Calculation questions

Status
Not open for further replies.
E

eljefetaco

Member
Location
Fanwood, NJ
1. In a home the demand (load applied for service calculation) for a 12kw
range and a 4kw oven is ___kw?
A. 11
B. 11.2
C. 12
D. 16

2. The maximum motor-running overload protection would be __ amps for a 3 phase 3hp 230 volt motor.
A. 15
B. 20
C. 22.1
D. 29.1
 
QUESTION 1:

Take the two ovens and add together. (220.55 note 4) Then apply Colum B for two appliances. 65% times 16kw. 10.4kw?

QUESTION 2:

FLC 9.6 times 1.40% 430.32.C

NEW QUESTION:

1. The Branch circuit load for one 6kw oven would be__ kw
A. 6
B.4.8
C. 4.2
D. 5

2. Then branch circuit demand for one 8kw range in a residence would be __ kw?

A. 12
B. 8
C. 6.4
D. 5.2

The first one the answer is 6kw. 220.55 Note 4. The second I thought would be 8kw. The answer in my book says 6.4% Is the addition of the residence the difference. Or am I confusing load and demand?
 
Look at Table 220.55 and see col. B (3 1/2kw thru 8 3/4kw) -- What is the percentage (demand factor) for one appliance?
 
80% for one. I see that, but how does that differ from note 4." The branch circuit load for one wall mounted oven or one counter mounted cooking unit should be the name plate rating of the appliance." Do I use the nameplate for one then apply table? If so is the above question wrong?
 
eljefetaco said:
80% for one. I see that, but how does that differ from note 4." The branch circuit load for one wall mounted oven or one counter mounted cooking unit should be the name plate rating of the appliance." Do I use the nameplate for one then apply table? If so is the above question wrong?
Click to expand...

Note 4 states that you may use the Table for one range. It then states one oven or one counter mounting cooking unit must use the nameplate. A range is a combination of those two units so diversity enters into the equation again. The cmp is assuming that all 4 burners along with an oven will not be going at the same time. One wall oven will be on and use the entire kw of the unit. Well, one cook top will not usually be on at once but it could be thus the need for the full kw rating of that.
 
eljefetaco said:
QUESTION 1:

Take the two ovens and add together. (220.55 note 4) Then apply Colum B for two appliances. 65% times 16kw. 10.4kw?
Click to expand...

Remember now you are not trying to find the demand for the branch circuit in your question. You stated you are doing the math for a service calculation. Since you are doing "demand" loads...apply them and try it again. AH...and dont forget the lower of the choices you come up with when using the tables...
 
Last edited:
eljefetaco said:
NEW QUESTION:

2. Then branch circuit demand for one 8kw range in a residence would be __ kw?

A. 12
B. 8
C. 6.4
D. 5.2

The first one the answer is 6kw. 220.55 Note 4. The second I thought would be 8kw. The answer in my book says 6.4% Is the addition of the residence the difference. Or am I confusing load and demand?
Click to expand...

READ-4. Branch-Circuit Load. It shall be permissible to calculate the branch-circuit load for one range in accordance with Table 220.55. The branch circuit
load for one wall-mounted oven or one counter-mounted cooking unit shall be the nameplate rating of the appliance. The branch-circuit
for a counter-mounted cooking unit and not more than two wall-mounted ovens, all supplied from a single branch circuit and located in the same
room, shall be calculated by adding the nameplate rating of the individual appliances and treating this total as equivalent to one range.

Now, using Table 220.55 you have (2) options here. Do the math on one and pick for the other....You are allowed to use in your case Column B or Column C and accept the lower of the two for question # 2.
 
Before y'all get too far into this, keep in mind the part in the Table title/header that says, "Column C to be used in all cases except as otherwise permitted in Note 3."
 
Exactly....which is why I gave him two options on his second question above. In that example he is solving for Branch Circuits and in some of his others he is solving for service calculations. These are two different issues he needs to be able to split up.
 
Status
Not open for further replies.
Top