I am going about 150 feet to a shed, and plan to run number 10 gauge wire.
This is simply a shed, and I want to be able to run power tools and have
some lights in the shed. I plan to use UF wire, and of course go 2 feet
Someone advised to run 10/3 instead of 10/2, but I forgot the reason
why. It seems they were indicating I could have TWO circuits instead of
one. Is that correct ? If so, then it seems that I could have 2 separate
20 amp circuits, but I am not sure.
When we say 10/3 wire, is that two main live wires, and one common
Thanks a lot !!
No, not two singles, you MUST connect to a single- 240 volt breaker (opens
both legs of the ungrounded conductors simultaneously). Run to a larger
outlet box and split both circuits off from there, one for recepts and one
If it's a fairly long run, I would go along with RBM and set overcurrent at
20 amps (to account for voltage drop).
With 12/3 you could run about 125 ft (from circuit origin to shed) with a 3%
voltage drop (about 8 volts) at 240 volts (another reason to use 240 out to
the shed instead of 120).
With 10/3 you could run about 200 ft (assuming the same 16 ampere load,
gives about 8 volts voltage drop.)
>>>I am going about 150 feet to a shed, and plan to run number 10 gage
>>>This is simply a shed, and I want to be able to run power tools and have
>>>some lights in the shed. I plan to use UF wire, and of course go 2
>>>Someone advised to run 10/3 instead of 10/2, but I forgot the reason
>>>why. It seems they were indicating I could have TWO circuits instead
>>>of one. Is that correct ? If so, then it seems that I could have 2
>>>separate 20 amp circuits, but I am not sure.
>>>When we say 10/3 wire, is that two main live wires, and one common
>>>Thanks a lot !!
Dennis et al
If the circuit is to be split into two separate circuits, without two or
more ungrounded current carrying conductors terminating on the same yoke
or strap, and the installation is governed by the US National Electric
Code (NEC), then there is no requirement to use a two pole breaker
unless the circuit will supply 240 volt loads.
Some will argue very forcefully that it is good practice but I disagree.
A double pole breaker will open both circuits on a fault or overload
thus plunging the entire building served into darkness because a saw
hung up in a piece of paneling for instance.
Separate buildings always need a building disconnecting means. On
residential property this can take the form of a common snap switch or
set of three way switches in each ungrounded conductor. Better practice
is to use a double pole switch that will open both ungrounded conductors
simultaneously. Best practice would be to use a disconnect that is
listed for use service equipment which would be required if it were not
"This alternating current stuff is just a fad. It is much too dangerous
Along that line I'd suggest using a 30amp breaker at the house, to
protect the feed wire from over current, and a small panel in the
outbuilding, with some 20 amp breakers for the local circuits.
Then you can have multiple circuits in the building, preventing what you
fear, everything going dark on a fault. And you don't have to go back
inside the house to reset the circuit.
And you can have specialty circuits with different over current
protections if you need to protect a specific device.
When you specify 10/3 wire, you normally get a cable with 4 wires in it.
There will be a black,red,white, and an uninsulated wire. The best way to
wire it is to connect the black and red wires to the breaker box so that you
have 230 volts across them and the white wire is the neutral. There will be
115 volts from the white wire to the black wire and also to the red wire.
The bare wire is the ground and it might be referred to as the green wire.
Number 10 wire is good for 30 amps, but if you are running it 150 feet and
try to use the full 30 amps the voltage drop may be too much.. Try to
ballance the load on the two circuits if you can. This is not always
possiable while using differant tools. You could put the lights on one
circuit that you don't use much and use the other one for the tools.
Yup, we even got telephones without wires and 'puters and funny colored
It is tricky to run the 'lectric heaters in our igloos, you have to keep
turning them off so the ice can harden up again.
We have a 12 lane highway, but you have to watch out for the 18 wheel
snowmobiles, they think they own the road.
Wood stoves in ice fishing shantys can be a challenge!
Kidding aside though, knew a guy on Lake Champlain near Canada that had a
wood stove in his along with TV, sofa, chairs and then some. This was not
a typical shanty. Occasionally they drilled a hole and fished by accident
when they got drunk enough.
That's what I did. Came off a thirty amp breaker in the main panel
with 10/3 went to a shop and split into two 20 amp circuits at a
My advice, run two. I ran mine thinking I would just use a few tools
and lights. Shop developed into something bigger with several 220
volt machines. I had to run another line out.
10awg is the minimum size that you can run and legally use as a feeder to a
subpanel. (minimum feeder size is 30 amps).
If you know you are going to have larger loads than just lights and outlets,
rather than running a second line, run larger wire.
Instead of running UF cable, I would run (2) PVC conduits, one for power,
and one for communications. I would make them a minimum of 2" diameter,
maybe 3" for power. Allow for expansion, once the conduit is in the ground,
it's easier to pull new wire, than replace the conduit or buried cable.
For a 150' run, I would go up at least one gauge to allow for voltage drop,
and go up at least one gauge above your intended load to allow for expansion.
That would mean #6, which is rated for 50 amps, would be my suggested minimum,
allowing for a 40 amp subpanel, with allowance for some voltage drop.
Since it is in conduit, you will be pulling individual wires, not UF cable.
You will probably want to pull some phone and CATV cabling in the other
conduit. Just remember that any cabling in underground conduits needs to be
waterproof, and should be considered to be under water.
-- Welcome My Son, Welcome To The Machine --
Bob Vaughan | techie @ tantivy.net |
You can run also 220 and 110 both if you use the third conductor as a
neutral. This would require you to have a separate grounding rod at the
shed. I'm not up on the latest code and I believe it has changed as to
when you may or may not use a ground rod at an outbuilding like this.
I'd check with a local inspector or electrician who is familiar with the
Don't confuse this any more than you have to. Feed it from a 2 pole
20a breaker in the house and use GFCI receptacles in a 4" square box
as soon as it gets ointo the shed. Feed 12/2 to the rest of the down
stream outlets connected to the "load" side of the GFCI.
If you put another sub panel out there you kick a whole other can of
worms, ground rods etc. This "multi-wire" circuit is just ONE circuit
in NEC speak so your life is easier. You can still tap off of the
"line" side of the GFCI with both phases to feed 240 volt outlets.
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