Question : Problem: What limits how much power modules you can put into an APC Symmatra 3 phase room UPS unit?

I have an APC SYCF80KF in the datacenter.  It currently has 5 power modules in it.  It has room for 3 more power modules.  I was told by another employee that we can not put more power modules in it because the building generator is not sized for it.  Can someone help me understand what is the actual purpose and function of the power modules, and what can prevent us from putting more of them in?

Answer : Problem: What limits how much power modules you can put into an APC Symmatra 3 phase room UPS unit?

Default configuration is 5 power modules, providing 50kW output capacity.

Your generator is sized to carry a certain max load, of which 50kW is reserved for this APC unit.

Before you install 8 modules, you need to answer the following questions:

1. do you need higher load capacity, or more runtime?  Power modules do not add runtime.  Add more external batteries.

If you get past question #1, then:

2. was the electrical wiring feeding the APC unit sized accordingly?
3. is the shutoff sized accordingly?
4. is the power meter / monitoring equipment sized accordingly?
5. is there enough reserve in the generator to supply this higher load?
6. is the wiring / cutover sized accordingly?

For each additionl 10kVA module, I believe this adds ~36 amps.
50kVA = 175A
80kVA = 280A.
Somebody check my math?

Wire gauge would be 2/0 for 175A.   Need 250kcmil for 230A.  Conduit/bundling would reduce the rating.

But, now we're getting deep into the territory of an electrician.  Please don't use my bar napkin scrawling for your own calculations.

Needless to say, the electrician would have required a specification for load so the shutoffs, breakers, cutovers, cable, conduit, etc would be sized correctly.  It is common to overbuild...but only at the specific request of the person paying for the job.

Check with your facility manager.