Hello from a new guy with some questions.

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Aleman

Senior Member
Location
Southern Ca, USA
Just want to introduce myself. My name is Steve K and I am employed as an Maint Electrician/Industrial Electrician. I am not certified but lately I have been doing a lot of electrical work. My background is with machinery and industrial controls, PLC's, automation, along with some electrical installation work. I understand a lot of what I am doing but I run into questions about what I see. I have noticed that different electricians do work to their personal standards which at times does not seem correct to me.

An example...120V single phase circuits with no ground wire, using the conduit for the ground.

Another example is multiple hot conductors sharing a single neutral. In this case the hots are different phases but from what I understand the proper way to wire would be a separate neutral for each hot.

One more that I am not sure about is a 100A 208 3 phase 4 wire service. The ground buss is being used for the single phase branch circuits but the conduit itself is what connects the panel to the ground in the main switchgear. There is no separate wire for ground and the ground buss is not connected to the neutral buss. That doesn't seem right to me, but I did see something on the net that suggested 3" conduit would be considered ok as a ground conductor. Is this correct?

I have an Ugly's and a pdf copy of the NEC but the thing reads like a lawyer wrote it. So whatever advice I can get here would be greatly appreciated.

Steve
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Another example is multiple hot conductors sharing a single neutral. In this case the hots are different phases but from what I understand the proper way to wire would be a separate neutral for each hot.
Again this is compliant
 

George Stolz

Moderator
Staff member
Location
Windsor, CO NEC: 2017
Occupation
Service Manager
Welcome to the Forum. :)

An example...120V single phase circuits with no ground wire, using the conduit for the ground.

Usually compliant. Notice that in 250.118, a conductor-type EGC (equipment grounding conductor) is only one of many options.

Another example is multiple hot conductors sharing a single neutral. In this case the hots are different phases but from what I understand the proper way to wire would be a separate neutral for each hot.
Perfectly compliant and a better use of resources than using dedicated neutrals. You use less material and suffer less from voltage drop.

210.4 lays out what must be done when multiwire circuits are used.

One more that I am not sure about is a 100A 208 3 phase 4 wire service. The ground buss is being used for the single phase branch circuits but the conduit itself is what connects the panel to the ground in the main switchgear. There is no separate wire for ground and the ground buss is not connected to the neutral buss. That doesn't seem right to me, but I did see something on the net that suggested 3" conduit would be considered ok as a ground conductor. Is this correct?

The equipment grounding conductors should be connected to the service neutral at the service disconnect. Are you certain it's not there, or could you have not seen it? A simple green screw through the neutral bar is a pretty easy thing to not notice if you're not looking for it.

I have an Ugly's and a pdf copy of the NEC but the thing reads like a lawyer wrote it. So whatever advice I can get here would be greatly appreciated.

Get used to reading the NEC, and participate on forums like these to aid in reading it. Consider buying a handbook when you're starting out, it can be money well spent, as long as you read it. :)
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
One more that I am not sure about is a 100A 208 3 phase 4 wire service. The ground buss is being used for the single phase branch circuits but the conduit itself is what connects the panel to the ground in the main switchgear. There is no separate wire for ground and the ground buss is not connected to the neutral buss. That doesn't seem right to me, but I did see something on the net that suggested 3" conduit would be considered ok as a ground conductor. Is this correct?

I have an Ugly's and a pdf copy of the NEC but the thing reads like a lawyer wrote it. So whatever advice I can get here would be greatly appreciated.

Steve

The egc should be isolated from the neutral once you leave the main service panel. At the main service panel the equipment grounding conductor (EGC) is bonded to the service neutral. Again EMT is suitable as an equipment ground and it can be 1/2" emt.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
On your 3 phase 4 wire "service"..........
Is this actually a "service" ie: being fed directly by the utility or is it a "sub-panel", downstream from a service panel or is it a panel fed by a in-house transformer ?
The connections for grounding for each of the above would vary.
 

Aleman

Senior Member
Location
Southern Ca, USA
I called it a 100A service because it comes off a 100A breaker located at the main service panel. I don't know all the correct terminology. Which is one of the reasons I am here. So please correct me where I am wrong. Thanks for the reply.


On your 3 phase 4 wire "service"..........
Is this actually a "service" ie: being fed directly by the utility or is it a "sub-panel", downstream from a service panel or is it a panel fed by a in-house transformer ?
The connections for grounding for each of the above would vary.
 

Aleman

Senior Member
Location
Southern Ca, USA
Welcome to the Forum. :)



Usually compliant. Notice that in 250.118, a conductor-type EGC (equipment grounding conductor) is only one of many options.


Perfectly compliant and a better use of resources than using dedicated neutrals. You use less material and suffer less from voltage drop.

210.4 lays out what must be done when multiwire circuits are used.



The equipment grounding conductors should be connected to the service neutral at the service disconnect. Are you certain it's not there, or could you have not seen it? A simple green screw through the neutral bar is a pretty easy thing to not notice if you're not looking for it.



Get used to reading the NEC, and participate on forums like these to aid in reading it. Consider buying a handbook when you're starting out, it can be money well spent, as long as you read it. :)


Thanks George and Dennis for the info. I have the NEC2011 and couldn't find a 250.118. Also looked at the 210.4 and didn't see specifics about sharing the neutral. You are right I have to get used to reading this book. As I understand the shared neutral...since the hots are not from the same phase the neutral currents will cancel each other so one wire is ok. If there were 3 20A circuits from the same phase then you would need 3 neutrals or you would exceed the ampacity rating of the single wire. Please correct me if I'm wrong.

I will consider buying a handbook. Next time I am working that building I will look at it again. What makes this a little confusing is that the previous work is not consistent. Separate ground conductors in some panels and circuits and in others the conduit is used for the ground conductor. Is there any reason to not use a separate wire other than cost?
 

George Stolz

Moderator
Staff member
Location
Windsor, CO NEC: 2017
Occupation
Service Manager
Look at Figure 230.1 in the NEC.

The conductors after the 100A breaker in the service are feeder conductors. The panel they serve have the branch circuits, correct?
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
Now that you have clarified that your 100 amp panel is a sub-panel (one downstream from the service panel), the install sounds correct.As long as you have a mechanically intact metallic conduit system (no flex) between your service panel and this (sub) panel, 250.118 provides that you have an adequate grounding means.
As you are not allowed ro connect the grounded (neutral) and grounding together at any point beyond the service, your equipment grounds at this panel would connect to ground bars.

Please keep in mind, the answers you find here do not fit every situation. For instance the introduction of flex in the conduit run, the differences in a transformer fed system, the special requirements were this a 480 volt system and a number of variables could make our answers invalid for your particular installation. At this point, we should be able to assist in your confirming Code compliance on installations. Without proper training you should not attempt to perform any of these installations.
 
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Aleman

Senior Member
Location
Southern Ca, USA
Now that you have clarified that your 100 amp panel is a sub-panel (one downstream from the service panel), the install sounds correct.As long as you have a mechanically intact metallic conduit system (no flex) between your service panel and this (sub) panel, 250.118 provides that you have an adequate grounding means.
As you are not allowed ro connect the grounded (neutral) and grounding together at any point beyond the service, your equipment grounds at this panel would connect to ground bars.

Please keep in mind, the answers you find here do not fit every situation. For instance the introduction of flex in the conduit run, the differences in a transformer fed system, the special requirements were this a 480 volt system and a number of variables could make our answers invalid for your particular installation. At this point, we should be able to assist in your confirming Code compliance on installations. Without proper training you should not attempt to perform any of these installations.

Thanks for the info. I don't anticipate doing any installation work on anything other than branch circuits, and possibly adding a sub-panel on occasion. However, I am now doing more electrical work than I used to which is why I am trying to learn as much as I can. The 1st thing I told my boss when I interviewed was that I was not a certified electrician. I got the job because of my other qualifications. The new installations are contracted out, I take care of the little stuff. But what I do I want to be right and I need to understand what right is. So, here I am and you guys are being a huge help.

I still don't see a 250.118 in my copy of the NEC. What am I missing? I do see 250.1 where it mentions Ground Fault current path and gives examples of that which includes metallic raceways.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
I still don't see a 250.118 in my copy of the NEC. What am I missing? I do see 250.1 where it mentions Ground Fault current path and gives examples of that which includes metallic raceways.

Someone who rather not use wire for an equipment ground must have removed that page from your Code book :D
In the 11 Code it's on Page 70-122, 08 Code 70-114
 

jeremysterling

Senior Member
Location
Austin, TX
I have noticed that different electricians do work to their personal standards ...

You got that part right! Welcome to the Forum!

I was in a similar position to yours with lots of questions and I looked in the NEC and my Ugly's for answers. I learned that the NEC is a Code with minimum requirements and is not a design manual. The Ugly's is a very useful reference, but again, not a design guide.

As George said, you could try to get a Handbook. You may even try some of Mike Holt's books, I learned a lot from them.
 

Aleman

Senior Member
Location
Southern Ca, USA
Someone who rather not use wire for an equipment ground must have removed that page from your Code book :D
In the 11 Code it's on Page 70-122, 08 Code 70-114

I am kind of embarrassed I didn't see that. I won't bother trying to explain why I missed it. That would just make it worse.
 

Aleman

Senior Member
Location
Southern Ca, USA
You got that part right! Welcome to the Forum!

I was in a similar position to yours with lots of questions and I looked in the NEC and my Ugly's for answers. I learned that the NEC is a Code with minimum requirements and is not a design manual. The Ugly's is a very useful reference, but again, not a design guide.

As George said, you could try to get a Handbook. You may even try some of Mike Holt's books, I learned a lot from them.

Well, I think I will order a print copy of the NEC for starters. PDF is ok but I need the book to thumb through. Thanks.

Steve
 

Aleman

Senior Member
Location
Southern Ca, USA
Another question

Another question

Here's another one. We have a small control panel with something like a 30 amp service 460V. This a panel to control a process, PLC and drives etc. Then someone installed another panel in the vicinity. Instead of running out another circuit for the new panel, they tapped off the feed to the 1st panels disconnect switch. So both have local disconnects but they are running off the same circuit. I think this pretty much half ass work. But is it legal?
 

George Stolz

Moderator
Staff member
Location
Windsor, CO NEC: 2017
Occupation
Service Manager
The first step to wisdom is to discard the quality of looking down on how someone has completed a task; but to try to assign a code violation to it instead.

Second step, take and draw pictures. I can't see squat from your description.
 

Smart $

Esteemed Member
Location
Ohio
Here's another one. We have a small control panel with something like a 30 amp service 460V. This a panel to control a process, PLC and drives etc. Then someone installed another panel in the vicinity. Instead of running out another circuit for the new panel, they tapped off the feed to the 1st panels disconnect switch. So both have local disconnects but they are running off the same circuit. I think this pretty much half ass work. But is it legal?
One thing you must learn is Code terminology. "Service" regards conductors and equipment supplying utility power to a premises. Anything load side of the one or more service disconnecting means is not a service. Please go to Article 100 Definitions and memorize the definitions of Service, Feeder, Branch Circuit, and variations thereof... for starters.

The supply to the control panel is a feeder, assuming the panel has a disconnecting means with ocpd (overcurrent protection device). Feeder taps are permitted. Refer to 240.21(B), the so-called "tap rules"...
 
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