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I got a USB wall socket fitted. When it was installed, I tested the USB port with a tester with the switches off, but the USB outlet was live. Is this normal?

manassehkatz-Moving 2 Codidact
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sean kelly
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    Hello, and welcome to Home Improvement. It's hard to understand your question; would you edit it to clarify? (Some punctuation would be great...) – Daniel Griscom Apr 09 '19 at 15:03
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    Could you please provide the actual switch/outlet you used. – Ben Apr 09 '19 at 16:34
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    This can only be a UK question. – Harper - Reinstate Monica Apr 10 '19 at 00:39
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    @Harper How can you be so sure? From what I can tell, "outlet" is quite an unusual word in the UK. – Omar and Lorraine Apr 10 '19 at 08:11
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    @Wilson While that's true, switches are [mostly] a UKism. Still, it wouldn't hurt for the OP to provide the important details, as there are a boatload of countries and socket types in existence. – Lightness Races in Orbit Apr 10 '19 at 16:17
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    @LightnessRacesinOrbit ...You have never encountered an American "light switch," which often actually control a power outlet? O_o I can assure you that I have had switches in my home my entire life and called them such. – jpmc26 Apr 10 '19 at 17:46
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    @LightnessRacesinOrbit , Americans do use the word "switch" for the plastic rectangle on the wall which is used to turn outlets or lights on or off. Usually, the important part is a plastic lever of various shapes with the insides safely hidden. Sometimes, a slider. Rarely, a button or two on old models. – Christopher Hostage Apr 10 '19 at 18:07
  • @LightnessRacesinOrbit 'Switch' is used all over the world. – user207421 Apr 10 '19 at 19:35
  • @LightnessRacesinOrbit "switches are [mostly] a UKism" Meaning they're called something else outside the UK? As an American, I can't imagine what other word to use than "switches" ... – DarthFennec Apr 10 '19 at 20:02
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    I'm surprised a question with so little background information has 12 upvotes already! – Bort Apr 10 '19 at 20:02
  • @DarthFennec Meaning (as far as I know) they are not generally offered in other nations. But I could be wrong! – Lightness Races in Orbit Apr 10 '19 at 23:41
  • @user207421 The word, yes. The feature? – Lightness Races in Orbit Apr 10 '19 at 23:42
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    @LightnessRacesinOrbit Ah, after looking at the answers I realize I misunderstood. There are switches built into the outlets themselves, I'd never seen that before. I was thinking about "lightswitches" elsewhere on the wall that are connected to specific outlets, which we have (and I think those make more sense, personally). We also have individual circuit breakers built into some outlets, which can technically be used as switches, though that's not their actual purpose. – DarthFennec Apr 10 '19 at 23:58

2 Answers2

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In the US, no the USB ports will not have power when the outlet is not powered. Most outlets in the US don't have power switches on them, so if you switch them off there is no way for power to be provided.
US typical USB outlet

In the UK, outlets often have power switches. In that case, your USB ports are usually powered while the outlet switches are off. This is because the outlet assembly itself is always powered, but the switches only control the outlet and not the USB power transformer.

    UK typical USB outlet

You said cheers in your original post, so I'm assuming you're probably British and have the UK type of USB outlet. Yes, this is normal.

Other answers are assuming that you are in the US, where that wouldn't be normal.

Brock Adams
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Dotes
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  • Unless the entire outlet is on a switched spur. where switching off the spur would turn off the USB (and the outlets regardless of the switches on the outlet) – ratchet freak Apr 10 '19 at 08:16
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    That's a correct description of the UK situation. I've just removed one and while it was off the wall I measured the power consumption of the USB charger: 2W with nothing plugged in and the switches off – Chris H Apr 10 '19 at 08:35
  • @ChrisH "2W with nothing plugged in and the switches off" so you mean it was consuming electricity even when it was idle? (not an expert) – Rich Apr 10 '19 at 08:51
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    @Rich exactly, it takes some power to even know whether there's anything there to charge. The maximum output of the one pictured would be about 15W (mine 10W). That's one of the reasons I took mine out, and I don't like having stuff I can't turn off easily. – Chris H Apr 10 '19 at 09:14
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    @ChrisH thanks for the explanation. It's a shame there isn't a physical switch to control the USB ports, either like the ones for the plugs or one that is activated by something being inserted into the USB socket. – Rich Apr 10 '19 at 09:57
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    @Rich you and I would prefer a switch, but it adds cost and I guess many people want the convenience of just plugging in the USB. I doubt you could switch the mains side with something operated by inserting a plug, because mains switches require a certain amount of material and therefore force to be robust enough, but switching the 5V side by insertion wouldn't help as the power supply would be idling as it is now. – Chris H Apr 10 '19 at 10:53
  • @ChrisH it should take very much less than 2W at idle (less than 1mW, ideally)... but it's not really surprising that these tend to be really low quality devices. – hobbs Apr 10 '19 at 21:57
  • @hobbs yes, always-on mains and built to a budget. Not a good combination. The idle power is on a par with branded phone chargers a few years ago and unbranded now. The major brands are much better these days – Chris H Apr 11 '19 at 04:47
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Sometimes power supplies/transformers can hold voltage in capacitors to make it look like they are on for a short time after they are unplugged. Rather than checking with a tester, plug a phone (or anything that actually consumes power) into the charger and operate the switch to see if it is still on when the switch is off.

It's not impossible for the USB portion to have power all the time, but I've never seen a USB receptacle that would allow for it in the US.

edit: UK outlets can have integrated switches where this is much more plausible. See the other answer for the UK...

JPhi1618
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    I have the British type as shown in Dotes' answer.

    I'm trying the experiment and so far it is charging my phone perfectly well with both switches off. I'll look in a few minutes but I'm pretty sure no capacitors are doing the charging.

     – chasly - supports Monica Apr 09 '19 at 21:02
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    @chaslyfromUK, that makes sense. Our receptacles are different in the US and don't have integrated switches like that so it would be hard for this to happen. The UK based answer is right, but I'm leaving this answer because it can explain why voltages or small led lights stay on even after a charger is unplugged or switched off. – JPhi1618 Apr 09 '19 at 21:04
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    Update - Yes, completely charged my phone from 80% to 100% while mains sockets switched off. – chasly - supports Monica Apr 10 '19 at 08:19