What is the minimum amp rating required for a service disconnect in a one-family dwelling unit?

In a one-family dwelling unit, the National Electrical Code (NEC) sets the minimum service disconnect rating at 100 amps. This rating is established to ensure that the electrical system in the dwelling can handle the typical load requirements without overheating or failing. A 100 amp service allows for adequate capacity to support the basic electrical needs of a home, including lighting, heating, appliances, and other equipment.

Having this minimum rating is crucial not only for safety but also for providing enough power for modern living, where households often have many electrical devices. Electrical installations are designed with this 100 amp standard in mind to avoid issues such as overloading circuits or insufficient power supply.

The other options present ratings higher than the minimum requirement. While a service disconnect rated at 200 amps or even 400 amps could be beneficial for larger homes or those with significant electrical needs, it is the 100 amp rating that serves as the foundational guideline for standard one-family dwellings per code regulations. Therefore, option B accurately reflects the required minimum standard for service disconnect in a residential setting.