Overhead Service- Conductor and Trough sizing

[2Broke2Sleep]

Hi, this is my first new service build as an EC. I've got a 4 unit residential complex with 200A panels inside each residence. On the outer wall I have what is depicted, 4 meters piped into 4 x 200A Disconnects, which are piped into interior panelboards. I have the meters, disconnects, and panelboards in place, but I have not yet sized the overhead or the trough that is going above the meter enclosures. I am weighing costs of: one mast with large conductors vs. two masts with parallel conductors . The plans are inaccurate/missing the service and the owner/builder won't get them revised, he just wants me to install to code and he said he will get them revised based on what I do if needed.

I don't have it in front of me but I did a load calc using mike holts spreadsheet and a single mast would call for 600kcmil conductors. I plan on using Polaris Taps to branch off each service with 2/0 to the line side of each meter from within the trough. It would be nicer to have some kind of busbar I could mount inside the trough to land the conductors on but I am looking for the most cost effective install right now.

Looking at NEC 2017 / 366.22 (A): Sheet Metal Auxiliary Gutters. The sum of the cross sectional areas of all contained conductors and cables at any cross section of a sheet metal auxiliary gutter shall not exceed 20 percent of the interior cross-sectional area of the sheet metal auxiliary gutter..................

So working that out with (12) 2/0 thhn conductors and (3) 600 kcmil conductors would be:

Ch. 9 Table 5 :
THWN/THHN 600kcmil Approximate Area 0.8676 in^2 x 3 = 2.6028 in ^2
THWN/THHN 2/0 Approximate Area 0.2223 in^2 x 12 = 2.6676 in ^2

Sum of above: 5.2704 in ^2
** 5.2704 / 20% = 26.352 in ^2
So technically I could use a tiny 26 square in. trough legally if I could actually fit all the conductors inside one.

 

[2Broke2Sleep]

As you can see limited space..... I took over this job from someone that had done everything on this unit but the meter/mains....
I think I might end up being forced to use a guy-kit to attach to roof, something I've also never done before....

 

[2Broke2Sleep]

 

[2Broke2Sleep]

For parallel masts with 300kcmil in two separate runs:
Ch. 9 Table 5 :
THWN/THHN 300KCMIL Approximate Area 0.4608 in^2 x 6 = 2.7648 in^2
THWN/THHN 2/0 Approximate Area 0.2223 in^2 x 12 = 2.6676 in ^2

Sum of above: 5.4324 in ^2
** 5.4324 / 20% = 27.162 in ^2

 

[2Broke2Sleep]

I expect my application of 310.15 (7) to be correct here, using 2/0 for all service conductors up until the load side of the first disconnect....

 

[2Broke2Sleep]

Just popped in my head that I need mast rated hubs to attach to this trough... Is there a product someone could recommend/link me to that would accomplish this? I was thinking Meyers hubs but I need to check to see if they are rated for use with masts (Per NEC)

 

[augie47]

As short as the risers would be, I would be more prone to use 4 separate risers if POCO allows.
IF you are going with the wireway take into account the length of the Polaris as they may be the deciding factor.
As to your wireway "hub" a myers hub should woprk but keep in muind some jurisdictions will require it be a bondimng type hub with jumper..

 

[infinity]

Not that it changes much but what you would be using is a wireway not an auxiliary gutter. Also get rid of the offset nipples as they are not permitted to be screwed into a hub. Hubs can be rotated 180° so that they are father from the back of the enclosure to give you more space to work with and you can use RMC nipples.

 

[2Broke2Sleep]

Not that it changes much but what you would be using is a wireway not an auxiliary gutter. Also get rid of the offset nipples as they are not permitted to be screwed into a hub. Hubs can be rotated 180° so that they are father from the back of the enclosure to give you more space to work with and you can use RMC nipples.

Curious if that is stated in NEC or is that a listing violation?

 

[infinity]

Curious if that is stated in NEC or is that a listing violation?

A listing violation. Those hubs are only designed to be used with the tapered threads on either RMC and IMC. However they're used with PVC terminal adapters, SE cable connectors, EMT connectors, etc. every day. Most inspectors don't care but if you find one that wants to be by the book then you could have a problem.

 

[don_resqcapt19]

Also look at 376.23, 376.56 and 230.46.

 

[codeunderstanding]

Not that it changes much but what you would be using is a wireway not an auxiliary gutter. Also get rid of the offset nipples as they are not permitted to be screwed into a hub. Hubs can be rotated 180° so that they are father from the back of the enclosure to give you more space to work with and you can use RMC nipples.

In the diagram shown why wouldn't that meet the definition of a auxiliary gutter? Wouldn't the trough be supplementing the meter sockets?

 

[electrofelon]

A few comments: you may well have done it the way you did because materials shortages, but using a meter center with disconnects or even just a four gang meter without disconnects would be a lot less work look cleaner and probably cheaper.

I don't like the offset and nipples either. I usually don't care about these listing violations of screwing the "wrong" things into hubs, but the thing was with the offset nipple is you're not going to be able to get them tight as well so they're just going to be sitting there loose.

I didn't read through everything carefully enough to see if you took it into account but remember you can't use the residential sizing/83% rule for the common riser conductors.

 

[don_resqcapt19]

In the diagram shown why wouldn't that meet the definition of a auxiliary gutter? Wouldn't the trough be supplementing the meter sockets?

In general if it is connected to the other enclsoure using nipples, it is a wireway and not an auxiliary gutter.

An auxiliary gutter must increase the wiring space of the enclosure that it is used with. They are typically designed and sold by the manufacturer of the enclosure for that purpose. A common example would be a motor control center "top hat".

Most everything that electricians call "gutters" are really "wireways", and actual auxiliary gutters are pretty rare.

 

[wwhitney]

Most everything that electricians call "gutters" are really "wireways", and actual auxiliary gutters are pretty rare.

So at an indoor location, if I have a NEMA 1 cabinet containing a panelboard (e.g. I have a "load center"), and I install a NEMA 1 wireway abutting it, and I cut a big rectangular hole in the side of both enclosures where they are touching, and I take a suitable measure to remove or cover sharp edges around the hole, then:

A) Have I turned the Chapter 376 wireway into a Chapter 366 auxiliary gutter? and
B) Is any code violation or other requirement I've overlooked? Neither Chapter 312 on Cabinets nor Chapter 366 on Auxiliary Gutters requires listing of the enclosures. And I'm assuming that the modified wireway will still meet the 366.100 Construction Specifications, although that bears confirming.

Thanks,
Wayne

 

[don_resqcapt19]

So at an indoor location, if I have a NEMA 1 cabinet containing a panelboard (e.g. I have a "load center"), and I install a NEMA 1 wireway abutting it, and I cut a big rectangular hole in the side of both enclosures where they are touching, and I take a suitable measure to remove or cover sharp edges around the hole, then:

A) Have I turned the Chapter 376 wireway into a Chapter 366 auxiliary gutter? and
B) Is any code violation or other requirement I've overlooked? Neither Chapter 312 on Cabinets nor Chapter 366 on Auxiliary Gutters requires listing of the enclosures. And I'm assuming that the modified wireway will still meet the 366.100 Construction Specifications, although that bears confirming.

Thanks,
Wayne

Maybe, it would be like porn...I would have to see the installation to know if I see that installation as expanding the wiring space in the panelboard cabinet.
If you installed it because you are using a larger conductor that the combintation of the panelboard and its cabinet was designed for, and if your large opening provided enough additional space to comply with the requirement in 312.6(B), I would likely say it is a wireway. I can't really think of any other application where I would see it as a wireway>

 

[Charged]

No comment on the actual content in the post but This was a great inside look on what your direction was in this instance as the contractor…..…on the other end, it can be daunting being put in the position day in and day out being asked to revise the drawing how it was done and being put In a position to take legal responsibility for it or tick everyone off……I did note however that the information was left off the plans

 

[2Broke2Sleep]

Update: Took off the offset nipples and replaced with PVC. Right now I am forced to go over head with one of the feeders across/ontop of the roof. I was looking through my 2017 NEC and didn't find the Ambient Temp adjustment for rooftops table the previous versions had. All the 2017 specifies now is you're either 7/8" above the roof or you're not.... Am I correct in saying all I need are some conduit rooftop supports that come in around a foot or less? I was planning on going high 24" but glad I waited to finish until I confirmed I'd be within guidelines.....

 

[infinity]

All the 2017 specifies now is you're either 7/8" above the roof or you're not.... Am I correct in saying all I need are some conduit rooftop supports that come in around a foot or less?

Yes, if you get 7/8" or above you do not need to be concerned with ampacity adjustments.

 

[augie47]

Yes, if you get 7/8" or above you do not need to be concerned with ampacity adjustments.

I believe you still need to take ambient into account but there is not "roof top:" adder when you are 7/8" above, Am I incorrect ?