Electronics > Repair

"Double insulated, do NOT earth." Why?

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MarginallyStable:
EN-60335 section 27 "Provision for earthing"

"Class 0 appliances, class II appliances and class III appliances shall have no provision for protective earthing. Class II and class III may incorporate earth for functional purposes"

Class II being double insulated



brabus:

--- Quote from: soldar on October 03, 2023, 10:27:58 pm ---(...)
You are not trying to find the truth, rather you are trying to defend your original position no matter what. It seems to me you are now just dishonestly trying to defend a position you know is wrong.

--- End quote ---

No need to defend anything: the truth is the norms.
Plus, accusing someone of dishonesty is a way of describing one's self.

So, the EN60335 refers back to the 61140, which states:


"This requirement shall be fulfilled when the equipment is properly installed". Fixing an earth wire to an insulated device does NOT make it Class I. It makes it a dangerous bodge.

But let's go deeper and search among other norms, such as the CEI 64-8/4, paragraph 413.2.2.4, or the EN60335/2/23. Here the connection of conductive parts that could become in contact with hair or skin is explicitly forbidden. No discussion about Class I or II, just don't connect the PE to them. Ever.

What are you going to do if you see this symbol (please note, it has nothing to do with Class I or II)? https://www.iso.org/obp/ui#iec:grs:60417:6032

tooki:

--- Quote from: soldar on October 03, 2023, 03:36:44 pm ---OK, I think I found the source of confusion:


--- Quote --- EN 60335-1

class I appliance
appliance in which protection against electric shock does not rely on basic insulation only
but which includes an additional safety precaution, in that conductive accessible parts are
connected to the protective earthing conductor in the fixed wiring of the installation in such a
way that conductive accessible parts cannot become live in the event of a failure of the
basic insulation
NOTE - This provision includes a protective earthing conductor in the supply cord.

class II appliance
appliance in which protection against electric shock does not rely on basic insulation only
but in which additional safety precautions are provided, such as double insulation or
reinforced insulation, there being no provision for protective earthing or reliance upon
installation conditions
NOTE 1
Such an appliance may be of one of the following types:
– an appliance having a durable and substantially continuous enclosure of insulating material which envelops all
metal parts, with the exception of small parts, such as nameplates, screws and rivets, which are isolated from live
parts by insulation at least equivalent to reinforced insulation; such an appliance is called an insulation-encased
class II appliance;
– an appliance having a substantially continuous metal enclosure, in which double insulation or reinforced
insulation is used throughout; such an appliance is called a metal-encased class II appliance;
– an appliance which is a combination of an insulation-encased class II appliance and a metal-encased class II
appliance.
NOTE 2 The enclosure of an insulation-encased class II appliance may form a part or the whole of the
supplementary insulation or of the reinforced insulation.
NOTE 3 If an appliance with double insulation or reinforced insulation throughout has provision for earthing, it
is considered to be a class I appliance or a class 0I appliance.

--- End quote ---

--- End quote ---
Genuine question, then (not being argumentative, I am actually curious): How does Apple have its laptop chargers certified as double-insulated? These chargers use a detachable, modified C8 mains input with a ground stud, onto which either an earthed cable (using a C7 plug and the ground stud) or an ungrounded mains plug (“duck head”) can be snapped. (In the past, there also existed ungrounded cable versions.) This means that the same charger can be floating or grounded, and consequently, the laptop’s aluminum enclosure can be floating or grounded. (When floating, many users can feel the tingle from the interference suppression capacitors.) The ground stud is the only external metal item on the charger body itself (since it’s always covered by the duck head or cable when in use), but the DC plug has exposed metal, including the ground.

I, too, would interpret the section of the standard to prohibit a ground on a class II appliance, in that by having one it ceases to be class II.

Yet clearly the Apple chargers are compliant (since they are externally certified, not to mention under enormous scrutiny by the media, etc), with the double insulation symbol on them, yet have an optional ground. There must be some detail we are missing, methinks.

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