18
3
I live in a hostel where there is no grounded/earthed connection. Will it harm my laptop or charger?
Pavan
Posted 2012-08-15T09:54:57.343
Reputation: 181
Earthing: Is it important for laptops
Answers
18
Your laptop is almost certainly of a "class 2" design. Meaning it is electrically double insulated. You can Identify this by checking for a symbol which looks like a square, within a slightly bigger square.
Alternatively, a European GS or VDE standard may have been attached, covering class 2 implicitly.
This covers all Class 2 appliances in europe, and means that the appliance does not need a circuit protective conductor (Green/Yellow earth wire) in order to be used safely.
You will find this on your transformer block between the mains plug and the laptop DC jack. Meaning that both parts are protected from "Direct contact" fault conditions. Now known in Britain as "Basic Protection", as of IET Wiring Regulations 17th edition (2008).
You may find that the earth pin in your plug is there only to facilitate the interface with the socket, and is not actually wired to anything. The cable running from it may also be of a 2-core double insulated design (Phase and Neutral only).
Your laptop is safe. But the building itself is another story entirely. I suggest you avoid having a shower.
I would like to add a comment to Daniel Beck's conversation in the question comments, but do not have sufficient privillages.
The voltage you have measured is the result of a reference point differential, and is unlikely to be capable of carrying a current. This is why the apparent voltage would disappear if you connected the extraneous conductive part of your mac book to the local earth (A grounded reference point).
The metal case of your mac book is separated by two layers of insulating material from any electrical parts by design.
You will also find the Class 2 logo somewhere on your macbook's transformer block.
John David Ravenscroft
Posted 2012-08-15T09:54:57.343
Reputation: 349
1No, GS label doesn't imply class II device (but the double square does indeed). There are plenty of laptop adapters that aren't class II, e.g. HP PA-1650-02H; and this one has a GS label. – Fizz – 2015-09-24T13:53:02.657
1
Also by "class 2" you surely mean "class II". https://en.wikipedia.org/wiki/Appliance_classes#Class_II
– Fizz – 2015-09-26T23:59:38.103This is fantastic information. I was just browsing for questions to answer and stumbled upon this. Today I learned! "Appliance classes" -- adding to my knowledge for future use. Thank you! – allquixotic – 2012-08-15T18:07:12.557
1You are welcome :) Although I must say that this is the first time my knowledge has be useful outside of working as an electrician! – John David Ravenscroft – 2012-08-15T18:16:09.687
8
The ground or earth is there primarily to protect you from electrocution.
So long as your laptop and charger are in good condition, are of double-insulated design, and are used safely (not in the bathtub or shower) you and they will come to no harm.
If the equipment is designed with the expectation that it be earthed, by connecting it to a non-earthed supply you are running a small additional risk that a fault or damage in the equipment may lead, in the worst case, to something exploding in your face or catching fire while you are asleep. These are the sort of risks of death and injury we take every day when crossing the road.
RedGrittyBrick
Posted 2012-08-15T09:54:57.343
Reputation: 70 632
1Grounding's primary purposes are to protect against overvoltage, particularly from lightning strikes, which can destroy equipment and start fires, and to set a voltage reference point and stabilize voltage in a system (since the earth is the closest thing to a stable voltage reference point in any given spot on the planet), and it does also provide a certain degree of safety to humans. It also reduces hum in electronics and keeps you from getting shocked in the shower. On the other hand, the primary purpose of GFCI is definitely to protect humans from electrocution. – Craig – 2016-12-11T06:55:06.410
5
If your laptop charger/adapter says "connect only to grounded outlet", you'd better not do otherwise, because its safety depends on this connection. Example HP PA-1650-02H says that on its label (click to enlarge).
Contrary to what some claim here there are plenty of laptop adapters/chargers that are only class I according to IEC60950-1, meaning they need an earth connection to ensure safety. The aforementioned HP adapter is one such example.
If you have a multimeter/ohm-meter you can easily determine if an adapter/charger is class I by measuring the resistance between its output negative pin and its input earth prong. If that resistance is close to 0 ohms, then it's a class I device. The aforementioned HP adapter, of which I have one sample, indeed measures close to 0 ohms that way.
Note that a class I device can carry nearly all the same certification marks that a class II device, as you can see in the image. The important one that's missing is the square-in-square. That's only present on class II devices.
Fizz
Posted 2012-08-15T09:54:57.343
Reputation: 298
2
GS certainly does NOT mean double insulated. Another example, adapter from dell latitude e5550 Class I device with GS mark printed By the way I have never encountered class II laptop adapters in Greece (those that have the 2-squares symbol).
– chefarov – 2016-05-30T20:55:05.823
3
As an electronics designer I'm confident in saying that very many well known makes of laptop supply (dell, lenovo among others) are certainly NOT double insulated. The VDE mark CERTAINLY DOES NOT mean double insulated, class 1 kit can be VDE approved too. The negative side of the output jack is grounded to mains earth- hence they use a 3 pin cloverleaf mains input. In turn this appears on exposed metal connector shells like USB and VGA. Yes the voltages between the parts within the laptop are low, but fed from an unearthed socket the whole assembly has no direct connection through the power supply to either pole of the mains. Now, if the stray capacitances plus any filter capacitors between the two poles of the mains and the secondary side are roughly equal, then to AC the output will 'float' to about half mains voltage, but this voltage will fall away as soon as much current is drawn (e.g. by a meter). 80VAC from 220V 50Hz is very believable. This 'earth leakage' is certainly enough to damage some powered CMOS USB hubs for example, and you may just about feel it. Please take care when connecting together devices and peripherals fed from a mixture of earthed and un-earthed supplies, if possible its much better to be either all one or all the other.
Mike P_J
Posted 2012-08-15T09:54:57.343
Reputation: 41
Yeah, there's a lot of misinformation on electrical things on this site, in this thread in particular. Example of HP laptop adapter that's only class I (i.e. secondary is earthed, and not isolated/double-insulated): PA-1650-02H. In general if the adapter doesn't have the square-in-square on it, it's not class II. – Fizz – 2015-09-24T13:49:01.343
I don't see any reason for a ground if the device is all plastic. The output of the charger which is all plastic is only two wires. – Ronen Festinger – 2016-06-08T17:39:46.450
2Can you try to rephrase your answer so that it can be understood by non-electricians, please? – Thomas Weller – 2014-01-22T21:17:54.047
1Also, use more than one paragraph. – Kevin Panko – 2014-01-22T21:36:34.323
0
I remember in the past I was using may laptop which is connected to the internet by Ethernet and the charging cable disconnected.
Once I was walking back to my laptop as soon my hand touched the laptop it discharged electrostatic charge.
After that, the LAN connection was damaged. I think that would have never happened if I had connected the power cable which was earthed.
basm
Posted 2012-08-15T09:54:57.343
Reputation: 11
1@Indrek: "Bottom line: laptops are Class III appliances". Not necessarily so. Do you know what voltage powers the CCFL for older laptops' screen? Arround 600V (generated by an inverter). That clearly fails the class III SELV requirements. I'd be impressed if you can show me a laptop with CCFL backlight that got Class III certification. – Fizz – 2015-09-24T17:32:41.373
@RespawnedFluff Fair point, although an academic one as all modern laptops use LED backlights. That said, as far as I recall, for an appliance to qualify as Class III, it only needs to be powered by a SELV power supply (which laptop chargers are). That does not necessarily mean the appliance itself cannot step up the voltage for individual components. It's been a while since I've read up on this, though, so if you can say for sure that Class III appliances need to stick to extra-low voltages, then consider my comment retracted. – Indrek – 2015-09-26T23:39:02.727
@Indrek: No, laptop chargers are definitely not SELV (class III) if they themselves use mains power. Please post [a link to] a label photo (or better, regulatory approval document) of such PSU if you really think such a beast exists. – Fizz – 2015-09-26T23:50:08.990
@RespawnedFluff Class III and SELV are not synonyms. With that in mind, please re-read my comment. – Indrek – 2015-09-27T22:09:06.160
8I really hope your laptop doesn't have a metal enclosure (like my Macbook Pro). You will be the earth. – Daniel Beck – 2012-08-15T10:00:49.740
@DanielBeck That'll only be an issue if the laptop's enclosure happens to be at non-zero voltage, which it normally shouldn't be. And even then the voltages are too low and the resistance to earth too high for the user to feel anything more than a tingle. – Indrek – 2012-08-15T13:17:13.770
1@Indrek Got it measured once, 80 something (volts?) between the metal notebook enclosure and the grounded heating when using the Apple duck head Europlug for the power adapter (which has no ground wire). Touching the laptop sometimes produces a weak tingling sensation as well. When using the cable with German CEE 7/4 Schuko plug instead, no sensation and no measurable difference between heating and laptop case. While I only measured my 2010 MBP, the pinching sensation was there for the 2005 and 2008 MBPs as well. Since then I haven't used the ungrounded Europlug adapters anymore. – Daniel Beck – 2012-08-15T14:18:36.917
@DanielBeck I'm not aware of anything inside a laptop that works at 80 V (most components use 20 V and lower), so most likely you were measuring one of (or a combination of): static, some sort of inductive current generated by the laptop's internal circuitry, or leakage current from the mains adapter to the DC cable's negative lead. In all cases the current is too low to be dangerous, though the effect can understandably be uncomfortable or even unsettling. Bottom line: laptops are Class III appliances, so a metal enclosure is not a shock hazard. – Indrek – 2012-08-15T15:08:04.430