Feeder to dwelling unit with 1 oven

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Grouch1980

Grouch1980

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New York, NY
I have a question on Note #4 from Table 220.55, where if you have one oven or one cooktop, the branch circuit load is taken at the nameplate... so that's to calculate the circuit breaker size feeding the appliance. What about the feeder to the apartment? Do you take 80% since it's only 1 appliance (from the 1st row), or is the feeder calculated with the nameplate of the oven or cooktop?
 
I believe I have the answer. For note 4, I size the branch circuit breaker to the nameplate (or as per the appliance instructions). For the feeder to the apartment, the appliance, one oven in this case, is taken at 80%. (along with the other loads of the apartment, whatever their demand percentages are).
 
Dennis Alwon said:
Imo, the feeder would be the nameplate also. Where are you getting 80% for a feeder?
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Well, note #4 is only for branch circuits. Whereas the rest of the chart / notes are for feeder / service sizing. Logically, I can understand why the feeder should be at 100% as well, since how would the feeder be smaller... but I don't see where the chart says the feeder would be at 100% also. I'm assuming it allows 80% for the feeder since you're feeding a dwelling unit.. and there will be diversity between all the different loads.
 
I agree that at first reading of 220.55, with a single wall oven, the branch circuit sizing is governed by Note 4, while the feeder load is governed by row 1 of the table. Below is an example I made up with 3 appliances.

Cheers, Wayne

So if a residential kitchen has an induction cooktop rated 30A @ 240V (7.2 kW) plus two wall ovens rated 10A @ 240V each (2.4 kW), then:

The branch circuit tap rules say you can put them all on one circuit, and Table 220.55 Note 4 says you can treat them as a single range with a nameplate of 12 kW. Then column C says you can treat it a 12 kW range as an 8 kW load. That means you can put them all on a single 40A 240V circuit?

Then for feeder load purposes, you have 3 appliances, with the cooktop falling under column B, and the wall ovens falling under column A. So the feeder load is 2 * 70% * 2.4 + 1 * 55% * 7.2 = 7.32 kW.

Does that all sound correct?
 
wwhitney said:
Well for the whole apartment you could do the optional method, but if you are doing the standard method, is there a difference?

Cheers, Wayne
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I don’t have the code in front of me, but I’m pretty sure there is a difference. I’m looking to do the standard calculation.
 
Grouch1980 said:
I don’t have the code in front of me, but I’m pretty sure there is a difference. I’m looking to do the standard calculation.
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Between a feeder carrying all of the dwelling unit, and a feeder within the dwelling unit carrying the oven, among other things? I don't see anything in 220 Part III that says that.

Cheers, Wayne
 
wwhitney said:
Between a feeder carrying all of the dwelling unit, and a feeder within the dwelling unit carrying the oven, among other things? I don't see anything in 220 Part III that says that.

Cheers, Wayne
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I'm asking about the feeder carrying all of the dwelling unit. If the dwelling unit has a single oven, do you take that single oven at 80%, using the standard calculation.
 
Grouch1980 said:
I'm asking about the feeder carrying all of the dwelling unit. If the dwelling unit has a single oven, do you take that single oven at 80%, using the standard calculation.
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I believe you are correct. At first I was thinking it was the nameplate but it seems that 80% may be correct for the feeder calculation using the standard calculation.
 
Dennis Alwon said:
Wayne I think he is talking about the feeder to the apartment not the feeder for the ranges / oven, etc.
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Dennis the circuit feeding the range isn’t likely a feeder and the one feeding the apartment is a feeder for the range, so without looking at the code wording, I concur with Wayne’s statement.
 
I got it. Right, so the main feeder to the apartment can be taken at an 80% demand factor, with regards to the single wall oven. Based on row 1 of Table 220.55

Great... thanks everyone for the feedback!
 
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