In Article " Non-Dwelling Buildings Load Calculations- Part One ", I introduced a List for ordinary Non-Dwelling Buildings Loads which was as follows:
- Lighting loads,
- Receptacles Loads,
- Kitchen Loads,
- Heating, Ventilation and air conditioning Loads (Non-Coincident Loads),
- Motor Loads,
- Other Loads.
Again, but for above Non-Dwelling Buildings Loads, I will explain the following points:
- Where and how to distribute each type of load in a dwelling unit as per NEC code?
- How to calculate its Demand load for feeder and service sizing calculations?
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Important!!!
All design Calculations for Non-dwelling Buildings will be as per
NEC standard calculation method but I will explain design calculations as per
NEC Optional calculation method only for the following Non-Dwelling buildings
as permitted by NEC, Part IV. Optional Feeder and Service Load Calculations:
Schools,
Existing Installations,
New Restaurants.
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I explained the Design Calculation for first type of Non-Dwelling Building loads which is Lighting loads in Article " Non-Dwelling Buildings Load Calculations- Part One ".
Also, I explained parts one & Two of Design Calculation for second type; Receptacle loads for Non-Dwelling Buildings in Articles:
Today, I will explain the Design Calculation of third type of loads in Non-Dwelling Building Loads which is Kitchen Load.
Third: Kitchen Load
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Definition:
Kitchen: An area with a sink and
permanent provisions for food preparation and cooking.
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Important!!!
Kitchen equipment is
not limited to restaurants; it can be a portion of a load calculation for a
school.
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Rule#1: commercial electric cooking equipment Load (see below image for kitchen)
As per NEC section 220.56, it
shall be permissible to calculate the load for commercial electric cooking
equipment, dishwasher booster heaters, water heaters, and other kitchen
equipment in accordance with Table 220.56 (see below image). These demand
factors shall be applied to all equipment that:
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Important!!!
Demand factors of table 220.56 shall not apply to space-heating,
ventilating, or air-conditioning equipment.
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Important!!!
As per table 220.56, No derating is
allowed for only one or two pieces of kitchen equipment.
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Important!!!
Because commercial
electric cooking and other kitchen
equipment is used more intensively and
for longer periods of time than electric cooking equipment in a dwelling unit, the
demand factors in Table 220.56 do not provide a comparable demand
to that permitted for dwelling unit cooking appliances until
there are six or more commercial appliances.
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Important!!!
Because commercial
electric cooking and other kitchen
equipment is used more intensively and
for longer periods of time than electric cooking equipment in a dwelling unit, the
demand factors in Table 220.56 do not provide a comparable demand
to that permitted for dwelling unit cooking appliances until
there are six or more commercial appliances.
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Important!!!
Unlike Table 220.55,
Table 220.56 is not just for ranges and cooking appliances; it will apply for all equipment that has either thermostatic control or
intermittent use as kitchen equipment
(like commercial electric
cooking equipment, dishwasher booster heaters, water
heaters, and other kitchen equipment).
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Rule#2:
Comparing the demand load to the
sum of the largest two kitchen equipment loads
As per NEC section 220.56, the calculated demand
load for the feeder or service must not be less than the sum of the largest
two kitchen equipment loads. Two cases are available:
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Example#1:
What is the demand load for a restaurant with two 14-kW stoves, a 6-kW oven, a 5-kW dishwasher, a 3-kW booster heater, and a 4-kW food waste disposer?
Solution:
The total number of units is six.
The demand factor percent in Table 220.56 for six units is 65 percent.
The total rating of the equipment = 14 + 14 + 6 + 5 + 3 + 4 = 46 kW
The load after applying the Table 220.56 demand factor = 46 × 65% = 29.9 kW
Comparing the demand load to the sum of the largest two kitchen equipment loads
The absolute minimum rating is the total combined rating of the largest two kitchen equipment loads = 14 + 14 = 28 KW
Since the demand load of 29.9 kW is higher than the sum of the two highest rated units, it is permissible to use the demand load.
Example#2:
What is the demand load for the following commercial kitchen equipment: five 3-kW ovens, one 5-kW cooktop and two 20-kW ranges?
Solution:
The total number of units is eight.
The demand factor percent in Table 220.56 for eight units is 65 percent. T
The total rating of the equipment = 3 + 3 + 3 + 3 + 3 + 5 + 20 + 20 = 60 kW
The load after applying the demand factor = 60 × 65% = 39 kW
The sum of the largest two kitchen equipment loads = 20 + 20 = 40
Since the demand load of 39 kW is lower than the sum of the two highest rated units, the demand load must not be used.
The minimum load for these eight units of kitchen equipment is 40 kW
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Important!!!
As
per NEC section 220.55, demand factors in Table 220.55 cannot be applied to commercial kitchen equipment.
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Definition:
An instructional program
Building: a building in which a discipline and an organized sequence or
grouping of courses leading to a defined objective such as a major, degree,
certificate, license, the acquisition of selected knowledge or skills, or
transfer to another institution of higher education. For example A high
School Classroom.
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Rule#3:
Cooking Appliances Load in instructional
programs
Calculating the Cooking Appliances Loads in Instructional programs
building will have the following cases:
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Important!!!
Household electric cooking equipment
installed in other than dwellings units
and not in instructional programs must be
calculated in accordance with Table 220.56.
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Example#3:
A high school classroom will be converted into a culinary arts classroom. Five 12-kW, 240-volt household electric ranges will be installed. A separate panelboard will be installed to supply the ranges. What is the kilowatt-demand load for the feeder and panelboard supplying power to these ranges?
Solution:
Since the ranges will be used in instructional programs and they are household electric ranges. So, table 220.55 note#5 will be applied.
The feeder and panelboard could be sized on 100 percent of the equipment’s nameplate ratings, which is 60 kW, but this is not necessary. Look in the left column of Table 220.55 for five appliances.
Because of the range ratings, the maximum demand is in Column C. The maximum demand required for five 12-kW, 240-volt house-hold electric ranges is 20 kW.
Example#4:
A high school classroom will be converted into a culinary arts classroom. Five 12-kW, 240-volt commercial electric ranges will be installed. A separate panelboard will be installed to supply the ranges. What is the kilowatt-demand load for the feeder and panelboard supplying power to these ranges?
Solution:
Since the ranges will be used in instructional programs and they are not household (commercial) electric ranges.
Therefore, it is not permissible to apply the demand factors from Table 220.55. Demand factors for commercial electric cooking equipment are in Table 220.56.
Look in the left column of Table 220.56 for five units of equipment and follow across for the demand factor.
The demand factor percent for five units is 70 percent.
These five ranges have a total rating = 5 × 12 = 60 kW
The load after applying the demand factor = 60 × 70% = 42 kW
The feeder and panelboard supplying power to these five commercial ranges must be capable of carrying a load of at least 42 kW
In the next article, I will continue explaining load calculations for other types of loads in Non-Dwelling Buildings. Please, keep following.
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