What earthing protects against
The earth pin carries no current when everything is working. That is exactly why a broken earth gives no sign at all: the device runs perfectly, right up until the fault it was there to catch.
What it is for
Inside an appliance with a metal body, one thing can go wrong that matters more than the others: a live conductor working loose, or insulation failing, and touching the chassis. The case is now at mains potential and looks completely normal.
With an earth connection, that fault has somewhere to go. Current flows from live to earth immediately, and it flows in a quantity that a breaker or an RCD notices — the circuit disconnects in milliseconds, usually before anyone has touched anything.
Without one, nothing happens. The chassis sits there energised and waits. The path to earth that eventually completes the circuit is whoever picks it up.
Class I and Class II: which of your things care
Appliances that rely on an earth for this protection are Class I. Appliances built so that a single insulation failure cannot energise anything touchable — two independent layers, or a plastic body with no exposed metal — are Class II, and they carry a square inside a square moulded into the casing. A Class II device has no earth pin because it does not want one.
Nearly everything with a two-pin figure-eight lead is Class II: chargers, shavers, laptop bricks. Of the 28 classes we track, 6 need an earth:
- Desktop computer — 200–600 W, electronic psu
- Travel kettle — 600–1000 W, resistive heating
- Travel iron — 400–1000 W, resistive heating
- Full-size steam iron — 1000–2400 W, resistive heating
- Handheld clothes steamer — 800–1600 W, resistive heating
- Baby bottle warmer — 100–500 W, resistive heating
The pattern is not an accident. They are the things with a metal body, a heating element, or water in them, and often all three.
The part almost nobody publishes: plugs that fit and drop the earth
A plug fitting a socket and a plug being earthed by that socket are two separate questions, and the second one is not visible. There is no resistance, no wobble and no warning. We record it as its own column, and these are the 13 combinations on file where the plug goes in and the earth does not follow:
| Plug | Into socket | Why the earth is lost |
|---|---|---|
| Type A | Type B | A Type A plug has no earth pin at all, so nothing gets earthed in a Type B socket. Only matters if the thing you are plugging in needs one |
| Type C | Type E | A Type C plug has no earth pin at all, so nothing gets earthed in a Type E socket. Only matters if the thing you are plugging in needs one |
| Type C | Type F | A Type C plug has no earth pin at all, so nothing gets earthed in a Type F socket. Only matters if the thing you are plugging in needs one |
| Type C | Type H | A Type C plug has no earth pin at all, so nothing gets earthed in a Type H socket. Only matters if the thing you are plugging in needs one |
| Type C | Type J | A Type C plug has no earth pin at all, so nothing gets earthed in a Type J socket. Only matters if the thing you are plugging in needs one |
| Type C | Type K | A Type C plug has no earth pin at all, so nothing gets earthed in a Type K socket. Only matters if the thing you are plugging in needs one |
| Type C | Type L | A Type C plug has no earth pin at all, so nothing gets earthed in a Type L socket. Only matters if the thing you are plugging in needs one |
| Type C | Type N | A Type C plug has no earth pin at all, so nothing gets earthed in a Type N socket. Only matters if the thing you are plugging in needs one |
| Type C | Type O | A Type C plug has no earth pin at all, so nothing gets earthed in a Type O socket. Only matters if the thing you are plugging in needs one |
| Type E | Type F | A Type E plug expects an earth pin sticking out of the socket. A Type F socket hasn't got one, so it goes in and earths nothing. That mismatch is the whole reason the hybrid CEE 7/7 plug exists |
| Type F | Type E | A Type F plug takes its earth from clips on the side. A Type E socket earths through a pin instead, so nothing meets. That mismatch is the whole reason the hybrid CEE 7/7 plug exists |
| Type K | Type E | The Danish earth pin has nothing to touch in a French socket |
| Type K | Type F | The Danish earth pin has nothing to touch in a Schuko socket |
The Europlug is most of the list
A Type C plug has two pins and no earth contact anywhere on it, so it unearths in every earthed socket it fits — and it fits 8 of them: Type E, Type F, Type H, Type J, Type K, Type L, Type N, Type O. This is by far the most common way a traveller loses an earth without noticing, because the Europlug is also the most accommodating plug in Europe.
Schuko and French sockets earth by different mechanisms
The subtler entries are Type E and Type F, which look interchangeable and are not. A French Type E socket has an earth pin protruding from it, which mates with a socket in the plug. A German Type F Schuko earths through clips on the sides of the recess. Each plug fits the other's socket and finds nothing to connect to. The same applies to the Danish Type K, whose earth pin has nothing to touch in either.
What to do about it
- If the device is Class II (square-in-square, plastic body, two-pin lead), none of this matters. Buy the cheap adapter.
- If it is Class I (three-pin plug, metal anywhere you can touch), buy an adapter that is explicitly earthed for that socket type — not a universal block with a decorative third pin.
- If you cannot get an earthed adapter for that pairing, that is a real reason to leave a metal-bodied appliance at home, and one of the few places where this site will say so plainly.
The tool flags earth loss per device rather than per country, because it depends on which plug is on the end of your particular lead.