> just imagine if a small portion of standard-looking outlets did not output 220V (or whatever standard you have) and say 330V.
We have something like that here in Brazil. On cities which use 127V as the standard voltage (some cities use 220V), you can get 220V by using a pair of phases instead of a phase and the neutral, and it's common to find a few standard-looking sockets which are 220V instead of 127V. They might be colored red, they might have a yellow sticker saying "220V" next to it, or they might be completely unmarked. If your device is 127V only, or it has a manual 127V/220V switch which is on the 127V position, and you plug it into one of these 220V sockets, it will be damaged.
(The standard we use for consumer AC power plugs and sockets, NBR 14136, does not make a distinction between voltages; the same plugs and sockets are used for both 127V and 220V.)
That sounds incredibly error prone and actually quite dangerous! At least a lot of AC to DC converters are universal voltage and frequency, but not all appliances!
In Australia we have only one voltage that will ever come out of a single phase socket, but the standards took the opposite approach with current ratings - the sockets are cleverly designed in terms of their current capacity so (assuming it’s been installed correctly) you can’t make mistakes without illegal and dangerous modifications. In the standard socket, you can have 10 amp, 15 amp or 20 amp, and they all have different sized pins. For the 15 amp plug and socket, the ground pin is larger, so a 15 amp plug cannot fit into a 10 amp socket. A 20 amp plug has all three pins larger, so it doesn’t fit in a 10 amp or 15 amp socket. But a 10 amp plug can still fit and sit snugly in a 15 or 20 amp socket, and a 15 amp can still fit into a 20 amp socket with no problems. It’s pretty clever.
For bigger stuff, or anything three-phase, you then have big industrial circular ones, which I think have a similar system to not let you plug a higher current device into a socket that can’t supply enough current. I believe there are also three phase plugs and sockets both with neutral and without neutral, and if the plug has a neutral pin it doesn’t fit into a socket that doesn’t supply neutral.
> But a 10 amp plug can still fit and sit snugly in a 15 or 20 amp socket, and a 15 amp can still fit into a 20 amp socket with no problems. It’s pretty clever.
That sound dangerous. The larger fuse sized for the 20A socket will not protect the smaller conductors in the cable sized for the 10A plug, they can get overloaded.
The three-phase / industrial CEE plugs and sockets used in the EU are sized for 16A/32A/63A/125A. It's perfectly legal and safe to make a passive adapter that lets you plug a 32A appliance or distribution box into a 16A socket, you just can't load it higher than the 16A fuses on the socket. Going the other way around (16A plug into a 32A socket) you MUST have a circuit breaker in between to provide the required overload protection.
That doesn't make sense though. The fuses aren't to protect the load; they are to protect the circuit. It's up to whatever device you are plugging in to not draw more current than it can handle.
If I have a 3 Watt doohickey, I don't go looking around to find a 0.025A socket, I plug it in to my 15A wall socket and everything works great.
Yeah, the risks mainly come with extension cords, like plugging a bunch of 10A appliances into a single 20A outlet via a 10A rated extension cord with multiple 10A outlets.
Appliances themselves with their own input fuses and captive cables are less risky, although some kind of internal wiring short could still get all melty.
It's true that sizing the plugs that way does prevent you from plugging a 20A appliance into a 10A extension cord, which makes sense.
It's not dangerous in practice. Reading through NEC in the US, there's plenty of leeway for mixing ampacity ratings on circuits, within certain limits. For example, it's fine to have 10x 15A duplex on a 20A circuit. It results in less wiring, and allows for logical grouping of circuits. Electrical code starts from the the most common causes of electrical failures, and tries to design down from there. The ampacity ratings on devices and various components of the circuit are designed to reject the common causes of failure, and conductor failure at the device isn't one of them (appliance manufacturers are more likely to get their devices certified, so if there's a failure in the appliance, some other part of the appliance's electrical system will fail before the conductors do).
So the ampacity of the connector (duplex and plug) is meant to reject certain combinations (plugging a 30amp appliance into a 15amp duplex/circuit). It's obviously very easy to get around that by just wiring things together wrong (18AWG wire on a 30Amp circuit), but by design, a 30amp appliance with the proper plug cannot be plugged into a 15amp outlet.
Of course, this is informed by the electrical code in my home country, so I understand that other places and people have different experiences, but electrical accidents have been on a steady downward trend since the 80's, so the NFPA NEC has to be doing at least some things right.
It is indeed very regional, e.g. the UK has its own thing going on with ring mains and fused plugs.
Over in my 230V corner of the EU, CEE 7/3 sockets are pretty much the only thing I'm aware of for new wiring, with the unearthed CEE 7/1 sockets still present in older installations. Both are rated for 16A, with either 10A/1.5mm² or 16A/2.5mm² branch circuits from the distribution board. It would be unheard of to wire those up with any higher ampacity at risk of overloading the sockets - although recent experience with e.g. EVs has shown that they're not actually suitable for sustained loads at 16A, given e.g. wear and tear on the sockets.
Unearthed appliances do commonly have CEE 7/16 plugs rated for 2.5A, particularly things like wall warts or USB chargers, which does fit into a CEE 7/3 socket.
I recall seeing CEE 7/16 (2.5A europlug) sockets, although those may have been imports from elsewhere in the EU. I suppose those would have the same issues if wired up to the same distribution circuits. But extension cables for those are rarer, the only ones I've ever seen are CEE 7/7 plug (16A) -> CEE 7/16 sockets (2.5A).
For residential/commercial loads over 16A / 3.2kW, it's all CEE / IEC 60309 connectors, and those are treated like distribution circuits with overload protection sized appropriately for the connectors/cables.
"ampacity" means "capacity in amperes" or more literally "ampere capacity." You could say current capacity too but it takes longer. Ampacity is the language used in the electrical code.
"amp" also seems to be more common to write than "A" for electricians. Remember that the SI standardization of unit abbreviations is actually a pretty modern thing, so lots of fields existed before unit abbreviations were standardized and continue to use existing practices.
Nah, it's fine to be nitty. If you glance at my comment again, you'll see my usage devolve from A to amp halfway through, my brain can't help but write what it sounds like to me.
Yes though, ampacity is the correct word (for my home country). "Current" is an instantaneous measurement of current flow. That they use the same unit is pretty convenient for planning circuits.
https://en.wikipedia.org/wiki/Ampacity#:~:text=Ampacity%20is....
> In the standard socket, you can have 10 amp, 15 amp or 20 amp, and they all have different sized pins.
Yeah, Brazilian NBR 14136 does that too. It has 10A and 20A variants, and the only difference is that 20A has slightly larger pins, so it won't fit into a 10A socket. (And the international standard it was based on, IEC 60906-1, has only a 16A variant with an intermediate pin size, so the 10A plug would fit into its socket and its plug would fit into the 20A socket.) Annoyingly, that's the only difference, making it quite hard to tell just by looking whether it's a 10A or 20A plug/socket; you have to try and see if it fits.
Brazil should use outlets to indicate the voltage. With Type A for 127V, the worldwide standard for 120V plugs. Then Type N for 220V, where there is no standard but Type N is pretty good design. Changing outlets is pretty easy to do.
> With Type A for 127V, the worldwide standard for 120V plugs.
That would be going backwards, and losing all the safety features of the new NBR 14136 ("type N") standard; to make it worse, we already did use something like "type A" (with "universal" sockets which accepted both flat and round pins, and sometimes even grounded "type B" together with these two, it was a mess) for both 127V and 220V, so you'd still have (in older buildings) these "type A" plugs being used for 220V.
In my old house (US) there was an outlet that was setup that way. Two phases plus ground on a bog standard looking 120V outlet. Made the discovery when we plugged a 500W work light into it while renovating and it exploded after a few minutes.
That's odd, because in a lot of contexts (hospitals, EMS, etc.), red outlets are used to denote outlets that are connected to battery/UPS, i.e. critical loads, versus the regular, which can be 'sacrificed' in an outage.
We have something like that here in Brazil. On cities which use 127V as the standard voltage (some cities use 220V), you can get 220V by using a pair of phases instead of a phase and the neutral, and it's common to find a few standard-looking sockets which are 220V instead of 127V. They might be colored red, they might have a yellow sticker saying "220V" next to it, or they might be completely unmarked. If your device is 127V only, or it has a manual 127V/220V switch which is on the 127V position, and you plug it into one of these 220V sockets, it will be damaged.
(The standard we use for consumer AC power plugs and sockets, NBR 14136, does not make a distinction between voltages; the same plugs and sockets are used for both 127V and 220V.)