Load Calculations & Branch Circuits Flashcards

For a single household electric range rated 12 kW, what is the demand load per NEC Table 220.55, Column C?

Answer: 8 kW

Column C lists 8 kW as the demand load for one range not exceeding 12 kW.

What demand factor may be applied to four or more fastened-in-place appliances (other than range, dryer, space-heating, A/C) in a dwelling?

Answer: 75%

NEC 220.53 permits a 75% demand factor when four or more such appliances are on the same feeder.

What minimum VA must be included for a household electric clothes dryer when none is specified, per NEC 220.54?

Answer: 5000 VA

NEC 220.54 requires a minimum of 5000 VA or the nameplate rating, whichever is larger.

When sizing a feeder for fixed electric space heating, what demand factor is generally applied to the heating load?

Answer: 100%

Fixed electric space heating is calculated at 100% of the total connected load per NEC 220.51.

In the standard method, when may the air-conditioning load be omitted from the service calculation?

Answer: When smaller than the heating load

NEC 220.60 allows omitting the smaller of two non-coincident loads, so A/C is dropped if it is less than the heating load.

A dwelling has 10 kVA of fastened-in-place appliances (six units). What demand load is used?

Answer: 7.5 kVA

With four or more appliances, the 75% factor applies: 10 kVA x 0.75 = 7.5 kVA.

What is the minimum feeder/service conductor size requirement basis for a one-family dwelling rated 100 amperes?

Answer: Not less than service rating

Service conductors must have an ampacity not less than the calculated load and the service rating.