10 foot tap rule

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wyboy

Senior Member
I had always thought that any feeder tap had to land in a OCPD. After reading 240.21(B)(1) i am reading that if all other conditions are met a 10 foot tap mat land on a MLO panel without landing in a main OCPD. Am i reading this right? :sick:
 
C

Carultch

Senior Member
Location
Massachusetts
wyboy said:
I had always thought that any feeder tap had to land in a OCPD. After reading 240.21(B)(1) i am reading that if all other conditions are met a 10 foot tap mat land on a MLO panel without landing in a main OCPD. Am i reading this right? :sick:
Click to expand...


At tap terminal 1, it is connected directly to a feeder, or in a spare lug on equipment to which the feeder terminates. This feeder is ultimately protected by an OCPD at its source.

At tap terminal 2, it connects to an OCPD dedicated to the tap circuit, where the tap conductors have at least as much ampacity as that OCPD.
 
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wyboy

Senior Member
The NEC reads: The ampacity of the tap conductor is not less than the computed load in accordance with Art. 220, and not less than the rating of the equipment containing overcurrent devices supplied by the tap conductors or OCPD at the termination of the tap conductors.

The equipment containing overcurrent devices supplied by the tap conductors is a MLO panel board. Where does it say it has to land in a separate OCPD as stated and required in taps over 10 feet?
 
dkidd

dkidd

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here
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PE
wyboy said:
I had always thought that any feeder tap had to land in a OCPD. After reading 240.21(B)(1) i am reading that if all other conditions are met a 10 foot tap mat land on a MLO panel without landing in a main OCPD. Am i reading this right? :sick:
Click to expand...

Not less than the rating of the equipment containing
an overcurrent device(s) supplied by the tap conductors
or not less than the rating of the overcurrent
protective device at the termination of the tap conductors.

So, the MLO panel is equipment.

See http://forums.mikeholt.com/showthread.php?t=94903
 
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W

wyboy

Senior Member
I see your point. Thanks!! I thought that was right but couldn't find the reference under the tap rule.
 
infinity

infinity

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Location
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Journeyman Electrician
wyboy said:
I had always thought that any feeder tap had to land in a OCPD. After reading 240.21(B)(1) i am reading that if all other conditions are met a 10 foot tap mat land on a MLO panel without landing in a main OCPD. Am i reading this right? :sick:
Click to expand...

I've seen 10' taps landed in dimmer racks without a main OCPD but a panelboard would be different.
 
J

jaggedben

Senior Member
Location
Northern California
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Solar and Energy Storage Installer
Interesting... This was a 2014 NEC change. Before that it read:

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.
Click to expand...
 
J

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
david luchini said:
I'm not sure how you would meet 408.36 doing that.
Click to expand...

It's kinda weird, but if you had tap conductors feeding a panelboard that was rated as high as the tapped conductor, you'd be fine with MLO. Fits under Exception 2, it seems.

Example: 125A feeder to a 125A panelboard is tapped to a new sub. Calculated load for the new sub is 40A. Tap conductors are rated for 40A but the new sub is rated 125A because hardly nobody makes anything smaller than that. The new sub can be MLO in this case. (And let's just say for argument that the calculated load on the original sub turns out to be less than 85A, which is actually not that unlikely in a lot of situations.)
 
C

Carultch

Senior Member
Location
Massachusetts
dkidd said:
Not less than the rating of the equipment containing
an overcurrent device(s) supplied by the tap conductors
or not less than the rating of the overcurrent
protective device at the termination of the tap conductors.

So, the MLO panel is equipment.

See http://forums.mikeholt.com/showthread.php?t=94903
Click to expand...


You cannot terminate the load side of feeder tap conductors to anything other than a single overcurrent device, single fused disconnect, or single set of fuses.
 
Smart $

Smart $

Esteemed Member
Location
Ohio
jaggedben said:
Interesting... This was a 2014 NEC change. Before that it read:
Click to expand...
Here's the origin ROP for the clause "equipment containing an overcurrent device(s)".

______________________________________
10-32 Log #2151 NEC-P10 Final Action: Accept in Principle
(240.21(B)(1))
________________________________________________________________
Submitter: Phil Simmons, Simmons Electrical Services
Recommendation: Revise text to read as follows:
(1) Taps Not over 3 m (10 ft) Long. If the length of the tap conductors does
not exceed 3 m (10 ft) and the tap conductors comply with all of the following:
(1) The ampacity of the tap conductors is
a. Not less than the combined calculated loads on the circuits supplied by the
tap conductors, and
b. Not less than the rating of the equipment containing an overcurrent
device(s) supplied by the tap conductors or not less than the rating of the
overcurrent protective device at the termination of the tap conductors.
(2) The tap conductors do not extend beyond the switchboard, panelboard,
disconnecting means, or control devices they supply.
(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.
Substantiation: This proposal is intended to clarify the application of the
existing requirement and state the specific type of device as an overcurrent
device. This clarification is needed since a conductor fits within the definition
of “device” in Article 100. The submitter is quite confident such an application
or interpretation would not meet the intention of the Code Panel who is
responsible for this Article.
The term “equipment containing an overcurrent device(s)” could be a main-lug
panelboard, a fusible switch, a switchboard or a motor control center.
Panel Meeting Action: Accept in Principle
Add exception after 240.21(B)(1)(b) and revise text to read as follows:
(1) Taps Not over 3 m (10 ft) Long. If the length of the tap conductors does
not exceed 3 m (10 ft) and the tap conductors comply with all of the following:
(1) The ampacity of the tap conductors is
a. Not less than the combined calculated loads on the circuits supplied by the
tap conductors, and
b. Not less than the rating of the equipment containing an overcurrent
device(s) supplied by the tap conductors or not less than the rating of the
overcurrent protective device at the termination of the tap conductors.
Exception: Listed surge protective device(s) (SPD) installed in accordance with
285.23 or 285.24.
(2) The tap conductors do not extend beyond the switchboard, panelboard,
disconnecting means, or control devices they supply.
(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.
Panel Statement: The panel added a new exception following 240.21(B)(1)(b)
to address the installation of surge protective device(s) (SPD).
Number Eligible to Vote: 11
Ballot Results: Affirmative: 11
Click to expand...
 
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