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Before I ask, I understand how extension cords work to a point. I understand if anything is plugged in, it needs to stay under the rated wattage and amperage. I also understand the way cords are rated by gauge. Though i don’t understand what the 3 in 12/3 means. If I use the wrong words please feel free to fix this. I’m just unsure on these safety questions that seemed unanswered when I looked it up.

Hi. I have a shed, 50ft should be long enough. I had a couple questions.

The main one is, can I plug a 1 to 3 adapter as long as I keep the total wattage and amperage under the rating?

I also had a question, is a USB hub considered an “extension”?

Also on a triple tap, is it safe to plug in a power strip?

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  • Why are you running an extension cord to a shed for something that sounds like it merits a permanent branch circuit or feeder? (Namely, the minifridge)
    – ThreePhaseEel
    Commented Apr 15, 2021 at 0:35
  • If you do this, 50f is a fair ways so use a 12 or 10 guage extension cord. many splitters mean many contact points, so fewer in total is better. All of your devices will have their power consumption in Watts written on them, which you can add up to figure out if you're overloading the circuit. A set up like this should only be plugged into a GFCI circuit.
    – K H
    Commented Apr 15, 2021 at 7:59

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So long as the total draw of all devices plugged in remains below the amp capacity of the power strip, the extension cord, the permanent wiring, and the breaker, you'll be fine.

I believe the admonition against plugging in a power strip is that

  1. You are not allowed (by NEC) to use an extension cord for permanent wiring. i.e. if you need an outlet on the other side of the room for your entertainment center, you should have one wired in, don't run a cord across the floor, around the walls, (especially under a carpet!), whatever, to provide more-or-less permanent power to another location.
  2. A power strip will allow you to plug multiple items in at the same time, greatly increasing the chance of overloading the circuit. If you plug in your miter saw, table saw and router into the power strip and you've got 3 people, each using a tool, you'll very quickly overload the circuity. The breaker will pop, but you could cause damage to the strip and/or extension cord before it does.

If you're using the extension cord as the only supply of power to the shed, and you're planning on leaving it plugged in all the time, that would (I believe) constitute a permanent installation and is banned.

Most importantly, if the cord is stretched across the lawn from the house into the shed, it'll be in the way of the lawn mower. It doesn't take much imagination to figure out what could go wrong there.

If you roll out the extension cord to plug in a fan and a radio while you're out in the shed gardening, then you roll it back up and put it away at the end of the day, then you shouldn't have any issues with the extension cord or with the temporary use of a power strip (to enable plugging in two reasonably low power devices).

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  • The only things i’m actually plugging in is going to be a TV and a mini fridge. The rest would be maybe a phone charger, a laptop charger. no lights, no space heaters. i may want a fan but probably not.
    – user282951
    Commented Apr 14, 2021 at 15:02
  • Does this seem dangerous at all?
    – user282951
    Commented Apr 14, 2021 at 15:03
  • 1
    Both a TV and a mini-fridge, @user282951, imply to me that this is a permanent installation and that's not allowed by code. I'm not clear on "I have a shed, 50ft should be long enough" - does that mean the extension cord is bringing power to the shed, or that you have power in the shed, but not enough outlets/where you need them?
    – FreeMan
    Commented Apr 14, 2021 at 15:07
  • there is not power in the shed, and i would probably not be moving the extension cord but these things won’t be on 24/7. The shed is more of like a man cave maybe? This would be bringing power To the shed.
    – user282951
    Commented Apr 14, 2021 at 15:10
  • 2
    "Does this seem dangerous at all?" Yes - the reason extension cords are not allowed for non-temporary installations is because they're not durable enough to take damage and keep working safely. If you're rolling the extension cord up at the end of the day, it's out of harm's way. If you leave it connected so you can use your man-shed whenever you want and your fridge items don't spoil, the cord will get stepped on, rained on, sun-shined-on, chewed on, etc. This is bad.
    – Fredric Shope
    Commented Apr 14, 2021 at 15:22
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12 Gauge.

3 Conductor.

USB devices are so low current I wouldn't worry about them.

You can plug in as many things as you want as long as the total current is below the cord's specification.

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  • I know most of the internet says no to plugging in power strips into extension cords, would I be able to plug a power strip into an extension cord with a 3 conductor(lowes.com/pd/…)? Or should I avoid this still?
    – user282951
    Commented Apr 14, 2021 at 14:40
  • The advice not to do it comes because it is a slippery slope, and electricity is so dangerous that it is advisable to err on the side of caution. So your extension cord will not instantly catch on fire if you plug in a power strip, but doing so enables a condition (plugging in many devices with too much draw) that could cause it to catch on fire. Many people think it is best to simply not create the condition that would allow a problem to occur, then you don't have to worry about guarding against it. But - I agree with Steve - USB devices should be fine.
    – izzy
    Commented Apr 14, 2021 at 15:42
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#12 means 12 AWG wire size. That's a very beefy extension cord and you should be alright for anything that won't trip a 15A breaker (or a 20A breaker for that matter).

You are welcome to unfurl the extension cord for a day or a week to power the shed, but you need to believably plan to coil it up and put it away soon. If you are aiming to bring permanent power out to the shed, a whole bunch of other rules apply and you'll need to do an overhead line, or some pretty deep trenching, or shallow trenching with special/expensive conduit.

A USB hub is nothing by itself. If it has a power supply, then it's considered a DC power supply.

Extension cords are designed to be flexible, and are called cordage.

In-wall or in-ground house wiring is not made to flex, but is made to live inside walls.

When grounding became a thing, they went different ways.

With in-house wiring, ground was required everywhere and their naming treated grounds like an extra -- /2 cable (black, white) became "/2+ground" cable. Once grounds became universal and every cable had ground, they stopped saying the "+ground" part. So /2 has 3 wires (one bare).

Meanwhile, in cordage, groundless cords are still allowed. So groundless /2 (black-white) was still a thing; they needed a separate name for grounded black-white-green. They chose to call the latter /3 (confusing though that may be).

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