 42 space panel the neutral or ground as far as I read should not be bonded.. while they will be metered but not by the poco.. picture me like a monkey learning to talk.. lol when explained..

There is a current trend in the electrical world to change the terminology around Equipment Grounding to Bonding and your confusion is evidence why I think it is a mistake. That's just an off topic rant.

More direct to your question... There is one place in a building where the neutral, more properly called the Grounded Conductor, and all the other metal parts of the electrical system and especially all the Equipment Grounding Conductors are "BONDED" and that is at the service or at the source of a separately derived system. This is called the Main Bonding Jumper or System Bonding Jumper. Everywhere else the neutrals and equipment grounds are kept separate from each other.

 

[mbrooke]

I do not have the code book here at the moment.. but was able to obtain an explanation yet another section of the nec states that the main service panel or first disconnect at the service entrance should only be bonded.. so now im still confused.. any panel that branches off the main shouldn't be bonded?

Let's say I had 14 sub panels (branches?) 60 amps 3 phase each in separate buildings.. all fed off a 42 space panel the neutral or ground as far as I read should not be bonded.. while they will be metered but not by the poco.. picture me like a monkey learning to talk.. lol when explained..

Everything boils down to ohms law, and sadly, the code does not acknowledge, understand or even give lip service the 3rd pillar or leg of the stool.


The neutral like all conductors has Z. Z results in voltage drop. Bonding the neutral to ground after the first disconnect puts current onto the protective system since current takes all paths. Because the protective system also has impedance, differences of voltage occur between all objects directly or indirectly in contact with the protective system.

Further, the division of current results in net current, where for example, a hot wire might carry 10 amps but a neutral and conduit only 2.5 amps. This results in inductive heating and high EMFs, both problems onto themselves.

 

[Jamespcboyd]

okay so I get what's being said ...neutral bonded in the main switching device enclosure. In turn its bonded to the ground.. Neutral = Ground in the SE .. okay so let's say you run one sub panel.. you terminate ground wire and neutral together + Ground Bar to 2x Ground rod.. let's say you run another sub panel off that sub panel... you terminate the neutral to neutral bar and ground to ground bar.. Yet the Neutral is never considered a current carrying conductor on a high leg delta system but on a 3 phase wye it is... why would anyone want a wye system? Lol and why was the ground the easiest part of the system so hard for me to figure out.. correct me if I'm wrong about any of that.. but that way makes sense.. so it must be right..

Separately what's the difference between any of the bonding or not bonding if you use any EMT or Ridgid conduit between the main.. sub panel.. or subs off the sub.. its all the same at that point.. Metal conducts... not as well as copper or aluminum.. but it does Conduct..

 

[Jamespcboyd]

2x Ground rod at every panel.... is what It should say

 

[mbrooke]

On a 3 phase wye the neutral is not considered a current carrying conductor unless you have high harmonic loads. Ideally we'd have 139/240Y and connect all loads phase to phase, but we are "stuck" with what we have.

Regarding ground rods: They do not aid in opening a breaker. 25 ohms is much to high vs the 0.6 ohms needed to trip a 20 amp breaker.

 

[ptonsparky]

Properly installed metallic raceways will provide a better return path than a minimally sized equipment grounding conductor.

 

[tortuga]

okay so let's say you run one sub panel.. you terminate ground wire and neutral together + Ground Bar to 2x Ground rod.. let's say you run another sub panel off that sub panel... you terminate the neutral to neutral bar and ground to ground bar..

Jamespcboyd: the Neutral and EGC should not terminate on the same grounding bar in a feeder panel all the feeder panels would terminate the same after the main service panel or disconnect enclosure.
It says your occupation is "Training" are you an electrical trainee or do you train people in another industry?
If your an electrical trainee, helper (or apprentice) I highly recommend owning a code handbook as it has helpful illustrations.
Mike Holt has a great grounding and bonding books, videos and classes, I have used them for years.
Here is a grounding pdf with some basics related to your question:

https://www.mikeholt.com/instructor2/img/product/pdf/1292432628sample.pdf

 

[mbrooke]

Properly installed metallic raceways will provide a better return path than a minimally sized equipment grounding conductor.

How do we know this is true? And with age? Z for every 1000 feet of 1/2, 3/4, 1, 2 inch EMT ect?

 

[ptonsparky]

How do we know this is true? And with age? Z for every 1000 feet of 1/2, 3/4, 1, 2 inch EMT ect?

How do you know it isn't? I pull wire but the conduit guys say wasted money.