Lamp Grounding 1

[redtailET]

I understand why toasters aren't grounded due to the exposed burners, and I understand why some appliances aren't grounded when the enclosures are non-metallic. But what about Lamps (desk, table, & night-stand); these never have a safety ground even if the lamp is made of metal. Why is this?

 

[ScottyUK]

I hope you meant 'toasters are grounded'.

Lamps and power tools frequently use 'double insulation' where two discrete insulation systems exist, either of which is sufficient to prevent electric shock. It is a tradeoff of risk against probability. While it is usually possible to receive an electric shock from such an item, it is highly unlikely unless the appliance is being subjected to gross misuse.

----------------------------------

Sometimes I only open my mouth to swap feet...

 

[resqcapt19]

Scotty,
Most toasters here in the USA are only a two wire cord. There is no protective grounding conductor from the wall outlet to the toaster.
Don

 

[ScottyUK]

Really? I'm surprised. I suppose 120V is less likely to prove fatal than our 240V. Yet another difference between our nations!


----------------------------------

Sometimes I only open my mouth to swap feet...

 

[itsmoked]

Naw, toasters get someone every year! Never seen a grounded toaster. Plus they are usually clean, shiny, metal.

Damn! My toast is stuck! Where's something to tease it out? Oh, here's the butter knife. Allll most have itBZZZZZZZZZZZZZZZZZzzzzzzzsizzle.

A nice piece of toast..wasted.


That little spot of theater brought to you by:

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[Kiribanda]

ScottyUK,

FYI.

CEC supports Double insulation (Rule 10-408(3)), but NEC still does not, the reason being "How to prove by test the condition of the Reinforced Insulation?".

Therefore, you can see 120 V Toasters with 2-wires in NA. If anybody needs ground fault protection, he has to use a receptical with GFCI!

But in IEC world, where IEE 16 th edition (or IEC 60364)is the governing document,double insulated equipments with 2 wires are widely used.

Thanks

 

[RAVWARD]

Sorry, I am pluggging my question in also. How about cooking ranges which are 240 V and those have only two power lines and a neutral. How they are gounded.

Thanks

 

[dpc]

Range wiring with no equipment ground is "grandfathered" into the NEC. The two hots and a neutral is the traditional wiring method in the USA back to Thomas Edison, I think. The NEC Code panels have never had the gumption to change it. The neutral is grounded at the service panel of course. And apparently few people are electrocuted on electric ranges.

 

[RAVWARD]

It is weird that when everbody know this is a big flaw and they dont correct it. Everywhere we see, they use a ground and neutral connection seprate when it comes to 120 V single phase and if we connect them togather there will not be enough current to trip the breaker during a ground fault. So, what happens in case a line wire gets shorted to cooking metal, what trips the breaker.

 

[dpc]

As long as the neutral is intact, it can carry the fault current and the breaker will trip.

I don't know that I would consider it a serious flaw. The method has a good track record. If lots of people were being electrocuted by their range, the Code would probably get changed.

 

[Skogsgurra]

Nothing is connected to the lamp housing. Insulation fault in the live wire will make the housing live, too. No current in the neutral. It is a dangerous way of making things. We (Scandinavia) had that before central heating, stainless kitchen benches and other grounded items made it impossible.

There is an exception in the code; if there are no grounded equipment in a room - then you may have two-prong (no PE) outlets in that room.

Gunnar Englund

http://www.gke.org

 

[redtailET]

Thanks to all for the info. Some follow-up questions:

If lamps and various appliances have floating metallic enclosures, why ground any enclosure? Who decides which electrical devices require safety grounds for enclosure protection and which do not? What is the criteria they use? Waiting around for electrocutions to justify safety grounds for a particular device just doesn't seem right.

 

[Skogsgurra]

Right. It isn't right. Society is not perfect. Not yet.

Gunnar Englund

http://www.gke.org

 

[dpc]

In the US, these appliances (toasters, etc) all have UL approvals so they must meet whatever standards UL has put forth for that type of appliance.

This is what determines why some are two wire and others three wire. (Not that it will necessarily make sense) It's pretty difficult to sell an electrical appliance that is not UL approved, so that becomes the lowest common denominator in the US.

 

[waross]

I am more familiar with Canadian installations where electric ranges have had ground wires for possibly 50 years.
I was under the impression that electric ranges under the NEC were grounded by using the neutral conductor as a common neutral/grounding conductor.
Can anyone verify this?
thanks
respectfully

 

[itsmoked]

dpc; UL, The U stands for "underwriter" as in Fire Insurance Underwriter. UL is for FIRE prevention. They don't care if a truck load of people fry as long as there is NO FIRE that some insurance company will have to shell out for. If UL was concerned about electrocution toasters would be very different.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[RAVWARD]

I apologize for asking this question here. But I have asked this question in Motors forum by L-N-G. But I guess it did not get that much attention.
WAROSS gave some interesting comments about canadain ranges having four wires. I am not sure, if my home's cooking range has four wires or not. But I will check tonight though. Just out of curosity, here is the link

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/bregnd.html#c3

This link states about a fault in case of 120 V system. For example if we dont have a ground wire and a fault happens, we will get a shock. How do we cope up same situation in case of electric ranges. May be, I am just being more inquisitive about this cooking range thing.
Thanks

 

[itsmoked]

I bought a point of use electric water heater at Orchard Supply Hardware. I was shocked(no pun intended) to see that the water entered a short U tube and in the U tube was a coil of Nichrome. The water ran directly on the live wire.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[dpc]

waross,

It certainly used to be the case that ranges were wired with only three wires. But I haven't checked the NEC on this in some years, so it's possible it could have been changed.

itsmoked,

Yes, I'm well aware of the derivation and history of UL. But their current standards and requirements go well beyond fire prevention these days. There are shock prevention requirements in many of the UL standards that I'm familiar with. UL would love to be involved in just about everything, unfortunately. As to why the toaster standards have no requirement for a three-wire cord, I have no idea.

One of the problems with UL is that the initial product standards are developed when the first manufacturer submits his product for certification. Sometimes the standards developed leave a lot to be desired.

 

[jghrist]

I replaced my range a couple years ago. I had to run new 3/c + ground cable to do it because there was no ground in the existing cable. I'm not sure if it was an NEC requirement, but it was in the installation instructions to use a grounding conductor. Another one of those "simple" home projects gone complicated.

I'm probably a lot safer using the range than turning on a lamp. ;-) Especially considering that the new range is one of these glass top ones with no exposed metal.