Mike Dolt Enterprises
Mike Dolt Enterprises
User: Frank6172, Location: Maryland
Asked on: Wednesday, April 30, 2025 at 10:14 am EDT
Answered on: Wednesday, April 30, 2025 at 10:15 am EDT
Question: Hi All,We are trying to figure out if it's load side connection so supply side connection for this project. Here is the site situation:1. It's an apartment complex with 3 separate buildings but there's only one utility meter located in building 1. The pad-mounted stepdown transformer is located next to building 1.2. Building 1 has the 277/480V service with switchgear and utility service disconnect and there are (2) 277/480V to 120/208V transformers in the electrical room.3. Building 2 and 3 are fed by those 2 transformers located in building 1 through trench and both buildings have main disconnects and MDPs.We plan to use 208V inverters for building 2 and 3 and 480V inverters for building 1. We also want to do the interconnection at the main disconnect for each building.Are we doing the supply side connection or load side?
Based on your description, here's the breakdown and determination of whether you're doing a supply-side or load-side connection for each building: Building 1
Because the building where you are connecting the PV system is the same building as the utility disconnect and meter, you are doing the load-side connection.
Building 2 and 3
You are doing the load-side connection for building 2 and 3. The utility meter is in a different building so they do not share the same utility disconnect.
Key Considerations and Best Practices
NEC Compliance
Ensure your design fully complies with the National Electrical Code (NEC), specifically Article 705 (Interconnected Electric Power Production Sources) and other relevant articles. Also, check with local code.
Utility Interconnection Agreement
A critical step is working closely with your utility company. They will have specific requirements for interconnection, including protection, metering, and safety.
Single-Line Diagram
Create a detailed single-line diagram showing the entire system, from the utility transformer to each inverter and disconnect, including all protective devices and metering points. This is essential for communication with the utility and electrical inspectors.
Overcurrent Protection
Carefully analyze and coordinate overcurrent protection devices (fuses and circuit breakers) to ensure proper protection of the PV system, the building's electrical system, and the utility grid.
Rapid Shutdown
Pay close attention to rapid shutdown requirements, which are often mandated by the NEC for PV systems on buildings.
Professional Engineering Review: It's highly recommended to have a qualified professional engineer (PE) review and stamp your design, especially given the complexity of this multi-building system. This helps ensure code compliance, safety, and proper system operation.By carefully considering these factors and working closely with the utility, you can ensure a safe, reliable, and code-compliant PV system interconnection. Flag for review