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Old 04-26-2010, 03:21 PM   #1
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14-3 AWG as 12-2 AWG


My question may sound stupid for pros, sorry - I tried to do online research but canít find answer anywhere.
I have 3-wire 14 AWG cable (3 wires + ground), need to run 80í underground. For 12A load it has to be 12 AWG if Iím right. Can I run 14 AWG and connect two power conductors together at both ends to make it a single hot conductor? I guess I will be getting about 8 AWG with two conductors used together as one. Will it work/is it OK with the code? Is 14 AWG neutral, left unchanged, is OK for that load?
Thank you in advance

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Old 04-26-2010, 03:25 PM   #2
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14-3 AWG as 12-2 AWG


What you are describing is parallel conductors. It is not OK. Code dictates the smallest conductor permitted to be paralleled is a 1/0.

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Old 04-26-2010, 03:47 PM   #3
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14-3 AWG as 12-2 AWG


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Originally Posted by lowesvisa View Post
Can I run 14 AWG and connect two power conductors together at both ends to make it a single hot conductor?
Two #14s paralleled would give the cross sectional area of a single #11.
http://en.wikipedia.org/wiki/American_wire_gauge

In principle it would work, assuming equal current sharing. But this sharing depends on the mostly unpredictable and variable contact impedances of the connections at each end, so most of the time it wouldn't work.

If you cleaned off the copper oxide tarnish and twisted both #14s along their whole length you'd do somewhat better.

I guess this is why the NEC doesn't like doing this. They tend to be risk-averse.

Last edited by Yoyizit; 04-26-2010 at 04:03 PM.
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Old 04-26-2010, 03:56 PM   #4
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14-3 AWG as 12-2 AWG


A 12A load does not need #12 wire either.

What exactly is this 12A load?
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Old 04-26-2010, 04:05 PM   #5
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14-3 AWG as 12-2 AWG


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Originally Posted by lowesvisa View Post
Can I run 14 AWG and connect two power conductors together at both ends to make it a single hot conductor? I guess I will be getting about 8 AWG with two conductors used together as one. Will it work/is it OK with the code?
Assuming for a moment is was ok to effectively increase the size of the conductors by tying two (or more) together, you would still have to increase the size of the neutral as well. The neutral is going to conduct just as much current as the hot. The only difference is the voltage potential relative to 'ground'.
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Old 04-26-2010, 04:47 PM   #6
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14-3 AWG as 12-2 AWG


Also, if this is nmb and not uf cable, it can not be run outside underground anyway.
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Old 04-27-2010, 09:29 AM   #7
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14-3 AWG as 12-2 AWG


Thank you very much, everybody.
I didnít know it is called ďparallel conductorsĒ, tried to google it and got the following code paragraph. It is permissible if ...
310.4
"(b) The ampacity of each individual conductor is sufficient to carry the entire load current shared by the parallel conductors".
From what I found most of the pros think it is helpful to prevent voltage drop only, not carrying an extra load. Looks like thatís exactly what I need: it is UF cable I want to use to power my electric lawn mower and leaf blower in the back yard. The line is protected by 15A breaker anyway. Just want to put an extra outlet where my 75í 12 AWG extension cord canít reach, and only what I have is 250í of 14 AWG UF cable (I need only 80' run to get about 150' with the extension cord)). The mower uses 12 A as I know (blower actually uses 13 A at max speed), and voltage drop is the biggest concern with a long cable I guess. Just not sure if 14 AWG neutral still contributes to the voltage drop.
Please correct me if Iím wrong. Thank you again.

Last edited by lowesvisa; 04-27-2010 at 09:32 AM.
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Old 04-27-2010, 09:35 AM   #8
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14-3 AWG as 12-2 AWG


By code you can't use 14-3 & run the conductors in parallel
Either use 15a breakers & run 2 circuits as a MWBC
OR
Buy 12g wire

15a is good for 1800w
Voltage drop for a 12a load on 14g wire will be slightly over what is recommended
Not really that high tho
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Old 04-27-2010, 10:53 AM   #9
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14-3 AWG as 12-2 AWG


Quote:
Originally Posted by lowesvisa View Post
(blower actually uses 13 A at max speed), and voltage drop is the biggest concern with a long cable I guess. Just not sure if 14 AWG neutral still contributes to the voltage drop.
#14 is 2.6 milliohms per foot.
For a max 5% drop @120v @13A you'd need a max R of 6v/13A = 460 milliohms.
This is a max of 178' [90' of two conductor] cable.

Last edited by Yoyizit; 04-27-2010 at 11:13 AM.
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Old 04-27-2010, 01:58 PM   #10
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14-3 AWG as 12-2 AWG


Thank very much you for your answers. I will use that 14/3 for lights only then.

I have another question. Can I run a single 12 AWG 80’ THHN wire in the same conduit with 14/3 (it will be going to a light controlled from inside of the house and located next to the future receptacle) and use it with that free 14 AWG connector just to prevent bigger voltage drop? 12 AWG THHN for hot, free 14 AWG from that UF cable for neutral, no ground since it will GFCI protected.
Thank you in advance
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Old 04-27-2010, 02:03 PM   #11
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14-3 AWG as 12-2 AWG


You can't run a circuit without a ground, even with GFCI protection
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Old 04-27-2010, 02:31 PM   #12
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14-3 AWG as 12-2 AWG


Thanks. I’m thinking then about buying some cheap THHN wire on ebay, 2x100’ - around $35 total. Can I at least use that free 14 AWG conductor as ground and just run 2 extra THHN wires in the same conduit with that 14/3?
Thank you
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Old 04-27-2010, 02:50 PM   #13
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14-3 AWG as 12-2 AWG


Underground in conduit you must use THWN
I do not think you can use the extra wire in the cable unless it is part of a MWBC like I suggested
--not to be used with wires outside of the cable
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Old 04-27-2010, 03:25 PM   #14
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14-3 AWG as 12-2 AWG


If the wires are smaller than #4 they need to be insulated in the correct colors.

Also all conductors of the circuit need to be run together. You cannot just pick and choose a conductor from here and there.
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Old 04-28-2010, 10:02 AM   #15
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14-3 AWG as 12-2 AWG


Quote:
Originally Posted by lowesvisa View Post
Just not sure if 14 AWG neutral still contributes to the voltage drop.
Quote:
Originally Posted by HooKooDooKu View Post
The neutral is going to conduct just as much current as the hot.
When electricity flows through a wire, there is going to be a voltage drop. It's called Ohms law...

Voltage Drop = Current * Resistance (E=IR)

Wire Resistance:
1000' of #14 has 2.5 ohms of Resistance
1000' of #12 has 1.6 ohms of Resistance
1000' of #10 has 1.0 ohms of Resistance

You want to go 80', but that's 160' of wire the electricty is going to flow through (it's just that 80' out, you're going to insert a power tool). So for you the chart should be:

160' of #14 has 0.40 ohms
160' of #12 has 0.26 ohms
160' of #10 has 0.16 ohms

So for your situation, with a 13A load, the voltage drop in just the wire is going to be:
#14 = 5.2 volts
#12 = 3.4 volts
#10 = 2.1 volts

If you did use the 14/3 and tied the hots together to reduce the wire resistance, you would only reduce the resistance for the 1st 80' of the wire. The other 80' would still have the same resistance.

As Yoyizit pointed out, the 5.2 volt drop on a 120 volt circuit is within the recommended maximum voltage drop of 5%. But it also means fewer volts going to your equipment. As you can see, things improve just a little bit with #12, and you get most of the voltage drop back if you pony up for #10.

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