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Just wondering, most of all equipment at home have components/circuitry inside to transform high voltage (AC) into lower voltage (mostly DC), also all modern LED lambs. Modern products become more and more efficient and operates at low voltages. Still we have only very high voltage sockets at home.

Also nowadays many manufacturers provide adapters with their consumer products. The amount of adapters is enormous, I think I have at least 40 adapters lying around the house. All of them are near or below 24 volts. For example my laptop adapter output 19 volts.

Would it be more efficient to have a (isolated) 24v AC socket instead of 240v? The transformation is done at the fuse box (what is the name in English, cupboard with energy meter). To step down isolated 24v AC is much easier (requires less components and no transformer i guess) for each product. Or is there any downside doing this? It will reduce the amount of repeating components required for many products, cables, transformers etc.

I know why AC is used instead of DC to transport electricity so that is why I suggest 24v AC. Or do we need a higher voltage?

What could be the reason why we don't have this green environment socket? Any downsides or is there no reason at all?


mess of adapters

Codebeat
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    This question has been asked before. No idea what search terms will bring up the old question thought. – The Photon Apr 29 '19 at 21:46
  • @ThePhoton Okay thanks, on this site? – Codebeat Apr 29 '19 at 21:48
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    Some things need high power, and having a voltage 10x lower means 100x more resistive losses. Some things also need high voltage, and everyone already has high voltage, so imagine how much effort it would be to get them to switch withou some overwhelmingly supported low power socket (*cough* usb) – BeB00 Apr 29 '19 at 21:48
  • Yes, somewhere on this site. – The Photon Apr 29 '19 at 21:49
  • https://electronics.stackexchange.com/questions/420505/why-do-we-use-alternating-current-and-not-direct-current-for-mains-power-plugs-w/420511#420511 – Janka Apr 29 '19 at 21:54
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    Datacenters did efficiency analysis and found that the traditional telecom -48 VDC distribution was _less efficient_ than 240 VAC. The trend is now 380 VDC. – user71659 Apr 29 '19 at 21:56
  • @Janka. Hmm yes, that question is very close, however 24 DC and I think that is not a good idea. – Codebeat Apr 29 '19 at 21:56
  • What DC voltage would you be recommending? I suspect that you'll be replacing all the AC/DC converters with DC/DC converters. – Transistor Apr 29 '19 at 21:58
  • Well, then I repost my answer without the DC part. It's still valid. – Janka Apr 29 '19 at 21:58
  • Because running your toaster oven, blender or vacuum, or even your computer, off 24V requires too much current and house wiring would be too thick. 1500W is 24V@63A. The voltage drop for just a 10 foot run of 8AWG wire at 63A is 79V dwarfing the 24V supply. Even more meagre 500W loads (like a small desktop PC), would need 8AWG to run just 10 foot (no more than 5% voltage drop). – DKNguyen Apr 29 '19 at 22:07
  • Aha, thank you all for the quick answers! – Codebeat Apr 29 '19 at 22:09
  • Copper is expensive, tools and processes and labor to bend, snake, and otherwise install is also vastly more costly. – jonk Apr 29 '19 at 22:09
  • I may be mistaken, but isn't the 120VAC stepdown transformer shared? Not each house has its own? In that case, that would mean each house would needs its own stepdown transformer or the 24VAC public stepdown transformer which already requires unreasonable wires sizes. A public transformer would be so far away you would need even copper bars running to the house. – DKNguyen Apr 29 '19 at 22:13
  • At @all, I don't talk about distribution, distribution is still 240v AC only at the home-installation it is transformed to 24 AC. That is what I mean. – Codebeat Apr 29 '19 at 22:14
  • Ah, well in that case, still unreasonable wire sizes. Just less unreasonable, but still really unreasonable. – DKNguyen Apr 29 '19 at 22:15
  • higher voltage capacitors hold up better for dropouts of the powerline – analogsystemsrf Apr 30 '19 at 02:33

2 Answers2

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The typical voltage loss on the average household cable of 1,5mm² cross section with an average length of 50m (forth and back) from the meter cabinet to your applicance is about 1V per 1A.

  • 1V isn't much for 230V.
  • 1V is much for lower voltages.
  • For lower voltages, you need more current for the same power, so the voltage loss on the cable gets worse.

That's why you want to have 230V at your electrical outlets.

Janka
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The country where I am from (Brazil) uses both 110V and 220V AC 60Hz.

In many projects where high current is necessary (Lighting, projectors, etc), 220V is preferred and can make life a LOT easier by maintaining current draw per "device" under 10A (we have different plugs for 10A, 20A). That also goes for circuit breakers, cable thickness, etc.

So if that is already an issue between 110V and 220V using not even that much power, just imagine the issue if you switch down to even lower voltages.

Added to that, there is the issue of labeling 110V and 220V plugs and devices, so adding a new connector for lower voltages would be another issue. Now compound that with the nightmare that has been (USB 2.0, USB 3.0, USB C, etc - which one do you pick and how long is it gonna last?).

Also, recently in our country we have changed from an older plug to a new one similar to the European and Swiss one. That alone without changing voltages was quite controversial.

So besides a few technical reasons already mentioned by other answers and comments I would say that there are a lot of practical and "popularity" issues with having to implement a new standard for housing voltages/wiring - unless we are at some point that one is clearly a lot better, I don't see how it would be practical to implement it.

Wesley Lee
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  • Particularly power-hungry devices like a clothes dryer or an oven are often wired for 240V even in the US, where otherwise the power is universally 120V. We have different sockets for 240V, though. – Hearth Apr 29 '19 at 22:18
  • Hai, thanks for the nice answer. Yeah, the USB socket hell haha. Not pratical, too expensive, more current, thicker wires, greater loss. I think we have the complete conclusion ;-) – Codebeat Apr 29 '19 at 22:20