Need a second opinion please

[Kyell]

Hello the following was provided via a manfacture of a machine for our plant.
I am using a 400amp breaker (from) a buss duct for this application
I have sized my wire at 500kcmil copper for this application.
Please I am second guessing my self on this. Thank you in advance for your responses
B. Mandl

ESA-10 (75kW):
Power during typical operation: 185 kVA 220 A at 3x480V,
Inrush current: typically, 450 A for 20 sec (max. 5 starts per hour),
Main Circuit Breaker: 400 A

 

[HEYDOG]

Did the manufacturer spec out wire size, overcurrent protection? what type of equipment is this? Motor load, heater load, etc.
I am sure there will be someone on here who knows…..I am wondering how long it will take the breaker to trip at an inrush of 50 amps above its rating!

 

[Kyell]

okay to answer your question ...manufacture did NOT specify the wire size, only the main breaker. OCP Equipment type is a Hammer forge for gun barrels the specs I listed are all I have from the manufacturer. Largest motor load is 200amps normal running amp draw is 220A.
Bob

 

[winnie]

With a careful analysis you might be able to reduce your wire size. However without further info your existing selection is almost certainly fine.

Assuming 75C terminations (double check! ) the conductor ampacity is 380A. The load is 220A, so the conductors are sufficient for the load.

The ampacity falls between two standard breaker sizes, so you can round up.

If you have a continuous load and need to multiply by 1.25, you are still good.

What point has you second guessing?

Jon

 

[Kyell]

I received wrong information ONCE from this company they sent spec (schematics) that specified 4/0. Wrong for a similar but different machine
I guess I just needed to hear from someone else I had not made a mistake. 3 million dollar machine. I am not even in charge but it has landed on my shoulders. Thank you B.Mandl

 

[winnie]

As I said, with careful analysis you might be able to reduce the wire size, especially for motor loads. Plausibly this system could be fed with 250 kcmil conductors and protected by the 400A breaker. However this would require careful consideration of all of the various rules; you often see this for motor loads where the circuit breaker is for wire short circuit protection, and the motor overload protection also protects the wire from overload.

The worst case is that you've oversized the conductors a bit.

Note that you might have a problem if some aspect of the machine limits the allowed wire size, eg. installed lugs or built in raceways.

-Jon

 

[jim dungar]

I am sure there will be someone on here who knows…..I am wondering how long it will take the breaker to trip at an inrush of 50 amps above its rating!

I would think it would trip in maybe 2 or 3 hours at a 12% overload.
Breakers are typically able to carry currents equal to motor overloads which are commonly rated 600% for 20 seconds.