40A or 50A Circuit

[sparkchaser1961]

Almost.

12.5kW - 12kW = .5kw + 5% = .525 + 8kW = 8,525 watts

8,525 kW / 240V = 35.52 A = 40A circuit.

This is way I read it too.

 

[aftershock]

That stinks on the inspectors side. I would think if they don't have a formal written amendment to the code then there is no change from what ever code cycle they are using 02' 05' or 08' If you go by NEC you will not go wrong as it gives you more back up then BillyBob the inspector saying "well thats the way I want it".

I will give example:
According to the 2002 code, we are suppose the bury our ground connection. The one that grounds the meter base. Consider: a ground rod must be 8' into the ground and we use 8' ground rods.
Shelby county, TN does not require the ground rod and connection to be below grade, rather they want the ground rod and connection above grade.
Bartlett TN is in Shelby CO but they have their own Insp dept and they follow the current code. Groud rods are to be below grade using the listed "acorn" clamps.

I just wish Shelby CO would go strictly by the NEC book so I have some reference to do my job.

 

[acrwc10]

Almost.

12.5kW - 12kW = .5kw + 5% = .525 + 8kW = 8,525 watts

8,525 kW / 240V = 35.52 A = 40A circuit.

This is way I read it too.

I don't understand how you can go to an Article that is titled "Feeder, and Service load calculations" and from that extrapolate that a 12.5 KW load need only be feed by an 8.5KW circuit?????????????????? These are for the combined loads of the whole service or Feeder, The table you are basing this on is not for rating the final branch circuit, if it was that would mean the more ranges you put in the smaller and smaller you could size those branch circuits. When figuring the Service size yes the more ranges the less the demand factor but that doesn't mean you under size the circuit to the range it self.
PLEASE educate me on this one.

 

[acrwc10]

I will give example:
According to the 2002 code, we are suppose the bury our ground connection. The one that grounds the meter base. Consider: a ground rod must be 8' into the ground and we use 8' ground rods.
Shelby county, TN does not require the ground rod and connection to be below grade, rather they want the ground rod and connection above grade.
Bartlett TN is in Shelby CO but they have their own Insp dept and they follow the current code. Groud rods are to be below grade using the listed "acorn" clamps.

I just wish Shelby CO would go strictly by the NEC book so I have some reference to do my job.

The best I can tell you is a quote I heard from an inspector years ago " the only consistency in inspectors is their inconsistency".

 

[kbsparky]

I don't understand how you can go to an Article that is titled "Feeder, and Service load calculations" and from that extrapolate that a 12.5 KW load need only be feed by an 8.5KW circuit?...PLEASE educate me on this one.....

Ahem .... Article 220 is titled "Branch-Circuit, Feeder, and Service Calculations"

Section 220.18(C) allows one to apply demand factors for range loads in accordance with table 220.55 ...

 

[acrwc10]

Ahem .... Article 220 is titled "Branch-Circuit, Feeder, and Service Calculations"

Yes but Table220.55 being referenced is under "Feeders and Service load Calcs" The branch circuit part of that article tells you how many VA to allot for receptacles,outlets,and track light, etc. for the purpose of determining the size of a feeder or service.

 

[kbsparky]

It appears that you composed a reply before I added a clarification. Section 220.18(C) is contained within part II of 220, which is part of the Branch circuit calculations section of that article. It references the use of table 220.55

 

[ivsenroute]

You guys may want to read Note 4 of Table 220.55 as someone else had mentioned in an earlier post.

 

[acrwc10]

OK a KW of 12.5 @ 240v = 52 ampere, now unless you are in the sticks heating your house with that we know it is not a continuous load, But it is much more then the 35.5 amperes that keeps getting kicked around. It is possible that the load could be at 45-50 amps for an extended period of time ( say the oven is on self clean or what ever ) the conductors for a 35 amp load are going to be at least #8 and the conductors for a 50 amp load could be as small as a #8 if in a pipe or MC, even SE under 2005, so the only issue here is the breaker it self, and anyone who has put an amp probe on a heavily loaded circuit will know this isn't going to trip in most installs. The argument I am making is just the miss understanding of table 220.55 as I am sure it could put other scenario's into play that may not be as close in rating.

 

[augie47]

Yes but Table220.55 being referenced is under "Feeders and Service load Calcs" The branch circuit part of that article tells you how many VA to allot for receptacles,outlets,and track light, etc. for the purpose of determining the size of a feeder or service.

I don't like the way it works, ut in addition to Note 4 to 220.55, take a look at 210.19(A)(3) it deals specificially with the branch circuit for household ranges.

 

[acrwc10]

I don't like the way it works, ut in addition to Note 4 to 220.55, take a look at 210.19(A)(3) it deals specificially with the branch circuit for household ranges.

210.19(A)(3)
Household Ranges and Cooking Appliances. Branch-circuit conductors supplying household ranges, wall-mounted ovens, counter-mounted cooking units, and other household cooking appliances shall have an ampacity not less than the rating of the branch circuit and not less than the maximum load to be served. For ranges of 83/4 kW or more rating, the minimum branch-circuit rating shall be 40 amperes.

 

[M. D.]

the proper note, for a single range,.. is note 1 and the range could be as large as 16,000 watts on a 40 amp circuit ,..unless we can prove this guy, and all those who proof read for him ,. wrong:smile:

http://ecmweb.com/mag/electric_stumped_code_40/

Q. I have a 50A receptacle for a range that says the terminations are rated for 75?C conductor sizing. I used 8 AWG Type NM cable, with 90?C conductors, and the inspector failed me. Where did I go wrong?

A. The ampacity for conductors contained in Type NM cable is based on the 60?C rated column of Table 310.16, not the 90?C insulation rating of the conductors [334.80]. According to Table 310.16, 8 AWG is only rated 40A in the 60?C column; therefore, you would be OK if a 40A device protected the circuit. However, the largest range permitted on a 40A circuit would be 16kW, as per Table 220.55. Column C demand load for one 16kW range using Note 1 would be 9.6kW, and this works out to be 40A at 240V.

 

[e57]

I just wish Shelby CO would go strictly by the NEC book so I have some reference to do my job.

Come play in my neck of the woods - throw what you think you know in the fire... Acorns are illegal, and for most applications you must pipe no less than EMT to the rods with hubs. (Armored or bare only indoors, and bare may be used in the back of the building only if it has no access to the street. Does it say this anywhere - NO!)

That said - you could not have 8/3 for 50A in 1999 either....

336-26. Ampacity
The ampacity of Types NM, NMC, and NMS cable shall be that of 60?C (140?F) conductors and shall comply with Section 310-15.
The 90?C (194?F) rating shall be permitted to be used for ampacity derating purposes provided the final derated ampacity does not exceed that for a 60?C (140?F) rated conductor.

IMO its a poorly written code...

 

[acrwc10]

the proper note, for a single range,.. is note 1 and the range could be as large as 16,000 watts on a 40 amp circuit ,..unless we can prove this guy, and all those who proof read for him ,. wrong:smile:

http://ecmweb.com/mag/electric_stumped_code_40/

I can't say as I trust everything I read in EC mag. Because I have read some really bad commentary in the past.
That said, the more I read (and re-read) this section of the code I am beginning to see how this method of sizing the branch circuit for a range can be used, ALTHOUGH I have yet to see a manufactures installation instructions on an oven/range of this size NOT say "dedicated circuit & 50 amp" so even if table 220.55 & notes allow it, code section 110.3(B) would not allow it. Go figure ? So in a nut shell, if I am wrong I'm right and if I'm right it wouldn't matter anyhow because you would fall back on 110.3(B) :smile::smile::smile:

 

[jwelectric]

I wasn?t going to comment on this very simple thread that has been brought into question with a lot of debate but I was asked to so here it is and it is so simple.

ARTICLE 220 Branch-Circuit, Feeder, and Service Calculations
II. Branch-Circuit Load Calculations
220.14 Other Loads ? All Occupancies.
(B) Electric Dryers and Household Electric Cooking Appliances. Load calculations shall be permitted as specified in 220.54 for electric dryers and in 220.55 for electric ranges and other cooking appliances.

220.55 Electric Ranges and Other Cooking Appliances ? Dwelling Unit(s).
The load for household electric ranges, wall-mounted ovens, counter-mounted cooking units, and other household cooking appliances individually rated in excess of 1? kW shall be permitted to be calculated in accordance with Table 220.55. Kilovolt-amperes (kVA) shall be considered equivalent to kilowatts (kW) for loads calculated under this section.


Notes

• Over 12 kW through 27 kW ranges all of same rating. For ranges individually rated more than 12 kW but not more than 27 kW, the maximum demand in Column C shall be increased 5 percent for each additional kilowatt of rating or major fraction thereof by which the rating of individual ranges exceeds 12 kW.

So now look at this post for the correct answer to the original post.

 

[gndrod]

Appliances...II. Installation

Appliances...II. Installation

422.10 Branch-Circuit Rating. This section specifies the ratings of branch circuits capable of carrying appliance current without overheating under conditions specified.

422.10(A) Individual Circuits. The individual branch circuit shall not be less than the marked rating of the appliance or marked........
......."Branch circuits and branch-circuit conductors for household ranges and cooking appliances shall be permitted to be in accordance with Table 220.55 and shall be sized in accordance with 210.19(A)(3)."

Comment.***Table 220.55 Demand Factors is for Branch-circuit, Feeder, and Service Calculations, while 210.19(A)(3) is specifically for conductor minimum ampacity and size.

If Table 220.55 is a clear cut case for sizing branch circuit conductors, why was the Article 422.10 changed in the NEC 2008? rbj

 

[M. D.]

Well,..Mikey ole pal ,...you certainly have a way with words... :roll:

I wasn?t going to comment on this very simple thread that has been brought into question with a lot of debate but I was asked to so here it is and it is so simple.

 

[jwelectric]

If Table 220.55 is a clear cut case for sizing branch circuit conductors, why was the Article 422.10 changed in the NEC 2008? rbj

I just reached up and grabbed a book and it states in 422-5 Exception 3 that branch ciruits supplying cooking appliances are premitted to be sized in accordance with Table 220-19 which is the same as Table 220.55 today. This is out of the 1984 cycle so I wouldn't think that it is something new

 

[acrwc10]

Well,..Mikey ole pal ,...you certainly have a way with words... :roll:

Wise guy,

 

[M. D.]

Wise guy,

Nawh,.. I just thought that intro was,.. a bit much,.. is all:smile:

And just so you know,.. that article I quoted was in EC&M written by Mike Holt ,..at least it is his name on it.