Green Screw & Ground/Neutral Question

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Old 06-30-20, 07:52 PM
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Green Screw & Ground/Neutral Question

Asking a question about electrical is sometimes confusing because people do things differently... even when both ways are ok/correct but people still seem to disagree.

For example, I had a very experienced electrician of 40+ years install a sub panel for me a while back & while some people agree its correct, others disagree.

I took advice from someone here because, whether some of you believe it or not, I really do value every electrician here that has given me advice. Meanwhile, I have other experienced electricians that disagree.

My question is about the green screw that comes with every breaker panel, while a ground bar does not. I have yet to EVER buy a breaker panel, whether main or sub, or in this additional scenario, a main disconnect, that comes with a ground bar, I have to buy one extra, but it does come with that green screw that I always throw away. Personally, I learned to wire with a ground bar, not a green screw in the neutral bar. As well, some here noted in a picture I posted a while back that the sub panel that I had installed was done wrong because the ground was connected to the neutral bar. (For a note: I bought a new ground bar, installed it & moved the ground from the neutral bar to the ground bar)

I have a friend that is helping me install my first ever meter base & main disconnect for my new shop. He almost gets beyond aggravated at me that I want to wire it with a ground bar & not connect the ground to the neutral.

I have watched a dozen or more Youtube videos & most or all of them use a ground bar & put ground wires there. Put neutral on neutral only. As I understand you guys, you say the same..... and I agree.
BUT....... If its the case, why does every breaker panel come with no ground bar, but does come with a green screw to ground out the neutral bar & put the grounds & neutrals on the same (neutral) bar?
There is a tag on every green screw that says...... "Use this screw to ground the neutral bar when required." Ok, so when it it required? When is it NOT required? What the heck am I supposed to do?

To go back to my previous thread about the sub panel, This house, built in 1968 has the old two wire system.... in the house, there is only a black (hot) & a white (neutral). The system is grounded in the meter base with the ground & the neutral on the same lug in the meter base. From that point forward, there is no... none... zero ground wires. Not otherwise in the meter base or in the breaker panel or in the house that I know of. The way I understand it, is the ground is attached to the neutral in the meter base & that makes the neutral wire & everything its connected to... from that point forward.... a neutral & ground.

Another point, when I install this new main to the shop, Entergy is pulling the line from teh pole & connecting to the meter base & I'll bet (& I don't know for sure) that they connect that meter base the same as with this house. They'll pull ONLY three wires & connect the ground rod to the neutral in the meter. So, if NEC says you cant connect the ground to the neutral, why does the meter base only come with three lugs? Two hots & a neutral? There is NO lug for a 4th wire.. a ground?

Look, I am just trying to learn. I understand that old electricians know many "tricks to the trade" & almost all do things a little differently than some others might do it. But.... I'm just at my witts end about everyone doing things differently & its either: "both ways are legal, its just preference" or "both ways are ok, this way is just simpler" or everyone is ripping everyone else cause they "don't know what they're doing & they are incompetent".

Personally, I want to add a ground bar in my new 200 amp main disconnect & take it into the breaker panel & to the ground bar. I prefer coming into my panel with 4 wires...... 2 hots, a neutral (to the neutral bar) & a ground to the ground bar). My friend is all but beside himself.

And I am just aggravated in general over this whole thing.
 
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Old 06-30-20, 08:07 PM
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You should review the diagrams here: https://www.doityourself.com/forum/e...-diagrams.html

In general the green screw is used for the service panel (contains service disconnect after meter) and nowhere else. Exception is detached building where only has 3 wire feed that was legal at the time but no longer is.

If you buy more expensive panels then they will come with a separate grounding bus.
 
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Old 06-30-20, 08:12 PM
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That screw is bonding screw for neutral bar and it is used to bond neural bar to chassis of the panel, thus grounding it.
You are supposed to bond neutral to ground at the first means of the disconnect. Usually this is your main panel. This is the only case you would used that screw included with the panel.

With all sub panels, neutral should be separated from ground with one exception. The exception is when 3 wire feed is used, where neutral wire also serves as ground. However, this is no longer allowed and must use 4 wires to sub panels.
 
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Old 06-30-20, 09:15 PM
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Another way to look at this: If you have separate ground and neutral wires supplying the panel then they need to go to separate bars. With that there should not be a bonding screw (a.k.a main or system bonding jumper).
 
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Old 07-01-20, 03:05 AM
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The bond screw is included when the panel is used as a service. It ensures an effective ground fault path to trip the breaker.

In a service panel the neutrals and grounding conductors can share the neutral bar.
 
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Old 07-01-20, 03:45 AM
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The neutral is technically called the "grounded conductor" because it is not always "neutral" meaning the same voltage potential to the ungrounded (hot) conductors. In single-phase dwellings, it does have the same voltage to the ungrounded conductors so I will keep calling it the neutral.

The neutral is where the ground is derived. The neutral is bonded (electrically connected) at the source transformer to a wire that runs to the earth. The same is done at the main service disconnect by installing a water pipe ground, Ufer ground and/or ground rods. This creates no difference of potential on the neutral at the transformer and the main service. It also is an additional path back to the source, the transformer. The green screw is installed to bond the steel box of the panel to the neutral which is connecting it to all the other parts of the grounding system. (neutral wire, ground rod, water pipe) Notice how everything leads back to the earth?

In the main service, the neutral and ground wires can connect to the same bar as they are bonded together. If you install a ground bar in the main service only the ground wires should connect to that. If you connect a neutral to a ground bar you will have current flowing through the steel box of the panel, which is not a good thing.
 
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Old 07-01-20, 05:17 AM
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A meter base does not need separate neutral and ground conductors going to the load. But if there is a (usually unsealed) compartment underneath with a master breaker set or two then 4 wire feed (for 120/240 volt service) must come out of that for the downstream panel(s)..

"The way I understand it, is the ground is attached to the neutral in the meter base & that makes the neutral wire & everything its connected to... from that point forward.... a neutral & ground."

The branch circuits, with no ground wires (equipment grounding conductors) downstream from the fuse box to the (two prong) receptacles, etc. are officially considered ungrounded The neutral is not refered to as "the ground." Portions or the whole system can be rendered grounded by retrofitting with separately run EGC or (more likely with the aforementioned 1960's vintage house) rewiring with modern wiring methods.
 

Last edited by AllanJ; 07-01-20 at 05:34 AM.
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Old 07-01-20, 06:01 AM
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Hi, check this link out, choose your state, it gives all the requirements for that service, pages around 60 to 75.
https://cdn.entergy-texas.com/userfi...ndards/CIS.pdf
Geo
 
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Old 07-05-20, 10:03 AM
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I have a friend that is helping me install my first ever meter base & main disconnect for my new shop. He almost gets beyond aggravated at me that I want to wire it with a ground bar & not connect the ground to the neutral.
Has he slapped you around yet because he should! Using a ground bar is fine, but what you want to do is not! The Grounding Electrode Conductors from ground rod and water service are REQUIRED to be terminated on the neutral bus so without the neutral bonding screw the panel box and your ground bar are not grounded. The purpose of that green screw is to bond the ungrounded box to neutral/ground.

 
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Old 07-05-20, 04:21 PM
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Joe, you been here a long time & are no doubt knowledge able in electrical work. I mean no disrespect but, you need to re-read my post & understand what I said.
 
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Old 07-06-20, 08:48 AM
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Could you extract the sentences of your post that you feel that Joe took issue with and which you feel thsat Joe overlooked, and repeat them below?

Your post altogether is too long for even me (with some experience) to reread.

<<< . "Use this screw to ground the neutral bar when required." Ok, so when it it required? When is it NOT required? What the heck am I supposed to do? >>>

You have to do the homework to find out when the green screw needs to be used. Some of which you did by creating this thread.
 
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