Okay, let's break down your proposed installation and the relevant NEC sections to see if it aligns with code requirements.

Your Understanding & Proposed Installation 400A Service

You're upgrading to a 400A service.

Service Point

The utility's meter is at the property line, defining the service point.

Parallel Conductors

You plan to run parallel 4/0 AL conductors from the meter to the house.

(2) 200A Disconnects

You want to install two 200A fused service disconnects side-by-side on the exterior of the house.

Each disconnect fed by one set of 4/0 AL conductors.NEC Analysis1. NEC 230.40 Exception No. 2 (Services with Multiple Disconnects)This is the key section you're relying on. This exception allows multiple service disconnects (up to six) in a single-family dwelling under specific conditions. Summary

NEC 230.40 Exception No. 2 basically states that for a single-family dwelling, you can have up to six service disconnects, and they can be grouped in one location. The sum of the overcurrent protection for these disconnects can exceed the ampacity of the service-entrance conductors, provided that you can demonstrate the calculated load in accordance with Article 220 doesn't exceed the service-entrance conductor ampacity.2.

NEC 230.2 (Single Service) This section generally requires only one service to a building. However, there are exceptions that allow for additional services, but those usually don't apply to a single-family dwelling upgrade.3. NEC 230.71 (Maximum Number of Disconnects) This generally restricts the number of service disconnects to six per service. Your plan stays within this limit.

Analysis and Considerations Parallel Conductors

The code permits paralleling conductors, as long as the conductors meet the requirements outlined in NEC 310.10(H). This includes: Being the same length Being the same conductor material Being the same size Having the same insulation type Being terminated in the same manner. Being sized 1/0 AWG or larger (NEC 310.10(H)(1))

Disconnect Rating

Each disconnect is rated at 200 amps. This aligns with the plan to split the 400-amp service.

Sizing of Service-Entrance Conductors

The 4/0 AL conductors per set would be rated for 230 amps each at 75 degrees Celcius (NEC 310.16). Two sets will give you 460 amps total, which is sufficient for your 400 amp service.

Load Calculation is Critical

NEC 230.40 Ex 2 allows the sum of the overcurrent protection of your disconnects (400 amps) to exceed the ampacity of your service entrance conductors (460 amps)
if your calculated load according to Article 220 does not exceed the ampacity of the service-entrance conductors. You must perform a thorough load calculation according to Article 220 to ensure your calculated load is less than the conductor ampacity (460A). If your load calc exceeds 460A, then the conductors will need to be upsized. Grouping Disconnects

The disconnects must be grouped per NEC 230.72(A).

Is your Installation Correct?Yes, your proposed installation could be code-compliant, provided the following conditions are met


Load Calculation

A thorough load calculation per Article 220 must demonstrate that the calculated load does not exceed the ampacity of your service entrance conductors (460 Amps).2.

Proper Installation

All work must be performed according to the NEC and local codes, including proper grounding, bonding, and conductor termination methods.3.

Inspector Approval

The final determination of code compliance rests with your local electrical inspector.4.

Conductor Paralleling Requirements

Make sure the parallel conductors meet the requirements outlined in NEC 310.10(H)

Disclaimer: I am an AI chatbot and cannot provide definitive electrical code interpretations. Always consult with a qualified and licensed electrician for electrical installations and to ensure code compliance.* This information is for educational purposes only and should not be considered a substitute for professional advice. Electrical work can be dangerous, so please prioritize safety and hire a professional. Flag for review