Symmetra RM 6KVA unit module slots query

[CameronTQldAU]

Hi, I recently purchased a new Symmetra rack chassis UPS solution. The channel partner/vendor recommended two Power Modules and five Battery Modules, so we followed that for the PO.

When I received the consignment and began assembly and initial pre-commissioning tests, I noted an unusual behaviour. I began by loading a Power Module into the L1 slot then powered up the frame. The Power Module was not detected. I powered down and moved the Power Module to slot L2 and powered up the frame again. This time the module was detected. I unboxed the second Power Module and plugged it into slot L1. Again, not detected. I placed the second Power Module into slot L3. Not detected. I swapped the Power Module in slot L2 with this Power Module. Module detected! (Ok, so neither Power Module is faulty). I placed the first Power Module into slot L3. Not detected. I placed this Power Module into slot L4. Module detected!.

Ok, so the two Power Modules are detected if are in slots L2 and L4, but not L1 and L3. Weird.

I placed the first Battery Module into slot R2. (the R1 slot contains the two Intelligence Modules, from the factory). Nope, the configuration and detection of the Power Modules in unchanged. I *did* find though, that when plugged the third Battery Module in (R4, with R3 already containing the second Battery Module and R2 still having the first Battery Module) that *now*, a Power Module in slot L1 *is* detected!

So my final configuration that was taken to the commissioning and Production workload environment was as follows: Power Modules in slots L1 and L2 and Battery Modules in slots R2-R4 and L3-L4.

Schneider Support seemed to be unable to provide any explanation to this behaviour of the slot interactions, nor any guidelines to the back-plane design other than what is in the standard instation instructions (ie, Power Module only for L1, Power Modules or Battery modules for L2 to L4, Battery Modules only for slots R2-R4)

I am wondering whether there would be success in powering up all slots if says we had bought only two Power Modules and two Battery Modules?  

So not an ongoing problem or issue for us now, but was just intrigued why the slots behaved in this manner. Has anyone else found similar situation?

regards

Cameron