Air compressor opinion

dm9289

Industrial Maintenance Electrician
Location
Pennsylvania
Occupation
Industrial process repair/ maintenance Electrician
We have an air compressor @ 480 v the full package current is 293amps.
For wire and breaker sizing does this sound correct
293x1.25=366A
500kcm copper THHN @ 75degrees=380amps
400amp Circuit breaker
 

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Equipment of this nature is generally specified with a minimum circuit ampacity (MCA) and a maximum overcurrent protection device (MOCP). Do you have access to that information?
Thank you for your reply but only the tag shown. I have been reaching out to the manufacture. I did find online they recommend 500kcm. It is a Y delta start. It does some form of cycling but never shuts off.
 
Thank you for your reply but only the tag shown. I have been reaching out to the manufacture. I did find online they recommend 500kcm. It is a Y delta start. It does some form of cycling but never shuts off.
Probably an air screw. Smaller ones do eventually shut down, if no air demand after a preset time. Timer resets, don’t know about the big ones.
 
Wye Delta starts require some extra load calcs. These starters do not involve a drive. The concept is to start under wye config and then revert back to delta to run. The compressor is being ran using both winding configs. This helps reduce inrush current loads on startup
 
I have not dug deep yet but has the 2 sets of contacts
Well if from the starter to the compressor is 6 conductors for the Wye start Delta run configuration then the conductors are sized at 72% of the FLC. (58*125%) since the conductors will each carry 58% of the FLC.
 
The nameplate says it has a 200HP motor and an additional 7 HP of other loads.

It also shows a ridiculously low SCCR of 5kA.
 
The nameplate says it has a 200HP motor and an additional 7 HP of other loads.

It also shows a ridiculously low SCCR of 5kA.
That's why I initially though that the circuit feeding this would be terminating in a control panel. I guess we need more details to give an accurate answer.
 
That's why I initially though that the circuit feeding this would be terminating in a control panel. I guess we need more details to give an accurate answer.
There is at least a Y-D starter and some power distribution blocks. I don't know of any 200HP starter that is only 5kA rated, but I might be thinking of 47 years ago.
 
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