Yes, that's a perfectly valid setup according to the NEC. Here's why: NEC 215.3(A)(1) requires the feeder conductors to have an ampacity not less than the noncontinuous load plus 125% of the continuous load. A 200amp service is capable of handling the potential calculated load of the dwelling unit. You are protected by a breaker rated lower than the service conductors ampacity. You mention you have a 150 amp sub panel. This breaker will protect the feeder from overloading. It's often more cost-effective to use larger gauge wire than necessary for the entire run, especially if it simplifies the installation at the feed-through lugs. Since your lugs can accept the larger wire, you're avoiding using a reducing connector or other adaptation. Future Proofing

Using a 200A-rated feeder allows for easier future upgrades if the load requirements change.

Important Considerations



Wire Size and Ampacity Tables

Ensure that the 200 amp-rated wire you are using is properly sized for a 200 amp load per NEC Table 310.16 (or other applicable table based on conditions of use). The specific wire gauge needed will depend on the insulation type (THHN, THW, etc.) and whether it's copper or aluminum.

Grounding/Bonding

Make sure your grounding and bonding are properly installed according to NEC requirements, specifically related to feeders.

Calculated Load

It's crucial to correctly calculate the load for the dwelling unit to ensure that the 150 amp subpanel and its breakers are adequate for the actual load.

Local Codes

Always check with your local electrical inspector or building department for any specific requirements or interpretations that may apply in your area.

In summary: You can use 200 amp-rated feeder wires to feed a 150 amp subpanel as long as the lugs are rated for the wire, the wire is sized correctly for its ampacity rating, the 150 amp breaker protects the feeder, and the installation meets all other applicable NEC requirements and local codes. Flag for review