40 amps from NEMA 5-20r

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mbrooke

mbrooke

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Would a duplex receptacle overheat if two separate circuits were run to each set of contacts with a NEMA 5-20p pluged into each half? Both appliances drawing 16 amps continuously? Seems legal, but I'm being told its cheesy design.
 
Probably one of those things where the quality of the receptacle matters.

Something with really heavy contacts and a horsepower rating rather than the cheapest device from 'big orange' even though both are nominally rated for the full 16A on a continuous basis.

-Jon
 
winnie said:
Probably one of those things where the quality of the receptacle matters.

Something with really heavy contacts and a horsepower rating rather than the cheapest device from 'big orange' even though both are nominally rated for the full 16A on a continuous basis.

-Jon
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Hope so. FWIW Utilities are known for getting the most out of their assets.
 
"Legal" - depends on what the recept install docs show.

The Leviton 5-20r dual (5362-SW, "heavy duty industrial") install doc only shows 1BC or 1MWBC, but not 2BC's. So I suspect you cannot get 40A on one dual recept yoke, at least not this make/model.

If you broke off both fins and brought in two 20A BC's, the recepts can handle it, but would still be a NEC violation if the install doc reads like the 5362, etc.
 
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FionaZuppa said:
"Legal" - depends on what the recept install docs show.

The Leviton 5-20r dual (5362-SW, "heavy duty industrial") install doc only shows 1BC or 1MWBC, but not 2BC's. So I suspect you cannot get 40A on one dual recept yoke, at least not this make/model.

If you broke off both fins and brought in two 20A BC's, the recepts can handle it, but would still be a NEC violation if the install doc reads like the 5362, etc.
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I think this could be seen as the installation instructions not being intended to be exhaustive, leaving other possible variations to the professional electrician. The counter argument against the limitation is that if the intent were not to allow the neutral to be separated too, there would not be a breakout tab on the neutral side.
 
GoldDigger said:
I think this could be seen as the installation instructions not being intended to be exhaustive, leaving other possible variations to the professional electrician. The counter argument against the limitation is that if the intent were not to allow the neutral to be separated too, there would not be a breakout tab on the neutral side.
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That's an ok argument EXCEPT the directions show how it may be used.

I could also argue that a fin on each side is because it was easier to use all the same stamped metal parts to make the item.

If the install doc shows examples of how it may be used, then I do not apply the "what about" clause. It showed one BC with pass-through, and a one MWBC. If two BC's were allowed then why not show it? I have no doubts each recept can carry 20A (40A on the yoke).

I'll send a Q to Leviton support contact and ask, lets see what they say.
 
LarryFine said:
Is it 40a, or is it still 20a, just at greater voltage? :unsure:
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If we are not limiting it to an MWBC, it could be two 20A circuits on the same phase. No question of a higher voltage.
I suppose that since they could not be recombined in any way you would have to leave it at two 20A circuits, not 40A of anything.
 
If wired on to a MWBC, you could plug two separate appliances in, each with a 20A cord cap, each drawing 16A on a continuous basis.

I don't see a significant difference in thermal load if this were wired with two completely separate branch circuits.

The 'current balancing on the neutral' aspect of the MWBC would not matter at the contact blades, only at the connection to the circuit wiring. I agree there would be less heating at the neutral terminal wiring, but I think the contact blades heating would be the dominant factor.

-Jon
 
mbrooke said:
Would a duplex receptacle overheat if two separate circuits were run to each set of contacts with a NEMA 5-20p pluged into each half? Both appliances drawing 16 amps continuously? Seems legal, but I'm being told its cheesy design.
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The NEC answer to your question is 210.7, it is specifically allowed and I have done it many times in my career.

Roger
 
winnie said:
If wired on to a MWBC, you could plug two separate appliances in, each with a 20A cord cap, each drawing 16A on a continuous basis.

I don't see a significant difference in thermal load if this were wired with two completely separate branch circuits.

The 'current balancing on the neutral' aspect of the MWBC would not matter at the contact blades, only at the connection to the circuit wiring. I agree there would be less heating at the neutral terminal wiring, but I think the contact blades heating would be the dominant factor.

-Jon
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With a MWBC with both loads 'on', you get 16A, not 32. There is no way to get "each drawing 16A" with a handle tied 20A ocpd for MWBC. 16A would still be the max on the yoke, whether it be one BC 20A ocpd or a 2pole tied 20A ocpd for MWBC. Think about it, if there was anything more than 20A load side(s) the ocpd(s) would trip.

The only way to get 40A on the yoke is with two BC's, which I thought was the Q at hand?
 
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roger said:
The NEC answer to your question is 210.7, it is specifically allowed and I have done it many times in my career.

Roger
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Not if the instructions do not show two BC's as a wiring option. So best to get make/model that 1) does not have a NRTL lab listing, and 2) has no install instructions. The "professional electrician" as was mentioned earlier should apply these tests before installing the item. Still bound to understanding a listing even if no install instructions are present, and vice-versa.
 
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GoldDigger said:
If we are not limiting it to an MWBC, it could be two 20A circuits on the same phase. No question of a higher voltage.
I suppose that since they could not be recombined in any way you would have to leave it at two 20A circuits, not 40A of anything.
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I would not put two 20's from same phase. Use both poles to reduce magnetic field emanating from the recept/yoke. Have to check, but I think hospitals/labs have some rules around this when recepts are side-by-side but fed from different BC's.
 
FionaZuppa said:
I would not put two 20's from same phase. Use both poles to reduce magnetic field emanating from the recept/yoke. Have to check, but I think hospitals/labs have some rules around this when recepts are side-by-side but fed from different BC's.
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Reduce the magnetic field how? Or, two ask it another way,,, in what way is the magnetic field increased? You would have balanced current hot to neutral on circuit A1 and balanced current hot to neutral on circuit A2, there is no net current.
 
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