Cooking , Electric Dryer and Appliance Calculations 3

Cooking , Electric Dryer and Appliance Calculations 3
© Ted “Smitty” Smith E Light Electric Services, Inc.

The first several slides of this presentation are a review of calculations. Read them over and take some notes as they will help you on your journeyman’s exam as well as while doing this drill. Click the slide to advance to the next slide as you are ready. You will reach a slide which says “START”. This is the beginning of the timed portion of the drill. Click that slide and the questions slides will start running. Each slide will remain in place for 3-5 minutes depending on the difficulty of the calculation. A sound will go off letting you that it has moved to the next slide. Attempt to answer the question. If you finish before the timer goes off, click the slide and it will go to the next question. If you do not finish, simply stop working that problem and start on the next. When you reach the end of the timed portion you will see a slide that says “STOP”. Click on that slide and each of the questions will reappear and this time you can click them to move to the next slide, which will have the answer. Please call me if you have any issues or questions and I will be happy to arrange a time for us to review. Directions

Cooking Calcs Tips to Remember
Use column C of Table for any cooking appliances which have a nameplate rating of 12 kW or less. Remember: The number listed in column C is the total demand. It is not a demand factor.

Cooking Calc Tips If you have cooking appliances that are rated over 12 KW use Note 1 to the table if all the ranges have the same nameplate rating. If the ranges have different name plate ratings, Use note two and get an average first and then use Note 1. When getting the average, remember that anything that is rated less than 12, consider it to be 12 KW for the purposes of doing the average

Cooking Calc Tips Brady Bunch Rule NOTE 3 to T220.55
Be sure to do the squeezes on Column A and the squeezes in Column B and then add them together. Then compare that total to what Column C requires. Use the smaller between the Total of Column A and B and what the demand in C reads.

Cooking Calc Tips If you are having a hard time remembering Cooking Calcs steps and processes, Go to the exam prep page and review the Cooking Calcs training module.

Steps for A SFD Load Calculation
1. Lighting and Receptacle Load Square Footage x 3 T220.10 Add 4500 VA for Small Appliance Branch Circuits and Laundry Circuit Squeeze using T220.42 2. Cooking Demand T220.55 3. Electric Dryer Demand T (5000 or nameplate whichever is higher) 4. Fastened in Place Appliances Demand (Do not include anything used to cook, dry clothes, air conditioning or heating.) 5. 25% of the largest motor. ( Only account for 25% here. The 100% will be covered somewhere else in the calculation.) 6. Heating/AC Demand. Do not squeeze but only account for the larger of the two loads )

Click here to start the timed portion of the Drill

NOTE VERY IMPORTANT ALL OF THE CALCULATIONS IN THIS DRILL ARE ASSUMED TO BE FOR DWELLING UNITS

1. What is the demand load, on the ungrounded service-entrance conductors of a residence for on 8.5 kW rated electric range?

Answer 1 6.8 kW Table Column B 8.5 x .80= 6.8

2. The demand factor for (6) residential electric clothes dryers install in a multifamily dwelling unit is ___________.

Answer 2 75% Table No calc needed

3. A single family dwelling has three (3) ovens, one rated 6 kW, one rated 8 kW, and one rated 3.5 kW. The kitchen also has a counter mounted cook top rated at 6 kW and a broiler rated at 3.5 kW. The feeder demand will be ________ on the ungrounded conductors for the cooking equipment.

Use column B- 5 appliances= 45%
Answer 3 12.2 kW Table Note 3 Use column B- 5 appliances= 45% =27 27 x .45= 12.15

4. It shall be permissible to apply a demand factor of ___________ to the nameplate rating of four (4) or more fastened in place storage-type electric water heaters in a multifamily dwelling, when calculating the demand load on the service entrance or feeder conductors.

Four or More Appliances you can take the 75% demand Factor
Answer 4 75% 220.53 Four or More Appliances you can take the 75% demand Factor

5. When doing residential service and feeder calculations, electric clothes dryers are to be calculated at a Minimum of ______________ watts (VA) or the nameplate rating, whichever is larger.

5000 watts or the Nameplate Rating, WHICHEVER IS GREATER
Answer 5 5000 220.54 5000 watts or the Nameplate Rating, WHICHEVER IS GREATER

6. For residential electric ranges rated at 8
6. For residential electric ranges rated at 8.75 kW or more, the Minimum branch circuit rating shall be at Least ______________.

Answer 6 40 Amperes 210.19(A)(3) Article 210 is Branch Circuits and the minimum ratings of Circuits are found starting at through This is a good thing to remember

7. What is the demand on the main service entrance of a single family dwelling for the following fastened place appliances: Water heater 4800 VA Dishwasher 1200 VA Garbage Disposal 1150 Trash Compactor 800 VA Attic Fan VA

Answer 7 6863 VA Or kVA 220.53) =9.150 9.150 x .75= 6.863

8. What is the branch circuit demand load, in amperes, for one 240 volt, single phase, 6 kW wall mounted oven located in a dwelling unit?

Single Phase current formula
Answer 8 25 Amperes T Note 4 Single Phase current formula I=P/E 6 kW x 1000/240V= 6000/240=25

9. When doing dwelling unit service and feeder calculations, when a residence has an electric clothes dryer rated at 240 volts, 30 amperes, the demand load, in VA, to be applied to the ungrounded line conductors is ______________.

Answer 9 7200 VA or 7.2 kVA 220.54 Power Formula VA=E x I
VA= 240 volts x 30 amperes= 7200 VA

10. Determine the demand load to be added to the grounded service entrance conductor for one 10.5 kW residential electric range.

Answer 10 5600 Watts or 5.6 kW T220.55 Column C 220.61(B)(1)
8kW x .70= 5.6 kW allows us to account for 70% of the ungrounded conductor load for a neutral

11. An 18 kW residential electric range has a demand load of __________ on the service.

8kw in column c must be increased by 30%
Answer 11 10.4 kW or 10,400 Watts T220.55, Column C Note 1 to Table 18 kW- 12KW= 6Kw over 12 6 x 5= 30 8kw in column c must be increased by 30% 8000 x 1.30= 10400

12. When sizing a branch circuit for a 5 kW, 240 volt, single-phase commercial booster heater installed in the kitchen of a restaurant, the branch circuit conductors are required to have the ability to carry at least _____________ amperes.

Single phase current formula
Answer 12 21 amperes 220.56 Single phase current formula I= P/E 5kw x 1000/240 volts= 5000/240= 20.8 amperes

13. A twelve unit multifamily dwelling complex is to have a 9 kW electric range installed in each unit. When sizing the service entrance conductors, the total demand of the cooking equipment is ___________ voltamperes.

Look at 12 appliances and go to Column c for the total demand
Answer 13 27 kW or 27,000 watts T220.55, Column c Look at 12 appliances and go to Column c for the total demand

14. A residential branch circuit is to supply two wall-mounted ovens rated at 4.5 kW each and one counted mounted cooktop rated at 6 kW. The appliances are rated 240 volts, single phase. The demand load on the branch circuit conductors is __________________ amperes.

Answer 14 38.3 Amperes T220.55, Note 4 Single phase current formula
I=p/e 6kw+4.5kW+4.5kW= 15kw Treat as one range 15kw-12kw= 3kw x 5=15 We must increase a single range of 8000 by 15% 8000 x 1.15= 9200 9200/ 240= 38.3

The demand factor of an electrical is the ratio of the maximum demand for a system to _______________. The total connected load of the system 125% of the total connected load of the system 125% of the total connected continuous load of the system 80% of the total connected non-continuous load plus 125% of the total connected continuous load of the system

The total connected load of the system
Answer 15 The total connected load of the system Article 100 Definitions Article 100 contains the definitions of words which are used in the nec so that we all know what the nec means when a word is used so there are no misunderstandings Always remember that the way we use a word may be different than how the nec uses the word When understanding a code requirement, we have to understand how the nec uses the word

16. What is the service demand load, in kW, for six storage type electric, water heaters rated at 5 kW each, installed in a multifamily dwelling unit? 30 kW 24 kW 22.5 kW 26 kW

6 water heaters x 5kw= 30 kw connected load
Answer 16 22.5 kW or 22,500 watts 220.53 6 water heaters x 5kw= 30 kw connected load 30 kw x .75 = 22.5 kW demand

17. The feeder and service neutral demand load for electric clothes dryers shall be calculated at __________ of the demand load as determined by Table for dwelling units. 100 percent 75 percent 80 percent 70 percent

Answer 17 70 percent 220.61(B)(1) The NEC allows us to size the neutral or grounded conductor at 70% of the ungrounded conductor demand in most cases

18. What is the branch circuit demand load, in amperes, for one 13
18. What is the branch circuit demand load, in amperes, for one 13.5 kW rated, 240 volt, single-phase residential electric range? 33 amperes 37 amperes 50 amperes 58 amperes

Answer 18 37 amperes T220.55, Notes 1 and 4
Single phase current formula I=p/e 13.5 kw rounded up= 14 14-12= 2 x 5= 10 Increase Column c for 1 appliance by 10% 8000 x 1.10= 8800 8800/240= 36.66

19. What is the demand load, in kW, for feeder and service conductors for the following commercial kitchen equipment installed in a restaurant? Water heater 6 kW Dishwasher 2 kW Booster heater 7.5 kW Oven 6 kW Waste Disposal 1.5 kW Mixer 2.5 kW 13 kW 17 kW 26 kW 19 kW

6+2+7.5+6+1.5+2.5= 25.5 connected load x 65%
Answer 19 17 kW or 17,000 watts 220.56 T220.56 = 25.5 connected load x 65% 25.5 x .65= 16.5

20. What is the demand load, in kW, on the grounded service entrance conductor for a multifamily dwelling when 6 electric ranges are installed. Each range is rated for 9.5 kW. 15 kW 21 kW 26 kW 34 kW

21 kw demand for 6 ranges in column C
Answer 20 15 kw or 15,000 watts T220.55, Column c 220.61(B)(1) 21 kw demand for 6 ranges in column C 21,000 x .70= 15,000

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