Help with exam prep Code calculation

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77401

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Need Help with this please. The instructor had a different answer for this than most everyone else had but everyone had good reasons for how they came up with their respective answers.

Single family dweling.
12 KW cook top
10 KW oven
9 KW oven
Cooktops & Oven are 240v Single phase.

WHAT IS the Demand load for the cooking equipment.
Table 220.55 Which Notes?????
 
7

77401

Banned
Location
South of the Border in Houston, Texas
Piere
This was in a prep class there was no answer to choose from. Not a multiple choice as on the test.
Instructor gave 16KW
giving this...
12 + 10 + 9 = 31 kw
note 1
31-12=19 x 5% = 95%
1 range = 8kw + 95% = 15.6kw
= 16kw

I think he's wrong
Your opinion? or answer?
 
bdarnell

bdarnell

Senior Member
Location
Indianapolis, IN
Occupation
Retired Engineer
Then it's note # 2. No question. Branch circuit load and demand load are different animals. Either he has a misunderstanding, or simply worded the question wrong.
 
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bjp_ne_elec

Senior Member
Location
Southern NH
You have to use Note 4 first - as it allows one counter-mounted unit and up to two wall-mounted ovens - then use Note 1.

So it's:

12 + 10 + 9 = 31 kW

31 kW - 12 kW (Note 1 - what exceeds 12 kW) = 19 kW

19 x 0.05 = 0.95 = 95%

8 kW (Column C) + 0.95*8 = 15.6 kW

15.6 kW/240 = 15600/240 = 65 A
 
7

77401

Banned
Location
South of the Border in Houston, Texas
bjp_ne_elec said:
You have to use Note 4 first - as it allows one counter-mounted unit and up to two wall-mounted ovens - then use Note 1.

So it's:

12 + 10 + 9 = 31 kW

31 kW - 12 kW (Note 1 - what exceeds 12 kW) = 19 kW

19 x 0.05 = 0.95 = 95%

8 kW (Column C) + 0.95*19 = 26.05 kW
Click to expand...

I don't "think" your answer is right either!
I took the Texas Exam today & this was on the test! as the prep course said it would be.
But All I can remember was the 4 choices were.
a)10
b)12
c)16
d) can't remember this

Anyway the course preached the answer was 16. these guys take the course to fail & get the rewiews for the answers to teach us. I don't agree with the 16 answer but in a week moment I put it for my answer.

BUT your last line is different from what the class gave me.
Heres what they gave....(last line)
1 range = 8kw + 95% = 15.6 or 16 kw
8000 x .95 = 7600
7600 + 8000 = 15.6kw

On your last line? what is the "*19"
I don't see your math for 26.05kw
 
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bjp_ne_elec

Senior Member
Location
Southern NH
77401 - it looks like you read my post before I corrected it. Take a look at my post - I changed it within minutes - and you must have gotten in before my changed post was saved.

The only thing that I'm struggling with is that the total adds up to over 27 kW - but when you read Note 4, there are no restrictions limiting total kW. This note does say you take the sum of the three - and the three you were given in original problem fits Note 4.

In your post, I'm not aware of anything that would allow you to round up. I guess it depends on how the exact question was worded - but nothing in the Code would explain a rounding up of the total kW.

Thanks,

Brett
 
7

77401

Banned
Location
South of the Border in Houston, Texas
brett
I see how this could apply
Bu t I also see note 2 working and an answer of 12kw

I'll report back on the awswer when the ICC lets me reeiew the answers.
I have another question about a question regarding "compact Copper" conductors. I only know of compact aluminun conductors.

THANKS EVERYONE!
 
B

bjp_ne_elec

Senior Member
Location
Southern NH
77401 - interested in how you got 12 kW - can you lay it out? I have a Master's test coming up, and would like to see this - just in case it comes up.

Thanks

Brett
 
A/A Fuel GTX

A/A Fuel GTX

Senior Member
Location
WI & AZ
Occupation
Electrician
I think you guys are confusing DEMAND and BRANCH CIRCUIT ratings. The OP stated DEMAND in his question and therefore I believe that note 4 is irrelevant as that addresses BRANCH CIRCUITS. Note 2 would be used for calculating DEMAND.
 
A/A Fuel GTX

A/A Fuel GTX

Senior Member
Location
WI & AZ
Occupation
Electrician
I think for demand calcs, cooktops and ranges are one in the same. A range is a combination of a cook top and and an oven. So I say you need to use note 2 for demand calcs.....
 
mikeames

mikeames

Senior Member
Location
Gaithersburg MD
Occupation
Teacher - Master Electrician - 2017 NEC
m73214 said:
I think you guys are confusing DEMAND and BRANCH CIRCUIT ratings. The OP stated DEMAND in his question and therefore I believe that note 4 is irrelevant as that addresses BRANCH CIRCUITS. Note 2 would be used for calculating DEMAND.
Click to expand...


m73214,

Is correct note 4 is not to be used for demand load.



77401 said:
my 12 kw was based on note 2 but note 2 only applies to ranges only.
Click to expand...

The article 220.55 that note 4 is in simply put refers to all Household cooking appliances so note 2 also applies to the "oven" ranges as well.


The answer is 14kw

12 10 and 9 are the ratings

note 2 says for any under 12kw use 12kw

so the 10 and 9 each becom 12

therfore

12+12+12 = 36 Kw total

the average of that is 36/3 which = 12 kw

12KW is not over the base 12kw so there is no added 5% calculation

We then look right to table 220.55 col C and look up 3 ranges and it tells us it is 14KW
 
M. D.

M. D.

Senior Member
I think it is note 4 as follows

Combined cooking appliances can be treated as one in this case.

12 + 10 + 9 = 31 (combined unit rating)

31 - 12 = 19 kw amount over 12 kw that needs to be increased by 5%

19 x 05=.95

8,000 x .95 = 7,600 (demand as if it were 1 range x 5% multiplier)

7,600 + 8,000 = 15,600 or 16 kw , ...600 being a major fraction

15,600 watts / 240 volts = 65 amps

I guess I'm a 16 kw guy. answer (c)
 
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