Feeder Tap to MLO Load Center

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Jon456

Senior Member
Location
Colorado
NEC 240.21(B)(2) states that taps not over 25' long must terminate in a single circuit breaker, so a Main Lugs Only panel would not comply. However, 240.21(B)(1) makes no such stipulation for taps not over 10' long. As I read it, that means I can run a feeder tap to a MLO panel as long as the tap conductor is no more than 10' from the tap to the lugs. Is that correct?
 

jumper

Senior Member
NEC 240.21(B)(2) states that taps not over 25' long must terminate in a single circuit breaker, so a Main Lugs Only panel would not comply. However, 240.21(B)(1) makes no such stipulation for taps not over 10' long. As I read it, that means I can run a feeder tap to a MLO panel as long as the tap conductor is no more than 10' from the tap to the lugs. Is that correct?

I believe you missed a part.

(2) The tap conductors do not extend beyond the switchboard,
panelboard, disconnecting means, or control devices
they supply.
 

Jon456

Senior Member
Location
Colorado
The tap conductors do not extend beyond the switchboard,
panelboard, disconnecting means, or control devices they supply.

I did read 240.21(B)(1)(2), but thought it meant that, after the tap conductors enter the panel (that they are supplying), that they do not extend beyond that panel.

If in fact the entire length of the tap conductors must be contained within a single panel (in essence, restricting 10' taps to being no more than jumpers within a single enclosure), then what are we to make of 240.21(B)(1)(3) ?:

"Except at the point of connection to the feeder, the tap
conductors are enclosed in a raceway, which shall extend
from the tap to the enclosure of an enclosed switchboard,
panelboard, or control devices, or to the back of an open switchboard."

I think 240.21(B)(1)(2) needs clarification.
 
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dana1028

Senior Member
NEC 240.21(B)(2) states that taps not over 25' long must terminate in a single circuit breaker, so a Main Lugs Only panel would not comply. However, 240.21(B)(1) makes no such stipulation for taps not over 10' long. As I read it, that means I can run a feeder tap to a MLO panel as long as the tap conductor is no more than 10' from the tap to the lugs. Is that correct?

408.36 - requires OCP at the source or at the panelboard.
 

Jon456

Senior Member
Location
Colorado
408.36 - requires OCP at the source or at the panelboard.
Would Exception 2 apply if the rating of the OCP on the tapped conductors is not greater than that of the panelboard? Note that the MLO load center (with less than 42 overcurrent devices)would have OCP on each of the several branch circuits served by that load center. But the tap conductors would not terminate on a single OCP (as required for 25' taps).
 

Jon456

Senior Member
Location
Colorado
Why not?

Why would the NEC specifically state, for taps up to 25' long, that the tap conductors must terminate in a single circuit breaker, but not make the same stipulation for taps up to 10' long? If it's not explicitly prohibited, then isn't it permitted?
 
My reasoning was if the following are complied with the conductors actually feeding the MLO would not be taps.
I can't explain the reasoning for the single CB termination of the 25' rule. But I don't see how it can be done and still comply with 408.36

tap conductors:
240.21(B)(1)(b.) Not less than the rating of the device supplied by
the tap conductors or not less than the rating of the
overcurrent protective device at the termination of
the tap conductors

408.36 Overcurrent Protection. In addition to the requirement
of 408.30, a panelboard shall be protected by an
overcurrent protective device having a rating not greater
than that of the panelboard

240.2 Tap Conductors. As used in this article, a tap conductor is
defined as a conductor, other than a service conductor, that
has overcurrent protection ahead of its point of supply that
exceeds the value permitted for similar conductors that are
protected as described elsewhere in 240.4.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Why not?

Why would the NEC specifically state, for taps up to 25' long, that the tap conductors must terminate in a single circuit breaker, but not make the same stipulation for taps up to 10' long? If it's not explicitly prohibited, then isn't it permitted?

The panelboard requires an OCPD device due to 408.36. You could have a 10' tap to a different piece of equipment without an OCPD if it wasn't a panelboard as long as it met all the conditions of the 10' tap rule.
 

kwired

Electron manager
Location
NE Nebraska
The panelboard requires an OCPD device due to 408.36. You could have a 10' tap to a different piece of equipment without an OCPD if it wasn't a panelboard as long as it met all the conditions of the 10' tap rule.

That is correct. It is not a violation of the 10' tap rule. It is a violation of overcurrent protection for the panelboard.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
Why not?

Why would the NEC specifically state, for taps up to 25' long, that the tap conductors must terminate in a single circuit breaker, but not make the same stipulation for taps up to 10' long? If it's not explicitly prohibited, then isn't it permitted?

perhaps becasue a tap that is <10' is also <25'?
 
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