Adding one more server to a rack that's already near its circuit's rated capacity is how you trip a breaker at the worst possible time.
A PDU rated for 30A doesn't mean the circuit feeding it is; set the alert threshold against the circuit breaker's actual rating, derated to the commonly recommended 80% continuous-load limit.
Server power draw spikes briefly on boot and under burst load. Use a threshold that requires load to stay elevated for a few minutes before alerting, so a routine reboot cycle doesn't page anyone.
If racks share an upstream panel or UPS, a single rack's PDU can look fine while the shared circuit upstream is close to its limit. Group related PDUs so capacity alerts reflect what's actually shared.