Help me understand grounding

[mbrooke]

Modern, double-insulated appliances, have a 'square within a square' safety symbol.

Correct- but I don't think all 2 prongers come with it... anyone got some appliances they can film lol?

 

[StarCat]

That isn’t double insulated.
double insulated simply means that one failure doesn’t result in a fault that would cause harm.
if the inside of that box was coated in plastic it would meet the guidelines.
in the case of your picture, if the wire burns off the terminal, it can touch the case, so not double insulated.

IMO

Exactly what type of device is this and for what country and voltage? It is similar to a steam well. I am taking note there appear to be 2 elements that are protected by the apparent neutral [White Hi Temp line] headed to the other end along with what appears to be an extra black wire paried with it?/? Do you have a wiring diagram. Its puzzling. Its a little hard to see the phase separation with respect to the load by the photo.
The lower control almost looks like a mechanical timer, but could be a T-stat. The upper control almost looks like an infinite switch, and with this type of device you are correct. Its quite common to see a wire burned off and loose in the cabinet. I have seen it scores of times, and in those cases the ground appears to have been critical.

 

[Electricmo]

Here is why.

 

[mbrooke]

Exactly what type of device is this and for what country and voltage? It is similar to a steam well. I am taking note there appear to be 2 elements that are protected by the apparent neutral [White Hi Temp line] headed to the other end along with what appears to be an extra black wire paried with it?/? Do you have a wiring diagram. Its puzzling. Its a little hard to see the phase separation with respect to the load by the photo.
The lower control almost looks like a mechanical timer, but could be a T-stat. The upper control almost looks like an infinite switch, and with this type of device you are correct. Its quite common to see a wire burned off and loose in the cabinet. I have seen it scores of times, and in those cases the ground appears to have been critical.

Its a simple toaster oven, nothing special.

 

[electrofelon]

If you think about it hard enough you could make a case that bringing an equipment ground into a house might be the most dangerous thing you could do..

I'm in my living room in a wood frame house built over a crawl space. Go ahead and energize every metal thing in there.... as long as everything is plugged into good ole' fashioned two pronged recpts I'm never going to get shocked until some do gooder comes in and properly wires up a three prong recpt

Yup, we've become so obsessed with grounding, I think we forget there are some substantial disadvantages. I could totally see people in another planet saying, "What?!? So you set it up to have a short circuit with high fault currents if there is a problem??? That is the dumbest thing I have ever heard!"

 

[winnie]

There are ways to do residual current detection that don't involve microelectronics. Not as sensitive as a GFCI, but I am sure you could make a device that detected 10A ground faults that was as reliable as a thermo-magnetic breaker.

Rather than solidly grounded systems, you could have resistance grounded systems where fault current was limited to say 10A or 50A or some easily detectable but still relatively low value.

Or today I think it would be entirely plausible to have 'GFCI everything' and a resistance grounded system for normal residential use. I wouldn't mandate it, but would be delighted if it were an available/allowed option.

-Jon

 

[mbrooke]

There are ways to do residual current detection that don't involve microelectronics. Not as sensitive as a GFCI, but I am sure you could make a device that detected 10A ground faults that was as reliable as a thermo-magnetic breaker.

Rather than solidly grounded systems, you could have resistance grounded systems where fault current was limited to say 10A or 50A or some easily detectable but still relatively low value.

Or today I think it would be entirely plausible to have 'GFCI everything' and a resistance grounded system for normal residential use. I wouldn't mandate it, but would be delighted if it were an available/allowed option.

-Jon

You know, I like the way you think.

One could make a residual current solenoid breaker which would be as reliable as anything else. 5 amps trip is not unreasonable.

 

[ActionDave]

There are ways to do residual current detection that don't involve microelectronics. Not as sensitive as a GFCI, but I am sure you could make a device that detected 10A ground faults that was as reliable as a thermo-magnetic breaker.

Rather than solidly grounded systems, you could have resistance grounded systems where fault current was limited to say 10A or 50A or some easily detectable but still relatively low value.

Or today I think it would be entirely plausible to have 'GFCI everything' and a resistance grounded system for normal residential use. I wouldn't mandate it, but would be delighted if it were an available/allowed option.

-Jon

I do not favor of the current expansion of GFCI protection. I would be in favor of GFPE protection on the majority of circuits.

 

[oldsparky52]

I do not favor of the current expansion of GFCI protection. I would be in favor of GFPE protection on the majority of circuits.

I'm curious as to the reason you feel this way.

 

[ActionDave]

I'm curious as to the reason you feel this way.

I have not fully formed the words to make a clear and simple case but I'll do my best.....
The 5mA threshold for GFCI protection makes some sense in some cases like swimming pools, kitchens, bathrooms, outdoor recpts. 5mA is just too low to make work on every circuit though.

GFPE level of protection between could be almost universal. It would sniff out ground faults before they became a hazard and make us all safer while being reliable.

 

[oldsparky52]

I have not fully formed the words to make a clear and simple case but I'll do my best.....
The 5mA threshold for GFCI protection makes some sense in some cases like swimming pools, kitchens, bathrooms, outdoor recpts. 5mA is just too low to make work on every circuit though.

GFPE level of protection between could be almost universal. It would sniff out ground faults before they became a hazard and make us all safer while being reliable.

Pretty clear and succinct. Makes sense to me.

 

[hhsting]

Why do metal frame small appliances like toaster ovens, radiators and mixer come with a 2 prong plug? Doesn't code require an EGC for all none double insulted equipment? What about UL?

Oh yea toaster and some other household appliances are just two prong. I always wondered why they don’t have EGC. Where in NEC it says double insulated equipment not require EGC?

 

[LarryFine]

Pretty clear and succinct. Makes sense to me.

I agree. Stop that.

 

[mbrooke]

Oh yea toaster and some other household appliances are just two prong. I always wondered why they don’t have EGC. Where in NEC it says double insulated equipment not require EGC?

Nowhere that I know, the opposite actually- anything not double insulated needs and EGC.

 

[boboduane]

Oh yea toaster and some other household appliances are just two prong. I always wondered why they don’t have EGC. Where in NEC it says double insulated equipment not require EGC?

Are they not protected with a Gfi? Should be as that would be on a kitchen countertop. There is your protection

 

[mbrooke]

Are they not protected with a Gfi? Should be as that would be on a kitchen countertop. There is your protection

Since when does code allow GFCIs to be used as protection alone when an EGC is also present?