220.55 and 40A range circuit

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I think the end of this depends on determining if we agree with Table 220.55 and its Footnote 1. That footnote and the table define demand (LOAD) for a range over 12 kW through 27 kW as follows:

From Table 220.55; Demand = Load = 8kW + (0.05)(8kW)(Nameplate kW - 12kW)

That results in the following:
Nameplate kW = 12; Load = 8 kW
Nameplate kW = 16; Load = 9.6 kW; Amps = 40
Nameplate kW = 22; Load = 12 kW; Amps = 50
Nameplate kW = 27; Load = 14 kW; Amps = 58.33
 
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It appears I may have been mistaken here, I assumed this was just a replay of the thread I linked to.

It seems this is a different question.
 
210.21(b)(4)

210.21(b)(4)

I'll throw this out to you. 210.21(B)(4) Range recepticle rating- the ampere rateing of a range recepticle shall be permitted to be based on a single range demand load as specified in table 220.55
 
Hi Bob (iwire), i believe the range calculation discussion (at least the last one I posted an answer) was on the 8/02/06. The post is similar to the same questions being asked by the OP that concerns both addressing 220.55 for calculating demand factors of ranges and 210.19 the actual range loads being served conductor sizing. Ref post #28 by yours truely. (apples and oranges) Happy New Year.
 
Hi steve (hillbilly),
Your math is correct for [220] demand factor calculations only. Use [210.19] for loads being served for determining the range branch circuit conductor size and disconnect needed for the kw rating of the unit. The load is a 70 amp circuit. That electrical range is exceptional in size. I am curious to know the brand and model. Tx rbj
 
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I'm a little late to this section but have I missed a post referencing note 4 to table 220.55??

if not I would think this impacts the discussion.
 
gndrod said:
Hi steve (hillbilly),
Your math is correct for [220] demand factor calculations only. Use [210.19] for loads being served for determining the range branch circuit conductor size and disconnect needed for the kw rating of the unit. The load is a 70 amp circuit. That electrical range is exceptional in size. I am curious to know the brand and model. Tx rbj
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I believe that use of 210.9 for selecting the range circuit load is based on disregard of the explicit requirements of Article 220.

NEC 220.1 Scope. "This article provides requirements for calculating branch circuit, feeder, and service loads. . . . "

It couldn't be more explicit. Article 220 provides the requirements for calculating the loads for selecting the OCPDs and the conductors.

I won't repeat all of the previous citations, but they all lead directly to Table 220.55 as the basis for calculating the branch circuit loads, and therefore, the conductors and OCPDs, for residential cooking appliance circuits.

CPALs comment above regarding Note 4 of Table 220.55, not previously cited, reinforces that conclusion.
 
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Bob NH,
Are you saying the 16kw range BC and disconnect can be #8 with a 40a breaker? Please explain the rational of pre-empting [210.19(A)(1)] load being served conductor requrements. Doesn't [220.55] apply to DF calculations only?
 
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gndrod said:
Bob NH,
Are you saying the 16kw range BC and disconnect can be #8 with a 40a breaker? Please explain the rational of pre-empting [210.19(A)(1)] load being served conductor requrements. Does [220.55] apply to DF calculations only?
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The rationale is as follows. Take these IN ORDER.

1. 210.19(A)(1) General says that branch-circuit conductors shall have an ampacity not less than the maximum LOAD to be served.

2. 220.1 explicitly states that Article 220 provides requirements for CALCULATING LOADS, including branch circuit loads.

3. 220.14(B) states that "Load calculations shall be permitted as specified . . . in 220.55 for electric ranges and other cooking appliances."

4. 220.55 states that the LOAD for ranges and other cooking appliances shall be permitted to be calculated in accordance with Table 220.55.

5. Note 4 of Table 220.55 states, "Branch-Circuit Load. It shall be permissible to calculate the branch-circuit load for one range in accordance with Table 220.55."
This answers the question about demand factor only. It is permitted to use Table 220.55 for branch-circuit loads and sizing of conductors and OCPD.

6. Table 220.55, including Note 1, provides the instructions for calculating the demand (LOAD) for ranges from 12 to 27 kW.
The code permits the LOAD to be defined as something less than the nameplate rating.
From Table 220.55; Demand = Load = 8kW + (0.05)(8kW)(Nameplate kW - 12kW)

7. Results of that calculation are:
Nameplate kW = 12; Load = 8 kW; Minimum 40 Amp circuit per 210.19(A)(3)
Nameplate kW = 16; Load = 9.6 kW; Amps = 40
Nameplate kW = 22; Load = 12 kW; Amps = 50
Nameplate kW = 27; Load = 14 kW; Amps = 58.33

So a 40 Amp circuit is permitted for a range with a 16 kW or less nameplate rating.
 
Bob NH said:
The rationale is as follows. Take these IN ORDER.

1. 210.19(A)(1) General says that branch-circuit conductors shall have an ampacity not less than the maximum LOAD to be served.>>>This section applies to ampacity for a maximum LOAD being served and has nada to do with a service demand factor calculation specifically 220.1. Please read calculation for determining a service, 220.55 does just that alone and has nothing to do with SIZING a circuit load conductor.

2. 220.1 explicitly states that Article 220 provides requirements for CALCULATING LOADS, including branch circuit loads. >>> Again note the provision for calculating loads that include branch circuit loads for the overall service(s) being determined. (I.e. See Annex D Demand Factor adjustments for calculating Service centers)

Article 220 is specifically not for size amp calculations of circuit conductors.
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How about the manufacturers install instructions that a Westinghouse smooth top, 13.5 kw range, very common is Sw Florida, is to be installed on a 50 amp Ckt. My AHJ 40 says is fine as per code?? .......I don't like it but "That's the way it is". "Who ya gonna call"????
 
gndrod said:
Bob NH said:
The rationale is as follows. Take these IN ORDER.

1. 210.19(A)(1) General says that branch-circuit conductors shall have an ampacity not less than the maximum LOAD to be served.
>>>gndrod This section applies to ampacity for a maximum LOAD being served and has nada to do with a service demand factor calculation specifically 220.1. Please read calculation for determining a service, 220.55 does just that alone and has nothing to do with SIZING a circuit load conductor.

2. 220.1 explicitly states that Article 220 provides requirements for CALCULATING LOADS, including branch circuit loads.
>>> gndrod Again note the provision for calculating loads that include branch circuit loads for the overall service(s) being determined. (I.e. See Annex D Demand Factor adjustments for calculating Service centers)

gndrod >>> Article 220 is specifically not for size amp calculations of circuit conductors.
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I cited the Code paragraphs for every point that I made and presented them in logical order. It would be helpful for the discussion if you would cite the paragraphs that support your rebuttal. There are assertions but no code citations in your rebuttal.

Article 220 specifically IS for calculations of circuit conductors. Read the first sentence of the Scope paragraph 220.1. You saying that it isn't does not change the facts.

Take it by the numbers in my list. I note that you SKIPPED Point 3 of my list.

3. 220.14(B) states that "Load calculations shall be permitted as specified . . . in 220.55 for electric ranges and other cooking appliances."

220.14(B) is explicitly in the Branch Circuit Load Calculations section.

Note 4 of Table 220.55 explicitly states that the branch circuit load for one range may be calculated in accordance with Table 220.55. Where is your rebuttal for that?
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Hi Bob,
You are stating LOAD Calculations and not CONDUCTOR sizing calculations. 220.14(B) is a good example as was 220.55 and 220.1. These are actual conditions you are misreading as far as related code section applications. Please do not look for a rebuttal. That is dangerous in the electrical trade, especially with safety issues of wiring a 16kw range on a #8awg Cu conductor BC with an OCPD of 40 amps per a demand factor section. Heck even a 12kw fully lit range will draw over 45 amps. Put an amprode on the line and see what it reads but do not touch the BC wiring pleeaasse.

Just remember Article [220] BRANCH CIRCUIT, FEEDER, AND SERVICE CALCULATIONS for Service Demand Factor Calculations and Article [210]BRANCH CIRCUITS for ampacity of maximum loads being served over B-C conductors are not to be confused with intrinsic LOAD REFERENCES.
You'll do fine when both Articles are interpreted separately in the context they are meant to be applied.

1...[210.19] Conductors-Minimum Ampacity and Size, for (A) Branch Circuits not more than 600Volts.

2...[220.10] Branch Circuit Load Calculations, for 220.12, 220.14, 220.16 etc., are only part of the main application of calculation methods as stated in 220.1. Circuit load calculations are not conductor size calculations if you read the two sections carefully.
 
gndrod said:
Hi Bob,
You are stating LOAD Calculations and not CONDUCTOR sizing calculations. 220.14(B) is a good example as was 220.55 and 220.1. These are actual conditions you are misreading as far as related code section applications. Please do not look for a rebuttal. That is dangerous in the electrical trade, especially with safety issues of wiring a 16kw range on a #8awg Cu conductor BC with an OCPD of 40 amps per a demand factor section. Heck even a 12kw fully lit range will draw over 45 amps. Put an amprode on the line and see what it reads but do not touch the BC wiring pleeaasse.

Just remember Article [220] BRANCH CIRCUIT, FEEDER, AND SERVICE CALCULATIONS for Service Demand Factor Calculations and Article [210]BRANCH CIRCUITS for ampacity of maximum loads being served over B-C conductors are not to be confused with intrinsic LOAD REFERENCES.
You'll do fine when both Articles are interpreted separately in the context they are meant to be applied.

1...[210.19] Conductors-Minimum Ampacity and Size, for (A) Branch Circuits not more than 600Volts.

2...[220.10] Branch Circuit Load Calculations, for 220.12, 220.14, 220.16 etc., are only part of the main application of calculation methods as stated in 220.1. Circuit load calculations are not conductor size calculations if you read the two sections carefully.
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I believe you are completely wrong. You have not cited any basis for your conclusion.

Circuit loads are the ONLY basis for sizing overcurrent devices and conductors.

Why won't you address the provisions of Note 4 of Table 220.55 that explicitly permits use of Table 220.55 for a single range?

Why won't you address the fact that 220.14(B) is specific to the BRANCH CIRCUIT CALCULATION for ranges?

Why won't you cite the code paragraphs that support your assertion that circuit load calculations are not to be used for determining conductor sizes? Why don't you cite the paragraphs that I should "read carefully". You haven't cited the paragraphs because there is absolutely no code paragraph that supports any other basis for designing the circuit.

Why won't you address the issue that 210.19 says size the conductors for LOAD, and 220.55 defines how to calculate the LOAD. There is NOTHING in the code that says that the load for a range circuit is the nameplate rating of the appliance. Article 220 (Section 220.55) says the the nameplate rating IS NOT the load for the range circuit.
 
Hi Cavie,
The AHJ may be correct because of wire and termination methods used in the application. (i.e. high temp wiring and connector compliant ratings)
If the range was a 16kw load I would be suspicious and concerned that the constant tripping would encourage someone to change out the breaker to a 60 amp CB.
 
Ok Bob, I will address note 4 in Article 220 from a DEMAND FACTOR LOAD TABLE..

4. Branch Circuit Load. It shall be permissible to calculate the branch-circuit load load load load for one range in accordance with Table 220.55.

I will stop there as the rest of the note supports the first sentence implicitly. As you will notice at the top of the page it reads... Table 220.55 Demand Factors and Loads, and other Household Cooking Appl.....etc.

Bob, This is a DEMAND FACTOR TABLE! This is for DF calculations for the Service loads only.

Does this make sense? This Table does not set the load conductor ampacity size requirements. I hope you can see this...have a Happy New Year. rbj
 
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RBJ, I'd have to agree with Bob NH on this one. Note 4 is extremely explicit that this demand table can be applied at the branch circuit level.

If you can provide some text stating that the demand table can only be applied at the service calculation level, please do. :)
 
Since my edit button appears to not work right this minute, let me add this in a second post:

I do agree that there may be conflicting permissions on this subject, as I noted in a post in the thread that Bob linked to.
 
gndrod said:
Ok Bob, I will address note 4 in Article 220 from a DEMAND FACTOR LOAD TABLE..

4. Branch Circuit Load. It shall be permissible to calculate the branch-circuit load load load load for one range in accordance with Table 220.55.

I will stop there as the rest of the note supports the first sentence implicitly. As you will notice at the top of the page it reads... Table 220.55 Demand Factors and Loads, and other Household Cooking Appl.....etc.

Bob, This is a DEMAND FACTOR TABLE! This is for DF calculations for the Service loads only.

Does this make sense? This Table does not set the load conductor ampacity size requirements. I hope you can see this...have a Happy New Year. rbj
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I think that all that is necessary has been said and I hope that I can keep my personal resolution to make this my last post on this thread. Perhaps gndrod who profiles himself as a "wiring author" will furnish a link to a peer-reviewed and published paper that supports his position.

Those who accept Table 220.55 as the basis for calculating the branch circuit loads will continue to use 40, 50, and 60 amp breakers and conductors for ranges up to 27 kW nameplate ratings.

Those who agree with gndrod will spend the early part of 2007 looking for 70 amp to 110 amp branch-circuit breakers and conductors for their 15 to 27 kW nameplate-rated ranges.

I just found a NEMA site (I know they don't make code rules.) that appears to support the use of Table 220.55 to establish branch circuit ratings in the manner that I have discussed in this thread. It follows the same logical process that I used from 210.19(A)(3) to 220.14(B) to Table 220.55. Everyone can decide for themselves between NEMA and gndrod. http://www.nema.org/stds/fieldreps/faqs.cfm#branch

QUESTION on the NEMA site: A range branch circuit is calculated and installed at 40 amps. The range installed is rated at 13 kW. Does the wiring need to be changed?

ANSWER: No. NEC? 210.19(A)(3) requires that the minimum circuit for ranges rated 8.75KW or more be 40 Amps. 220.14(B) permits Table 220.55 to be used to size branch circuits supplying electric ranges. Table 220.55 Note 1 requires where ranges exceed 12KW the demand listed in Column C must be increased by 5% for each KW the range exceeds 12KW. This range exceeds 12KW by 1KW which means the demand of 8KW in column C must be increased by 5%, which works out to be 8.4KW (35 Amps).
 
Really stirred up a hornets nest with this one.
It seems to me that (by code) the 40A circuit is allowed to supply a 16 KW range.

Note 4 of Table 220.55 specifically allows calculation of the branch circuit load according to Table 220.55.

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

You can't use the KW rating of the range (usually) because it's not around when you rough in the circuit, although I'll admit, I've never seen (until the other day) a 16KW, free standing (30"), residential range.

I'm going back for some other work and I'll get the make and model.
I might also check the amps with various elements turned on.

This is a regular customer of mine who bought herself a new range. I was looking the installation over (vendor delivery and hook-up) to make sure the ground and neutral were wired properly.
When I saw the 16KW my mind said "oh crap", and knew that I needed to dig deeper.
The installation manual made no mention of circuit size. All it had was 16KW/240V on the factory tag, so I ran the calculation.
I can talk the customer into a up-grade (to 6/3, 60A), but I want to be sure that it's necessary.
It won't be easy (a real PITA) to replace.

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.

Anyway, I was suprised when the calculation added up exactly to 40 amps, so I posted my question.
It's possible that the manufacturer listed it at 16KW exactly to allow it to be connected to a 40A circuit.
It still seems small, but apparently (IMO), it's code worthy.

thanks for the replies
steve
 
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