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Old 12-14-2011, 12:25 AM   #1
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Default Double Tap Rule

Where can I find code on this?

I need to feed a 240 Volt 30 Amp Disconnect Serving a stackable washer/dryer as well as a 240 Volt 100 Amp Sub Panel from a single 100 amp breaker located in an apartment complex combo meter section. After installing a gutter underneath the Meter Combo Section and re routing my existing sub panel branch circuits to it; installing new #2 Branch Circuits from the Main Circuit Breaker to lug into a listed connector in my gutter, my question is:

Can I install #10 wire from my connector to supply my 30 Amp Disconnect as long as my disconnect is within 10' of the tap and the Disconnect is Fused at 30 Amps?

Any help is greatly appreciated... Thanks

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Old 12-14-2011, 12:38 AM   #2
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Old 12-14-2011, 12:40 AM   #3
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Conductor tap rules are in Article 240... and they're for feeders, not branch circuits. Is your 30 amp disconnect an overcurrent device or just a switch of some sort?

EDIT: Nevermind, just read that it's a fused disconnect.

I dunno gimme a minute.
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Old 12-14-2011, 12:45 AM   #4
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(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 device 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.

(4) For field installations, if the tap conductors leave the
enclosure or vault in which the tap is made, the ampacity
of the tap conductors is not less than one-tenth of
the rating of the overcurrent device protecting the
feeder conductors.
Informational Note: For overcurrent protection requirements
for panelboards, see 408.36.
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Old 12-15-2011, 02:20 AM   #5
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I appreciate the response. Im still confused as to what size wire i can use to run to my discos from the actual tap/splice point.

1a says size the conductor to allow for the combined load of all circuits on the tap. I would like to assume that they are referring to the conductors coming off the main over current device, supplying the tap.
However, thats not really stated clearly but it would make sense.

4 states that my field wire cannot be less than one tenth the main over current device.

I have an 100 amp rated subpanel calc'd out at 38 Amps with existing #2 Aluminum feeders supplied by a 100 amp CB. I would like to intercept and tap off to a 30 Amp Disco with #10's. #10's fall within the minimum reqs of #4

Any more help would be greatly appreciated.

Last edited by brybedo; 12-15-2011 at 02:23 AM.
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Old 12-15-2011, 09:44 AM   #6
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It sounds like the circuit supplying the 100 amp sub panel is just a normal feeder. And you just want to tap off of that for your 30 amp disconnect for the washer/dryer.

If the tap between your 100 amp feeder and the 30 amp disconnect is 10 feet or less, then:

1) The tap conductors need to be sized for the load served (the washer/dryer) and no less. #10 will be fine, assuming your 30 amp figure is correct.

2) The tap conductors need to be sized no less than the device or overcurrent rating at the end of the tap. If you have a 30 amp disconnect, then #10 will still be fine.

3) Don't extend your tap beyond your 30 amp disconnect.

4) Make sure your tap conductors are in raceway or enclosure the whole way.

5) If the conductors leave the enclosure where they're tapped off of the main feeder, then they can't be rated less than 1/10 of the feeder ampacity. If you have a 100 amp feeder, then this means you can't tap with a 10 amp circuit or less. Again, your #10 will be fine.

That's my take on it.
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Old 12-15-2011, 12:56 PM   #7
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how and where will the connection of the #10 conductors be made? you know that you can't put them under the lugs of a breaker with the other conductor that feeds the sub panel.
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Old 12-15-2011, 01:01 PM   #8
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Quote:
Originally Posted by stars13bars2 View Post
how and where will the connection of the #10 conductors be made? you know that you can't put them under the lugs of a breaker with the other conductor that feeds the sub panel.

Polaris or split bolts? How do you want to do it?
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Old 12-15-2011, 11:08 PM   #9
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Quote:
Originally Posted by brybedo View Post
I appreciate the response. Im still confused as to what size wire i can use to run to my discos from the actual tap/splice point.

Any more help would be greatly appreciated.

just going by this ^^^and the title, and thought there may be some room for education, but since you are helping with the job I guess I was wrong again.

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