Aside: it is generally considered safer to have the outlets ("receptacles") installed with the ground at the top, but we don't tend to do this in NA because ground at the bottom makes it look like a little face and humans like faces.
Edit: Adding link to EETimes: https://www.eetimes.com/document.asp?doc_id=1272972#
I'm not sure there's any basis for this. See this article for example:
https://www.archtoolbox.com/materials-systems/electrical/gro...
The real reason why this was done historically was perhaps due to this:
> Back in those days, there were very few plastic faceplates on AC receptacles and switches. They were almost all made of metal. All that holds a faceplate in position is one short screw for an AC receptacle. If the screw loosens and falls out, the faceplate will drop down and short out the two power prongs on anything that is plugged into that outlet. Such accidents used to be commonplace which is why power receptacles were put in upside down.
With plastic faceplates it no longer applies. Which is why most newer medical facilities have them in regularly facing. It was done for a reason, but people forgot what that reason is, then myth turned into legend and people kept doing it cargo cult style without knowing why it started ("safer" requires an explanation). The whole "drop a metal tool" justification was likely a rationalization to a practice people didn't understand, but doesn't actually make sense.
That all being said, it isn't less safe to put them "upside down." It just might interfere with some consumer electronics that assume a certain orientation (like those plugged in perfume bottles, smart home sensors, or similar).
Also, in many houses you'll see the outlets oriented both ways in living and bedrooms, and there's a reason for this: what you'll see is all the outlets oriented one way (usually with the "face" right-side up), except for one outlet, which is upside-down. That outlet is the one that's controlled by a wall switch, so you're supposed to plug a floor lamp into it, which can then be switched on with the wall switch when you enter the room. Inverting that one outlet makes it much easier to see which outlet you're supposed to use.
It requires the flat conductive sheet to somehow re-orientate itself in the air from horizontal to completely vertical in the two feet between your desk and the top of the plug (unlikely).
If this is a problem you regularly encounter, this hack isn't the safe solution, the safe solution is an Recessed outlet/Outlet Cover. That way the metal sheets that assault your outlets cannot hit any of the pins, and you aren't relying on luck for how it will fall/rest after it contacts the ground pin.
Most people aren't suffering this issue, so a solution isn't needed.
It is all about risk mitigation. When building for long term use and safety, scenarios like a short from something falling are designed away.
Think super cheap insurance. And liability management. People can perform to code and that compartmentalizes damages and responsibilities. Couple that with licenses and it's all public safety oriented.
All of it adds up.
Where risk is higher, say in the parent example, yes. By all means use a product intended to manage those risks.
Costs are marginal otherwise, might as well take the cheap insurance.
Then you'd want to install Recessed outlets, Outlet Covers, or GFCI Outlets. Since they're designed to be safer, this simply relies on luck that the conductive object bounces off of the neutral pin and away (which may not occur).
Plus the cost isn't free as has been discussed in this thread elsewhere. It breaks a lot of consumer electronics.
Yes, recessed or covered receptacles would be a better option, for some values of better. I mean, most people wouldn't accept covered receptacles in their living space because they are "ugly" and would prevent many pieces of furniture from being placed in front of the receptacles (which by code are spaced every 12 feet at the most). And recessed receptacles are going to be a tight fit in most existing residential boxes. Forget smart devices fitting recessed, it's hard enough to fit those into regular boxes once you add some wire nuts back there...
So, yes, there may be some more effective options, but installing devices ground-up reduces a not uncommon hazard without resorting to changing out boxes or adding covers to everything.
Sometimes the effort required is crazy, but given that effort, the stuff actually does go in there.
Did someone do the math on all that, or was it more empirical, or?
Anyone know?
There are wire fill factors in the NEC - basically if you have a junction of a conductor of this size (gauge) then it must have this many cubic inches to go with it.
The simplest outlet (a receptacle) would have 2 conductors (hot and neutral) and those each require a certain number of cubic inches based on their size (12AWG and 14AWG being the most common). The cubic inches of a box are typically stamped on the box and the amount of conductors ('wire fill') must be below the box capacity. Ground doesn't (didn't?) count in the calculation as it shouldn't carry current normally so it's not a conductor.
If you've worked in a box at or near capacity (especially with a AFCI or GFCI/RCD) you will always put in a larger box given the chance.
It's not that this happens to any one person a lot, it's that with billions of receptacles in use throughout just our country alone (tens of billions? Just a WAG), it collectively happens kind of a lot. I've only experienced it once in my life.
I'm also just a home gamer, though I have done my research via reading relevant parts of the code for wiring and passing inspection on my kitchen remodel including adding circuits, pigtailing my aluminum wired house, etc... It was somewhere in there I came across the "safer, it's code in hospitals" idea. Though my memory is that the hospitals I've seen all had metal faceplates, but that's just from memory.
Good counterpoint.
Every person who comes over that knows anything about electrical stuff instantly says 'your plugs are upside down'...and then I have to explain to them how/why it works :)
The inspector had no issue with it though, thankfully! In health/saftey critical installs (like hospitals), the ground MUST be on top, according to our local code. It's optional for residential.
Have you run into any appliances or devices that are "optimized" for a ground-down configuration?
Aside: One regret I have in my kitchen remodel is not replacing all the boxes with dual gang.
So, the article offers an explanation of why it's really useful to ground one of the two AC wires in the first place: AC generated by the power company may not be the only source of electrical charge on the wires. I must admit, that was not something I thought about before.