CODE CALCULATIONS Lesson 13

After determining the lighting load for a dwelling unit by using the volt-amperes per square foot, how much additional load calculation is necessary for 15- and 20-ampere general-use receptacle outlets?

0 VA per outlet 220.14(J)

When branch-circuit and feeder loads are calculated, which of the following nominal system voltages is not used unless specified?

115/230

Which one of the following lists all the standard ampere ratings permitted for branch circuits supplying two or more outlets for fixed electric space-heating equipment?

15, 20, 25, and 30 A 424.4(A)

Calculate the following for a 34-ampere noncontinuous load and a 27-ampere continuous load. Determine the minimum size THWN copper branch-circuit conductors necessary to supply the load.

210.19(A) BC conductor size = (100% noncontinuous load) + (125% of continuous load) = (34 × 1.00) + (27 × 1.25) = 34 + 33.75 = 67.75 A Table 310.16 75°C copper column 67.75 A = 4 AWG THWN

Calculate the following for a 7-ampere noncontinuous load and a 17-ampere continuous load. Determine the minimum size THWN copper branch-circuit conductors necessary to supply the load.

210.19(A) BC conductor size = (100% noncontinuous load) + (125% of continuous load) = (7 × 1.00) + (17 × 1.25) = 7 + 21.25 = 28.25 A Table 310.16 75°C copper column 28.25 A = 10 AWG THWN

Calculate the following for a 34-ampere noncontinuous load and a 27-ampere continuous load. Determine the minimum standard size OCPD necessary to supply the load

210.20(A) BC OCPD selection = (100% noncontinuous load) + (125% of continuous load) = (34 × 1.00) + (27 × 1.25) = 34 + 33.75 = 67.75 A 240.6(A) OCPD rating = 70 A

Calculate the following for a 7-ampere noncontinuous load and a 17-ampere continuous load. Determine the minimum standard size overcurrent protective device (OCPD) necessary to supply the load.

210.20(A) BC OCPD selection = (100% noncontinuous load) + (125% of continuous load) = (7 × 1.00) + (17 × 1.25) = 7 + 21.25 = 28.25 A 240.6(A) OCPD rating = 30 A

Determine the general lighting load for a one-story office building that measures 125 feet by 150 feet.

220.12 and Table 220.12 Unit load for offices = 1.3 VA per sq. ft. Lighting load = Area × unit load = (125 × 150) × 1.3 = 18,750 × 1.3 = 24,375 VA

Determine the maximum number of 20-ampere receptacles permitted to be installed on a 120-volt, 20-ampere branch circuit. The circuit supplies only receptacle loads in a commercial occupancy.

220.14(I) Load for receptacles = 180 VA Max. number of receptacle outlets = (20 × 120) ÷ 180 = 2,400 ÷ 180 = 13.33 → 13

Determine the maximum number of 15-ampere receptacles permitted to be installed on a 120-volt, 15-ampere branch circuit. The circuit supplies only receptacle loads in a commercial occupancy.

220.14(I) lists the load for each single or each multiple receptacle on one yoke at 180 VA. Max. numberof receptacle outlets = (15 × 120) ÷ 180 = 1,800 ÷ 180 = 10

What is the lighting load for a two-story dwelling unit when the outside dimensions of the building measure 60 feet by 125 feet?

220.14(J) Unit load for dwelling units = 3 VA per sq. ft. Lighting load = Area × unit load = (60 × 125 × 2 floors) × 3 = 15,000 × 3 = 45,000 VA

What is the lighting load for a three-story dwelling unit where each floor has 900 square feet of space?

220.14(J) Unit load for dwelling units = 3 VA per sq. ft. Lighting load = Area × unit load = (900 × 3) × 3 = (2,700) × 3 = 8,100 VA

What is the lighting load for a one-story dwelling unit that is 1,700 square feet in size?

220.14(J) Unit load for dwelling units = 3 VA per sq. ft. Lighting load = Area × unit load = 1,700 × 3.0 = 5,100 VA

A one-story office building measures 125 feet by 150 feet. After the lighting calculations are completed, what are the additional load calculations for general-purpose receptacle outlets, when the actual number of general-purpose receptacle outlets is unknown?

220.14(K)(2) Unit load for general-purpose receptacles = 1 VA per sq. ft. Receptacle load = Area × unit load = 18,750 × 1 = 18,750 VA

What is the lighting load for a 625 square foot structural addition to an existing one-family dwelling?

220.16(A)(1) Additional load to be calculated using 220.14 Unit load for dwelling units = 3 VA per sq. ft. Lighting load = Area × unit load = 625 × 3 = 1,875 VA

A fixed appliance (non-motor operated) in an industrial building is rated at 28 amperes and is supplied by an individual branch circuit. The load is continuous, and the branch-circuit device is not rated for continuous loading at 100% of its rating. Determine the minimum standard size branch circuit required to supply this appliance.

422.10(A) and 210.22 Min. BC rating = marked rating × 125% = 28 × 1.25 = 35 A

What minimum standard size overcurrent protective device is required to serve a fixed electric space-heating load of 24 amperes?

424.4(B), branch circuit to be sized at 125% of the load OCPD = 125% × load = 1.25 × 24 = 30 A OCPD required

Two lengths of industrial infrared heating equipment are installed on a common branch circuit. Each piece of baseboard is rated at 240 volts and 11 amperes. Determine the minimum size Type THWN copper conductors required to serve this load.

424.4(B), branch-circuit conductors sized at 125% of the load Total load = 11 × 2 = 22 A Ampacity = 125% × load = 1.25 × 22 = 27.5 A Table 310.16 10 AWG THWN has an ampacity of 35 A

What minimum size copper conductors, Type THWN, are required to serve a fixed electric space-heating load of 24 amperes?

424.4(B), branch-circuit conductors to be sized at 125% of the load Ampacity = 125% × load = 1.25 × 24 = 30 A Table 310.16 10 AWG THWN has an ampacity of 35 A

A fixed appliance in a dwelling unit has a nameplate marking of 50 amperes. What is the rating of the individual branch circuit required to supply this appliance? The load is noncontinuous.

50 A 210.22

A 15-ampere, 120-volt branch circuit in a residential dwelling unit is permitted to supply 12 general-purpose receptacles.

Note: Unlike commercial and industrial occupancies, there are no limitations to the number of receptacles that can be installed on residential branch circuits because, for residential-type occupancies, the Code has specific rules for the placement of receptacles. These specific rules for placement act much like "required minimum quantities." In other types of occupancies, no such rules exist for the placement of receptacles. The correct answer is 'True'.

Two lengths of industrial infrared heating equipment are installed on a common branch circuit. Each piece of baseboard is rated at 240 volts and 11 amperes. Determine the minimum standard size overcurrent protective device required to serve this load.

Total load = 11 × 2 = 22 A 424.4(B), branch circuit is sized at 125% of the load OCPD = 125% × load = 1.25 × 22 = 27.5 A = 30 A OCPD required

A continuous load is a load where the maximum ? is expected to continue for three hours or more.

current