Range Wire Sizing

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George, me too! I still haven't heard Mike explain how the last sentence of 210.19(A)(3) negates the rest of the paragraph. I think if the last sentence was all you had to go by it would be the only sentence in the article.
 
I would also like to see Mike explain how his interpretation can get around 210.23.

210.23 Permissible Loads.
In no case shall the load exceed the branch-circuit ampere rating. An individual branch circuit shall be permitted to supply any load for which it is rated. A branch circuit supplying two or more outlets or receptacles shall supply only the loads specified according to its size as specified in 210.23(A) through (D) and as summarized in 210.24 and Table 210.24.
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210.23 applies to all branch circuits and does not have any exceptions.

So I say again, under current NEC rules you can not connect a range that after applying demand factors requires more than 40 amps to a 40 amp branch circuit. :)
 
Bob,

I think we all agree with you. I also think Mike is playing with everyone. I can't believe he is that narrow-minded.

So I guess I'll play along and contribute to the length of this thread.
 
If Mike is "playing" with us I would have a problem with that. Deliberate "playing" with interpretations of the NEC on this forum muddies the water for a lot of folks in their early stages of this trade that are here to learn. Someone taking Mike's point of view on this subject and applying it in the field could cost them when they have to correct the installation. That's not too funny to me. I don't think that's what Mike Holt intended this forum to be about. That being said, I don't think Mike is "playing" and I base that on past experience of Mike's debates on this forum. He digs his heals in when he thinks he's right and it takes an act of congress to convince him when he's wrong. I think that's what will eventually happen with this topic and Mike has been big enough in the past to concede when he's been convinced he's wrong. It's coming, just wait.
 
Once again, I have been ignoring a thread because it had gotten so long as to be intimidating, before I could get up the courage to pay attention to it. I am only up to page 3 or 4, so my comments might not be up to speed with the discussion.

Mea culpa. I'll be more brave in the future.

jwelectric said:
As I have asked more than one time could someone explain away these words that are found in 210.19(A)(3)
For ranges of 8? kW or more rating, the minimum branch-circuit rating shall be 40 amperes.
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I'll give it a shot.

georgestolz said:
jwelectric said:
The way I read it is that I could install a 27kw range on a 40 amp circuit
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Mike, you are adding something to that last sentence. You are changing the word "minimum" to maximum. There's no two ways about it.
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Yes there are, and no he didn't. IMHO Mike has misinterpreted the wording, but you and Bob are misinterpreting Mike's misinterpretation. IMO, Mike is not changing "minimum" to "maximum." Rather, Mike is incorrectly interpreting the word "minimum" to mean "sufficient," in too broad a manner.

Here is my (i.e., the only correct :wink: 8) ) interpretation:
  • Consider a set of 20 ranges on display at a store. A homeowner is going to buy one of them, and you are going to install the branch circuit for whatever he decides to buy.
  • The set includes ranges rated in KW at 8.75, 10, 15, 17, 22, and a bunch of others. None are smaller than 8.75 KW.
  • Every member of this entire set would fall under 210.19(A)(3).
  • No matter which range is purchased, you cannot install a branch circuit rated below 40 amps. I think that much you will all agree with.
  • The question is whether you can install a 40 amp branch circuit for a range rated, let us say, at 17 KW.
  • Mike is saying "yes," because the 40 amp minimum applies to the entire set, and therefore to each and any single member of the set. That is Mike's misinterpretation. That is his failure in logical reasoning. This type of invalid reasoning is called "arguing from the general to the specific."
  • The truth is that the word "minimum" applies to the entire set, but that does not make it apply equally and separately to each and every member of the set.
  • In other words, if you apply the word "minimum" to a single member of the set, the word "minimum" does not mean that "nothing higher is needed, regardless of which member of the set you select." It means that "nothing smaller is acceptable, regardless of which member of the set you select."
  • If you wish to discover whether the "minimum" is also "sufficient" for any specific range, you need to look elsewhere in the code.
  • You only need look one sentence earlier. I agree with Bob and George on that. The rating of branch circuit conductors shall be not less than the maximum load to be served.
 
charlie b said:
I agree with Bob and George on that. The rating of branch circuit conductors shall be not less than the maximum load to be served. [/list]
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So on a 12KW range, is the maximum load 12KW or is it 8KW from 220.55 Column C? The way I read this, I could have a 12KW range on a circuit rated at 8KW. Or am I wrongly thinking that Demand and Load are the same thing?
 
I think there was some discussion on that topic somewhere in the middle pages. I haven't yet built up the courage to dig through that discussion in detail and to dig through the code itself, in order to discover the truth for myself.

Here is what I would like the code to say, if I were free to write the code my own way. It will take me some digging to discover whether or not the code is actually written this way.

WARNING: The following is fiction. It is my wish list. It may or may not bear any resemblance to the NEC.
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  • Article 220 should be used for calculating the load on a service or feeder. Nothing else. Specifically, it should not be used to size branch circuits.
  • Article 220 gives us opportunities to build a system with a capacity less than 100% of all installed equipment. The concept is that there is a good chance that the owner will not be running all equipment in the entire house, all at full capacity, and all at the same time.
  • On the other hand, there is a very good chance that the equipment served by a single branch circuit might be running at 100% of its capacity for long periods of time.
  • Therefore, the branch circuit (and here I am including the breaker and the conductors) should be sized for the maximum load (meaning "connected load," not "calculated load") that the branch circuit could (not "probably might") carry.
  • Therefore, if the range is 12KW, I would include a load of 8KW for the purposes of the service load calculation. But I would use 12KW (i.e., 50 amps at 240 volts) for the purposes of sizing the branch circuit.
I am more than willing to withdraw from this position, if anyone can prove that the code says otherwise. I am willing to concede, for example, that though a range is rated for 12KW, it is unlikely that the cook will be simultaneously running all four burners and the oven at max capacity.
 
charlie b said:
Therefore, if the range is 12KW, I would include a load of 8KW for the purposes of the service load calculation. But I would use 12KW (i.e., 50 amps at 240 volts) for the purposes of sizing the branch circuit. [/list]
I am more than willing to withdraw from this position, if anyone can prove that the code says otherwise. I am willing to concede, for example, that though a range is rated for 12KW, it is unlikely that the cook will be simultaneously running all four burners and the oven at max capacity.
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I agree completely. The way the codes reads now, I could have a 12KW range on a circuit designed for 8KW with #8 CU on a 35A breaker per 220.55 Note 4.
 
m73214 said:
So on a 12KW range, is the maximum load 12KW or is it 8KW from 220.55 Column C? The way I read this, I could have a 12KW range on a circuit rated at 8KW. Or am I wrongly thinking that Demand and Load are the same thing?
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The load is the demand load in this case of ranges. 8 kw would be the load to be served if the name plate rating did'nt require something more.Name plate rating superceeds over demand rating.If the name plate rating said 40a min, 50a max then you could go with #6 /50a breaker,or min #8/40a breaker.
Rick
 
m73214 said:
I agree completely. The way the codes reads now, I could have a 12KW range on a circuit designed for 8KW with #8 CU on a 35A breaker per 220.55 Note 4.
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No, the minimum branch circuit rating for single ranges 8-3/4 or more is 40a.
 
jwelctric wrote 210.19 A (3)
This last sentence clearly states that the MINIMUM circuit allowed for a range 8 ? kw or more RATING is 40 amps
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Mike would you please read and comment on the First sentance? I am not being a smart ass, I do need to know the answer. Should I just block it out with a black sharppie and pretend it isn't there?. It seems to be of no use if we are going to referance 220.55.

210.19 A (3) has not exceptions. No FPN, no notes. nothing. Just a very plain statement.
 
This is one of those times that I agree with Mike. I've been silent watching this too and went through a similar thought process a few years ago. I had assumed that a range circuit should be sized for the maximum nameplate value. However, every house I've seen built in the last 10 years has a 40A range circuit and an installed range that is 10KW or more. So either everyone is doing something wrong, or else the consensus here is wrong.

To me, the issue comes down to which rule takes precedence -- the size for maximum load to be served, or size for the calculated maximum demand load for a range. The code provides no clear answer, so I would size for nameplate to be safer.
 
on a practical note, I wire mostly spec homes that arnt sold till after the fact, I have no clue what appliances the future homeowner will buy with their allowances. I have always installed 8/3 on a 40amp breaker, I have never in all my years had a call due to a breaker tripping, I agree that if the nameplate is know at rough-in time it should be sized accordingly, but do most of you agree to my install based not knowing, but do you think I should install for maximum size? (remeber 8/3 romex is over a dollar a foot and rising}
 
jeff43222 said:
So the 14.4 kW range I mentioned when I started this little discussion should be on a 60A circuit? 14.4 kW ? 240V = 60A.
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Why do you keep interrupting? Oh, I forgot, sorry. :D

No, I'd say a 40A minimum for you, Jeff.

14.4kW is 2 kW over 12 kW, so using column C...
8kW x 110% = 8.8kW
8800W / 240 = 36.66 amps
40 amp branch circuit minimum.

I'd use a 50A with 6/3. :)
 
suemarkp said:
This is one of those times that I agree with Mike.
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Take two aspirin, a shot of Tequila, and call us in the morning. :D

However, every house I've seen built in the last 10 years has a 40A range circuit and an installed range that is 10KW or more. So either everyone is doing something wrong, or else the consensus here is wrong.
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What do you think after my last post? Does that effect your thinking? A 14.4kW range should get a 40A circuit, under the concensus.

(Unless I've had another delicious math blunder. :oops: )
 
RUWired said:
No, the minimum branch circuit rating for single ranges 8-3/4 or more is 40a.
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But........according to 220.55, Col C, Note 4, A range up to 12KW is considered to be 8KW for calculating branch circuit load. Maybe 210.19 (A) (3) should read 8KW instead of 8 3/4KW.
 
georgestolz said:
What do you think after my last post? Does that effect your thinking? A 14.4kW range should get a 40A circuit, under the concensus.
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Perhaps I'm not following the consensus, or the consensus is wavering.... I agree with what you posted -- a 40A circuit for a 14 KW range. It seemed to me that prior to this the consensus was that the calculated demand was not permitted to be considered maximum connected load.
 
The 40A branch circuit is good up to a range with a 16kW nameplace. This 16kW is 4 over the 12kW, so we need 20% over the 8kW from table 220.55. This would be a load of 9.6kW, or 40A.
 
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