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Discussion Starter · #1 ·
In another thread, I walked around and started counting ... this was a mistake, as long ago, our family of four had moved from a "duplex" plug arrangement to a "power strip" arrangement (6 being better than 2, in most cases). Wall-warts far exceeded devices with just a straight two- or three-prong plug.

The good news is that, during the abandonment of the duplex in favor of the 6-plex or more, we utilized SPD versions everywere. Thus, anything plugged into them gets a bit of surge protection at the end of the circuit; a load center SPD is also in place.

The bad news is that most everything plugged into these power strips/6-plex's are wall-warts, with an electronic device behind that. I won't get into the THD being created by these things, as by their nature they only clip some power from what goes by; I believe this is a function of the standards of some years back which only stated they have to eat bad power, not release clean power after eating bad.

Instead, I was looking to understand more of their characteristics, and why they might possibly die. Some short answers:

  • they are always on, if you plug them in and have not planned for a way to turn them off without "unplugging them".
  • cheap ones (excuse me, "inexpensive" ones) have a collection of low-end capacitors, and these have a short life of a few thousand hours
  • due to potting materials and sealed construction methods, you won't easily be opening them up for inspection/repair.
  • there might not be a wall-wart, but most surely there is a SMPS power board or equivalent inside; unknown if this is also "always on", but most likely is, if you have an LED that is green/red, or it has a remote, etc.

Being as they are always on, that equates to at least two years. So, these things go out on you, at the two-year mark or higher, depending on how you use them. If you leave them plugged in all the time ... you get a shorter life span, and this would also equate to "phantom load". I have not yet been successful in finding out if SMPS folks have solved the phantom load problem or hit the mark of releasing clean power.

Some of my power strips are actual SPD power strips, and all have some form of on/off switches. While I do my best to turn them off at the power strip level (off at bedtime, on in the morning), the rest of the family expects them to be on all the time, and won't assist with such on/off hassles. Again, most wall-warts are staying on, and drawing some amount of load all the time. I can only guess at the rest of the world ...

I have had a few wall-warts die on me, and can't really tell if they died due to old-age, surges, or anything else. I recycle everything (and anything electronic), so I've opened up (after quite a struggle) all wall-warts that have died. Remind me to vote for "right to repair", which might also mean "able to recycle". Sure enough, a collection of various electronic parts, including a bunch of caps.

Luckily, wall-warts remain relatively cheap ... I mean, inexpensive ... if one dies, try to get a better one. While you are at it, try to get SPD-type power strips, with on/off & such.

And, mark the device name on the wall-wart (we use a gold "sharpie" pen), as once separated, they tend to remain separated ... some have little to no markings, and very few have ever had the device name on it.

Still digging into SMPS's ... what a story ...
 

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One one of my houses I installed a green switch by the front door to rid myself of phantom loads and even I could not believe the power savings I got; about half what I had before.

it saved a lot of worrying too as then I would often travel out of state. In going out the door I would flip the switch and then take a picture of it off. Then if the wife asked, “did I leave the stove on” there it was in a picture, the stove, well pump and other devices were all shut off and I had a picture of it.

I did wire that house with 12 instead of 14 gauge wire which some power savings should be attributed too.
 

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I have had a few wall-warts die on me, and can't really tell if they died due to old-age, surges, or anything else.
Yes, I have had a few die on me too. This one is very old, but I think it is more of a quality issue than age. I have had to replace bulging capacitors in many items and it seems that they are always some brand that I don't recognize. The bulging capacitor below (1000uf 25v) is a Gloria brand. I prefer to use well known brands such as Nichicon, Panasonic, etc.
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Electrolytic capacitors have a limited life span, ussually 10-15 years, especially power filtering caps. While they are rated for thousands of hours that would equate to decades, real world that doesn't happen. Temperature, humidity, application, build quality, and circuit design parameters if poor will shorten the life of them.

Power caps on my valve amp were starting to dry out, letting 120hz buzzing come through the speakers. Right around 16yrs old. Amp was heavily gigged with during that time. ~$45 in Nichicon caps later the amp is quiet again at idle.

Those tiny wall warts are so cheap that its cheaper to replace them with another. Good to take them apart and learn about their operation though!
 

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I have had multiple wall warts and SMPS fail on me through the years, from USB wall warts to computer, server, and network equipment SMPS. Most failed simply because of age and from being powered 24x7.

But I can especially relate to wall warts that are on the really low-end/cheaply-made side of the spectrum. I have a about 18 Wyze Cams (CCTVs) which have had five (5) USB 5V wall warts fail on me. Tearing down some of them (which practically destroys it) indicates that the capacitors have failed (bloating and/or leaking).

I also have a bunch of IoTs that are always receiving power... Zigbee hubs, smart plugs, switches, bulbs, Alexa, Google, cameras, STBs, etc. Not to mention UPSs, servers, network switches and WiFi, among others. I'm sure they cost me some on parasitic draw but that's just the cost of convenience.
 

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Discussion Starter · #6 · (Edited)
Given that (inexpensive, wall-wart) SMPS devices can cause THD, and well-designed (expensive, power brick) SMPS devices hopefully reduce THD, we should be able to approximate what's happening in a house as follows:

1. Count the number of wall-warts and power bricks throughout the house.

2. the ratio of small devices to large, and/or the ratio of inexpensive to expensive gives you a quick percentage value of probable THD present on your wiring.

In my case, I have about a 75% ratio of small/cheap to large/expensive SMPS devices, that are plugged into the house's mains AC wiring. Thus, I have a THD problem of 3, on a scale of 1 to 4, where:

1 = "not worth my time"
2 = "think about doing something"
3 = "do something, anything"
4 = "oh, sh&t"

A power source (grid or gen) does add a factor of THD to a home, but mainly it "enables" THD to start happening inside a home, to the degree that you leave these things plugged into mains or switched on (if you have a means of switching them off).

As I'm at a 3, I've placed SPD power strips at strategic locations, and they have on/off at the individual plug level ... the wall-warts are thus grouped, and each has an on/off.

I've begun turning off the ones where I don't use the device constantly (for example, a short-wave radio). Overall, this is reducing my ratio of THD, from 3 to possibly 2.

There's an additional bonus of saving power, if the SMPS constantly eats some amount of power, even if the device behind it isn't "on".

Hope this helps ...
 

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Given that (inexpensive, wall-wart) SMPS devices can cause THD, and well-designed (expensive, power brick) SMPS devices hopefully reduce THD....
I think it's more accurate to say that any non-linear load (which is what SMPSs are) will introduce harmonics... some more than others. I don't think that any particularly expensive or even over-engineered SMPS can "lower" THD. All it can do is reduce its own emissions but whatever harmonics is already on the AC line, it still adds to it, albeit, to a smaller extent compared to an inferior design.
 

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Discussion Starter · #8 ·
That is exactly what I meant, and thanks for the clarification ...

Larger SMPS blocks hopefully have corrective circuitry to produce less THD than the others. I was shooting for a quick way to tell at a glance how bad the issue is. A quick count of such power blocks in your home, a quick comparison of small (cheap) ones to large (expensive) ones, and you could tell if you're at a 1 or a 4.

I'm also trying to figure out how the "THD police" (your grid utility) will get involved, if one is hooked up to the grid with a huge load of non-linear devices.

To a lesser degree, and the THD police would still get involved, what would the effect be of a neighbor with:
- a grow operation in his basement (lots of ballasts, etc.)
- a bitcoin operation
or similar, on your's or another downstream neighbor's home.

Another thread for some other day ...
 

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I think that the utility is resilient enough to tolerate most harmonics that are typical of those coming out of residential homes.

But if you're producing dangerous levels of THD for whatever reason, I'd like to think that you'll be the first one to know. You (or your neighbors) will see a spike in failing or malfunctioning loads. You (or a neighbor) will initially attribute this issue to the power supply (utility) but then after they get involved and starts poking around with PQ meters, they'll eventually find out the root cause and put you under notice to fix your equipment so the THD gets back down to safe levels.

At an industrial or commercial level, a solution to this is to use active harmonic filters, especially if you have loads such as VFDs. But in a home/residential setting and just to correct a high-impedance, non-inverter generator, it's not going to be any more cost-effective than just using an inverter generator in the first place.
 
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👆 Exactly.

The typical residential customer is not going to throw significant harmonic distortion back onto the grid. A wall wart, for example, is simply not going to be able to jerk the grid around due to the grid's low impedance. Industrial & commercial customers can throw significant harmonic distortion back onto the grid with large non-linear loads. This can get them into trouble with the grid operator. Throwing distortion back onto the grid would most likely be noticed by the nearby neighbors (industrial/commercial or residential) before other customers farther away on the grid. This is due to the point of common coupling.

Eaton has a ton of information about harmonics mostly geared towards the industrial/commercial customer here:
 

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Here's a very good demonstration of an active harmonic filter in action. It was able to correct a THD of 37% down to just 3% with a flick of a switch.

 

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Discussion Starter · #12 · (Edited)
Not sure it's that simple, as I've noted earlier ... what EE's do at the commercial/industrial level isn't really available to us at the home level. We can't go to BestBuy.com and get an AHF.

What I'm shooting for with the calcs up near the OP is a simple estimation of the problem caused by non-linear loads in the home. Only if one "knows" that there is a problem, and can estimate it, might one want to do something about it.

l've researched a new calc for the PC's in your home. If you have 4 pc's/laptops, add 0.5% THDv for each one. That's 2% THDv running around in your house wiring, when those are powered on, or their power blocks left plugged in. That's interesting, and starting to be real numbers, and is only a fraction of what you have in your home. Now add this 2% to the supposed 3% of the grid ... you are at 5%, and we've only just started.

It's not "one wall-wart", it's dozens on up to a hundred or so of these SMPS's, as these are in every single electronics device you have, and they are in every home of yours and all your neighbors. That's real THD in your home (a problem for you) and going back out on the grid (from each neighbor, and a problem for all), and I believe the grids are aware of the issue. There is no "easy" button for this ...
 

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Discussion Starter · #13 ·
A question for everyone, to relate this back to "generators".

On the supply side, we are getting 3% THD from the grid, and many of us are doing something with inverter-gen's to try to get that same 3% value. That's a good thing, and you've done it ... on the supply side only.

But that's not what's happening in your house, as now there is the "use" side of the equation. Every time you flip things on, THD levels build up.

If THD is bad coming from the supply, wouldn't it be bad on the use-side as well?

If we care enough to do something about the supply-side, do we care enough to do something about the use-side?
 

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so isolator outlets and iso filters for every item?
Tripplet made one back in the day (1980's) that worked well for video items.
we used them on the 18 foot tv projectors.
the noise hash was horrible until you used one on the video screen.
that LC tank thing.
they make iso bar's these days. do they work?
that is the question.
 
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