Three pin sockets with Class II supply

[westie101]

I'm sure that on the one I pulled apart the N & E were bonded to provide a return path for fault current

 

[JohnW2]

I'm sure that on the one I pulled apart the N & E were bonded to provide a return path for fault current

This is not an area I've had much cause to think about before, but I'm not sure I understand what a 'fault current' actually is in this context.

The IT equivalent of an L-N fault/fault current (i.e. due to a short between the two 'live' supply conductors) is straightforward enough, and protection against that doesn't rely in any way on any earthing/bonding. However, what is the equivalent of an L-E fault (and fault current) if there is no earth in the equation? The nearest equivalent I can think of is a fault resulting in one side of the supply becoming connected to extraneous conductive parts of the appliance - but, as I've been saying to BAS, 'so what?' (if the supply is floating) - and exactly what is this 'fault current' to which you refer? Indeed, what you are suggesting results in the exposed conductive parts being deliberately connected to one side of the floating supply (which you are calling 'neutral', but it could just as well be 'the other one', if the supply id floating relative to earth.

Kind Regards, John.

 

[ericmark]

I see the point that with a single socket to use two items would require an adaptor of some type which would bond the earths together so it seems no reason to fail the inverter.

 

[westie101]

Fault current is current other than the normal running current of a device or system.
Yes you are quite correct that as there is no reference to actual earth it doesn't actually matter as there will be no circuit involving earth.

Just pulled one apart for a peek, there is a G/Y wire to the earth pin that connects to the PCB and the housing

 

[JohnW2]

I see the point that with a single socket to use two items would require an adaptor of some type which would bond the earths together so it seems no reason to fail the inverter.

So it would seem - unless, that is, one considers what I think was the incredibly improbable scenario that BAS seemed to be postulating - namely that two separate exposed conductive parts of the same appliance simultanouesly developed faults to opposite sides of the supply. However, as I pointed out to him, the answer to that is to ensure that all exposed conductive parts of the appliance are bonded together - whether or not they are connected to earth (or anything else) would seem to be irrelevant with a floating supply.

Kind Regards, John.

 

[JohnW2]

How would you bond together the exposed conductive parts of Class I portable appliances if their Earth pins were connected to nothing in the inverter socket(s)?

BAS, whilst (or just after!) responding to eric's recent post, it occurred to me that you might have been referring to two or more different Class I appliances, in which case your comment makes more sense. Apologies if I misunderstood.

As you imply, one then needs bonding between, as well as within, the appliances, and that requires that their leads have CPCs which are joined together when they are 'plugged in'. However, that merely requires that the earth terminals of the two (or more) sockets be joined together (as, for example, would automatically be the case if the inverter had a BS1363 double socket) - there would be no need for them to be connected to anything else and, in particular, no need for them to be earthed.

In terms of house wiring systems, the distinction between earthing and bonding is often pedantic and semantic (with a lot of overlap) - but in the situation we're talking about here the two are very different.

Kind Regards, John.