Non-Dwelling Buildings Load Calculations- Part Four


In Article " Non-Dwelling Buildings Load Calculations- Part One ",  I introduced a List for ordinary Non-Dwelling Buildings Loads which was as follows: 

  1. Lighting loads, 
  2. Receptacles Loads, 
  3. Kitchen Loads, 
  4. Heating, Ventilation and air conditioning Loads (Non-Coincident Loads), 
  5. Motor Loads, 
  6. Other Loads. 


Again, but for above Non-Dwelling Buildings Loads, I will explain the following points:

  1. Where and how to distribute each type of load in a dwelling unit as per NEC code? 
  2. How to calculate its Demand load for feeder and service sizing calculations? 



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:

  1. Schools,
  2. Existing Installations,
  3. New Restaurants.




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 Receptacle loads - Third part for Non-Dwelling Building Loads which is Receptacle Loads.




Second: Receptacle Loads – Part Three

1- General –Use Receptacle Loads in Non-Dwelling Units


Important!!!
The receptacle outlets in Non-Dwelling Buildings will be counted to calculate their load, unlike the Dwelling buildings where the General-Use Receptacles Load is calculated with the general lighting Load by multiplying Building Area in (ft2) with its power density in (VA/ft2) from table 220.42 in below image.







Important!!!
General-Use Receptacles are not-continuous Loads, No need to multiply it by 1.25 to calculate their contribution in the total load.
But, if a Receptacle is dedicated for a specific device, then the actual load is used and If this dedicated load is continuous, then the 125% overrate is appropriate.




Rule#1: General-Use Receptacle Load (see below image)

As per NEC section 220.14(I), Receptacle outlets load shall be calculated at not less than:

  • 180 volt-amperes for each single receptacle,
  • 180 volt-amperes for each multiple receptacle (duplex or triplex) on one yoke/strap,
  • 90 volt- amperes per receptacle for multiple receptacles (four or more).







Important!!!
The general lighting load unit values specified in table 220.42 for guest rooms or guest suites of hotels and motels includes All general-use receptacle outlets of 20-ampere rating or less, including receptacles connected to Bathroom Branch Circuits,

So, no need to add the above outlets in load calculations per NEC method.




Example#1:


For a commercial building having 75 duplex and 10 single receptacles, what is the calculated load for these receptacles?



Solution:
As per NEC section 220.14(I), Receptacle outlets load shall be calculated at not less than:

180 volt-amperes for each single receptacle, 180 volt-amperes for each multiple receptacle (duplex or triplex) on one yoke/strap. 


So, Receptacle calculated load = (75+10) x 180 VA = 15,300 VA





Important!!!
In Commercial and Industrial Buildings, it is common to use  fixed multioutlet assemblies, which can be classified to two types according to method of usage as follows:

  1. Light use: which means that not all the cord-connected equipment is expected to be used at the same time, as defined in 220.14(H)(1). An example of light use is a workbench area where one worker uses one electrical tool at a time.
  2. Heavy use: which is characterized by all the cord-connected equipment generally operating at the same time, as defined in 220.14(H)(2). An example of heavy use is a retail outlet displaying television sets, where most, if not all, sets are operating simultaneously.




Rule#2: Fixed Multioutlet Assemblies Load (see below image)

As per NEC section 220.14(H), Fixed multioutlet assemblies used shall be calculated as follows:

  1. For Light use, each 1.5 m (5 ft) or fraction thereof of each separate and continuous length shall be considered as one outlet of not less than 180 volt-amperes.
  2. For heavy use, each 300 mm (1 ft) or fraction thereof shall be considered as an outlet of not less than 180 volt-amperes.







Important!!!
Fixed multioutlet assemblies are not-continuous Loads, No need to multiply it by 1.25 to calculate their contribution in the total load.
But, if Fixed multioutlet assemblies is dedicated for a specific device, then the actual load is used and If this dedicated load is continuous, then the 125% overrate is appropriate.




Important!!!
Fixed multioutlet assemblies in guest rooms or guest suites of hotels and motels are included in The general lighting load unit values specified in table 220.12.

So, no need to add the Fixed multioutlet assemblies in load calculations for these locations.



Example#2:


For a commercial building has 75 linear feet of fixed multioutlet assembly, with 15 feet of the assembly subject to simultaneous use. What is the calculated load for this fixed multioutlet assembly?



Solution:
Length of fixed multioutlet assembly Portion for Non- simultaneous use (Light Use) = 75 – 15 = 60 linear feet.

Calculated load for Light use portion = (60/5) x 180 VA = 2,160 VA Calculated load for Heavy use (simultaneous use) portion = 15 x 180 VA = 2,700 VA 

Total calculated load for this fixed multioutlet assembly = 2,160 VA + 2,700 VA = 4,860 VA





Rule#3: General-Use Receptacles and Fixed Multioutlet Assemblies Loads Demand Factors

As per NEC section 220.44, General-Use Receptacles and Fixed Multioutlet Assemblies  are subjected to demand factors by either of the following two methods:

  1. If the occupancy is one of the types (other than dwelling units) listed in Table 220.42, the receptacle load could be added to the general lighting load and made subject to the demand factors in Table 220.42.
  2. If the occupancy is not one of the types listed in Table 220.42 and receptacle loads greater than 10,000 volt-amperes, The receptacle loads are calculated (without the lighting load) with demand factors from Table 220.44 (in below image) applied.







Example#3:


The general lighting load, before applying demand factors, for hospital patient rooms is 100,000 volt-amperes. The receptacle branch-circuit load, calculated in accordance with 220.14(H) and (I), is 144,000 volt-amperes. What is the lighting and receptacle load after demand factors? 


Solution:
Since Hospital is one of the building types (other than dwelling units) listed in Table 220.42, the receptacle load could be added to the general lighting load and made subject to the demand factors in Table 220.42. 

Total load = lighting load + receptacles load = 100,000 VA+ 144,000 VA = 244,000 VA

Then apply demand factors for hospital from table 220.42 as follows:

Multiply the first 50,000 by 40 percent = 50,000 × 40% = 20,000 VA

The Remaining = 244,000 – 50,000 = 194,000 VA

Multiply the remaining by 20 percent = 194,000 × 20% = 38,800 VA


The lighting and receptacle load, after applying Table 220.42 demand factors= 20,000 + 38,800 = 58,800 VA




Example#4:

For a hospital building, the receptacle branch-circuit load is 144,000 volt-amperes. What is the receptacle load after applying the demand factors in Table 220.44?



Solution:
Applying the demand factors in Table 220.44

The first 10 kVA is multiplied by 100 percent = 10,000 x 100% = 10.000 VA

The remainder = 144,000 – 10,000 = 134,000 VA

Multiply the remainder by 50 percent = 134,000 × 50% = 67,000 VA
Then, the receptacle load, after applying Table 220.44 demand factors = 10,000 + 67,000 = 77,000 VA 



Example#5:


A store has a total of 80 duplex receptacles. What is the receptacle load after demand factors?



Solution: 

First, multiply the 80 receptacles by 180 volt-amperes. 

Receptacle load before applying demand factors = 80 × 180 VA= 14,400 VA
Second, Applying the demand factors in Table 220.44 

The first 10 kVA is multiplied by 100 percent = 10,000 x 100% = 10.000 VA

The remainder =14,400 – 10,000 = 4,400 VA

Multiply the remainder by 50 percent = 4,400 × 50% = 2,200 VA

Then, the receptacle load, after applying Table 220.44 demand factors= 10,000 + 2200 = 12,200 VA





Rule#4: Special case#1: where the actual number of receptacle outlets in banks and office buildings is unkown

As per NEC section 220.14(K), in bank and office buildings, if the number of receptacles is unknown, we can calculate the receptacles load by multiplying the bank or office building area in ft2 by the unit value (1 VA/ft2).




Rule#5: Special case#2: where the actual number of receptacle outlets in banks and office buildings is kown

As per NEC section 220.14(K), in bank and office buildings, if the number of receptacles is known, then we can calculate the receptacles load to be the larger of the following two loads:

  1. Load computed as per Rule#1 above,
  2. Load computed as per Rule#4 above.




Example#6:


In an 8,500 square foot bank, it is not known how many receptacles are there, what is the calculated load for receptacles?



Solution:
As per NEC section 220.14(K), in bank and office buildings, if the number of receptacles is unknown, we can calculate the receptacles load by multiplying the bank or office building area in ft2 by the unit value (1 VA/ft2).
The calculated load for receptacles = 8500 ft2 x 1 VA/ft2 = 8,500 VA 




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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