Does anyone know if the USB charger is permanently energised (when fitted as part of 13A sockets) or whether it's turned on via a micro switch when the USB plug is inserted (I'm guessing the former)?
I know the current draw of a USB charger is tiny when open circuit but, being 'old school', I always remove the USB lead plug when not charging our phones but this may be the cause of several USB leads becoming faulty. Maybe I should leave the USB leads connected permanently and relax?
I'd bet there is no microswitch. Surely everything is SMS now; I've never checked the current draw though.
All but certain there is no switch in ones we have. One powers a Amazon Dot
24/7 by the bed, another Senior Management has on her dressing table to charge phone/Fitbit etc. Neither get warm (checked with a non-contact Thermometer).But when an electrician gives the circuit an insulation test they cannot isolate the USB socket so what do they do?
Or do they need an isolating switch?
Simpler and easier not to have any.
[george]
Interesting point.
However, after some worked (a new CU) our system was tested to comply with Part P etc.
I don't recall the tester asking if we had any USB chargers plugged in. He may have.
A similar test was done later, when we has the Main Fuse uprated. Agian, I'm pretty sure I wasn't asked about USB chargers plugged in that time.
The plug in ones use the same/similar circuitry and are generally on
24/7, along with things like TVs on standby etc.
Some of the older type need the insulation test to be run at 250v as per this info from Megger
OK, thank you.
I can't recall if I had a installed a fixed one when the 2nd test was done, think yes. Certainly there would have been several USB chargers plugged in and on, if not loaded.
I have a faulty one I can take to bits over the Easter weekend.
"Hello, AW here ..."
Owain
Whilst not a mechanical disconnect (as such a feature might not prove that useful if the cable is always kept plugged in even when the device isn't) *some* sockets do have an electrical equivalent. For example, the BG sockets described at
- Smart USB - Standby mode when device is fully charged; AutoDetect's the USB device and adjusts charging pattern to suite; protective overload function
- USB charger standby mode when not in use
As with many things electrical, there is all sorts of varying quality out there:
What I do not like about usbs built in is that they chuck out crap onto the mains as the circuits tend to be bought in crap from China. At least if you get a plug in one, you can unplug it and see if its the guilty party. Brian
From the FAQs at
Re: testing, I think the insulation test would be reduced to 250v instead of 500v which if I remember right is permissible in the regs. Seem to recall that's how most neon indicator lights in sockets get blown is by L to N ring main wiring testing at 500v!
I'd guess they are designed to tolerate 500 volts or so from a megger?
Why should a neon blow under those circumstances? Double the current through the ballast resistor, but still bugger all energy.
Some can. But there can be other issues. E.g. Big live found one gave low resistance (c. 0.3 MO) on L-N test
I suspect it might be the resistor that doesn't like four times the expected power dissipation.
Just curious --- what kind of other mains-fed equipment is the noise interfering with?
I don't that charging circuits can put noise on the lines, but I've never noticed any effects from it & we have a lot of various DC power supplies plugged in at the same time in our house.
Yes you could very well be right My recollection was that ballasts were about 1 Megohm making it a quarter of a watt at 500 volts. But Google tells me my resistance is high by an order of magnitude. I guess ballasts are around 1/8 to 1/4 watt sized.
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