Incoming Breaker Sizing

[alanElec]

I have a Electrical Panel feeding two chillers of FLA 1003A ,two pumps of FLA 81 A,one AHU of FLA 12 A,a Lighting DB 16 A..The incoming breaker(Motorized ACB) size for this panel is 2500 A. Busbar rating 2500 A with SC rating of 100 KA for 1 sec.Can you guys pls tell me weather the incomer breaker size is adequate?Also the consultant had already sized the transformer for this panel as 1600 KVA..Is this correct?

 

[squeeky]

Dear Alansam,

Maybe the rest of the contributors are sleeping in another part of the world, so I will start.

How are you starting the motors and what settings do you have on the breaker? How long do the chillers take to get to nominal speed? It looks like you are running a car400v system. Is this correct?

 

[alanElec]

A Chiller is not a single Motor...The one we are using here has 4 Compressors(each compressor has inbuilt star/delta starter),each started in sequence as per HVAC demand.As per manufacturer data,max starting current is 969 A & Max full load amps 1003 A at 415 V.My system Voltage is 415 V.
Staring Current of Pump is 555 A and FLA is 81 A. However this starting current will not come to play.Reason being Pump is started first before the chiller and only after a certain delay(more than 1 min) chiller is started.

 

[rcw retired EE]

The US code would size the main at the sum of the loads + 25% of the largest motor. = 2366A. 2500A seems to be OK. There probably is some diversity in that the loads are most likely not all on continuously for a long period of time. That diversity will provide some margin.

Transformer size is close to the calculated load. 2366A @ 415V = 1700 KVA. Sum of full loads = 2115 A, neglecting the adder for 25% of the largest motor making the load current is right at 1500 kVA.