Tapping Service Conductors

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fatuus

Member
Location
Virginia
Occupation
Electrician
There is a 600amp 120/208 volt service. From the outdoor CT cabinet parallel 350kcmil enter the building into a trough. Per the engineered drawings there is no service disconnect. The parallel 350 is then tapped and 3/0 is used to feed (3) different 200 amp panels.

Is this legal? Can you tap the unfused conductors in the trough like this?
 

Smart $

Esteemed Member
Location
Ohio
Yes. Article 240 tap rules do not apply to service conductors. The service disconnecting means would be the 3 panel MCB's.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
I agree.
Keep in mind, however, the devil is in the details. The conductors, 350S and 3/0s would have to comply with 230.70 so the location of the panels in relation to where the conductors enter the building would be of paramount interest
 

steve66

Senior Member
Location
Illinois
Occupation
Engineer
I disagree.

The tap rules in 240 do not apply to service conductors, which means you can't tap them.

I see this as a violation of 230 - specifically that the overcurrent protection shall be nearest the point of entrance. How can that be when 3 taps are made inside the building?

I also see it as a violation of 230.90 : Each ungrounded service conductor shall have overload protection.

If the taps were outside the building, and prior to the service point, then it might be OK, and this is a common installation to feed separate meters. But then the 350 KCM wires wouldn't be service conductors, and you wouldn't be tapping the service conductors.

Edit: If the 350's fed a panel with (3) 200A breakers, that would be legal.

Also, how do you tap (3) sets of wire off (2) sets of wire in a trough? Most likely, one set of 350's would wind up supplying (2) sets of 3/0, and the other set of 350's will wind up supplying the other set of 3/0. Now the 350's aren't really even in parallel - they have unequal currents, and one set may be overloaded.
 
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MasterTheNEC

CEO and President of Electrical Code Academy, Inc.
Location
McKinney, Texas
Occupation
CEO
I disagree.

The tap rules in 240 do not apply to service conductors, which means you can't tap them.

I see this as a violation of 230 - specifically that the overcurrent protection shall be nearest the point of entrance. How can that be when 3 taps are made inside the building?

I also see it as a violation of 230.90 : Each ungrounded service conductor shall have overload protection.

If the taps were outside the building, and prior to the service point, then it might be OK, and this is a common installation to feed separate meters. But then the 350 KCM wires wouldn't be service conductors, and you wouldn't be tapping the service conductors.

Edit: If the 350's fed a panel with (3) 200A breakers, that would be legal.

Also, how do you tap (3) sets of wire off (2) sets of wire in a trough? Most likely, one set of 350's would wind up supplying (2) sets of 3/0, and the other set of 350's will wind up supplying the other set of 3/0. Now the 350's aren't really even in parallel - they have unequal currents, and one set may be overloaded.
So am I too assume you would not permit the applications of (2) 4/0 AL SE Cables on the load side of the meter to two separate 200A panels in a dwelling (assuming 310.15(B)(7) complied)....based on your statement...is that what you are implying as a violation of 230.90?

Because this also would apply to the allowance of up to six service disconnects grouped in one location....fed by a common set of overhead system - service-entrance conductors...so your implied statement affects alot of things currently done in the industry....or if I am missing what you are saying...please elaborate and set me straight please.....as must be reading something differently in your response.
 

steve66

Senior Member
Location
Illinois
Occupation
Engineer
So how does that opinion square with this provision of the code?


I'm still not sure how a tap on the inside of the building would allow the OCP to be nearest the point of entrance, but we all know nearest the point of entrance is an AHJ call.
 

steve66

Senior Member
Location
Illinois
Occupation
Engineer
So am I too assume you would not permit the applications of (2) 4/0 AL SE Cables on the load side of the meter to two separate 200A panels in a dwelling (assuming 310.15(B)(7) complied)....based on your statement...is that what you are implying as a violation of 230.90?

No, I wouldn't call that a tap at all. I'd call it two different sets of service entrance conductors.
 

MasterTheNEC

CEO and President of Electrical Code Academy, Inc.
Location
McKinney, Texas
Occupation
CEO
No, I wouldn't call that a tap at all. I'd call it two different sets of service entrance conductors.
So you are saying Service Conductors can't be tapped?.......Ok...how about this...since there is a good change my comments would be deleted anyway...lets just agree to disagree...and let the AHJ make that call.

Ok well let me call all the switchboard manufacturers out there and tell them they are not permitted to bring overhead system, service-entrance conductors into a building and then tap those service entrance conductors into a set of six different OCPD's to comply with Section 230.71(A).....and force them to install a single service disconnect. No worries I appear to be missing something here....so I must be interpreting what you are implying wrong.

In your logic (and please explain where I am wrong...I like to learn also) you can't bring in a set of service entrance conductors into a large switchgear and then meet the six disconnect rule with six individual OCPD's....installed in compliance with the NEC....we are clearly beyond the OP's question at this point but based on your responses we have to go deeper now..right.

P.S. this is not a chest pounding match...I am really interested in learning what you have to say on this issue...I am deeply interested.
 

Smart $

Esteemed Member
Location
Ohio
...

Edit: If the 350's fed a panel with (3) 200A breakers, that would be legal.

Also, how do you tap (3) sets of wire off (2) sets of wire in a trough? ...
You tap both 350 sets. There are various methods. Some use split bolts. Some use terminal or tap blocks.

As already mentioned, nearest point of entrance is ambiguous at best, and thus varies per AHJ. I believe most would allow such an installation. Of concern mostly is that first responders can determine where service conductors penetrate the wall, then proceed to inside location immediately adjacent to find the disconnecting means.
 
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