220.55 and 40A range circuit

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Bob NH said:
Perhaps gndrod who profiles himself as a "wiring author" will furnish a link to a peer-reviewed and published paper that supports his position.
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I hope this is not a disparaging comment on RBJ's profession?

The reason this forum exists is to discuss the NEC, and it frequently results in different interpretations and positions, there is no reason to diminish a person to establish a point.

I have seen one of RBJ's books, it was well done, if I might pitch my two cents in. I saw few if any comments that I might have taken issue with editorially.
 
georgestolz said:
I hope this is not a disparaging comment on RBJ's profession?

The reason this forum exists is to discuss the NEC, and it frequently results in different interpretations and positions, there is no reason to diminish a person to establish a point.

I have seen one of RBJ's books, it was well done, if I might pitch my two cents in. I saw few if any comments that I might have taken issue with editorially.
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It was not intended to diminish anyone's position. It was a simple inquiry asking that a "wiring author", who might have ready access to published material and references by himself or others to support his position, post that material or a link to it for the enlightenment of the viewers of this thread.

Every one of my posts on this article were based on the code, with citations. I have not been able to find any published material that supports the argument that gndrod made here. If he, or anyone else, have such material, I would like to see it.
 
Gentlemen, Seems I have touched on a subject that requires research in 2007 in deciphering the intents of the NEC and the applications of each Article in their respective use.

This discussion is about Art. 220 being used for calculation of Demand Factors to determine required minimum loads in an electrical service.

This discussion is also about using Art. 210 as the basis in determining conductor size selection of branch circuits.

I do not see the difficulty in understanding such an elemental requirement for applying the NEC. I will consult with peers on this matter when shop opens next year. Thank you for your patience and I will return with the answers from the NFPA electrical section soon. Happy New Year everybody.

spelling/grammatical content
 
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gndrod said:
Gentlemen, Seems I have touched on a subject that requires research in 2007 in deciphering the intents of the NEC and the applications of each Article in their respective use.

This discussion is about Art. 220 being used for calculation of Demand Factors to determine required minimum loads in an electrical service.

This discussion is also about using Art. 210 as the basis determining conductor size selection of branch circuits.

I do not see the difficulty in understanding such an elemental requirement for applying the NEC. I will consult with peers on this matter when shop opens next year. Thank you for your patience and I will return with the answers from the NFPA electrical section soon. Happy New Year everybody.

spelling/grammatical content
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I disagree with your statement of the question.

This discussion is about using Art. 220 as the basis for determining conductor sizes for branch circuits that serve cooking appliances in residences.

I believe that Article 220, and particularly 220.55 and Table 220.55, are properly used to determine conductor size of branch circuits for cooking appliances in residential occupancies.

You hold that Article 220 is not permitted for that purpose.

THAT is the question that must be answered with appropriate citations and references.
 
Bob, Disagreement builds nations and improves methods. I will get back with answers to interpretation and means of intent from the NFPA source...not NEMA.
 
Steve,

Steve,

hillbilly said:
If you can't use the branch circuit load to size the conductors and OCP, then what would you use?

.......The NPR and conductor type minimum ampacity with OCP required.

I always run a 6/3 cu for a (residential) range circuit, so it's never a issue.
I do remember that the range has a warming drawer, self cleaning feature, 4 surface elements and regular oven, so I suppose it's possible to get 16KW of heat out it of with everything turned on.

..........A good practice that I personally have done over 40 years of wiring ranges for safety factors of avoiding conductor and termination degradation or any liability litigation. These factors are not discussed in the NEC.
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Bob NH said:
It was not intended to diminish anyone's position.
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Glad to hear it. :)

gndrod said:
I always run a 6/3 cu for a (residential) range circuit, so it's never a issue.
I do remember that the range has a warming drawer, self cleaning feature, 4 surface elements and regular oven, so I suppose it's possible to get 16KW of heat out it of with everything turned on.
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If the range is nameplated at 16 kW, and you install 6/3 NM to it, you would have to use Table 220.55 to do so; it would be pulling 67 amps on a 65 amp conductor. :)
 
georgestolz said:
Glad to hear it. :)


If the range is nameplated at 16 kW, and you install 6/3 NM to it, you would have to use Table 220.55 to do so; it would be pulling 67 amps on a 65 amp conductor. :)
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Hi George,

I guess I posted a reply that was scrambled with steve's post and my reply at the same time. My comment was in support of his using a larger range circuit and not related to the present 16kw subject.

BTW, congratulations, you are the perfect person for the forum moderator diplomacy award. I might add you are in great company with the other moderators. :):) Tx, rbj
 
gndrod said:
BTW, congratulations, you are the perfect person for the forum moderator diplomacy award.
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Thanks, rbj. :D

I've been training for months to not fly off the handle if I could avoid it, I probably owe Gmack for the training. ;)

I might add you are in great company with the other moderators.
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I'd go one further and submit that I am the least qualified, and am honored to have been considered for the role. I'll echo what Bob once said; I don't amount to a whole lot in a crowd like that. :)

At least now my coworkers will quit making fun of me for all the time I spend online...right? Right?!? :D
 
georgestolz said:
At least now my coworkers will quit making fun of me for all the time I spend online...right? Right?!? :D
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:grin:

Keep telling yourself that, you may start to believe it. :grin:


They will call more often with code questions.
 
George,

Just participating on this forum is a character builder so you guys really have to be bullet proof.

Bob (iwire), I ran across the marathon 220.55 range calculation of 4-06-06discussion you mentioned earlier. Now that thread required wearing a Kevlar jacket.

I still have to reply on this one next week.

Happy New Year
 
I've been following this thread, and I recall the previous thread on the topic (and no, I'm not going to re-read it :) ..... and I don't think that I could make a stand on one side or the other with respect to what the code demands in this case.

Instead I'd like to suggest a change in direction for the discussion.

Rather than asking what the _code_ requires, I'd like to know what _reality_ requires.

With this much disagreement on the code interpretation, it is absolutely certain that there have been a large number of installs which follow the lower capacity interpretation.

I'm wondering what sort of experience there has been with these installs.

A 16KW nameplate range is _not_ a single 16KW heating element. It is a set of heating elements, separately controlled, with a total capacity of 16KW.

-Jon
 
Jon,

Just judging from range circuit failures, I have run across old circuits that were invariably wired with 6/3 Cu with no distinct failure problems. Upgrades requiring four-wire circuit connections posed questions on kitchen remods for cable changeovers but passed using the existing 3 wire circuits.

In one case of a newer 12 yo kitchen, the 8/3 wgnd conductors had heat degradation at the range termination where the wire connectors were somewhat scorched. Maybe that is why the HO was switching to gas. Who knows. The newer ranges with 14kw loading certainly require a cautious look at conductor sizing from a liability standpoint. I would not allow wiring a 16kw range on an #8 awg circuit unless the unit manufacturer specifically allowed it. You can imagine the tail chasing in a court of law trying to sort out the NEC minimum allowances as this thread has demonstrated so far. I guess the reality question is, would any contractor make a decision to wire #8 BC to a 16kw range? Would you?
 
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gndrod said:
Jon,

"I guess the reality question is, would any contractor make a decision to wire #8 BC to a 16kw range? Would you?"
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To add to that reality question.

If the electrician wired a range circuit for a residence, and (IMO...by code) installed a 40 Amp circuit to power that range, who's responsibility is it to insure the circuit is adequate if:
The range has not been selected when the house is rough wired?
The owner (sometime in the future) replaces that range with a larger unit?

As it is...again IMO...the code provides adequate safety by allowing the 40A circuit.
As stated many times on this web site...The code is not a design manual.
8/3NM is rated 50A at 75C, will be connected to a 50A receptacle and protected by a 40A breaker (max.).
Where is the safety concern?
Most likely, the home owner will get tired of nusiance breaker tripping (if it ever trips) and call a electrician or will simply learn what heating elements they can turn on at the same time.
I'm not saying that tripping breakers are a good thing, but will likely become a fact of life as range sizes (KW ratings) increase.

The only solution that I see to this (supposed?) problem is:
Either the code needs to change it's requirements and only allow 60 amp (or larger) circuits for residential ranges ...or...the range manufacturers need to design the range controls to prevent operation of all heating elements at the same time and fix the total at a certain (maximum) KW.

That or some other rule (I don't know what) needs to be established to match range loads to the circuit provided....maybe establish a maximum (range) KW allowed on residential and always wire for the max.
It's beginning to be a bigger problem as the KW rating of 30" residential ranges increase.
There are thousands of residential ranges out there that operate on 40A circuits.
Sooner or later, they will be replaced.
With what?
Most people buy a new range without considering the KW load, or even knowing what it means.
They have the range delivered and "installed" by a delivery man who simply attaches a cord and plugs it in.
Who's problem is it if it trips the existing breaker?
If the circuit is wired to code, it's the homeowners.
If it's not to code, it's the electrician's that wired it.
If we can't read and apply the code as written, what use is it?
Is it fact, or is every part subject to interpretation?
Where is the dividing line?
Just my opinion
steve
 
Steve, Well said and better than a good opinion. I would like to quote your remarks to the TCC for substantiation on the next 2011 cycle proposals.
Happy New Year.
 
georgestolz said:
If the range is nameplated at 16 kW, and you install 6/3 NM to it, you would have to use Table 220.55 to do so; it would be pulling 67 amps on a 65 amp conductor. :)
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I feel like I'm missing something here. How, in light of 110.14(C)(1), is #6 rated at 65A? Are you assuming that the terminals on the unit, breaker, and in the receptacle set (if one is used) are rated 75 degC? I'm on the design side so I don't see nameplates and terminal markings very often. It's entirely possible that everything in new equipment will be 75 degC rated, but there would still be a problem on older equipment for refits. You're not the only one in this thread who has quoted 75 degC ampacities rather than 60 degC ampacities.

Martin
 
hmspe said:
I feel like I'm missing something here. How, in light of 110.14(C)(1), is #6 rated at 65A? Are you assuming that the terminals on the unit, breaker, and in the receptacle set (if one is used) are rated 75 degC? I'm on the design side so I don't see nameplates and terminal markings very often. It's entirely possible that everything in new equipment will be 75 degC rated, but there would still be a problem on older equipment for refits. You're not the only one in this thread who has quoted 75 degC ampacities rather than 60 degC ampacities.

Martin
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If you are connecting a range with a cord or in a junction box, the only temperature that matters for branch circuit wiring is the temperatre rating of the outlet and the circuit breaker, or the cable and connection in the junction box. All of those that I have seen are rated to at least 75 C.

There was one comment in an earlier post about range wiring that I am not sure about: "8/3NM is rated 50A at 75C, will be connected to a 50A receptacle and protected by a 40A breaker (max.). "

NEC 334.80 says that NM cable must be used at the 60 degree rating, which is 40 amps for #8.
 
Bob NH said:
There was one comment in an earlier post about range wiring that I am not sure about: "8/3NM is rated 50A at 75C, will be connected to a 50A receptacle and protected by a 40A breaker (max.). "

NEC 334.80 says that NM cable must be used at the 60 degree rating, which is 40 amps for #8.
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You're right, I was incorrect in the way I worded that statement.
I should have said the conductors of #8 NMB are rated at 90C but must be selected using the 60C column.
That's why I said 8/3NM must be protected by a 40A breaker (max).
steve
 
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