Demand Loads: cooking equip. & appliance demands Flashcards
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.
True
True or False: The demand load of an electrical appliance is the MINIMUM an appliance may be required at a given time.
False: Maximum required at a given time
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?
Table 220.55
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.
True
When sizing branch circuits for cooking units, when does the demand factor not apply?
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.
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
The first column shows the number of appliances.
What do you do if a cooking appliance falls under BOTH column A and B?
The demand factors for each column shall be applied for that column and added together
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.
- 7 kW
- 0 kW
- 2 kW
- 5 kW
=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
What is the demand load, in kW, for the branch-circuit conductors supplying 8kW residential electric range?
- 0kW
- 4 kW
- 0 kW
- 2 kW
=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
Determine the demand load, in kW, to be added to the ungrounded service entrance conductors for 9.6 kW residential electric range.
- 6 kW
- 0 kW
- 0 kW
- 0 kW
=8.0 kW
Column C of Table 220.55 shows a demand of 8 kW for one range not over 12 kW rating
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
=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
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
=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
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?
- 0 kW
- 8 kW
- 0 kW
- 7 kW
= 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
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
=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
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
=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
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.
True
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
=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
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.
- 9 kW
- 6 kW
- 0 kW
- 4 kW
=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.
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
= 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
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
- 0 kW
- 6 kW
- 5 kW
- 8 kW
= 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.
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?
- 8 kW
- 0 kW
- 5 kW
- 6 kW
=6.8 kW
8.5 kW x 80% = 6.8 kW demand
The demand factor for six residential electric clothes dryers installed in a multifamily dwelling unit is _____
70%
80%
60%
75%
=75%
Table 220. 54
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
- 2 kW
- 6 kW
- 3 kW
- 1 kW
=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
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%
=75%
220.53
