No earth cable on light fitting

[ban-all-sheds]

Of course it is worse.

If you earth the metal case of Class II device it is less safe than it would be if you left it alone. Less safe is not "no worse".

You're ignoring the rest of my statement: I said no worse than if you'd used a device which was not double-insulated.

You are ignoring the fact that a Class I item must be earthed. There is no choice. Earthing a Class I item makes it safer, earthing a Class II one makes it less safe. Less safe is worse than safer.

There is a choice to not earth a Class II one, and it is a choice which you should exercise, because otherwise you have made it less safe, and that is worse.

 

[PBC_1966]

You are ignoring the fact that a Class I item must be earthed.

Not at all, that's the whole point. Earthing the casing of a class II device results in it being no less safe than if you'd installed a class I device instead. And what about class II equipment which is connected to something other than the mains supply such that leaving it unearthed might well introduce a greater potential risk than earthing it?

 

[ban-all-sheds]

Not at all, that's the whole point. Earthing the casing of a class II device results in it being no less safe than if you'd installed a class I device instead.

You are ignoring the fact that a Class I item must be earthed. There is no choice. Earthing a Class I item makes it safer, earthing a Class II one makes it less safe. Less safe is worse than safer.

There is a choice to not earth a Class II one, and it is a choice which you should exercise, because otherwise you have made it less safe, and that is worse.

 

[PBC_1966]

You are ignoring the fact that a Class I item must be earthed.

Did you not read my last post properly? I am not ignoring that fact; it is because a class I item needs earthing that I am comparing it with a class II item which is earthed.

There is a choice to not earth a Class II one, and it is a choice which you should exercise, because otherwise you have made it less safe, and that is worse.

Unless it's installed in such a way that earthing it would actually be safer overall than leaving it unearthed.

 

[winston1]

Why do you WANT to earth things which do not require it?

Because Winston says that one should. I have warned him about this before

This is what I actually said, "Take hi-fi, any one of the components could be class 1 and export the earth via connecting leads. Even if this is not the case I would earth it anyway as the sum of the leakage currents can cause a tingle."

That referred to interconnected hi-fi, not class 2 equipment generally.

 

[ban-all-sheds]

Did you not read my last post properly? I am not ignoring that fact; it is because a class I item needs earthing that I am comparing it with a class II item which is earthed.

Did you not read my last post properly?

You are ignoring the fact that a Class I item must be earthed. There is no choice. Earthing a Class I item makes it safer, earthing a Class II one makes it less safe. Less safe is worse than safer.

 

[JohnW2]

There is no choice. Earthing a Class I item makes it safer, ...

Indeed so - hence it is 'required'.

... earthing a Class II one makes it less safe.

That I don't understand. It will make the environment (very slightly) 'less safe', by unnecessarily introducing more touchable earthed metal (just as, for example, if one unnecessarily earthed a metal worktop, metal window frame, metal bath etc. etc.), but I don't see how it can make the item itself any less safe.

Kind Regards, John

 

[Gerrydelasel]

That I don't understand. It will make the environment (very slightly) 'less safe', by unnecessarily introducing more touchable earthed metal, but I don't see how it can make the item itself any less safe.

Because a class-II appliance is presumed to be safe regardless of the earth, since it is not connected to earth.
By earthing a class-II appliance, if the earth is faulty and somehow becomes live (e.g. it is broken and has touched live somewhere in the building), then the exposed metal of the appliance also becomes live.
An earthed Class-I appliance is only as safe as the earth, which is not infallible. By earthing a Class-II appliance you 'drag it down' to the level of Class-I safety (the appliance is still Class-II safe internally, but not externally, as it were).

 

[JohnW2]

Because a class-II appliance is presumed to be safe regardless of the earth, since it is not connected to earth.

By earthing a class-II appliance, if the earth is faulty and somehow becomes live (e.g. it is broken and has touched live somewhere in the building), then the exposed metal of the appliance also becomes live.

True - but that is just a variant of what I was saying about the environment becoming slightly less safe if one unnecessarily earths any exposed metal - and that's as true if the thing one is earthing is, say, a metal worktop as if it is a Class II electrical appliance. If the appliance really is Class II, then anything electrical within it is deemed to be adequately isolated from any outer metal casing, so earthing the latter cannot possible make the item, per se, any less safe.

There are two hazards of unnecessarily connecting touchable metal to 'earth'. Firstly, if (as usual) there are no faults affecting the 'earth'/CPC system, it affords a 'second point of contact' for someone who finds themself also touching something 'live'. Secondly, as you point out, in the presence of faults in the 'earth'/CPC system, the touchable metalwork could actually become 'live'.

An earthed Class-I appliance is only as safe as the earth, which is not infallible.

True (in the presence of faults). It can similarly be said that a Class II appliance is only as safe as its "double or reinforced insulation" (which I presume is not infallible) - so I imagine that there will be some people who would see merit in the 'belt and braces' approach of also earthing any exposed metal it had.

Kind Regards, John

 

[Gerrydelasel]

so I imagine that there will be some people who would see merit in the 'belt and braces' approach of also earthing any exposed metal it had.

I agree -I don't see the problem in earthing a Class-II appliance. If your earth is faulty then you've probably got bigger things to worry about than whether your Class-II appliances happen to be connected to it!

 

[EFLImpudence]

... earthing a Class II one makes it less safe.

That I don't understand. It will make the environment (very slightly) 'less safe', by unnecessarily introducing more touchable earthed metal (just as, for example, if one unnecessarily earthed a metal worktop, metal window frame, metal bath etc. etc.), but I don't see how it can make the item itself any less safe.

You two (J & P) really are labouring this unnecessarily especially as you have answered the question in your post.

I am sure Bas' it refers to the environment being less safe for persons and therefore the appliance itself is less safe for persons; it does not mean any harm will come to the appliance.

A live bath will not come to any harm but it will not do you any good touching it.

 

[EFLImpudence]

so I imagine that there will be some people who would see merit in the 'belt and braces' approach of also earthing any exposed metal it had.

I agree -I don't see the problem in earthing a Class-II appliance.

Three now.

If your earth is faulty then you've probably got bigger things to worry about!

The earth doesn't have to be faulty.

When a fault occurs (L to E) in an item elsewhere, ALL CPCs and exposed-c-ps and extraneous-c-ps become live until the OPD operates -

so, earthing items which do not need to be earthed (the metal of Class II appliances or a spoon) is foolish and making it (the environment and the Class II appliance) less safe for persons who may touch it.

 

[EFLImpudence]

Earth a spoon and then ask someone to go in the next room and engineer a L to E fault while you are eating your cornflakes.

Now imagine the spoon is the wrongly earthed metal case of a Class II item which you happen to be touching.
Now remove the wrongly applied earth and do it again - better?

 

[Gerrydelasel]

Earth a spoon and then ask someone to go in the next room and engineer a L to E fault while you are eating your cornflakes.

Perhaps naively I asume my earth is relatively low resistance and firmly bonded to earth, so my spoon remains harmless even if a live wire does touch earth.

 

[EFLImpudence]

Try it then.