Calculated Loads for Ranges- Huh

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Dennis Alwon

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So what is the feeder or service load for 2- 3 kva ovens and 1- 6kva cooktop?

Using Note 3 we get 2 * 3kva= 6kva. Demand for 2 units in Col. A Table 220.55 is 75%.

6kva * .75 = 4.5 kva

Also using Col. B for 1 unit at 6 kva we get 80% demand factor.

6kva * .8 = 4.8 kva

4.5 kva + 4.8 Kva = 9.3 kva


However if we run a branch circuit to feed all 3 units we can use note 4 and add all the units together and treat it as one range. That is 12 kva-- using Col. C we get 8 kva.

So in summary we can use 9.3kva for the feeder calculation but only use 8 kva for the branch circuit load. Do you agree? do you find that odd?
 

david luchini

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So in summary we can use 9.3kva for the feeder calculation but only use 8 kva for the branch circuit load. Do you agree? do you find that odd?

If all 3 appliances are connected to the same branch circuit, the feeder load would be 8kVA, same as the branch circuit load, IMO. See 220.40.
 

Smart $

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Ohio
...
So in summary we can use 9.3kva for the feeder calculation but only use 8 kva for the branch circuit load. Do you agree? do you find that odd?
I agree that you can. The question is will you?

I don't find it odd because the service/feeder load calculation would not end up less than the branch circuit load sum. I'd find it odd if it were the other way around... :D
 

Smart $

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Ohio
If all 3 appliances are connected to the same branch circuit, the feeder load would be 8kVA, same as the branch circuit load, IMO. See 220.40.
I considered that premise, but nothing really says you can't calculate the service/feeder load at the higher value.
 

Dennis Alwon

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If all 3 appliances are connected to the same branch circuit, the feeder load would be 8kVA, same as the branch circuit load, IMO. See 220.40.

220.40 states that the feeder can't be less than the branch circuit load. That does not mean that you calculate the feeder the same way. Note 4 is clear as a branch circuit load using all 3 as one. I don't see where you can do that as a feeder
 

david luchini

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220.40 states that the feeder can't be less than the branch circuit load. That does not mean that you calculate the feeder the same way. Note 4 is clear as a branch circuit load using all 3 as one. I don't see where you can do that as a feeder

220.40 says the calculated load on the feeder shall not be less than the sum of the loads on the branch circuits supplied. The load on the branch circuit supplied can be calculated as low as 8kVA. The sum of 8kVA and zero is 8kVA. The calculated load on the feeder shall not be less than 8kVA.

Note that you are permitted, but not required, to apply the demand factors in 220.55 to a feeder or service.
 
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Haji

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The odd thing, I think, is the demand KVA for the feeder calculated as 9.3KVA not equal to the demand KVA calculated for a single branch circuit of all the three equipment as 8KVA. The demand KVA i.e the actual KVA including any future expansion should not change, irrespective of whether it is calculated from feeder or branch circuit viewpoint, IMO. Otherwise, higher power demand than is necessary is required from the POCO.
 

david luchini

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Yes it5 shall be permitted to use the table or you can use the nameplate...That's another interpretation...

You can always use the nameplate, but you're not required to. If you use the table for the branch circuit calculation and the nameplate data with no demand factors for the feeder calculation, you've met the requirements of 220.40.

By the same respects, you can use the nameplate data for the branch circuit calculation if you wanted to. You are permitted, but not required, to use 220.55 for the branch circuit calculation.
 

Dennis Alwon

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By the same respects, you can use the nameplate data for the branch circuit calculation if you wanted to. You are permitted, but not required, to use 220.55 for the branch circuit calculation.


Yes, I agree that you can use the table but are not required. IMO, if you don't use the Table then you must use the nameplate- at least that is my take- I don't see 220.40 coming into play here for ranges
 

david luchini

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Yes, I agree that you can use the table but are not required. IMO, if you don't use the Table then you must use the nameplate- at least that is my take- I don't see 220.40 coming into play here for ranges

I don't understand your logic. You've calculated the branch circuit load to be 8kVA, per part II of Art. 220. 220.40 says the calculated feeder load shall not be less than the sum of the loads on the branch circuits supplied as determined by Part II of the article, which is 8kVA. There's no need to go any further.

220.40 comes into play for ALL feeder and service load calculations, whether there are ranges or not.
 

Smart $

Esteemed Member
Location
Ohio
I don't understand your logic. You've calculated the branch circuit load to be 8kVA, per part II of Art. 220. 220.40 says the calculated feeder load shall not be less than the sum of the loads on the branch circuits supplied as determined by Part II of the article, which is 8kVA. There's no need to go any further.

220.40 comes into play for ALL feeder and service load calculations, whether there are ranges or not.
And that amounts to, if using nameplate for branch circuit(s), you cannot use a lesser 'demand factored' value for service and feeder calculation.
 

david luchini

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And that amounts to, if using nameplate for branch circuit(s), you cannot use a lesser 'demand factored' value for service and feeder calculation.

Yes, if you used the 220.55 permitted demand for the branch circuit (8kVA) then the feeder load would be not less than 8kVA.

If you used the nameplate data for the branch circuit (12kVA) then the feeder load would be not less than 9.3kVA.
 

Dennis Alwon

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Retired Electrical Contractor
If you used the nameplate data for the branch circuit (12kVA) then the feeder load would be not less than 9.3kVA.

So how can you use the nameplate for the branch circuit and still have a feeder that is less than the branch circuit. I thought 220.40 says the feeder can't be less than the bc.
 

david luchini

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So how can you use the nameplate for the branch circuit and still have a feeder that is less than the branch circuit. I thought 220.40 says the feeder can't be less than the bc.

By applying the applicable permitted demand factor from Part III of Art 220. 220.40 says the feeder can't be less than the sum of the loads of the bc's supplied AFTER any applicable demand factors have been applied.

A feeder calculated load after the application of demand factors will almost always be less than the sum of the calculated loads of the branch circuits supplies by that feeder. That's the point of the demand factor. Your OP found an interesting case where it wasn't. But as has been pointed out, you are not required to apply the demand factor.
 

Haji

Banned
Location
India
For certain kitchen appliances and laundry appliances, NEC permits demand factors and for all other branch circuit appliances use name plate data to calculate feeder size, if no spare capacity is required.
 
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