Meter Bases, Main Disconnects, Sub panels and bus gutters cooperating with the NEC.

[Jay M]

Hi All, I am feeling a bit defeated at every turn because common sense should prevail but the more I speak with various electricians, the more frustrated I get. I am going to illustrate an electrical riser diagram with desired parts(see Image) and explain the situation. I am not an electrical engineer but with 20+ years of architecture behind me, I have a fairly decent understanding of the NEC, but I am by no means an expert. My electrical engineer friend, seems to think my riser design is good, but the local trades cant seem to wrap their head around the design without choking on a bunch of NEC codes and of course the old "well that's the way we always done it before". Before someone says did you search the forums? to which I will tell you I have and I have read much which leads me to believe my design is fine, but it never hurts to get another opinion. Thank you for your kind helping attitude in advance.

I am adding an addition to my home. As you can see from the diagram, I have a 200A service meter base that currently feeds the home. Due to the size of the addition, I am going to have to upgrade to 400A in the future. Today, I need to get power to the new Garage Panel, so I can start the finish out in that area of the addition. In the future I plan to add other panels at other floors of the home and then switch to the 400A service. I do not want to switch the service at the moment. Nor do I think I need to. In my design, the New Garage Panel will act as a subpanel of the existing 200A service initially. In the final configuration, all panels including the existing house panels, will be fed from the 400A service. I want to install the feeders for the New Garage Panel with the proper size today that I will need to use later when I switch to the 400A service. When I switch to the 400A service, I want to connect a new 400A Main Disconnect to a buss gutter and then run sub panels feeders from that bus gutter to the desired subpanel locations. Each subpanel will have a main breaker in it per the rating shown in the diagram. This is where it gets confusing for some reason with every electrician I have spoken with as they seem to think there is some sort of disconnect/breaker problem, but I dont see this. Based on the forums I have read on sub panel questions, my design should be completely allowed by the code. My electrical engineer ran the loads and we are around 320A total load at final build out.

I am hoping to understand where the NEC trips this up and how to work around it.

Thank you in advance and apologies for the long winded post.

 

[shortcircuit2]

I would think that gutter would be difficult to fit all those taps. Wire size should be 3/0 copper or 250MCM AL for taps at 200-amps. Then all equipment is 3-phase?

 

[Strathead]

There are places where that may fly, but not here in Florida, unless I am missing something. First off, you have service conductors running further than "at of nearest the point of entrance". Second, while you have less than 6 disconnecting means, they aren't grouped in a single location as required by code. Third, you have an equipment grounding conductor run to each "subpanel" when in fact as drawn each of those panels is a service disconnecting means and requires a bonding jumper. These issues can be resolved by placing a 400A service disconnect on the exterior of the building. BUT, then you likely have taps that violate the tap rules feeding all of the panels. You must measure your conductor lengths and verify that you comply with the 10 times or 3 times tap rules or 240 or have overcurrent protection for each panel feeder that is sized for the conductor. I don't think I missed anything.

 

[Jay M]

First off, you have service conductors running further than "at of nearest the point of entrance"

Yes, because the old portion of the house has the original service 170' away from the location where we propose to put the new 400A service. I am wanting to run 170' of wire ONCE that can backfeed the old main panels in the existing portion of the house once the new 400A service is in place. In the interim, I want to use the same wires to feed a new panel in the new addition.

Second, while you have less than 6 disconnecting means, they aren't grouped in a single location as required by code.

When the new service is put in place, I think the grouped location issue should resolve itself. But in the interim, it may be non-compliant.

Third, you have an equipment grounding conductor run to each "subpanel" when in fact as drawn each of those panels is a service disconnecting means and requires a bonding jumper.

Yes, we have bonding at all locations of panels. My engineer keeps telling me we need to ground the system together. I dont get that, as ground should be ground whether it grounds at each panel location or all ties together and goes to one single ground location.

These issues can be resolved by placing a 400A service disconnect on the exterior of the building. BUT, then you likely have taps that violate the tap rules feeding all of the panels. You must measure your conductor lengths and verify that you comply with the 10 times or 3 times tap rules or 240 or have overcurrent protection for each panel feeder that is sized for the conductor.

What are tap rules? I have not seen this before. Can you explain the 10 times or 3 times or 240? Is there a section in the NEC addressing this I can refer to? My plan is to make each new panel an off the shelf 200A panel with main breaker at each floor, so I can kill power at any floor without having to go to the main point of disconnect. The main disconnect for the whole system will be at the new 400A meter base located out side the house with the buss gutter inside the home directly on the other side of the wall(adjacent).

My feeder lengths by panel from buss gutter are:

to existing house 200A main disconnect: 170'
to new garage panel w/ 200A disconnect: 3'
to new basement panel w/ 200A disconnect: 10'
To new level 1 panel w/ 200A disconnect: 10'
to new level 2 panel w/ 200A disconnect: 20'

Thank you for your input. Greatly appreciated.

 

[Tulsa Electrician]

Those look more like service conductors than feeders based on pic.

Utility meter to wire way to panels that will be where MBJ is installed.

Lots of code issues.

Start at the utility and work from there. Be code compliant in step one. Then deal with the next.
Get one correct and the rest will fall in line.

Let's start with feeders or service conductors.

 

[augie47]

I think the immediate question will be what Code cycle is in effect. Anything after 2017 is going to require an outside emergency disconnect.
In addition, as mentioned, you need to address grouping of service disconnects and tap rules.
As drawn there seem to be Code issuers on all these points.

 

[tom baker]

You could start with reviewing Mike Holts understanding the NEC and then come back here for clarification

 

[don_resqcapt19]

....
When the new service is put in place, I think the grouped location issue should resolve itself. But in the interim, it may be non-compliant. ...

I don't see how...you show a basement panel, a garage panel, a level 1 panel and a level 2 panel. Based on your drawing, those all contain service disconnects and must be physically grouped.

 

[Strathead]

Yes, because the old portion of the house has the original service 170' away from the location where we propose to put the new 400A service. I am wanting to run 170' of wire ONCE that can backfeed the old main panels in the existing portion of the house once the new 400A service is in place. In the interim, I want to use the same wires to feed a new panel in the new addition.


When the new service is put in place, I think the grouped location issue should resolve itself. But in the interim, it may be non-compliant.


Yes, we have bonding at all locations of panels. My engineer keeps telling me we need to ground the system together. I don't get that, as ground should be ground whether it grounds at each panel location or all ties together and goes to one single ground location.



What are tap rules? I have not seen this before. Can you explain the 10 times or 3 times or 240? Is there a section in the NEC addressing this I can refer to? My plan is to make each new panel an off the shelf 200A panel with main breaker at each floor, so I can kill power at any floor without having to go to the main point of disconnect. The main disconnect for the whole system will be at the new 400A meter base located out side the house with the buss gutter inside the home directly on the other side of the wall(adjacent).

My feeder lengths by panel from buss gutter are:

to existing house 200A main disconnect: 170'
to new garage panel w/ 200A disconnect: 3'
to new basement panel w/ 200A disconnect: 10'
To new level 1 panel w/ 200A disconnect: 10'
to new level 2 panel w/ 200A disconnect: 20'

Thank you for your input. Greatly appreciated.

Since you aren't an electrician and this site isn't for do it yourselfer's I am going to wait until a moderator decides. but the first comment is in regards to the fact that your disconnect isn't on the outside of the building. Code requires your service disconnect to be located outside or nearest the point of entry inside and 6 disconnects or less grouped together. Everything you have drawn violates this at every turn. Bottom line, every panel needs a disconnect on the building it is in, either outside or immediately inside, however all the disconnects must be grouped in one location. The intent is that in the event of an emergency, the Fire Department can turn off all the electricity from one location and not have to shut off more the 6 disconnects or breakers. You need to rethink your entire design. What I would likely do is get a 600A outside panel mounted on the garage, and feed all the other panels with nothing larger than a 100A breaker (or the largest breaker that fits in the panel.

 

[Little Bill]

We're allowing the thread since an EE and electrician are involved, and mostly a "why" and not "how" questions.

 

[Krusscher]

What are tap rules?

240.21 you can't just tap your feeder wires from your existing panel to your garage with out any OCPD in between basically, and you definitely can't do that with your service conductors for your future connection. Strathead's suggestion would be what I would do as well.

 

[tom baker]

We're allowing the thread since an EE and electrician are involved, and mostly a "why" and not "how" questions.

And it’s a learning experience for all

 

[shortcircuit2]

The meter he listed in post 1 has a 400-amp service disconnect >>> Milbank U6230-X-400-K7 >>> 3-phase

Milbank - u6230-x-400-k7l-bl

www.milbankworks.com

 

[electrofelon]

Might be nicer to just replace the bussed gutter and those garage panels with a single nice distribution panel board that can take 200amp breakers . A Siemens P2 would probably do it. They can design it so it will have 250 frame breakers (probably QR frame) and also as many regular branch breakers as you want

 

[jaggedben]

Might be nicer to just replace the bussed gutter and those garage panels with a single nice distribution panel board that can take 200amp breakers . A Siemens P2 would probably do it. They can design it so it will have 250 frame breakers (probably QR frame) and also as many regular branch breakers as you want

Assuming this is single phase, I imagine a 'normal' 2x200A meter main would also suffice. If the total calculated load is around 320A then only one of those 4 panels could really need a 200A breaker. Feed the biggest one with 200A and the rest with 125A from the 200A panelboard.

I've just been working on a house with a 400A service and in a year it never drew over 100A. And that's with a new 40A car charging plug.

 

[jaggedben]

...


Yes, we have bonding at all locations of panels. My engineer keeps telling me we need to ground the system together. I dont get that, as ground should be ground whether it grounds at each panel location or all ties together and goes to one single ground location.

...

Earth does not typically carry enough current to trip a breaker if a hot conductor faults to exposed metal parts and energizes them. That's why everything needs to be bonded. The actual connection to earth is kind of secondary (though equally code required).

 

[electrofelon]

Wouldnt this look nicer than a bussed gutter and a bunch of crappy loadcenters?