Residential range rated 15kw

Tulsa Electrician said:
If the three are wall mounted ovens than No.
I think note 3 would apply if all wall mounted ovens.

If one is counter mounted and two are wall mounted. Yes, kinda. Need name plate info for sizing. So the 30 may to small for three.
If you treat them like one range.

Pretty sure the code is referring to a cooktop(counter mounted cooking unit) on the counter top surface and two wall mounted ovens.

Please let me know if I'm looking at this correctly. We have been discussing this topic at work. It all started with 40 amp breaker and conductor for a range on 50 amp receptacle.
The it took a turn from there to demands.
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2023NEC TX
Section 220.55 and T.220.55 and note number 6.
Example: Consider 3 household cooking appliances; one 8 kW + one 6 kW+ one 5kW = 19 kW total kW
19 kW - 12 kW = 7 kW
For every kW over 12 kW, increase Column C by 5 percent for each kW
7 kW x 5 percent = 35% or 0.35%
Treat these 3 household appliances as one (equivalent to one range) found in Column C and Note 6
One 8 kW x 1.35 % = 10.8kW 10.8kW x 1,000 watts = 10,800 watts
10,800 watts / 240 volts = 45 amps use type NM (romex)
T.310.16 60 degree column select a 6 AWG copper at 55 amps.
T.240.6 (A) there's not a 55 amp rated OCPD, round down to a 50 amp OCPD.

If you're interested in the rest of this particular installation, I will share that with you later.
I'm going to watch Houston destroy the LA Chargers 'changers', sorry, Cali fans. Don't Mess with Texas.

TX+MASTER#4544
 
I apologize Tx is correct.... You can use either method


TX+ MASTER#4544 said:
2023NEC TX
Section 220.55 and T.220.55 and note number 6.
Example: Consider 3 household cooking appliances; one 8 kW + one 6 kW+ one 5kW = 19 kW total kW
19 kW - 12 kW = 7 kW
For every kW over 12 kW, increase Column C by 5 percent for each kW
7 kW x 5 percent = 35% or 0.35%
Treat these 3 household appliances as one (equivalent to one range) found in Column C and Note 6
One 8 kW x 1.35 % = 10.8kW 10.8kW x 1,000 watts = 10,800 watts
10,800 watts / 240 volts = 45 amps use type NM (romex)
T.310.16 60 degree column select a 6 AWG copper at 55 amps.
T.240.6 (A) there's not a 55 amp rated OCPD, round down to a 50 amp OCPD.

If you're interested in the rest of this particular installation, I will share that with you later.
I'm going to watch Houston destroy the LA Chargers 'changers', sorry, Cali fans. Don't Mess with Texas.

TX+MASTER#4544
Click to expand...

I would use note 3

19kw x .55 demand factor= 10.45 kw

2. Over 83⁄4 kW through 27 kW ranges of unequal ratings. For ranges individually rated more than 83⁄4 kW and of different ratings, but none exceeding 27 kW, an average value of rating shall be calculated by adding together the ratings of all ranges to obtain the total connected load (using 12 kW for any range rated less than 12 kW) and dividing by the total number of ranges. Then the maximum demand in Column C shall be increased 5 percent for each kilowatt or major fraction thereof by which this average value exceeds 12 kW.
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3. Over 13⁄4 kW through 83⁄4 kW. In lieu of the method provided in Column C, adding the nameplate ratings of all household cooking appliances rated more than 13⁄4 kW but not more than 83⁄4 kW and multiplying the sum by the demand factors specified in Column A or Column B for the given number of appliances shall be permitted. Where the rating of cooking appliances falls under both Column A and Column B, the demand factors for each column shall be applied to the appliances for that column, and the results added together.
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Can anybody recommend a step by step explanation of this section? It always confuses me to no end. When you have multiple appliances as referenced above, and a mixture of large and small. It is like trying to follow spaghetti.
 
Birken Vogt said:
Can anybody recommend a step by step explanation of this section? It always confuses me to no end. When you have multiple appliances as referenced above, and a mixture of large and small. It is like trying to follow spaghetti.
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Generally, you don't run into this as a real-life situation.

This will help some. It is from the online version of NFPA LINK

The demand factors are based on the diversified use of household appliances, because it is unlikely that all appliances will be used simultaneously or that all cooking elements and the oven of a range will be at maximum heat for any length of time.
The values in Column C are applicable to installations where all ranges in the group have the same rating. Note 1 applies where the ranges are rated greater than 12 kilowatts, and Note 2 applies where the ranges in a group have different ratings. Column C must be used unless Note 3 is applicable. Notes 3 and 4 cover installations where the circuit supplies multiple cooking components, which are combined and treated as a single range.

Table Note 1. For household electric ranges, the size of the conductors must be determined by the rating of the range. According to Table 220.55, for one range rated 12 kilowatts or less, the maximum demand load is 8 kilowatts. Note that 210.19(C) does not permit the branch-circuit rating of a circuit supplying household ranges with a nameplate rating of 8¾ kilowatts to be less than 40 amperes.
The demand in Column C must be increased if an individual range is rated over 12 kilowatts but not more than 27 kilowatts. All ranges in the group must have the same rating to apply Note 1. If the ratings are different, refer to Note 2.
221020044304-CalEx_220.55_Note-1.JPG


Table Note 2. If ranges in a group installation have different ratings over 8¾ kilowatts through 27 kilowatts, the ratings are added together to determine the average rating and the maximum demand. The demand in Column C must be increased if the average rating is over 12 kilowatts. If the ratings are the same, refer to Note 1.
Table Note 3. For a group installation of ranges with ratings over 1¾ kilowatts through 8¾ kilowatts, the ratings are permitted to be added together for determining a demand factor. Ranges rated below 3½ kilowatts should be grouped independently of those rated 3½ kilowatts and above. The appropriate column (A or B) is used rather than Column C.
221020044401-CalEx_220.55_Note-3.JPG

221020044431-CalEx_220.55_Note-3b.JPG


Table Note 4. The branch-circuit load for one range is permitted to be computed by using either the nameplate rating of the appliance or Table 220.55. A counter-mounted cooking appliance has a smaller load rating than does a full-sized range with an oven. If a single branch circuit supplies a counter-mounted cooking unit and not more than two wall-mounted ovens, all of which are located in the same room, the nameplate ratings of the appliances can be added, and the total treated as the equivalent of one range. For feeder demand factors other than dwelling units (commercial electric cooking equipment, dishwasher booster heaters, water heaters, etc.), see Table 220.56.
Where a counter-mounted cooking appliance like the one illustrated below is used with a separate wall oven, it is permissible to run a single branch circuit to the kitchen and supply each with branch-circuit tap conductors installed as specified in 210.19(C), Exception No. 1.
21121093815-70HB20e210-24_edited.jpg

221020044506-CalEx_220.55_Note-4.JPG
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Dennis Alwon said:
I apologize Tx is correct.... You can use either method




I would use note 3

19kw x .55 demand factor= 10.45 kw
Click to expand...


The problem with this Table is that reading Notes 1 and 2 it make me and many others think that Col. C is just for ranges 8 3/4 thru 27kw but the table heading basically states col c is for all ranges.

Add to that that any range under 12kw is consider 12 kw but only when those ranges are over 8 3/4 kw. Since the example above shows all ranges less than 8 3/4 kw then we are free to use col C with ranges at their name[plate or note 3 as I had done
 
Little Bill said:
If the conductors are sized for 50A, how is a 40A breaker safer? Any overload over 50A would trip the 50A breaker.
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Id say when using a standard residential inverse time breaker as ground fault and short circuit protection (as we typically do ) it generally takes three times the breaker rating to trip the breaker in a few seconds, so a ground fault on a 50A breaker would need to pull 150 Amps to make the breaker trip in a few seconds.
A 40A breaker would only need to pull 120A to instantly trip, and therefore respond quicker to a ground fault or short circuit and in either case the equipment ground would be the same size for the 40 or 50,
So the closer the breaker is matched to the load you have less risk of burning out the equipment ground, especially the equipment ground that is internal to the equipment on a circuit board wiring harness.
A GFCI of course will trip on ground fault in no more than around 7mili seconds, but they introduce the nuisance trip problem.
I personally think a GFPE breaker is the most ground fault protection a residential range would need, and would be a better substitute for a GFCI than a standard inverse time breaker.
 
Dennis Alwon said:
I apologize Tx is correct.... You can use either method




I would use note 3

19kw x .55 demand factor= 10.45 kw
Click to expand...
TX+MASTER#4544

T.220.55
My example was for a single branch circuit for up to 3 household cooking appliances.
And applying Note 6.

Note number 3 is for a comparison of the two columns ( (A) and (B).
Results of the two columns could be used when calculating to determine which one yields the least/ most kW load.
Most likely used in a question where you want to determine the least kW vs the most kW ratings and select the least kW load as an answer to an exam question or in a real time value to determine the load.

TX+MASTER#4544
 
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