Sahib's Concern Over 240V to a Duplex

[david]

In reading this thread, I am reminded of the receptacles in my bathroom. I have a 20 amp duplex receptacle, with the hot tab removed. 120V on one receptacle, and the opposing 120V on the other receptacle. This way my wife can plug in her hairdryer(1800W) and curling iron(1500W) in the same duplex and not trip the two pole 20 amp breaker. I agree that when split, the receptacle becomes two individual receptacles. According to Haja, wouldn't she (shouldn't she) have been shocked and killed by now?

Just curious now how is the GFCI protection incorporated in this configuration

I know it could be done just asking how it's done for your bathroom

 

[Hv&Lv]

Just curious now how is the GFCI protection incorporated in this configuration

I know it could be done just asking how it's done for your bathroom

GFCI breaker... Shocking at how high they are...

 

[T.M.Haja Sahib]

Ugrounded appliances in kitchen?

Ugrounded appliances in kitchen?

I want to know one thing for certain.Are there any ungrounded appliances with metallic enclosures such as toaster,coffee maker etc., in kitchen? Thanks.

 

[T.M.Haja Sahib]

Not without context.

See below.

Then the house wife should not be doing any laundry or cooking on the stove because she will be subjected to a potential 240 volt shock as well.

The objection to use mwbc in kitchen is to avoid more severe shock from 240 V for un-grounded metallic enclosure appliances such as toaster and coffee maker and even for appliance with proper grounding and so the above pretext led me to exclaim,''Is there any meaning in 'minimizing electrical shock risk'or not?''

 

[hurk27]

See below.



The objection to use mwbc in kitchen is to avoid more severe shock from 240 V for un-grounded metallic enclosure appliances such as toaster and coffee maker and even for appliance with proper grounding and so the above pretext led me to exclaim,''Is there any meaning in 'minimizing electrical shock risk'or not?''

to have two appliances fault to there cases at the same time would be unrealistic odds wouldn't it? and most newer appliances have an EGC to the case that would fault the circuit, and the ones that don't are double insulated, so the likelihood of this happening would very remote, at least I have never heard of it happening in the 38 years of working as an electrician, now in Europe where you have 220 volts to ground, you would think this would be of a more problem but with the use of RCD's (GFCI's) it must not be a problem, even here in the US we used GFCI's for all the receptacles serving the counter tops, so again I don't think it is a problem.

 

[david]

See below.



The objection to use mwbc in kitchen is to avoid more severe shock from 240 V for un-grounded metallic enclosure appliances such as toaster and coffee maker and even for appliance with proper grounding and so the above pretext led me to exclaim,''Is there any meaning in 'minimizing electrical shock risk'or not?''

Just for the sake of arguing lets say this is a concern. Ensuring that utilization equipment in kitchens are not served with Multiwire circuits
Would be only the first step to addressing your concern.

You would still have utilization equipment with different Line to line potential within reach of each other. The same hazard that you are concerned with would still exist in the kitchen.

Would you go on to say that no equipment in a kitchen could be supply by two different branch circuits having a different line to line potential

Or would you advocate for GFCI protection on all kitchen equipment.

Then would we go on to address other area’s in a dwelling where equipment could be installed within reach of each other.

 

[T.M.Haja Sahib]

in the US we used GFCI's for all the receptacles serving the counter tops, so again I don't think it is a problem.

I do not think usage of GFCI's for all the receptacles serving the counter tops is mandated by NEC.Is it?

 

[hurk27]

I do not think usage of GFCI's for all the receptacles serving the counter tops is mandated by NEC.Is it?

Yep:

210.8(A)(6) Kitchens ? where the receptacles are installed to serve
the countertop surfaces

 

[T.M.Haja Sahib]

Just for the sake of arguing lets say this is a concern. Ensuring that utilization equipment in kitchens are not served with Multiwire circuits
Would be only the first step to addressing your concern.

You would still have utilization equipment with different Line to line potential within reach of each other. The same hazard that you are concerned with would still exist in the kitchen.

Would you go on to say that no equipment in a kitchen could be supply by two different branch circuits having a different line to line potential

By placing receptacles served by outer conductors of mwbc up to 4 feet apart in the kitchen,the likelihood of that hazard may be reduced.

 

[hurk27]

By placing receptacles served by outer conductors of mwbc up to 4 feet apart in the kitchen,the likelihood of that hazard may be reduced.

and appliances for kitchen use have 2 foot cords, so now what?

 

[david]

By placing receptacles served by outer conductors of mwbc up to 4 feet apart in the kitchen,the likelihood of that hazard may be reduced.

and appliances for kitchen use have 2 foot cords, so now what?

As hurk27 is pointing out that isolation of equipment from each other in a kitchen just may not be practical when you consider the cord lengths and the span of peoples arms You could go to patient care areas and look at a six foot separation then how much floor area would a kitchen have to have to accomplish this to make it affective. You might have to advocate for a different method to address your concern. Maybe you might want to consider redundant grounding in kitchens.

 

[T.M.Haja Sahib]

As hurk27 is pointing out that isolation of equipment from each other in a kitchen just may not be practical when you consider the cord lengths and the span of peoples arms You could go to patient care areas and look at a six foot separation then how much floor area would a kitchen have to have to accomplish this to make it affective. You might have to advocate for a different method to address your concern. Maybe you might want to consider redundant grounding in kitchens.

I just said it reduces the likelihood of injury by shock from 240V;it is not possible to eliminate it completly.I hope you see that people use separate receptacles differently from duplex receptacles.

And what you mean by redundant grounding in kitchens ?

 

[iwire]

I hope you see that people use separate receptacles differently from duplex receptacles.

What are you talking about?

 

[T.M.Haja Sahib]

What are you talking about?

Ask David about it.

 

[George Stolz]

I have moved this to a new discussion, as it has no bearing on the original question.

 

[Dennis Alwon]

Somehow we have gone from a dishwasher and disposal to appliance on the counter that are not grounded. I will say that I have a toaster that has mostly plastic but some metal and it is not grounded. I can only assume the metal parts are not capable of being energized because of the proximity to the power.

 

[George Stolz]

If you wish to feed the troll, please do so here.

Sahib, my choice of words is based upon the fact that the NEC, the NEC Handbook, the ROPs/ROCs, and the UL White Book all permit the use of MWBC on duplex receptacles. Based on this and previous discussions, it appears that you are in fact simply trolling for an argument.

 

[iwire]

The moving of contents from one thread to form new thread,I have no objection.

You get to star in your own thread, how could you object?


Now please explain how an average homeowner could get a 240 volt shock in an typical home kitchen with a 120/240 supply?

 

[renosteinke]

The NEC makes clear it is neither design manual or instruction book; prior knowledge of the trade is required.

Learning a trade is like learning a language; any single element, when looked at alone, can seem arbitrary or foolish. Yet, you're not in a position to speak the language until you know all of it- no matter how smart you are in another field.

I'm reminded of music teachers who won't let you quit until you're good enough to know what you're doing. Only then can you make an informed choice.

We have our ways, which may differ from others' .... but it does not follow that one is 'right' while the other is 'wrong.' Such a narrow view shows the limitations of an engineering education.

I weary of those who know other fields assuming that their knowledge of one field makes them automatic experts in another .... or that their field means they 'outrank' the other guy.

Some folks need to stick to polishing their slide rules, and stay away from electric work- a field they are clearly not competent to discuss.

And, yes, I agree that continually finding different ways to debate the meaning of 'is' makes one a troll. Trolls belong under bridges - not in this forum.

To reply to the OP's claimed concern .... receptacles only have a plug pattern that is defined by NEMA designation as "125v." That is not - repeat NOT- a voltage rating. Nor does such a marking have any bearing on the voltages of other items nearby. Rating tests use voltages way beyond 250v, and the system is intended for such use; witness the 300v difference of potential required before we have to instal partitions or barriers.

In short, the OP's concern is based on a false assumption.

 

[T.M.Haja Sahib]

Sahib, my choice of words is based upon the fact that the NEC, the NEC Handbook, the ROPs/ROCs, and the UL White Book all permit the use of MWBC on duplex receptacles. Based on this and previous discussions, it appears that you are in fact simply trolling for an argument.

Your quoting of NEC,the NEC Hand book etc etc does not still endow you with an unlimited knowledge to draw such a conclusion.

You appear to think that the objection against usage of mwbc in kitchen in particular is my own and so in your opinion I was a troll.

Not so,Look deeper into the technical literature on NEC.You would find the same controversy still unresolved.