What is the minimum size of the service entrance conductors for a dwelling unit with five 2-wire branch circuits?

The minimum size of service entrance conductors for a dwelling unit is determined by the total load of the circuits that are connected to the service. In this case, having five 2-wire branch circuits implies a certain amount of demand that must be accommodated.

Typically, for residential dwellings, the National Electrical Code (NEC) suggests that you need to provide sufficient capacity to handle the expected load, while also following the minimum requirements set by local codes. Each 2-wire branch circuit is generally rated for a maximum of 15 amperes. Therefore, with five circuits, you would calculate the total amperage as:

5 circuits x 15 amperes = 75 amperes.

To allow for additional load considerations, including future expansions or simultaneous operation of multiple circuits, it is prudent to round this number up to ensure adequate capacity. The common practice in residential wiring is to size the service entrance conductors to a minimum of 100 amperes.

This ensures that the dwelling can support not only the calculated branch circuit load but also any additional demand from future appliances or systems, thus complying with code requirements and promoting safety. Therefore, choosing 100 amperes as the minimum size of the service entrance conductors reflects sound electrical design principles to ensure safety and