Does the CMM run off the 24V or 56V when both are connected?

When a CMM4 has both 24V and 56V power supplies connected, which one powers the CMM4 and the attached switch?  Is there any way of controlling that, say by using the primary 24V rail and the secondary 56V to force it to run on 24?

We have a tower that's off the grid, and we're able to run 24V right off the batteries, but the 56V has to go through an inverter and then through the PS.  That's incredibly inefficient, so we want as much as possible running off the 24V rail.

Ted - When both power supplies are connected, the CMM and attached switch use the supply that's providing the higher voltage.  In this case, the 56 V power supply.  This is because the CMM uses a voltage summing decision process to determine what's connected (and incidentally provides a mechanism to allow redundancy without interruption). 

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Ted, the CMM will pull from the higher voltage source first.


Hi Ted,

We need both 56V and 29V power supply to power up the CMM4.  It will not work with 24V. Please refer the screenshots attached for more information.


Vijay Gnanamurtthi

I know that's not right, we've run CMM4s using just the 29V or just the 56V.  It can only supply voltages it's receiving to APs, but the CMM and switch will run on either.