Overview
Aurora now supports Load-Side Tap (LST) as an interconnection method for solar PV systems on homes with a Meter-Main Load Center (MMLC) and a downstream sub panel. If your project has this configuration, you can select “Load-Side with Disconnecting Means” in the IPS Interconnection wizard and Aurora will automatically generate a code-compliant plan set — including the single-line diagram, conductor sizing, NEC references, and required disconnects. This removes the need for manual drawings or external tools for this interconnection type.
Before you begin
- Your project must meet all of the following eligibility criteria for Load-Side Tap to be available:
- The main service panel is a Meter-Main Load Center (MMLC) with a main circuit breaker
- The downstream sub panel has a main circuit breaker (MCB) and is fed via lug connections from the MMLC
- The MMLC’s main breaker rating matches the sub panel’s main breaker rating
- The PV system’s maximum continuous output current x 1.25 does not exceed the MMLC main breaker rating
- If your project doesn’t meet these criteria, the Load-Side Tap option won’t appear in the interconnection wizard.
- The scope is limited to PV-only systems with up to two string inverters or microinverters. No ESS systems are supported at this time.
How to use Load-Side Tap in IPS
- Open your project in Aurora and navigate to the IPS section.
- In the Interconnection wizard, select “Load-Side with Disconnecting Means” as the interconnection method. This option appears only for eligible projects.
- Choose your preferred topology:
- Topology 1 — Feeder Breaker at Main Panel: Aurora removes the existing lug connection and adds a new feeder breaker to the MMLC bus, sized to match the MMLC main breaker. The solar inverter taps between this breaker and the sub panel’s main breaker.
- Topology 2 — New Breaker in Enclosure: The existing lug connection stays. Aurora adds a new feeder breaker inside a new NEMA 3R enclosure downstream of the MMLC lugs. The solar inverter taps between the enclosure and the sub panel’s main breaker.
- Aurora automatically checks eligibility, sizes the equipment, and generates the interconnection design. Review the proposed configuration on screen.
- Proceed to plan set generation as you normally would. Aurora produces the complete plan set output, including the SLD, conductor sizing, NEC references, and all required disconnect notation.
What you get
When you complete the interconnection wizard for a Load-Side Tap project, Aurora generates a full plan set that includes:
- Single-line diagram (SLD) reflecting the chosen topology
- Conductor sizing for the feeder and tap conductors
- NEC Article 705 compliance language and code references
- Required disconnect notation and equipment callouts
- This plan set is ready for permitting submission, the same as any other interconnection method in Aurora.
Limitations and FAQ
Q: What is a Meter-Main Load Center (MMLC)?
A: A MMLC is an all-in-one unit that combines the utility meter socket, a main circuit breaker, and a panelboard in a single enclosure. These are common in residential installations, particularly in certain U.S. regions.
Q: How is a Load-Side Tap different from a standard backfeed breaker?
A: A standard backfeed breaker installs at the main or sub panel bus. A Load-Side Tap connects to the feeder conductors that run between the MMLC and the sub panel, requiring a dedicated disconnecting means a minimum conductor size, and specific NEC compliance language. Aurora handles both methods.
Q: How do I know which topology to use?
A: A: Both topologies are code-compliant. The key factor is whether the MMLC bus can physically accommodate a new feeder breaker matching the main breaker rating (typically 150A–200A). Topology 1 requires adding that feeder breaker directly to the MMLC bus — not all meter-main load centers support a breaker of that size on the load side, and you'll need to verify the panel's dead front cover or manufacturer specs to confirm. Topology 2 avoids this constraint entirely by keeping the lug connection in place and adding a new breaker in an external enclosure downstream, making it the more universally applicable option. Consult your electrical team to determine which is appropriate based on the site's MMLC model and specifications.
Q: What if the Load-Side Tap option doesn’t appear in the wizard?
A: The option only appears when all eligibility criteria are met. The most common reasons it doesn’t appear are a mismatched main breaker rating between the MMLC and sub panel, or a PV system output that exceeds the MMLC main breaker rating. Other reasons include, not adding the sub panel component downstream of the MMLC to the design, not connecting the MMLC to the sub panel.
Q: Is Load-Side Tap available for all plan types?
A: Load-Side Tap is available to all Aurora customers using IPS for residential projects in the U.S. where the project meets the eligibility criteria above.