Amp draw/ industrial machine

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nizak

Senior Member
I got a call from a shop owner who is purchasing a piece of cnc equipment. They currently have 3 of these types of machines in place. Each is fed from a dedicated 120/240v Delta 3phase 50 amp breaker. The machine specs call for the 50A feed. These machines can be equipped with a parts conveyor, auto loader and turnings conveyor.The current set up uses non of the optional features.
A load check shows between 6 and 14.5A depending on the machining cycle. The panel feeding the existing equipment is full physically but only pulls 96A max with the total shop running all equip, lighting,etc.
The mfgr install states a 50A 3 phase 240v supply.
The closest panel in the shop that is not full is approx 180' away in a back storage area.
Does anyone see a problem with feeding the 4th machine off the same drop as the 3rd one that is currently operating? Savings to owner is almost $2K if existing drop can be utilized.
 

nizak

Senior Member
When you say load calc are you referring to the size of service feeding the building?Machine nameplates indicate 31 amps which includes all optional "add on" features available. Physical space does not allow for these features added. BTW, I forgot to include that the panel supplying this equipment is 200A, total building service is 400A capacity.
 

growler

Senior Member
Location
Atlanta,GA
I don't see anything really "wrong" with the idea.

It might not be to code depending on how your load calculation comes out.


I think Bob is saying you should find the actual size of the motors in the "two" machines that you would be installing on this circuit. If the conductors are big enough for the load then go for it.


The only thing I would worry about is starting current, if both machines start at the same time.

If this is a problem and the conduit is big enough you may be able to install a larger breaker in the panel where machine #3 is feed and pull larger feeder conductors and set a small sub panel near the machine #3 to feed both machines.

I would first do what I always do and call the manufacturer and see if they have a recommended circuit size for the machine without options. When you call ask if you can speak with an engineer.
 
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