- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Look at the example for ranges in annex D. It is a 3 phase load feeding single phase ranges. Art. 220.54 says
That number is found by taking 40 and divide by 3-- we get 13 and a remainder of 1 so there are 14 ranges connected between any two phases-- this is assuming one is not trying to install them on the same phases.
Now we have 14 ranges but art. 220.54 states we double that number-- hence 28.
We are now working with 28 ranges not 40 except for the initial calculation of 40 * 5000 = 200 kw.
Now we take T. 250.54 for 28 ranges not 40. 35% of 200000= 70000. Now we must also minus .5% for each range over 23. Since we are working with 28 ranges we get 28-23= 5. 5* .5%= 2.5%. 70000 * 97.5%= 68, 250 or 68.25 kw
Where two or more single-phase dryers are supplied by a 3-phase, 4-wire feeder or service, the total load shall be calculated on the basis of twice the maximum number connected between any two phases.
That number is found by taking 40 and divide by 3-- we get 13 and a remainder of 1 so there are 14 ranges connected between any two phases-- this is assuming one is not trying to install them on the same phases.
Now we have 14 ranges but art. 220.54 states we double that number-- hence 28.
We are now working with 28 ranges not 40 except for the initial calculation of 40 * 5000 = 200 kw.
Now we take T. 250.54 for 28 ranges not 40. 35% of 200000= 70000. Now we must also minus .5% for each range over 23. Since we are working with 28 ranges we get 28-23= 5. 5* .5%= 2.5%. 70000 * 97.5%= 68, 250 or 68.25 kw