Electrical question

[Marcel Birgelen]

I recently encountered a C14 PDU that had an internal locking mechanism with small release buttons for each C13 connector. I tried to pull the cord with normal force and it wouldn't budge. I liked that solution more than those locks that often come in the form of a metal clamp. I also dislike any solution involving tie-wraps, as it prevents you from unplugging the thing in case of an emergency.

I was mostly targeting Scott since he is in the USA and would have to contend with unknown voltages and less familiar IEC versions. I've seen Schuko power strips where the receptacles are in a zig-zag formation to get a greater density.

Those zig-zag layouts only work well if you only have "straight' plugs, not those with the cable at a 90 degrees of the plug. Also, there is this common "pest" nowadays, of many smaller appliances having their PSUs and power connector integrated. While this may work fine in low-density configuration, it's often a nuisance in many professional installs.

[Steve Guttag]

There is no locking IEC standard. QSC's DPA-Q and CX-Q amplifiers have locking IEC cords...they work because the same manufacturer is used for the IEC connector and the cord. BTX has some locking power cords but all it is going to do is provide some friction and not really a lock.

[Scott Norwood]

There is a locking C13 connector that has a little tab at the top that is supposed to snap into the PDU. It doesn't seem to work all that well, and it also doesn't seem to be very widely implemented. Good point about the unknown voltage--it's not really a problem with computers, since anything modern will run on 120-240 and is auto-switching, but it could definitely be a problem with table lamps and appliances. Do 220-240 volt light bulbs even exist for sale in the US?

[Steve Guttag]

I was mostly targeting Scott since he is in the USA and would have to contend with unknown voltages and less familiar IEC versions. I've seen Schuko power strips where the receptacles are in a zig-zag formation to get a greater density.

[Marcel Birgelen]

I like the Schuko plug style the best, myself, as far as safety and supporting the connector, but I like our NEMA types for specifying voltage and maximum amperage over the others. I do wish we had NEMA X-40 and Lx-40 versions (why the jump from 30 to 50A?).

In general, the Schuko plugs and receptacles are pretty safe and I do like them for general household and office purposes. The receptacles usually hold the plug pretty firm, but not so firm it's impossible to unplug, which I also find important.

Schuko has its shortcomings in high-density setups, like 19" racks, where it takes up considerably more space than C13/C14. Around here, the voltage on a C13 isn't so much of a problem, as everything on a single phase simply runs on 230V, my biggest problem with the C13 design is the lack of standardized retaining mechanism. Your average Schuko plug won't dislodge if you work on some equipment, but you only need to wiggle a C13/C14 plug a bit to get a bad connection.

I didn't need to look up the C15 plug, because I know that's the one with the notch, I have been frustrated by those connectors more than once... The only difference is the higher temperature rating, the power rating is the same...

[Steve Guttag]

Frank, the breaker protects the wire, not the receptacle. You'll find that the 15 and 20 receptacles can carry the same current so there isn't a safety hazard there. Over the counter circuits in kitchens are indeed to be 20A but that does not require 20A receptacles since one could have 5 things plugged into 5 different receptacles. None of them may add up to 20A. The argument for 20A receptacles is that if you did have a 20A appliance, then you couldn't plug it in...however, if you did, that would be the only thing, likely, that could run without tripping the breaker.

I have a requirement on my kitchen installs (well the one I have)...all over the counter receptacles are to be their own GFCI and they may not be stringed off of one. While slightly more costly (since each one is its own GFCI, it prevents nuisance trips when multiple appliances are plugged in. Mine never trip. I do have ONE receptacle that is powered off its neighbor GFCI but it is also the USB power supply for various phones and such but I made the exception there!

It is amazing how much more expensive 20A receptacles are than 15A...I'm sure it is all based on unit sales. 15A receptacles probably sell at 100:1 of 20A...possibly more.

[Frank Cox]

1. With regard to a 20A circuit feeding 15A receptacles, wouldn't that be unsafe since you could in theory plug two 10A devices into the 15A receptacle and not trip the breaker since you haven't exceeded the 20A circuit capacity but you've definitely exceeded the range of the 15A receptacle. ?
2. When the electrician rewired my kitchen about ten years ago he installed 20A circuits and receptacles for everything around the counter. He said that everyone wants to plug in toaster ovens and stuff now so it's standard to use 20A circuits in kitchens now. Couldn't prove that by me one way or the other, but that's what he told me.

[Steve Guttag]

Straight blade 15A and 20A receptacles are often used in branch circuits whereby they are normally not all filled. There is also the exception that a 20A branch circuit can feed 15A receptacles. Twist Lock circuits are almost always dedicated (one breaker per receptacle) so the breaker is the over-current protection as well. One wouldn't want a 20A device plugged into a 30A circuit.

In the lower Amperage (15A), you can get those in locking duplex too and set them up as branch circuits. But, if you have a device that needs a 20A twist lock plug, you are essentially saying, it is going to need more than 15A and therefore it gets its own circuit.

In a residential situation, rarely do you see 20A receptacles as there are very few places where more than 15A needs to be planned for. Obvious areas are the clothes dryer...which is is more than 20A and you can't plug your 15A plug in there...and the oven...where again, it is more than 20A and you can't plug your 15A plug into either. The only place that comes to mind where residential calls for a 20A receptacle is by the washing machine. That is a "designated" receptacle that has its own 20A service to ensure it can handle both a washing machine and a gas fired clothes dryer.

USB-C is light years better than micro-USB, in terms of how well it stays in. Mini-USB is too easy to break the connector.

[Scott Norwood]

The annoying thing about current USA twist-lock electrical connectors is that we can't plug a 20-amp connector into a 30-amp socket. They have to match exactly. Whereas a 20-amp Edison socket is designed to accept 15-amp plugs.

I'm not sure I see the problem with locking connectors in general. I tend to see non-locking connectors as having a design flaw in need of fixing. USB-C (not really an electrical connector) is particularly annoying in this regard.

[Marcel Birgelen]

Yep, Stab-Loc was the FPE trademark. Your friend was lucky they actually tripped, and many of them don't. That large spark from within was due to the Stab-Loc buss bar design, which always made very poor contact. That led to heating and arcing, which melted the back insulator and as soon as you put any pressure on a breaker, like trying to reset it, it would ground out to the can resulting in a big bang.

Apparently, they did still trip, though not all of them for any apparent reason... Looking at that picture of that failed panel gives me the shivers. I can see how such a bus-bar design can lead to increasingly oxidized contacts and therefore more heat, more damage and more arcing.

It's nothing special to see a small spark emitted behind a breaker bearing some load when being switched on, but in his case, it clearly was a case of bad arcing, obviously destroying the thing a bit more, every time it's being switched.

[Steve Guttag]

Scott,

Twist locks, which we do have an there are NEMA specs for them will never fly for consumer where "locking connectors" aren't used for much of anything...right down to HDMI and RCA connectors instead of BNC.

The biggest beef with the US style plugs are the ways one can get a shock by holding them wrong but other than that, I'll take them over other flavors, particularly IEC. Tell me, what is the current rating of the typical IEC connector, say a C13 (don't look it up or I'll then ask how it differs from a C15?) What is the voltage on a C13?

I like the Schuko plug style the best, myself, as far as safety and supporting the connector, but I like our NEMA types for specifying voltage and maximum amperage over the others. I do wish we had NEMA X-40 and Lx-40 versions (why the jump from 30 to 50A?).

[Scott Norwood]

One thing that I've seen a number of times and which is actually dangerous is power strips or extension cords where the plug can be inserted upside down, with the ground pin not connected to anything. This also interchanges the hot and neutral connectors (not normally a problem). I'm pretty sure that these designs don't get UL approval, and it is mostly older devices, anyway, but they are still pretty nasty safety hazards that could have easily been fixed in the design stage.

And, though I know that it will never happen, the US-standard Edison connector (NEMA 5-15P) is a really terrible design for many reasons. We should have gone to twist-locks or something like the UK standard power connector decades ago. Or even just IEC connectors for outlets.

[Tony Bandiera Jr]

Hey, it could be worse...Federal Pacific. Where the equipment that is plugged in is there to protect the breaker!

Gag, FPE or as I like to call it, Fire Prone Equipment. I have had more than one of those pieces of melt down or explode in my face. Those, and their counterpart, Zinsco.

GE recently split itself into three independent divisions... I've never really associated GE with quality. I've had to deal with GE HealthCare "engineers" and their products, which caused sufficient frustrations over the years I had to deal with them. Still, you'd expect a GE-branded product to be better designed than any random product you can buy from AliExpress.

GE appliances and other household goods used to be of decent quality, but their electrical controls/panels/transformers/breakers were all over the map. The breakers as mentioned are shit, the panels not too bad in construction, the transformers were noisy and ran hotter than the competitors, and their controls (motor starters, etc.) were again all over the map, from quite good to horrid.

Those are the guys behind the infamous Stab-Lock(?) breakers, aren't they? A good friend of mine still had them in his home in New Jersey. I only glanced at them in horror... Some of them regularly tripped and while switching them back on, a huge spark would emit from somewhere behind the panel... I wouldn't even dare to touch those with a 10ft. pole.

Yep, Stab-Loc was the FPE trademark. Your friend was lucky they actually tripped, and many of them don't. That large spark from within was due to the Stab-Loc buss bar design, which always made very poor contact. That led to heating and arcing, which melted the back insulator and as soon as you put any pressure on a breaker, like trying to reset it, it would ground out to the can resulting in a big bang.

FPE had a huge problem with defective molded case breakers (like in main power switchgear) where they would fail internally and start arcing merrily away. FPE's "solution" to this problem? They sent out warning stickers to all known users telling them to not try to open (turn off) or reset an arcing breaker.

Here is a typical failure of an FPE Stab-Loc panel: unnamed.jpg

[Marcel Birgelen]

GE recently split itself into three independent divisions... I've never really associated GE with quality. I've had to deal with GE HealthCare "engineers" and their products, which caused sufficient frustrations over the years I had to deal with them. Still, you'd expect a GE-branded product to be better designed than any random product you can buy from AliExpress.

Hey, it could be worse...Federal Pacific. Where the equipment that is plugged in is there to protect the breaker!

Those are the guys behind the infamous Stab-Lock(?) breakers, aren't they? A good friend of mine still had them in his home in New Jersey. I only glanced at them in horror... Some of them regularly tripped and while switching them back on, a huge spark would emit from somewhere behind the panel... I wouldn't even dare to touch those with a 10ft. pole.

[Steve Guttag]

Hey, it could be worse...Federal Pacific. Where the equipment that is plugged in is there to protect the breaker!