Main panel double tap

(Darryl C. McCauley, HI 1385) #1

Quick question Todays inspection Mobile with attached garage and storage. The main panel is a 200 amp mounted on the exterior. There are two subpanel in the house. Both feed come out of the main panel would this be a double tap I lean towards yes but need reinforcement.

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(Larry Kage, CMI) #2

Yes. -X

(Bruce A. King) #3

I think the correct terminology is double lug in that case.
Double tap would be the one to use on a breaker or single screw terminal branch circuit.

(Randall Romoser) #4

Yes, that is a double tap. A double lug is one that has provisions to land 2 wires, each under its own terminal screw on the same connector..

(Wesley Aksell) #5

This is probably a stupid question;

Since the panel(s) Darryl is calling "sub panels" are fed by a tap prior to the main breaker, wouldn't they also be main panels?

(Paul W. Abernathy) #6

Wesley,

Actually not a stupid question at all........their is no stupid question in the learning process.

The terminology for the main panel is the first point of of the service disconnection means, The term Sub-Panel actually does not appear anywhere in the NEC as it should really be "Remote Distribution Panel" or basically another distribution panel.

The problem with the TAP is the terminal is more than NOT....simply not rated for the double lugging taking place.

(Wesley Aksell) #7

I understand and agree that the tap is wrong.

My question is, since there is no overcurrent protection for the "Sub panel(s)", wouldn't they be main service panels?

I thought you could have more than one main service panel on one service.

If those terminals, or lugs were rated for more than one conductor, would multiple main service panels be possible?

(Wesley Aksell) #8

I understand about the term "Sub panel". Just an old habit. Anything after the main would be Load Side Equipment, "Distribution panel".

(Paul W. Abernathy) #9

Wesley,

The could be improperly tapped in to the main terminal lug but still the OCPD is not grouped at the same location as it should be and so if the "SUB" or "Remote Distribution Panel" is wired improperly without a OCPD then it simply does not protect the conductors feeding those panels and brings up an even bigger issue and safety violations.

The terminology of a main distribution panel is the first point in the system where the Grounded Conductor and Grounding Conductor ( or I prefer to call Bonding Conductors ) tie together. In theory THIS is the main distribution location.

Now if you are speaking of a multiple service panel location like we see in (2) 200A service panels for a combined 320A ( or 400A in most assumptions ) then BOTH are considered main disconnection means and are grouped at the same location and need to be bonding and grounded as such.

Once the improper tab is done and possibly no OCPD at the remote locations and even worse lets say they did not run a 4 wire setup to provide a low impedence path for the fault current...then we have additional safety concerns and most certainly should be written up...but it is not considered a main service panel due to design and proximity.

(ccbrands1) #10

no...they'de be called, in this case, incorrectly installed distribution panels.

as Paul states, more often than not, these lugs are not rated for 2+ conductors anyway. this one looks to be no exception.

problem is, when the owner goes to "shut off all power" to the building, they'll throw the main breaker in the service panel ( main panel )

this does not cut power to the incorrectly fed distribution panel ( sub-panel )
owner goes to rewire something and gets zapped...and doesn't know why.

(Wesley Aksell) #11

I am not disagreeing that the whole setup is wrong. It is wrong.

What I'm getting at is; lets assume, humor me here for a second, that the tap were made in an acceptable manor. And the other panels had main disconnects in them. Is it possible that a situation like that could be legal.

(Paul W. Abernathy) #12

No it could never be legal.

The NEC states that the Main Panel ( used for clarity ) needs to be as close as possible to the point of entrance from the outside meter can. While this distance can vary it would not be in most cases longer than 3-6 feet. In my area they will allow 3' of SE cable within the structure before it MUST terminate into an enclosure with an OCPD.

Now if you were allowed to simply TAP it within the enclosure it would still violate this requirement and put unprotected SE conductors within the structure.

I do understand where you are going and YES in a technical sense it has the same " POTENTIAL " as the main panel but just because it is tapped incorrectly or correctly to the service does not make it a main service panel since other factors MUST be in place.

Many of the items are in concept for understanding, many things in the electrical world you simply can't use logic for and in this case we see one of them. Even if the conductors were tapped lets say legally....they would not be protected running thru the structure and a violation of the NEC which is a minimum safety standard protocol.

again no situation would make them legal as they stand now, we don't know the other varibles as well in regards to the kind of wire ( 3 or 4 conductor ) that was run to these panels either.

OH..I had to add this ; I do understand you fella and in a working sense YES it works but no it is not safe and in the end safety is what we are going for when dealing with electrical wiring.

(Wesley Aksell) #13

I understand, I just didn't know if there ever could be a time or place where more than one main could be legal. I was not suggesting that this case should or could be legal.

(Greg Fretwell) #14

Wesley it is perfectly legal to have up to six service disconnects.
Typically it will be served from a gutter where the service entrance conductors get spliced and they then feed the disconnects. Paul has given you an example. On a 320 or 400a service it is common to use two 200a panels. Both will have main bonding jumpers and both disconnects will be labelled “main”.

This picture actually shows a 600a service (200 and 400) but the principle is the same

service.jpg

(Wesley Aksell) #15

Good picture Greg, I could imagine more than one main in my mind, but I have never seen it. I noticed that the two panels were bonded and so was the gutter.

We were taught in class that bonding should only take place in the box where the main service disconnect is, and that is where the earth grounding conductor should come from. My homes grounding conductor comes from the meter.

Funny thing about electrical, there are many exceptions to the rules. And if you don't work with it everyday like you guys, its hard to tell right from wrong.

Many of the questions asked here are common knowledge to you guys, but beyond others knowledge. Thanks for the help.

(ccbrands1) #16

is your main OCPD at the meter?

(Wesley Aksell) #17

One to two feet away on the same wall.

(Bruce A. King) #18

When the breakers are present that have two screw terminals and each has a wire connected it is not a double lug or a double tap unless two wires are under one single screw.

Lugs are large connection points for feeder wires etc.
Taps are on breakers (even the dual ones) and bus bars.

This has been discussed on here before.

Correct terminology is double lug for the original post.

(Paul W. Abernathy) #19

And thats the JOY i think Greg and Myself get out of helping you guys as much as possible. I can't speak for Greg but I take GREAT pride in knowing someone is learning and gaining knowledge that just might put them ONE LEVEL above the rest.

Never ever feel you can't ask a question no matter how basic is sounds and once all of us get to elaborating on it it brings out many other issues also and as someone said in some of our chats I think CEU credits could be worthy...lol

(Greg Fretwell) #20

There is always multiple bonding on the line side of the service disconnect. The NEC has finally recognized that.