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?
Feeder Tap to MLO Load Center
- Thread starter Jon456
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jumper
Senior Member
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- 3 Hr 2 Min from Winged Horses
I believe you missed a part.
(2) 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.
Last edited:
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
dana1028
Senior Member
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- San Francisco Bay area
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).
Twoskinsoneman
Senior Member
- Location
- West Virginia, USA NEC: 2020
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- Facility Senior Electrician
ANY OCPD on the supply side of the panelboard that is not greater that the rating of the panel board meets 408.36
Twoskinsoneman
Senior Member
- Location
- West Virginia, USA NEC: 2020
- Occupation
- Facility Senior Electrician
nope
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?
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?
Twoskinsoneman
Senior Member
- Location
- West Virginia, USA NEC: 2020
- Occupation
- Facility Senior Electrician
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.
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.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
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
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
perhaps becasue a tap that is <10' is also <25'?
kwired
Electron manager
- Location
- NE Nebraska
That is a good point.
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