There are also two pumps for the heating loops mounted to the left of the manifolds for the red pipes. Those are wired into the water heater which might have a feature to control them. It looks like there are 4 heating pipes per pump, all 8 of them return to the one manifold on the top.
The extra pump to the far left appears to be taking water from the white PEX in the floor, which would be return from the hot water faucets.
The extra pump to the far left appears to be taking water from the white PEX in the floor, which would be return from the hot water faucets.