Calculations

[Alwayslearningelec]

When figuring out the total loads within a panelboard and doing a calculation to size the MCB properly do you take the circuit breaker sizes or actually what the equipment draws? I understand the 125% and 100% of continuous and non continuous.

Well now that I think you would never add up the circuit breaker sizes....that would create an unrealistic MCB size.

 

[LarryFine]

Actual loads. Otherwise, we could never have 350 amps' worth of breakers in a 200a panel.

 

[xformer]

IMHO... Your calculations will result in load amps then choose an appropriate breaker.

 

[Alwayslearningelec]

Actual loads. Otherwise, we could never have 350 amps' worth of breakers in a 200a panel.

So you need equipment data sheets for that.

 

[drktmplr12]

So you need equipment data sheets for that.

there are a plethora of ways to calculate the load without data sheets, based on the facility type/occupancy. if your facility doesn't fall into one of the categories laid out in the NEC, you will need equipment data

for electric motors, the NEC requires you to use Table 430.250 to account for motor load unless they are low-rpm motors (1200 rpm, 900 rpm, etc). i recall in one of your posts you said no electric motors.

the process goes like this:

calculate the load based on what you are connecting -> use this to determine minimum size of conductor -> select OCPD that protects that conductor

 

[LarryFine]

So you need equipment data sheets for that.

Basically, yes. Standard load-calc info.