Grounded and ungrounded appliances, why ungrounded?

[AntonLargiader]

We just rearranged my daughter's room and as I plugged in her clip-on 2-prong metal desk lamp I wondered (again) why some such appliances aren't grounded. I took a good look at it, and it seems to be pretty well made, but any such device still seems like it could be one good cord tug away from having a loose wire energizing the metal body.

Pretty much every lamp in our house is like this. Probably yours, too.

Our toaster isn't grounded, as aren't the plastic-bodied coffee grinder and rice cooker. Stand mixer, microwave and Vitamix are. Circular saw isn't, drill is.

If grounding is a good overall preventive measure, why isn't it done more? Is it just that it's low on the injury-per-device scale so it doesn't get attention? Plastic-bodied stuff I can understand; I'm talking about metal stuff where there's just a plastic bushing keeping the cord from a sharp metal edge, or a single connection keeping a hot wire from popping out and touching a case.

Is there logic to where grounding is used, based on the likely location of use or some such factor? 4-wire is replacing 3-wire in 240V appliances, is 3-wire going to eventually replace 2-wire in these 120V appliances? Not the same thing, I know, as these are not grounded on the neutral.

Not going to rewire all of my 2-prong lamps... yet... just wondering.

 

[Rock knocker]

4-wire is replacing 3-wire in 240V appliances

Double insulated tools have to meet special requirements.

FYI 4 wire is not replacing 3 wire 240 appliances. It is all dependent on whether the appliance is 120/240 or just 240v.

 

[AntonLargiader]

FYI the relevant code is 250.114, governing the requirements and exemptions for cord & plug EGC. These items are exempt because they're listed, but that isn't really an answer to my underlying question.

EDIT: actually the lamps aren't exempt; they're just not covered. Only certain tools and appliances are covered, and they may get the double-insulated exemption. The wording is: Exception: Listed tools, listed appliances and listed equipment covered in [1 through 4] shall not be required to be connected to an equipment grounding conductor where protected by a system of double insulation or its equivalent. But lamps, small kitchen appliances, electric toothbrush chargers and so forth are not mentioned in 1-4.

 

[theoldwizard1]

FYI 4 wire is not replacing 3 wire 240 appliances. It is all dependent on whether the appliance is 120/240 or just 240v.

Items like electric stoves and electric dryers are an example where 4 wires are now required, but not too many years ago, 3 wires was the norm. Both of those appliances have 240V loads AND 120V load (typically timers and lights). In the "old days" the neutral on those appliances was "bonded" to the chassis.

 

[AntonLargiader]

Items like electric stoves and electric dryers are an example where 4 wires are no required, but no too many years ago, 3 wires was the norm. Both of those appliances have 240V loads AND 120V load (typically timers and lights). In the "old days" the neutral on those appliances was "bonded" to the chassis.

Just to clarify, he means "now required" and "not too many"

 

[Rock knocker]

Items like electric stoves and electric dryers are an example where 4 wires are (now) required, but (not) too many years ago, 3 wires was the norm. Both of those appliances have 240V loads AND 120V load (typically timers and lights). In the "old days" the neutral on those appliances was "bonded" to the chassis.

I wasn't talking about the 3 wire 120/240v loads of the past. The OP opined that 240v loads require 4 wires, I was just commenting that that is and has always been incorrect.

 

[AntonLargiader]

The OP opined that 240v loads require 4 wires, I was just commenting that that is and has always been incorrect.

Actually I said "4-wire is replacing 3-wire in 240V appliances." Stoves and dryers are the most common 240V appliances, and they have gone 4-wire.

True 240V devices like welders and compressors, not what I was talking about. They're not appliances to me.

The real point was about separating ground and neutral, which is somewhat related to my original question about why true grounding seems less important for certain things.

 

[Rock knocker]

Actually I said "4-wire is replacing 3-wire in 240V appliances." Stoves and dryers are the most common 240V appliances, and they have gone 4-wire

Even though you can quote NEC articles, you don't realize that ranges, stoves and dryers aren't 240v loads, they're 120/240v loads.

Makes you look like you have no idea of which you speak

 

[theoldwizard1]

just to clarify, he means "now required" and "not too many"

thanks !

 

[Ji m]

UL and other Listing Companies have requirements for manufacturers to meet their standards for listing.

Some of those standards are for grounded equipment,
and some of those standards are for ungrounded equipment.

The manufacturer decides which grouping of standards they would like to meet,
and they produce their products to meet them.

One company might decide its better/cheaper to double insulate their drill and forgo the cost of an added ground wire and additional outlet prong,

while another manufacturer may decide they'll spend the extra money to use the ground wire and not double insulate the cases.

As far as 3 and 4 wire ranges and dryers,
the National Electrical Code used to allow control wiring to operate on 115v using the ground wire as a neutral,
now they don't.

 

[sberry]

I forget now,,,, why isn't an electric heater grounded?

 

[Bert_]

As far as 3 and 4 wire ranges and dryers,
the National Electrical Code used to allow control wiring to operate on 115v using the ground wire as a neutral,
now they don't.

This is a bit of a technicality but they did not use the ground as a neutral but rather you were allowed to use the neutral as a ground.

The only reason it matters is that, for example, a stove could be wired with 6-3 without ground or #6 se cable, both having a neutral but no ground wire. Using 6-2 with ground was illegal even back then.

 

[laser3kw]

does it have to do with "appliances" having 120v controls in addition to 240v loads? that would require a true "neutral" to supply a 120v leg and then a true safety ground?
I am just guessing, I am learning like the rest....

 

[AntonLargiader]

That's exactly it. With 3-wire, the appliance had a neutral (for those 120V loads) and there was a ground strap that grounded the chassis to that neutral.

Here's a thread on that subject and I posted two pics at the end of it.

Separation of grounds and neutrals is also behind the non-bonding of subpanels.

does it have to do with "appliances" having 120v controls in addition to 240v loads? that would require a true "neutral" to supply a 120v leg and then a true safety ground?
I am just guessing, I am learning like the rest....

 

[Jlbc212]

Like the original poster I'm still wondering, particularly why the items like lamps, toasters and other powered devices with a metal case are not required to have a three prong cord.

 

[AntonLargiader]

Doing a little bit of reading, it seems that the ultimate goal in some cases is to prevent an arm-to-arm fault path which is often fatal. So in situations where it's likely that the person will be holding the appliance with one hand and poking into an energized component with the other (fork in toaster, unscrewing broken light bulb base from lamp, etc.) it's better to not have a solidly grounded metal case and instead let the fault current go through a much weaker path such as bare feet on a wooden floor or whatever.

It certainly is food for thought, as there is a trade-off that is based on the likely risk of a particular fault.

We have a stainless countertop in part of our kitchen, that isn't grounded. If a bare wire touched it we'd want it to be grounded, but if we were touching it and touched something hot with the other hand we wouldn't.

In any case, I think solid GFCI protection is a great idea!

EDIT: I have no idea what drives this line of thought from the regulatory side, though, although it could be in the standards of the NRTLs. NEC doesn't really seem to wade too deeply into it beyond specifying that appliances must be listed and then calling out a few specific ones that need either grounding or double insulation.

 

[sberry]

I have had this explained but outright forgot what it was. I was going to ask my tech but he is gone for the day.

 

[sberry]

If it developed a short in the middle of the element it would simply overheat.

 

[joel63]

If it developed a short in the middle of the element it would simply overheat.

I have seen this happen where an insulator had broken in a strip heater.

I just happen to be checking the amperage draw when the system was off.

 

[nadogail]

I have nothing relevant to add to the answers that have been posted.