Commercial Services
The Code refers to commercial locations as other than dwelling, or nondwelling locations. We could imply that a commercial location is any place that people don’t normally live. That’s a pretty broad definition covering a lot of different situations. Unfortunately, that’s the way the Code deals with commercial calculations. Let’s try and put some order to it by taking it a step at a time.
General Lighting
Article 220.12 covers general lighting loads for various occupancies. To determine minimum lighting requirements we would find the type of occupancy from Table 220.12, then multiply the square foot area by the unit load per square foot (vA) from the table. Keep in mind that these are estimates and may be less than what is actually installed.

2,500 sq. ft x 2 vA per sq. ft. = 5,000 vA
One thing that must be considered in a commercial load, such as a restaurant, is that our lighting will probably be used continuously (possibly all day and night). The Code defines a continuous load as “a load where the maximum current is expected to continue for three hours or more.” Article 210.20(A) requires us to rate continuous loads at 125%.
2,500 sq. ft x 2 vA per sq. ft. @ 125% = 6,250 vA
Not all commercial lighting is continuous. Lighting for hospital patient care areas, hotel and motel guest rooms, storage areas, and closets would not be considered continuous.
Other Types Of Lighting Circuits
Table 220.12 estimates general lighting demands for occupancies. Article 220.14 and exceptions lists other special lighting loads.
(1) Recessed Lighting Fixtures = Maximum Lamp Rating
(2) HeavyDuty Lamp Holder = 600 vA
(3) Track Lighting = 180 vA every 2 ft.
(4) Show Window Lighting = 200 vA every 1 ft.
(2) HeavyDuty Lamp Holder = 600 vA
(3) Track Lighting = 180 vA every 2 ft.
(4) Show Window Lighting = 200 vA every 1 ft.
Articles 600.5(A) and 220.14(F) also requires a sign circuit rated at a minimum of 1,200 vA for each commercial occupancy accessible to pedestrians. The above ratings are estimates at either continuous or noncontinuous duty.
For example, if a store has: 3 heavyduty lamp holders, 12 feet track lighting, 20 feet of showwindow lighting, and one exterior sign circuit. The lighting demand would be…
For example, if a store has: 3 heavyduty lamp holders, 12 feet track lighting, 20 feet of showwindow lighting, and one exterior sign circuit. The lighting demand would be…
(1) HeavyDuty Lamp Holder (600 vA x 3) = 1,800 vA
(2) Track Lighting (180 vA x 6) = 1,080 vA
(3) Show Window Lighting (200 vA x 20) = 4,000 vA
(4) Sign Circuit = 1,200 vA
Total = 8,080 vA
(2) Track Lighting (180 vA x 6) = 1,080 vA
(3) Show Window Lighting (200 vA x 20) = 4,000 vA
(4) Sign Circuit = 1,200 vA
Total = 8,080 vA
But, if the actual lamp ratings are known they must not only be considered, they must be rated continuous duty. Remember, Article 2203 and Table are considered estimates and may not provide sufficient capacity for the installation contemplated.
For example, if we knew that the store in the above problem actually had: 3 heavyduty lamp holders at 800 vA each, 6 track lights at 200 vA each, 30 show window lights at 150 vA each, and one exterior sign at 1,500 vA. The lighting demand would be...
For example, if we knew that the store in the above problem actually had: 3 heavyduty lamp holders at 800 vA each, 6 track lights at 200 vA each, 30 show window lights at 150 vA each, and one exterior sign at 1,500 vA. The lighting demand would be...
(1) HeavyDuty Lamp Holder (800 vA x 3 x 125%) = 3,000 vA
(2) Track Lighting (200 vA x 6 x 125%) = 1,500 vA
(3) Show Window Lighting (150 vA x 30 x 125%) = 5,625 vA
(4) Sign Circuit (1,500 vA x 125%) = 1,875 vA
Total = 12,000 vA
(2) Track Lighting (200 vA x 6 x 125%) = 1,500 vA
(3) Show Window Lighting (150 vA x 30 x 125%) = 5,625 vA
(4) Sign Circuit (1,500 vA x 125%) = 1,875 vA
Total = 12,000 vA
The actual lighting load exceeds the estimate and that’s what we’re going to have to use when we calculate our service requirements.
NonDwelling Receptacle Loads
Singlefamily, twofamily, multifamily dwelling, hotels and motel guest room receptacle loads are included in the general lighting load 3 vA per square foot requirement of Table 220.12.
This, unfortunately, is not the case with nondwelling receptacle loads. Table 220.12 will allow us to add an additional 1 vA per square foot for bank and office building general purpose receptacle outlets, where the actual number of outlets is unknown.
Most of the time, though, nondwelling receptacles are rated 180 vA each according to Article 220.14(I). Fixed multioutlet assemblies (220.14(H)) are rated 180 vA for every 5 feet in light duty situations, and 180 vA per foot in heavy duty situations.
Take the situation where the number of general use receptacles in a 3,000 square foot office building has not been determined. In that case, the demanded load to be added to the service calculation would be…
This, unfortunately, is not the case with nondwelling receptacle loads. Table 220.12 will allow us to add an additional 1 vA per square foot for bank and office building general purpose receptacle outlets, where the actual number of outlets is unknown.
Most of the time, though, nondwelling receptacles are rated 180 vA each according to Article 220.14(I). Fixed multioutlet assemblies (220.14(H)) are rated 180 vA for every 5 feet in light duty situations, and 180 vA per foot in heavy duty situations.
Take the situation where the number of general use receptacles in a 3,000 square foot office building has not been determined. In that case, the demanded load to be added to the service calculation would be…
3,000 sq. ft. x 1 vA = 3,000 vA
But, if we know that there are exactly 25 outlets in the office building, the demanded load
would be…
would be…
180 vA x 25 = 4,500 vA
It may be confusing to apply different calculations to the same loads. The Code seems to be make provisions for an educated guess, but, would prefer actual values when they are known.
General Lighting And Receptacle Demand Factors
The demand factors from Table 220.42 apply only to dwelling units, hospital patient care rooms, hotel and motel guest rooms, and warehouses.of guest rooms. There are also 6 heavyduty lamp holders in the parking area, 200 feet of track lighting, one sign at the front of the building, and 12 receptacles (outside of guest rooms).
(1) Motel (700 sq. ft. x 2 vA x 125%) = 1,750 vA
(2) Guest Rooms (1,000 sq. ft. x 2 vA) = 2,000 vA
(3) HeavyDuty Lamp holders (600 vA x 6) = 3,600 vA
(4) Track Lighting (180 vA x 10) = 1,800 vA
(5) Receptacles (180 vA x 12) = 2,160 vA
(6) Sign Circuit = 1,200 vA
Total =12,510 vA
(2) Guest Rooms (1,000 sq. ft. x 2 vA) = 2,000 vA
(3) HeavyDuty Lamp holders (600 vA x 6) = 3,600 vA
(4) Track Lighting (180 vA x 10) = 1,800 vA
(5) Receptacles (180 vA x 12) = 2,160 vA
(6) Sign Circuit = 1,200 vA
Total =12,510 vA
Here again, we are dealing with estimates of possible loads in a commercial building. We know that there is 700 square feet of motel area (1,700  1,000) at 2 vA per square foot (Table 220.12), this area is also considered continuous (125%). The guest rooms are not considered continuous, and, generaluse receptacles in these areas are included in the 2 vA per square foot. Receptacles, not in guest rooms, are calculated at 180 vA each. The track lighting is estimated at 180 vA for every 2 feet (20/2 = 10).
220.42 General Lighting. The demand factors specified in Table 220.42 shall apply to that portion of the total branch circuit load calculated for general illumination. They shall not be applied in determineing the number of branch circuits for general illumination.
*The demand factors of this table shall not apply to the calculated load of feeders or services supplying areas in hospitals, hotels, and motels where the entire lighting is likely to be used at one time, as in operating rooms, ballrooms, or dining rooms.
And, according to Article 220.44, receptacle loads, other than dwelling units, computed at 180 vA per outlet shall be permitted to be added to the lighting loads and made subject to Table 220.42.
For example, a motel includes: 1,700 square feet including 1,000 square feet receptacle loads to our demand factors according to Article 220.44.
*The demand factors of this table shall not apply to the calculated load of feeders or services supplying areas in hospitals, hotels, and motels where the entire lighting is likely to be used at one time, as in operating rooms, ballrooms, or dining rooms.
And, according to Article 220.44, receptacle loads, other than dwelling units, computed at 180 vA per outlet shall be permitted to be added to the lighting loads and made subject to Table 220.42.
For example, a motel includes: 1,700 square feet including 1,000 square feet receptacle loads to our demand factors according to Article 220.44.
Now, we can apply the demand factors in Table 220.42. We can also include the receptacle loads to our demand factors according to Article 220.44.
12,510 vA x 50% = 6,255 vA
Table 220.42 allows the first 20,000 vA of hotels and motels to be reduced to 50%. The next 80,000 vA (between 20,000 and 100,000 vA), is reduced to 40%. Anything over 100,000 vA would be reduced to 30%.
Other Commercial Loads
Dwelling units, hospitals, hotels and motels, and warehouses are covered under Table 220.42. What about other types of commercial installations ? At the bottom of Table 220.42 it states that all others are at 100% of the total voltamps. This means that we’re out of luck ! There are no demand factors for other types of commercial lighting loads. But, there are demand factors for commercial receptacle loads rated at 180 vA each.
When Table 220.42 cannot be used, then, Table 220.44 is the only way to go. Unfortunately, the first 10 kVa of Table 220.44 is rated 100%. In other words, there are no derating factors for the first 55 outlets.
180 vA x 55 outlets = 9,900 vA
But, after 10 kVa, or 55 receptacles, there’s a 50% reduction allowed. For instance, if a bank has 100 generaluse receptacles. The Table 220.13 demand for these receptacles would be…
180 vA x 100 outlets = 18,000 vA
(1) First 10 kVa @ 100% = 10,000 vA
(2) Remainder @ 50% (8,000 x 50%) = 4,000 vA
Total Demand = 14,000 vA
(2) Remainder @ 50% (8,000 x 50%) = 4,000 vA
Total Demand = 14,000 vA
Commercial Cooking Equipment
Remember Article and Table 220.56. It covers nonresidential, or commercial electric cooking equipment. In this situation, kitchen related equipment would be included; ranges, ovens, dishwashers, booster heaters, water heaters, coffee pots, toasters, etc. Airconditioning, spaceheating and ventilating equipment would not count.
220.56 Kitchen Equipment  Other Than Dwelling Unit(s). 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. These demand factors shall be applied to all equipment that has either thermostatic control or intermittent use as kitchen equipment. These demand factors shall not apply to spaceheating, ventilating, or airconditioning equipment. However, in no case shall the feeder or service calculated load be less than the sum of the largest two kitchen equipment loads.
220.56 Kitchen Equipment  Other Than Dwelling Unit(s). 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. These demand factors shall be applied to all equipment that has either thermostatic control or intermittent use as kitchen equipment. These demand factors shall not apply to spaceheating, ventilating, or airconditioning equipment. However, in no case shall the feeder or service calculated load be less than the sum of the largest two kitchen equipment loads.
Don’t forget that the demanded load of all of the cooking equipment cannot exceed the sum of the largest two kitchen equipment loads.
Here are the steps...
(1) Total the number of cooking equipment loads.
(2) Total all of the nameplate ratings of all of the appliances.
(3) Find the demand factor in Table 220.56.
(4) Multiply the sum of all the appliances by the demand factor.
(5) Compare the demanded load to the sum of the two largest loads.
For example, Say we have to find the feeder and service demand for the following commercial kitchen equipment loads...
1 Range at 15 kW
1 Oven at 8 kW
1 Dishwasher at 4 kW
1 Booster Heater at 4.5 kW
1 Coffee Pot at 1.5 kW
(1) Total the number of cooking appliances = 5
(2) Total the sum of all of the nameplate ratings = 33 kW
(3) Find the demand factor in Table 220.56 = 70%
(4) Multiply the sum by demand factor (33 kW x .7) = 23.1 kW
(5) Compare to largest two equipment loads (15 + 8 kW) = 23 kW
Here are the steps...
(1) Total the number of cooking equipment loads.
(2) Total all of the nameplate ratings of all of the appliances.
(3) Find the demand factor in Table 220.56.
(4) Multiply the sum of all the appliances by the demand factor.
(5) Compare the demanded load to the sum of the two largest loads.
For example, Say we have to find the feeder and service demand for the following commercial kitchen equipment loads...
1 Range at 15 kW
1 Oven at 8 kW
1 Dishwasher at 4 kW
1 Booster Heater at 4.5 kW
1 Coffee Pot at 1.5 kW
(1) Total the number of cooking appliances = 5
(2) Total the sum of all of the nameplate ratings = 33 kW
(3) Find the demand factor in Table 220.56 = 70%
(4) Multiply the sum by demand factor (33 kW x .7) = 23.1 kW
(5) Compare to largest two equipment loads (15 + 8 kW) = 23 kW
AirConditioning Versus CentralHeating
Noncoincidental loads, Article 220.60, are so dissimilar that it is unlikely that both of them will be used simultaneously. Airconditioners and centralheating units fit in this category. It would be impossible to turn them on at the same time when they’re on one thermostat. But, even if they weren’t, they would still be considered noncoincidental loads. In this case, the Code allows us to omit the smaller of the two when calculating feeders.
Say we have...
1 AirConditioner at 25,000 vA
1 CentralHeater at 23,500 vA
Let’s drop the CentralHeater (23,500 vA) and only apply the AirConditioner (25,000 vA) to our service calculation. That’s why we call it A/C versus Heat.
Say we have...
1 AirConditioner at 25,000 vA
1 CentralHeater at 23,500 vA
Let’s drop the CentralHeater (23,500 vA) and only apply the AirConditioner (25,000 vA) to our service calculation. That’s why we call it A/C versus Heat.
Miscellaneous Loads
Before we can total all of our loads we have to account for any miscellaneous items. Lawn sprinklers, fountain pumps could fall into this category along with ventilation fans or miscellaneous items not listed elsewhere. In this case, we would add their full nameplate ratings to our service calculation.
25% Of The Largest Motor
Remember Article 430.24 concerning several motors on the same feeder. There’s a strong possibility that we could have one, or more motors in a commercial building. If we have two or more of these, or other motors in a service calculation we will have to add 25% of the full load current (FLC) of the largest motor of the group. If the above airconditioner is the largest motor in our calculation:
25,000 vA x .25 = 6,250 vA
We would have to add 6,250 vA to our service calculation. If, in this situation, the centralheat was larger than the airconditioner we would have to find the next largest motor and add 25% of that motor full load current.
Service Requirements
As in other service calculations, to determine the feeder conductors, and the main service breaker (or fuse) we’ll have to total all of our voltamp demanded loads. To find total amps we’ll divide our total demanded load by 240 volts for singlephase services, or, 208 (x √3) for threephase services.
For example, a shopping center with a total demanded load of 365,000 vA, (208 volts, 3Ø ) would be…
For example, a shopping center with a total demanded load of 365,000 vA, (208 volts, 3Ø ) would be…
365,000 vA ÷ (208 v. x √3 ) = 1,014 amps
Service Main Breaker Or Fuse
240.6(A) Standard Ampere Ratings. Fuses and FixedTrip Circuit Breakers. The standard ampere ratings for fuses and inverse time circuit breakers shall be considered 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 125, 150, 175, 200, 225, 250, 300, 350, 400, 450, 500, 600, 700, 800, 1000, 1200, 1600, 2000, 2500, 3000, 4000, 5000, and 6000 amperes. Additional standard ampere ratings for fuses shall be 1, 3, 6, 10, and 601.
We’ll have to round up to the next higher standard size for our main breaker, or fuse. In this case a 1200 amp main would suffice.
We’ll have to round up to the next higher standard size for our main breaker, or fuse. In this case a 1200 amp main would suffice.
Main Feeder Conductors
We are going to need feeder conductors based on our 1200 amp main breaker. Unfortunately, there are no conductors from Table 310.15(B)(16) good for 1200 amps. If we must run conductors in parallel, which the following conductor types would best meet feeder requirements ?
☐ Three Groups Of #500 THHN
☐ Two Groups Of #900 THW
☐ Two Groups Of #750 THHN
☐ Two Groups Of #2000 TW
☐ Two Groups Of #900 THW
☐ Two Groups Of #750 THHN
☐ Two Groups Of #2000 TW