Table 220.55 question

[Square D]

Ok, this question comes from Ray Holders exam prep book-
Determine the MINIMUM size NM cable the NEC requires for branch circuit conductors, supplying a 10Kw 240 volt, single phase, residential electric range.

The provided answers in the back of the book suggests 220.55 Column B 80% to reduce the kw to 8000 Kw, then size the wire.
My question is, if Column B is for (3.5kw through 8.75 kw Rating) why choose this column when the electric range is 10,000? Thanks!!!

 

[Johnhall30]

I wasnt familiar with this table prior to looking into this question, but column C suggests that if you have one appliance you can use the maximum demand of 8kw to size the branch circuit

 

[infinity]

Yes you use column C since 10kW is more than 8¾ and less that the maximum for that column of 12 kW. 210.19(A)(3) also applies but it wouldn't change the conductor size.

 

[Square D]

Yes you use column C since 10kW is more than 8¾ and less that the maximum for that column of 12 kW. 210.19(A)(3) also applies but it wouldn't change the conductor size.

Thanks- maybe the writers didn't mean to put Column B as a code reference

 

[Square D]

I wasnt familiar with this table prior to looking into this question, but column C suggests that if you have one appliance you can use the maximum demand of 8kw to size the branch circuit

View attachment 2560462

Thanks does this mean there is an error in the answer key of this prep book?

 

[infinity]

Thanks- maybe the writers didn't mean to put Column B as a code reference

In this case you end up with the same 8kW but column C is the one that you would use. Could be an error.

 

[Square D]

I wasnt familiar with this table prior to looking into this question, but column C suggests that if you have one appliance you can use the maximum demand of 8kw to size the branch circuit

View attachment 2560462

Thanks for the reply!

 

[Square D]

In this case you end up with the same 8kW but column C is the one that you would use. Could be an error.

Ok thanks for the response.

 

[Dennis Alwon]

A better question would have been is what is the minimum size overcurrent protective device for a 10kw range.

 

[RWC/NC.]

210.19(A)(3)

 

[RWC/NC.]

Excuse the above misprint, but it's little "dark" out here on screened in porch.

 

[infinity]

I fixed it for you.

 

[petersonra]

How do you get past this when sizing conductors for a range?

(3) Household Ranges and Cooking Appliances. Branchcircuit
conductors supplying household ranges, wall-mounted
ovens, counter-mounted cooking units, and other household
cooking appliances shall have an ampacity not less than the
rating of the branch circuit and not less than the maximum
load to be served. For ranges of 83∕4 kW or more rating, the
minimum branch-circuit rating shall be 40 amperes.

How does a demand factor affect the maximum load the range might have?

 

[infinity]

How do you get past this when sizing conductors for a range?



How does a demand factor affect the maximum load the range might have?

The demand factor kW value from the table is considered the maximum load served. From Note #4 to T220.50:

Note #4. Branch-Circuit Load. It shall be permissible to calculate the branch-circuit load for one range in accordance with Table 220.55.

 

[Dennis Alwon]

How do you get past this when sizing conductors for a range?



How does a demand factor affect the maximum load the range might have?

Explain how a 16kw and a 9kw range both have the same amps when using the table... 40 amps for both

 

[Dennis Alwon]

210.19(A)(3)

You would be surprised how many people would miss that one.

 

[RWC/NC.]

My humblest respect offered, to forum moderators & staff. Have safe evening.