Three pin sockets with Class II supply

[ericmark]

I was under the impression that with a Class II supply like for example with a shaver outlet that there should be no provision for an earth so that no one will try plugging in a Class I item.

My inverter is clearly marked Class II only but has a 13A three pin socket. I have missed this in the past just did not read all the printing on the unit only looked at the 150VA 230V and looked no further.

My son's old inverter before he sold boat had a large bolt clearly marked earth and bonded with some 35mm to boat hull and to be honest never even thought about the little one I use in the car.

I had expected to find the negative was cross bonded to earth but of course there are still some earth return or positive earth vehicles so that would have really been not at option but there is no earth bolt on the unit to correct to earth even if I wanted.

In real terms it's a IT system and with such low power only ever likely to supply one item in the same way as with the shaver socket which is also an IT system. So not really a problem.

But if it was to be used at work rather than at home what would be the situation if presented for "PAT" testing? Should it be removed from service as it has a three pin socket and no earth?

And since unlike rest of Europe we don't have two pin sockets what could be used instead of the 13A outlet?

Your thoughts please.

 

[Spark123]

I don't think I'd class it as a class 2 supply, it is more like a supply which is electrically separate and has no earth nor any reliance on earth for protection, just like a shaver socket with isolation transformer.

 

[ericmark]

I don't think I'd class it as a class 2 supply, it is more like a supply which is electrically separate and has no earth nor any reliance on earth for protection, just like a shaver socket with isolation transformer.

It states under Cautions
Suitable for double insulated Class II appliances only

But has a socket able to take a Class I appliance.
The shaver socket does not have a socket able to take a Class I appliance it is the using of a socket with an earth hole which I see as a problem.

Same as with an extension lead for use with lawn mower for example can have 2 core cable but has two hole socket not three hole where it plugs into the mower. That's OK but to fit a 13A outlet would not be OK.

The question I think has been asked before over earthing with UPS supply should the supply to the UPS fail due to severed cable then there is no earth connection to the UPS but it is still providing power to class I equipment.

Same again with stand-by generator should the supply be lost one could also lose the earth.

With grid tie inverters they have an auto shut down should the supply be lost although not sure how that works? If one thinks about a line of houses all with solar panels and all with grid tie inverters how can they detect if cable is cut from main supply transformer? Especially if there are motors running!

The Question is if you came across the inverter during an inspection of in service electrical equipment would it need to be withdrawn from service?

If so which regulation would one quote as to why it was withdrawn? 331.1 (xi)?

 

[ban-all-sheds]

Eric - IIRC from previous posts you're the expert on what all the various symbols mean on ELV supplies etc - what's on this inverter?

If it's in a car there's no way it can get an earth, unless you stop and bang in a rod each time you want to use it

I've got a small inverter in my car - bought it as a "just in case" for my laptop, but I've never used it. I'll have a look sometime and see what it says.

 

[JohnW2]

If it's in a car there's no way it can get an earth, unless you stop and bang in a rod each time you want to use it

If neither side of the inverter's output is referenced to earth (intentionally or otherwise), why would one need an earth, even for a Class I appliance? I can't see what useful purpose it would serve.

Kind Regards, John.

 

[ban-all-sheds]

Two faults.

 

[JohnW2]

Two faults.

If one is in a situation in which the supply is not, and cannot be, referenced to earth, I find it very hard to see how having an earth supplied to an appliance can possibly achieve anything useful, no matter how many faults there are. Can you perhaps expand?

Kind Regards, John.

 

[ban-all-sheds]

411.6

 

[JohnW2]

411.6

I'm going to have to think about this, because it currently makes little sense to me. If the supply is totally floating with respect to earth, I can't see how any fault current can flow to earth, even if one is connected. I guess the penny might drop eventually!

Kind Regards, John.

 

[ban-all-sheds]

It can flow through you if you touch two exposed conductive parts when there have been two faults involving different live conductors.

 

[JohnW2]

It can flow through you if you touch two exposed conductive parts when there have been two faults involving different live conductors.

Yes, of course it would, and the way to avoid that (incredibly improbable) scenario is to bond all exposed conductive parts together. I still can't see how earthing those bonded parts would make one iota of difference to anything; with a totally floating supply, no current could ever flow in the earthing conductor - 'Electricity 101' tells us that a current can only flow in a complete circuit!

Kind Regards, John.

 

[ban-all-sheds]

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)?

 

[westie101]

Seems to me that it depends on where!
Does BS7671 apply in a car, boat, caravan or in the middle of a field? From what I can see it applies to buildings so quoting from it for other locations may not be appropriate, though it would indicate good practice

 

[ban-all-sheds]

The electricity doesn't know where it is, nor which regulations apply to it.

 

[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)?

Eh? The answer to that question seems so obvious that I am uncharacteristically lost for words in attempting to respond!

Bonding together the exposed conductive parts of an appliance means precisely what it says - and has nothing to do with what else those parts are (or are not) connected to.

Kind Regards, John.