Help with sizing parallel service conductors

[mike1061]

Avoid the GEC in EMT. You will need to bond each end. PVC sch 40 or if needEd Sch 80 if need physical protection. Sch 80 is considered equal to RMC

We can't use PVC here. Thanks though. I know you have to bond at both ends. A pain in the butt.

 

[mike1061]

Since the Chicago 2018 Electrical Code is the 2017 NEC with lots of amendments, you can still do a MLO with 6 service disconnects and no main. The service entrance conductors will have to have an ampacity at least equal to the calculated load, but do not have to have an ampacity equal to the sum of the ratings of the six service OCPDs.

Thanks. That's why I thought of that plan. Somehow it kinda goes against my belief of everything should have over current protection.

 

[Tulsa Electrician]

Thank you all for your input.
I went back and read the two applicable definitions in artical 100 in the 2014 NEC. Did a little paraphrasing posted a pic of the definitions from the book.
Netutal Conductor: " the conductor connected to the netutal point of a system"

Netutal point: "The common point - or mid point of a single phase portion of a 3- phase delta system
Very well defined.

What I find key is the informational note: " the vectorial sum of the nominal voltages form all the other phases with in the system that utilize the netutal,"

So as long as Larry said no one does something stupid.
Then yes I agree we have a Netutal.
Pretty sure this covers it. If I missed something let me know.
Sorry for the confusion.

 

[LarryFine]

There is a theoretical, natural neutral in a delta system that resembles a wye, where the voltage is equal to all three phases due to capacitance with the outside world.

By tying the central point of one secondary to earth, we "force" that neutral point away from its natural place, which is what drives the high leg to be of a higher voltage to earth.

A floating (ungrounded) delta will exhibit this equal-voltages-to-earth unless influenced by things like an accidental ground fault or unusual leakage to earth on one line, etc.

 

[LarryFine]

Have you ever noticed the bonding strap on the neutral terminal of a utility transformer? That strap is there on a 1ph unit as well as the main unit in any high-leg delta.

A high-leg full delta bank will have three of these units, but the bonding strap will be removed two of them. There is no difference in how the center transformer is wired.

 

[electrofelon]

I was going to save this question for another thread but since you made this comment.
what do you guys think about me just installing a six throw panel as the main? If you have more than six throws you need a main. The six throw panel saves all the money for an 800 or 1000 amp main. Those are expensive and then you would still have to use some kind of panel board to split it up.

About three years ago I priced a 1000 amp panel board both with just 6 200A breakers (MLO) , and with the 6 200's plus the addition of the 1000 main breaker. It was just about double the price, $4500 vs $9000. I use MLO whenever I can, unfortunately, where I do all my commercial work is on the 2020 code now.

 

[mike1061]

About three years ago I priced a 1000 amp panel board both with just 6 200A breakers (MLO) , and with the 6 200's plus the addition of the 1000 main breaker. It was just about double the price, $4500 vs $9000. I use MLO whenever I can, unfortunately, where I do all my commercial work is on the 2020 code now.

Did they get rid of the six handle rule for 2020?

 

[kwired]

I was going to save this question for another thread but since you made this comment.
what do you guys think about me just installing a six throw panel as the main? If you have more than six throws you need a main. The six throw panel saves all the money for an 800 or 1000 amp main. Those are expensive and then you would still have to use some kind of panel board to split it up.

If still on 2017 that is probably least cost method in many cases.

If on 2020, you can still have six mains but they can no longer be in one enclosure or same vertical section of a switchboard.

 

[kwired]

Did they get rid of the six handle rule for 2020?

No, but they can no longer be in same panelboard or same vertical section of a switchboard.

 

[don_resqcapt19]

If still on 2017 that is probably least cost method in many cases.

If on 2020, you can still have six mains but they can no longer be in one enclosure or same vertical section of a switchboard.

He is in Chicago, and if they do the future updates to their electrical code like they have been done in the past, it will be 20 years or so before they release a new version.

 

[kwired]

He is in Chicago, and if they do the future updates to their electrical code like they have been done in the past, it will be 20 years or so before they release a new version.

They just getting or recently gotten AFCI requirements then? Or since they require steel conduit for most part did they amend that out?

 

[petersonra]

If on 2020, you can still have six mains but they can no longer be in one enclosure or same vertical section of a switchboard.

So why would this be? it does not appear like there is any safety benefit to doing it this way.

 

[don_resqcapt19]

So why would this be? it does not appear like there is any safety benefit to doing it this way.

Exposure to energized line side busing.

 

[don_resqcapt19]

They just getting or recently gotten AFCI requirements then? Or since they require steel conduit for most part did they amend that out?

They added the following exception to 210.12.

Exception No. 1 to 210.12(A), (B), and (C): It shall be permitted to omit AFCI protection for that portion of the branch circuit enclosed in rigid metal conduit (RMC), intermediate metal conduit (IMC), electrical metal tubing (EMT), or Type MI cable sheath meeting the requirements of 250.118 along with metal outlet and junction boxes.

 

[petersonra]

Exposure to energized line side busing.

How are you ever exposed since the enclosure can't be open unless you have proven it is de-energized or you are wearing a moon suit (if needed) and rubber gloves.

 

[electrofelon]

How are you ever exposed since the enclosure can't be open unless you have proven it is de-energized or you are wearing a moon suit (if needed) and rubber gloves.

Another ridiculous code change without substantiation and trying to make the NEC a design manual.

 

[kwired]

How are you ever exposed since the enclosure can't be open unless you have proven it is de-energized or you are wearing a moon suit (if needed) and rubber gloves.

Ask NFPA, some of us don't necessarily like it either.

But as said probably to lessen chance of exposure to line side bus since you basically can not disconnect it in most cases without involving POCO.

Still pushing the limit on being a design manual though.

 

[LarryFine]

Exception No. 1 to 210.12(A), (B), and (C): It shall be permitted to omit AFCI protection for that portion of the branch circuit enclosed in rigid metal conduit (RMC), intermediate metal conduit (IMC), electrical metal tubing (EMT), or Type MI cable sheath meeting the requirements of 250.118 along with metal outlet and junction boxes.

Does that mean there are no AFCI requirements in Chicago?

 

[mike1061]

He is in Chicago, and if they do the future updates to their electrical code like they have been done in the past, it will be 20 years or so before they release a new version.

Sadly that’s true. We aligned with the 99 NEC in 2000 and the next one was 2017 in 2018. Before that we had our own crazy code.

 

[mike1061]

They just getting or recently gotten AFCI requirements then? Or since they require steel conduit for most part did they amend that out?

We got Arc faults in 2000 and in 18 everything has to be arc fault but they added the exception it we use conduit. Which I think is good.