Service Tap???

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jap said:
For instance,

I could see where the main panel could be drawing nearly full load and the 100 amp subpanel drawing only a fraction of it, and tripping out the 200 amp main if you do the subfeed thing.

Where as if you had tapped the service conductors in this same scenario, you would still be within the limits of the main, and the Service Conducors, and, no problems would occur.
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That doesnt make any sense, unless the SEC are rated over 200A for some reason. If the 200A is tripping, moving some of that load to the line side of the 200A breaker doesn't change anything other than allow you to overload the SEC!
 
electrofelon said:
That doesnt make any sense, unless the SEC are rated over 200A for some reason. If the 200A is tripping, moving some of that load to the line side of the 200A breaker doesn't change anything other than allow you to overload the SEC!
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If the 200 amp panel is drawing say 150 amps, and,you subfed the 100 amp panel from the 200 amp panel, and, the 100 amp panel is drawing 50 amps (200 amps total), and, the service conductors are rated at 200 amps, you will most likely trip the 200 amp breaker even though you haven't overloaded the 200 amp rated service conductors if run this way for any length of time.

In that same scenario, with a service tap, you would not trip the 200 amp, and, you still would not have overloaded the 200 amp rated service conductors.

JAP>
 
By moving the original service conductors to a splice box, assuming the splices are rated for 90C, and not knowing how/where the other end is terminated but if the other end can be rated 90C then I think you can make the case for using the existing service conductors at the higher 90C rating assuming the existing conductors are a 90C rated wire.

Sure is a lot of assumptions.
 
charlie b said:
. . . "are we allowed to tap a service"?
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augie47 said:
230.46, yes
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I can't quite get here from there. That article points you to four other articles that essentially address means and methods. But they do not have rules similar to the feeder tap rules that include requirements for conductor sizes (as compared to the conductor being tapped), distance limits, and overcurrent protection at the end of the tap. Even if I knew the AWG size of the service conductors and the distance between their new pull box and the new panel, how could I judge whether the installation would meet all relevant NEC requirements, especially as I don't know where any such requirements would be found?

I am still looking at this as a "non-trivial exercise."
 
charlie b said:


I can't quite get here from there. That article points you to four other articles that essentially address means and methods. But they do not have rules similar to the feeder tap rules that include requirements for conductor sizes (as compared to the conductor being tapped), distance limits, and overcurrent protection at the end of the tap. Even if I knew the AWG size of the service conductors and the distance between their new pull box and the new panel, how could I judge whether the installation would meet all relevant NEC requirements, especially as I don't know where any such requirements would be found?

I am still looking at this as a "non-trivial exercise."
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I think you are over thinking this. There arent really specific "tap rules" for SEC, at least they arent called that, but see 230.40, 230.70,230.71, 230.72, 230.90(A) EX 3. I think what you are hung up on is "tapping" a SEC with smaller sized wire - its fine, there is no OCPD there anyway so it doesnt matter that it is smaller. Best you can do is give it overload protection as required in 230.90. Think about it, we "split" SEC into multiple/smaller sets all the time: A bussed gutter above a bunch of meters, a multi gang meter socket without disconnects, etc......
 
jap said:
If the 200 amp panel is drawing say 150 amps, and,you subfed the 100 amp panel from the 200 amp panel, and, the 100 amp panel is drawing 50 amps (200 amps total), and, the service conductors are rated at 200 amps, you will most likely trip the 200 amp breaker even though you haven't overloaded the 200 amp rated service conductors if run this way for any length of time.

In that same scenario, with a service tap, you would not trip the 200 amp, and, you still would not have overloaded the 200 amp rated service conductors.

JAP>
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Ok well fair enough. I admit I would not sleep well at night having a 200 amp breaker with 199 amps on it ;) Also as old sparky said, perhaps you could get into a game with using the 90 degree ampacity for the common SEC, as long there werent any 75 degree terminations on them.
 
electrofelon said:
Ok well fair enough. I admit I would not sleep well at night having a 200 amp breaker with 199 amps on it ;) Also as old sparky said, perhaps you could get into a game with using the 90 degree ampacity for the common SEC, as long there werent any 75 degree terminations on them.
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Its got nothing to do with sleeping well at night.

Just clarifying that I did make sense even though you didn't think I did, I think. ;) :)

JAP>
 
jap said:
Its got nothing to do with sleeping well at night.

Just clarifying that I did make sense even though you didn't think I did, I think. ;) :)

JAP>
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No I still dont think it makes sense. If the 200 amp breaker is tripping, its for a reason. moving some of that load to the line side is masking the problem and overloading the SEC. Yes the SEC will probably be fine, but there is no "it will likely be fine" clause in the code.
 
I don't feel any of us find a Code problem in then proposal but there is warranted concern in doing so. The possibility of someone unknowingly adding a load that will exceed the conductors ampacity IMO is elevated in these situations (as compared to a commercial/industrial MLO panelboard)
It would be an unusal situation where you could not accomplish the same result by bringing both cables from a 400 amp meter base and increasing the riser size accordingly which would pretty much eliminate and risks..
 
charlie b said:


I can't quite get here from there. That article points you to four other articles that essentially address means and methods. But they do not have rules similar to the feeder tap rules that include requirements for conductor sizes (as compared to the conductor being tapped), distance limits, and overcurrent protection at the end of the tap. Even if I knew the AWG size of the service conductors and the distance between their new pull box and the new panel, how could I judge whether the installation would meet all relevant NEC requirements, especially as I don't know where any such requirements would be found?

I am still looking at this as a "non-trivial exercise."
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Would the connection violate 230.82 because it is connected to the supply side of the service disconnecting means?
 
shortcircuit2 said:
Would the connection violate 230.82 because it is connected to the supply side of the service disconnecting means?
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service entrance conductors are allowed to be connected on the supply side of a service disconnect

Both the existing 200 amp panel and a new 100 amp panel would be service equipment

That is why the service disconnect has to be located as soon as possible entering the building (stated in this thread for the state in question with in 15 ft)

To group multiple service disconnects that protect the service entrance conductors from overloads the calculated load for the building cannot remain unknown
 
Kind of curious why no one has commented on this that I posted:

It is the violation of 230.70(A)(1) in my opinion. If the tap box is outside, no problem, if it is inside then the disconnect(s) aren't "nearest the point of entrance."


All of the discussion about tapping is moot in light of this. Unless you all disagree with this interpretation.
 
Strathead said:
Kind of curious why no one has commented on this that I posted:

It is the violation of 230.70(A)(1) in my opinion. If the tap box is outside, no problem, if it is inside then the disconnect(s) aren't "nearest the point of entrance."


All of the discussion about tapping is moot in light of this. Unless you all disagree with this interpretation.
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200 amp service entrance conductors are allowed to enter into a building and tap/ splice up to six separate (200 amp for example) disconnects as long as the calculated load does not exceed the ampacity of the 200 amp service entrance conductor entering the building
 
Strathead said:
Kind of curious why no one has commented on this that I posted:

It is the violation of 230.70(A)(1) in my opinion. If the tap box is outside, no problem, if it is inside then the disconnect(s) aren't "nearest the point of entrance."


All of the discussion about tapping is moot in light of this. Unless you all disagree with this interpretation.
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the distance has been addressed in this thread several times the state in question allows 15 ft to meet that requirement
 
david said:
the distance has been addressed in this thread several times the state in question allows 15 ft to meet that requirement
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That is extremely generous and far outside the allowance here, however, I don't see how even the most reasonable AHJ would consider service conductors entering an accessible junction box with splices in it INSIDE the building as causing downstream OCP to be no longer nearest the entrance.
 
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