romex2121;Glad to see the Load Calcs are making sense now!
As to your example:
One range at 12,000Va,
One wall oven at 8,000Va,
One wall oven at 9,000Va.
Single Family Dwelling; 120/240V 1 Ph. 3 Wire.
There are Two "Options" for the total Demand Calculation of these Household Electric Cooking Units.
*** OPTION #1 ***1st Option is to use Table 220.55 (2005 NEC Article 220, Part III).
(1) 8.0 KVA Oven x 0.8 = 6,400 VA Demand
(per Column "B");
(1) 9.0 KVA Oven + (1) 12.0 KVA Range = 11,550 VA Demand
(per Column "C").
Total Electric Cooking Equipment Demand: 17,950 VA (74.79 Amps @ 240V 1PH)
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*** OPTION #2 ***2nd Option is to use Section 220.82(B) (2005 NEC Article 220, Part IV).
"First 10 KVA @ 100%, remaining at 40%"8.0 KVA + 9.0 KVA = 12.0 KVA = 29.0 KVA
First 10 KVA at 100%: 10.0 KVA x 1.0 = 10,000 VA
Remaining 19 KVA at 40%: 19.0 KVA x 0.4 = 7,600 VA
Total Electric Cooking Equipment Demand: 17,600 VA (73.34 Amps @ 240V 1PH)
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*** NOTE: The "Electric Cooking Equipment Demand" is only One Part of the complete Load Calculation figure.
There are still other parts to include, such as:
* General Lighting (Va per square foot),
* Small Appliance Branch Circuits,
* Laundry Circuit,
* Other Fixed Appliances,
* HVAC,
* Other Motor Loads - if used,
* Electric Water Heating - if used.
what size service would be needed to run this home ??? and also what size neutral would be needed for the service per calculation.
Please refer to the note above.
on a side note what the hell is up with article 220 ??
in annex D it says to refer to article 220.6 for the demand factor for ranges; in my 2008 NEC code book there is no article 220.6, in fact if you look thru the whole article there seems to be a lot of it missing
I am working off 2005 NEC - actually 2007 California Electrical Code, which uses 2005 NEC as the "Model Code"; so the Sections may be different between the Two NEC Versions.
Per the 2005 NEC, Household Electric Cooking Equipment Demand Factors are found in Table 220.55, which is in Section 220.55 (Part III).
This is Option #1
Option #2 is Section 220.82
Good luck!
Scott