Land #4AWG on a 120V 20A Duplex??

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Eng

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Is there anyway to downsize a #4AWG so that it can be landed on a 120V 20A Duplex Receptacle? I have an owner who wants UPS power from a source that is approximatley 350' away. I would need to run #4's for voltage drop. Anyway to terminate these to the receptacle?
 
Smart $

Smart $

Esteemed Member
Location
Ohio
Eng said:
Is there anyway to downsize a #4AWG so that it can be landed on a 120V 20A Duplex Receptacle? I have an owner who wants UPS power from a source that is approximatley 350' away. I would need to run #4's for voltage drop. Anyway to terminate these to the receptacle?
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Either use a compression (crimp) terminal or splice on a smaller conductor.
 
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gndrod

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Location
Ca and Wa
Eng said:
Is there anyway to downsize a #4AWG so that it can be landed on a 120V 20A Duplex Receptacle? I have an owner who wants UPS power from a source that is approximatley 350' away. I would need to run #4's for voltage drop. Anyway to terminate these to the receptacle?
Click to expand...

The above description leads me to believe that the UPS power from a source is to only have a single receptacle as the sole output. Should there be other loads and structure system, then I would consider having a multi-wire disconnect panel or equivalent. Otherwise I would agree with splicing in the outlet.
 
E

Eng

Member
gndrod said:
Hi David,
That was simultaneous and I agree. Only other thought would be the source end connection having to splice the 4 awg down to a 20 amp OCPD.
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Same thing would need to be done here also, I assume. Splice on a #12 in the panel and connect the #12 to the circuit breaker.
 
iwire

iwire

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Staff member
Location
Massachusetts
Eng said:
Is there anyway to downsize a #4AWG so that it can be landed on a 120V 20A Duplex Receptacle? I have an owner who wants UPS power from a source that is approximatley 350' away. I would need to run #4's for voltage drop. Anyway to terminate these to the receptacle?
Click to expand...

I have done this a bunch of times for roof outlets on a very large building, the engineer specified 4 AWG for those as well.

You will have an issue at the breaker and the receptacle.

I would reduce the conductors to 12 AWG at both ends. I would bring the 4 AWG close to the panel and the receptacle, set a good sized junction box and splice 12 AWG onto the 4 AWG.

A couple of points.

You still have to use no more than a 20 amp breaker

The equipment grounding conductor (if you run one) will also have to be 4 AWG per 250.122(B)
 
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gndrod

Senior Member
Location
Ca and Wa
Eng said:
Same thing would need to be done here also, I assume. Splice on a #12 in the panel and connect the #12 to the circuit breaker.
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20 amp OCPD using spliced #12 awg copper transition from a #4 copper conductor works. There may be an incompatibility if a splice is being made to an aluminum conductor though. The wiring transition will need a cu-al termination splice 'listed' component.

Sorry for the overlapped response Bob.
 
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hillbilly1

Senior Member
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Occupation
Owner/electrical contractor
A listed splicer/reducer would do the trick, does not have to be a compression type, they make them with set screw connections, insulated and uninsulated, most supply houses and the big box stores carry one or the other.
 
iwire

iwire

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Location
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hillbilly1 said:
A listed splicer/reducer would do the trick, does not have to be a compression type, they make them with set screw connections, insulated and uninsulated, most supply houses and the big box stores carry one or the other.
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That would be my route but you still wont fit those with 4 AWG in a typical device box.
 
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hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
iwire said:
That would be my route but you still wont fit those with 4 AWG in a typical device box.
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I agree, a separate splice box would be needed, though someone would try though.:lol:
A couple of years ago I fixed a short where the builder wired the house and spliced 6#6 and 2#10's in a standard metal octagon box. The poorly taped split bolt he used shorted against the cover. (yes, he actually put the cover on)
 
iwire

iwire

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Location
Massachusetts
gndrod said:
That would be a tight squeeze in a 2gg also.
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If I was being pressed to hide it in a wall I would use a 4 11/16" deep box with a single gang plaster ring.

More likely I would hide the junction box in the suspended ceiling right above the outlet and run the last 10' with 12 AWG. :)

For the roof outlets I mentioned I never actually saw how the guys handled that end the job was too large to wonder around. My part of it was installing panelboards at a number of locations with a gutter above them where we switched from 4 AWG down to I think 10 AWG to land on the breakers.
 
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hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
I was amazed at how he was able to tighten and tape three split bolts in that small of space either! He just twisted the ground and buried it in the bottom of the box. Wish I had taken a picture of it!
 
E

Eng

Member
Thanks for all the responses. I am planning on detailing out a junction box above the device box in order to splice the conductors. Ended up needed #3 vs #4 for this.

As I am looking at 314.16, the largest size conductor that the NEC gives a cubic inch rating for is #6. How do you size the junction box when dealing with #3's? Since they don't list a #3 for the cubic inch, I assume I will need to use 314.28?
 
iwire

iwire

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Staff member
Location
Massachusetts
Eng said:
As I am looking at 314.16, the largest size conductor that the NEC gives a cubic inch rating for is #6. How do you size the junction box when dealing with #3's? Since they don't list a #3 for the cubic inch, I assume I will need to use 314.28?
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Once you go larger than 6 AWG the box size is based on the conduits.


314.28 Pull and Junction Boxes and Conduit Bodies.
Boxes and conduit bodies used as pull or junction boxes
shall comply with 314.28(A) through (E).

Exception: Terminal housings supplied with motors shall
comply with the provisions of 430.12.

(A) Minimum Size. For raceways containing conductors
of 4 AWG or larger that are required to be insulated, and for
cables containing conductors of 4 AWG or larger, the minimum
dimensions of pull or junction boxes installed in a
raceway or cable run shall comply with (A)(1) through
(A)(3). Where an enclosure dimension is to be calculated
based on the diameter of entering raceways, the diameter
shall be the metric designator (trade size) expressed in the
units of measurement employed.

(1) Straight Pulls. In straight pulls, the length of the box
or conduit body shall not be less than eight times the metric
designator (trade size) of the largest raceway.

(2) Angle or U Pulls, or Splices. Where splices or where
angle or U pulls are made, the distance between each raceway
entry inside the box or conduit body and the opposite
wall of the box or conduit body shall not be less than six
times the metric designator (trade size) of the largest raceway
in a row. This distance shall be increased for additional
entries by the amount of the sum of the diameters of all other
raceway entries in the same row on the same wall of the box.
Each row shall be calculated individually, and the single row
that provides the maximum distance shall be used.

Exception: Where a raceway or cable entry is in the wall
of a box or conduit body opposite a removable cover, the
distance from that wall to the cover shall be permitted to
comply with the distance required for one wire per terminal
in Table 312.6(A).

The distance between raceway entries enclosing the
same conductor shall not be less than six times the metric
designator (trade size) of the larger raceway.

When transposing cable size into raceway size in
314.28(A)(1) and (A)(2), the minimum metric designator
(trade size) raceway required for the number and size of
conductors in the cable shall be used.

(3) Smaller Dimensions. Boxes or conduit bodies of dimensions
less than those required in 314.28(A)(1) and
(A)(2) shall be permitted for installations of combinations
of conductors that are less than the maximum conduit or
tubing fill (of conduits or tubing being used) permitted by
Table 1 of Chapter 9, provided the box or conduit body has
been listed for, and is permanently marked with, the maximum
number and maximum size of conductors permitted.
Click to expand...
 
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