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Comment by Lammy | Hacker News Reader

I built one of these to use a surplus APC power distribution unit (basically a really tall power strip with an ethernet port for monitoring) at my house, because the PDU has a molded 30 amp 120V locking plug that I didn’t want to cut off. There’s no 240V or three-phase plugs on the thing, and I’m not running any more or any different equipment than if I used a more traditional cheap power strip. It’s really nice to be able to have a tall sturdy PDU running up the back of my rack instead of that, though!

My adapter is obviously out of spec and I wouldn’t leave such a thing behind for an unsuspecting future tenant to find, but I don’t think there’s anything wrong with it in my particular situation. I love Rachel’s posts but I wish they didn’t have this pervasive air of looking down on the stupid people who did the horrible-thing-of-the-week :/

e: the PDU and plug in question: http://i.imgur.com/sUOzquZ.jpeg

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> I love Rachel’s posts but I wish they didn’t have this pervasive air of looking down on the stupid people who did the horrible-thing-of-the-week

I generally agree, but some things are over the line, and a fire hazard feels like a good case.

It's minimally a fire hazard and it's very handy to have when you know what you're doing.

But it ended up in the hands of someone who didn't. That really makes it a much bigger problem.

"This is OK if used by persons in the know" is not helping: Rachel wasn't/isn't in the know. So clearly, people without the proper knowledge can get their hands on this cable.

So certain are you?

I knew it was probably trouble just from a glance. Knowing this topic would bring out every single nitpicker, I did the actual research to be doubly-sure before writing the post.

You might be surprised how much extra shit goes into my posts just to avoid the inevitable backlash. It's not good enough to have a reasonable amount of knowledge. You have to go well beyond into the arcane to avoid the sniping from this crew.

And even then, well, THE ONE shows up time and again.

Is Beldin really nitpicking you?

The way I read Beldin's comment was that it essentially agrees with your post. And HN's guidelines say:

>Please respond to the strongest plausible interpretation of what someone says, not a weaker one that's easier to criticize. Assume good faith.

I also didn’t read that comment as nitpicking. It wasn’t doubting the author knowledge about the criticism, it was mentioning that the author was not aware of the reason of why that was made, was able to have access to it and could have used improperly if she didn’t know any better. But she did.

It is like someone else commented, there are reasonable, ocasional use cases for this that are safe, but the cable should be locked somewhere with the name of the person that knows why it was built in it; so it’s not out in the wild for abuse.

That’s only my perception of course.

I think what they meant was that someone left that thing lying around somewhere where random people would find it with no context. You had no clue what it was but took a second to think about it. The next person might just have used it because it seems to fit.

I meant to argue you were right for calling this out.

Perhaps you replied to the wrong person? The parent poster is agreeing with you.

> And even then, well, THE ONE shows up time and again.

I know this is your preferred response to all criticism, but the thing is, to the rest of us you're THE ONE. You swoop in to point out how terrible stuff is, explain how stupid your coworkers are for making it, talk about How It Should've Been Done, and move on to the next project.

I would go so far as to say that what you're doing with it is a relatively legitimate use of it, and plugging a machine that demands a higher amperage is unlikely to cause a problem because anything with a standard plug ending is likely to be circuit broken to the correct amperage. The scary device is the inverse of this device.

The inverse - 20 A plug to 15 A socket - would be perfectly fine and conform to code, you couldn't possibly pull an overcurrent that the breaker might fail to detect.

What's really scary is that in many commercial buildings you have combined 5-15/5-20 sockets (this sort:https://en.wikipedia.org/wiki/NEMA_connector#/media/File:Ele...) for circuits fused to 20 A. If you had rigged your locking to non-locking adapter with a 5-20 plug you'd again be fully code-compliant.

Look at the background of two photos! The shelving would indicate the offensive thing was found in a datacenter, it must have been a semipermanent hack, not something that someone might use in their office with the door locked and curtains drawn to set up equipment and otherwise keeps in a locked drawer.

I would have said that the inverse is scary because of overvoltage concerns.

They are both NEMA 5 series, rated for 125 V, so voltage isn't the concern here.

i think the problem is that in general, you can't assume that you'll be the only/last person to use that device, and you can't assume that the next person will understand the context in the way you do. I mean if you're doing it in your home, it's still kind of dodgy, but in a professional setting something like this definitely has no place, temporary or otherwise.

Like the conversations you have with yourself in the shower, for some people blogging is a chance to win an argument you already lost elsewhere. (Or at least one you wish you didn’t have to keep having every few years, which feels a bit like losing)

Rachel happened upon this cable, was curious enough to look into the details behind it and found this out.

Not everybody would look into details. Quite possibly, most wouldn't. I wouldn't, probably. If i happened upon this type of socket that needed powering and found this cable, I'd use it.

Maybe you're hoping that the company only allows people fully in the know near that equipment. That would prevent the problem... but how did Rachel then get her hands on the cable?

That cable doesn't bother me at all. What I find alarming is that it doesn't have a bright laminated warning label affixed to it in a _very_ permanent manner.

On the plus side, as long as the electricians who wired the place up were competent the risk of any harm resulting from ignorance is almost nonexistent. Circuit breakers are quite good at what they do and wiring generally has very wide safety margins.

Edit: On further thought, there is an issue here. Regardless of the breaker, that plug (the 5-15P) and associated receptacle are unlikely to be rated for 20 amps of sustained current. In that case, the breaker might not be able to prevent you from melting something or starting a fire.

That PDU is going to have a circuit breaker in it which is set for 30A.

You've essentially bypassed the circuit breaker on the PDU and are entirely relying on the circuit breaker in the panel to protect you from fire.

It's a choice, though not one that I would make in a residence.

Yeah, the breaker in the panel that’s going to trip at half the rated load of the PDU itself? I don’t see a problem here, as long as you’re making sure to stay under the constant load rating of the panel’s breaker.

Sure, a 15A breaker isn’t going to trip at exactly 15 amps because inrush current and all that - but this is no different from using a dumb, unprotected PDU.

> this is no different from using a dumb, unprotected PDU

I would caution that depending on exactly what electrical components are inside the PDU, under certain conditions (say, on plugging it in) it might briefly draw much more current than you would naively expect. (Based on the picture they posted though I doubt that's the case. It looks fairly "dumb" to me.)

For example, "I'll plug this UPS rated at 50 amps into a 20 amp circuit. It's fine because I'm only attaching 10 amps worth of equipment to it!" is unlikely to go well depending on (among other things) the rate at which the batteries charge.

Briefly drawing more power would not really be an issue. Circuit breakers don’t operate as binary devices in the sense that a 15A breaker works indefinitely at 14,999mA and then turns off at 15,000mA. They usually use a bimetallic strip to provide a gradual response (more current = more heat = faster trip) with an electromagnet actuated trip that creates an absolute limit.

See, for example, this PDF: https://download.schneider-electric.com/files?p_enDocType=Da...

Even at double the rated current you’re looking somewhere around 30-90 seconds before it trips.

If this weren’t the case, we’d be tripping breakers every time we fired up a stand mixer or a vacuum cleaner.

Yep, this is a totally dumb one. It is actually labeled "24 amps max, 20 amps max per outlet, 20 amps max per bank", hence the NEMA L5-30P so it can try to make sure that guarantee means something: https://download.schneider-electric.com/files?p_enDocType=CA...

The "banks" are just one half each of the total outlets. The PDU's lil segment display flashes between the integer-rounded Bank 1 load, Bank 2 load, and Banks 1+2 load, and the same data is available with more precision through the serial or Ethernet ports. I have my beefy workstation and NAS on the bottom bank and all my network gear on the upper bank, so right now my PDU is flashing between "3", "0", and "4" amps respectively (rounded): https://i.imgur.com/o50UJoO.jpg

Honestly I'd be more worried about fire hazard if I used an equivalent “legit” setup with three power strips and three Kill-A-Watts.

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