Based on your description, it sounds highly likely that this is indeed a split-bus panel. Let's break down why: High-Leg Delta and Single Pole Breakers

You're right, the presence of single-pole breakers in slots 25, 27, 29, and 31 on a high-leg delta service is unusual and a key indicator of a split-bus arrangement. In a standard high-leg panel, you typically need two-pole breakers to utilize the 240V available between phases. A split-bus design overcomes this limitation (more on that below).

"Sub Feed" Labels

The labels "Sub Feed" for both the 40A/2P breaker in spaces 14-16 and the devices in spaces 26 & 28 are the most definitive clues. This term means these points feed another downstream panel or a specific high-current load center.

Handle-less "Breakers" and Warning Labels

The devices in spaces 26 & 28, resembling breakers but without handles and having live terminal warnings, strongly suggest they are

feed-through lugs or a similar type of connector. These connect the output of the "Sub Feed" breaker to the bottom bus bars. The 40A/2P "Sub Feed" and Bottom Bus

Your hypothesis that the 40A/2P breaker sub-feeds phases A and C down to the bottom bus is very likely correct. This is how a split-bus panel allows for the use of single-pole breakers on a high-leg delta system.

How a Split-Bus Panel Works with a High-Leg Delta (simplified)

In a split-bus panel with a high-leg delta service, one section of the panel (typically the top) acts as the "main" section. It usually contains the main breaker and larger two-pole breakers for high-voltage (240V) loads.A smaller breaker (in your case, the 40A/2P) acts as a "sub-feed" breaker. This feeds power to the bottom section of the panel. The key here is that the sub-feed breaker only uses two of the three phases of the delta service (often A and C, as you suspect). This creates a 120V/240V single-phase source on the bottom bus bars, allowing standard single-pole breakers to be used for 120V loads. The "handle-less breakers" act as a terminal junction.

Confirmation

While I cannot confirm definitively without seeing the panel and tracing the wiring, all the evidence you've provided points strongly toward it being a split-bus panel.

Important Considerations



Safety

Work on electrical panels is inherently dangerous and should only be performed by qualified electricians.

Code Compliance

Split-bus panels have specific requirements regarding overcurrent protection and labeling. It's essential to ensure the installation meets all applicable codes.*

Documentation: Look for any diagrams or labeling inside the panel that might confirm the split-bus configuration and identify the phases being fed to the bottom bus.Before doing anything, I strongly recommend consulting with a licensed electrician to verify the panel's configuration and ensure it is safe and compliant. They can physically inspect the wiring and determine the precise arrangement. Flag for review