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Kansas Electrical Prep > Demand Loads: cooking equip. & appliance demands > Flashcards

Demand Loads: cooking equip. & appliance demands Flashcards

1
Q

True or False: A demand factor is the ratio of the maximum demand of the system, or part of a system, to the total connected load of the a system.

A

True

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2
Q

True or False: The demand load of an electrical appliance is the MINIMUM an appliance may be required at a given time.

A

False: Maximum required at a given time

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3
Q

What table relates to demand factor for household electric ranges, wall mounted ovens, counter-mounted cooking units and appliance over 1 3/4 kW rating?

A

Table 220.55

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4
Q

True or False: household electric ranges having a rating of 8.75 kW or more are required to be supplied by at least 40 ampere rated branch circuit.

A

True

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5
Q

When sizing branch circuits for cooking units, when does the demand factor not apply?

A

When the units are SINGLE cooking units.
Example ONE wall mounted oven
or ONE counter-mounted cooking unit. The nameplate rating of the appliance applies.

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6
Q

Table 220.55 is separated into four columns.
What does the first column show you?

of appliances
cooking equipment with a rating of less than 3 1/2 kW
cooking equipment with a rating of 3 1/2 to 8 3/4 kW
cooking equipment with a rating of not over 12 kW

A

The first column shows the number of appliances.

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7
Q

What do you do if a cooking appliance falls under BOTH column A and B?

A

The demand factors for each column shall be applied for that column and added together

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8
Q

A small residential duplex has 3 kW counter-mounted cooktop and 4kW wall mounted oven installed in each unit. Determine the demand load, in kW to be added to the unground service-entrance conducts for the cooking equipment.

  1. 7 kW
  2. 0 kW
  3. 2 kW
  4. 5 kW
A

=9.7 kW

col. A - 3kW +3kW = 6kW x 75% = 4.5 kW
col. B - 4kW +4kW =8kW x 65% = 5.2 kW
=9.7 kW demand

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9
Q

What is the demand load, in kW, for the branch-circuit conductors supplying 8kW residential electric range?

  1. 0kW
  2. 4 kW
  3. 0 kW
  4. 2 kW
A

=6.4 kW
8kW x 80% = 6.4 kW demand load

Column C is to be used when applying demand factors for electric ranges of not over 12kW rating

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10
Q

Determine the demand load, in kW, to be added to the ungrounded service entrance conductors for 9.6 kW residential electric range.

  1. 6 kW
  2. 0 kW
  3. 0 kW
  4. 0 kW
A

=8.0 kW

Column C of Table 220.55 shows a demand of 8 kW for one range not over 12 kW rating

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11
Q

A ten 10 unit apartment complex is to have a 10 kW electric range installed in each unit. When sizing the unground service-entrance conductors, the total demand load for the multiple ranges is _______.

30 kW
80 kW
25 kW
100 kW

A

=25 kW

Column C of Table 220.55 shows a demand of 25 kW for 10 ranges of not over 12kW rating.

Note: When applying maximum demand factors of the same rating over 12kW through 27kW, we are to apply note 1 AND column C of the table, which states an increase by 5% for each kW that exceeds 12 kW

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12
Q

What is the branch-circuit demand load, in amperes, for one 16 kW, 240 volt, single phase residential electric range?

33 amperes
50 amperes
40 amperes
67 amperes

A

=40 amperes

16kW - 12kW = 4kW x 5% = 20% increase in Column C
8 kW x 120% = 9.6 kW demand

I = 9.6 kW x 1000 / 240 volts
9600 / 240 = 40 amperes

When applying demand factor for multiple ranges, all having the same nameplate rating of more than 12kW, but not more than 27 kW, we are able to apply note 1 on table 220.55

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13
Q

A four unit residential town house has a 14kW electric range installed in each unit. What is the demand load for the ranges, in kW, to be added to the ungrounded service-entrance conductors when sizing the service?

  1. 0 kW
  2. 8 kW
  3. 0 kW
  4. 7 kW
A

= 18.7 kW

14kW - 12kW= 2 kW x 5% = 10% increase in Column C
col. C demand (4 ranges) = 17kW x 110% = 18.7 kW

When applying maximum demand factors for ranges having UNEQUAL ratings of 8 3/4kW through 27 kW we are to apply note 2 and Column C of Table 220.55

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14
Q

The vocational education department of a high school is to have (3) three electric ranges installed in a classroom; one 10 kW, one 11kW and one 12kW. The ranges are to be supplied by a 208 volt, single phase feeder from a sub panel. What is the demand load, in amperes, on the ungrounded feeder conductors?

58 amperes
67 amperes
136 amperes
142 amperes

A

=67 amperes

I= 14kW x 1000/ 208 volts
= 14,000/208
=67.3 amperes

When calculating the demand factors for ranges UNEQUAL ratings of 8 3/4 through 27kW, when the nameplate rating of any range less than 12kW, you are to use 12kW as MINIMUM and add the ratings together and divide by the number of ranges to obtain the average

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15
Q

Another classroom in the high school is to install two electric ranges, one 16 kW and one 11kW. Determine the demand load, in amperes, on the 208 volt, single-phase ungrounded feeder conductors.

67 amperes
76 amperes
58 amperes
63 amperes

A

=58 amperes

12kW (min) + 16kW = 28kW/2(ranges) = 14kW average

14kW-12kW = 2kW x 5% = 10% increase in Col. C.
Col C demand (2 ranges) = 11kW x 110% = 12.1 kW demand

I=12.1 kW x 1000 / 208 volts
= 12,100/208
=58 amperes

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16
Q

True or False: When sizing branch-circuit loads for single branch-circuit supplying a counter-mounted cooking unit and not more than two wall mounted ovens, it is permissible to add the nameplate rating of the appliances together and treat the result as one range.

A

True

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17
Q

A 240 volt, single-phase branch circuit (home run) is to supply one 6 kW rated counter-mounted cooking unity and two (2) wall mounted 4 kW rated ovens in a residential kitchen. What is the demand load, in amperes, on the branch circuit for the appliances?

22 amperes
27 amperes
33 amperes
37 amperes

A

=37 amperes
6kW + 4kW + 4kW= 14 kW connected load
14 kW - 12kW = 2kW x 5% = 10% increase in Col. C
Col. C deman (1 range) = 8kW x 110% = 8.8 kw Demand Load

I = 8.8 kW x 1000 / 240 volts
=8,800/240
=36.6 amperes

** section 220.61 permits an additional demand factor of 70 % for the neutral (grounded) conductor, for a feeder

18
Q

A four (4) unit apartment house is to have 10.5 kW electric range installed in each unit. Determine the demand load, in kW, on the grounded (neutral) service- entrance conductor for the ranges.

  1. 9 kW
  2. 6 kW
  3. 0 kW
  4. 4 kW
A

=11.9 kW

Col. C shows a demand of 17kW for the demand on the ungrounded conductors for the four electric ranges

17kW x 70% = 11.9 kW

    • In a residential occupancy, a 75% demand factor is permitted to be applied when 4 or more fastened in place appliances such as water heaters, trash compactors, garage door openers, dishwashers, etc.
  • ***Note: 220.53 This sections does not apply to ranges, clothes dryers, space-heating and air-conditions equipment.
19
Q

A one family dwelling unity is to have the following fastened in place appliances installed:

one -1200 VA dishwasher
one - 4000 VA water heater
one - 1150 VA garbage disposal
one - 700 VA attic fan
one - 1920 VA garage door opener

The demand load in VA, on the ungrounded service-entrance conductors the listed appliances is ______.

7728 VA
6728 VA
6276 VA
8970 VA

A

= 6728 VA

1200 VA dishwasher
4000 VA water heater
1150 VA garbage disposer
700 VA attic fan
1920 VA garage door opener
=8970 VA connected load x 75% = 6728 VA demand
20
Q

An 8 unit multifamily dwelling is to have the following electric clothes dryers installed in the laundry rooms of the tenants:

two - 4.5 kW rated
two - 5.5 kW rated
two - 6.0 kW rateW
two - 6.5 kW rated

The demand load, in kW, to be added to the ungrounded feeder conductors for the listed electric dryer is

  1. 0 kW
  2. 6 kW
  3. 5 kW
  4. 8 kW
A

= 27.6 kW

In residential occupancies, demand factors may also be applied to electric clothes dryers. Table 220. 54 Each dryer shall be calculated at a minimum of 5000 watts(volt -amperes) or the nameplate rating, which ever is larger.

2 dryers @ 5.0 kW (minimum) = 10 kW
2 dryers @ 5.5 kW = 11kW
2 dryers @ 6.0 kW =12 kW
2 dryers @ 6.5 kW = 13 kW
 = 46kW x 60% = 27.6 kW

An additional factor of 70% is permitted for the neutral (grounded conductor) for a feeder or service supplying electric clothes dryers for dwelling unity.

21
Q

What is the demand load, in kW, on the ungrounded service-entrance (line) conductors of a residence for one 8.5 kW rated electric range?

  1. 8 kW
  2. 0 kW
  3. 5 kW
  4. 6 kW
A

=6.8 kW

8.5 kW x 80% = 6.8 kW demand

22
Q

The demand factor for six residential electric clothes dryers installed in a multifamily dwelling unit is _____

70%
80%
60%
75%

A

=75%

Table 220. 54

23
Q

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 cooktop rated at 6kW and a broiler rated at 3.5 kW. The feeder demand will be _______ on the ungrounded conductors for the cooking equipment

  1. 2 kW
  2. 6 kW
  3. 3 kW
  4. 1 kW
A

=12.2

Table 220.55 & Note 3

Use column B - 5 appliances = 45% demand
6kW + 8kW + 3.5 kW + 6 kW + 3.5 kW = 27 kW connected load 27kW x 45% = 12.15 kW demand load

24
Q

It shall be permissible to apply a demand factor ____ to the nameplate rating of four 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.

50%
75%
80%
90%

A

=75%

220.53

25
Q

When doing residential service and feeder calculations, electric clothes dryers are to be calculated at a minimum of _____ watts (VA) or the name plate rating, whichever is larger.

3000
4500
5000
6000

A

=5000

220.54

26
Q

For residential electric ranges rated at 8.75 kW or more, the MINIMUM branch circuit rating shall be at LEAST ______

30 amperes
40 amperes
50 amperes
60 amperes

A

=40 amperes

210.19 (a) (3)

27
Q

Determine the demand load, in VA, on the service-entrance (line) conductors of a one family dwelling when the house has the following fastened in place electric appliances:

water heater         - 4800 VA
dishwasher           - 1200 VA
garbage disposal - 1150 VA
trash compactor.   - 800 VA
attic fan                 - 1200 VA

6,863 VA
9,150 VA
8,579 VA
11,438 VA

A

=6,863

water heater - 4800 VA
dishwasher - 1200 VA
garbage disposal - 1150 VA
trash compactor. - 800 VA
attic fan - 1200 VA
= 9,150 VA connected load x 75% demand
= 6,863 VA demand load

28
Q

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

40 amperes
30 amperes
25 amperes
20 amperes

A

=25 amperes

Note 4, Table 220. 55
Single phase current formula
I= P / E

I = 6kW x 1000/240
= 6000/240
= 25 amperes

29
Q

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 ______

3500 VA
5000 VA
6000 VA
7200 VA

A

=7200 VA

  1. 54
    Power Formula
    VA = E x I

VA = 240 volts x 30 amperes = 7200 VA

30
Q

Determine the demand load, in KW, to be added to the grounded (neutral) service entrance conductor for one 10.5 kW residential electric range.

  1. 6 kW
  2. 0 kW
  3. 5 kW
  4. 0 kW
A

=5.6 kW
Table 220.55, Col. C
Table 220.61 (B)(1)

Col. C demand 1 range = 8kW x 70% = 5.6 kW

31
Q

An 18 kW residential electric range has a demand load of ______ on the ungrounded line feeder and service-entrance conductors

  1. 0kW
  2. 4 kW
  3. 4 kW
  4. 6 kW
A

=10.4 kW

Table 220.55 Col C

18 kW - 12kW =6 kW x 5% = 30% increase in Col. C
Col C demand 1 range = 8 kW x 130% = 10.4

32
Q

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 _______.

30 amperes
35 amperes
21 amperes
25 amperes

A

= 21 amperes

Single phase circuit formula
I = watts / volts

I = 5 kW x 1000/240 volts
= 5000/240
=20.8 amperes

33
Q

A twelve (12) unit multifamily apartment complex is to have a 9kW electric range installed in each unit. When sizing the ungrounded (line) service-entrance conductors the total demand load for the multiple range is ______.

99 kW
30 kW
36 kW
27kW

A

=27kW

Table 220.55 Col. C

34
Q

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

  1. 4 amperes
  2. 3 amperes
  3. 1 amperes
  4. 8 amperes
A

=38.3

Table 220.55, Note 4
Single phase current formula
I = watts/volts

6kW + 4.5 kW + 4.5kW = 15kW connected load
Treat as one range
15kW - 12kW = 3kW x 5% = 15% increase in Col. C
Col C demand 1 range = 8kW x 115% = 9.2 kW demand load

I= 9.2 kW x 1000/ 240
=9200/240
=38.3 amperes

35
Q

The demand factor for an electrical system is the ratio of maximum demand for a system to ____.

A. the total connected load of a system
B. 125% of the total connected load of a system
C. 125% of the total connected continuous load of the system
D 80% of the total connected non-continuous load plus 125% of the total connected continuous load of the system.

A

=The total connected load of a system

36
Q

What is the service demand load, in kW, for 6 storage type electric water heaters rated at 5kW each, installed in a multifamily dwelling unit?

  1. 0 kW
  2. 0 kW
  3. 5 kW
  4. 0 kW
A

=220.53

6 water heaters x 5 kW = kW connected load
30 kW x 75% (demand factor) = 22.5 kW demand load

37
Q

For dwellings units, the feeder and service neutral demand load for electric clothes dryers shall be calculated at ________ of the demand load as determined by Table 220.54.

100%
75%
80%
70%

A

=70%

220.61 (B)(1)

38
Q

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

A

=37 amperes

Table 220.55, notes 1 &4
Single phase current formula
I = power/volts

I = 8.8 kW x 1000/240
8800/ 240
=36.6 amperes

39
Q

What is the demand load, in kW, for the feeder and service conductors for the following commercial kitchen equipment installed in a restaurant?

Water heater 6.0 kW
Dishwasher 2.0 kW
Booster heater 7.5 kW
Oven 6.0 kW
Waste Disposal 1.5 kW
Mixer 2.5 kW

13kW
17kW
26 kW
19 kW

A

=17kW

Add all
6
2
7.5
6
1.5
2.5
=25.5kW connected load x 65% demand = 16.5 kW demand load
40
Q

What is the demand load, in kW, on the grounded (neutral) service-entrance conductor for a multifamily dwelling when 6 household electric ranges, each having 9.5 kW rating, are installed

15kW
21 kW
26 kW
34 kW

A

=15kW

Table 220.55 Col. C
220.61 B, 1

21 kW demand (6 ranges) in Col. C
21 kW x 70% neutral demand = 15 kW demand load

Kansas Electrical Prep (6 decks)

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