Sizing loads to industrial machinery

Mark1990

Member
Location
Rochester ny
We have in our factory a trim press machine with a nameplate FLA of 192 amps at 460 v 3 phase. No resistive load, just a control plc and 2 servo motors. Avg draw using a clamp on meter is 10 to 15 amps. It is fed from a 30 amp breaker with #10 wire and we have not had any problems for the 8 years this machine has been running, 3 shifts , five days a week. I need to relocate this machine within our factory. I’m stumped at finding a code allowace for under sizing a load, even though experience shows 30amps is more than enough. I hate to install a 200 amp service unnecessarily,but i dont want to be violating any codes at the same time. Any help would be greatly appreciated.
 

MrJLH

Senior Member
Location
CO
We have in our factory a trim press machine with a nameplate FLA of 192 amps at 460 v 3 phase. No resistive load, just a control plc and 2 servo motors. Avg draw using a clamp on meter is 10 to 15 amps. It is fed from a 30 amp breaker with #10 wire and we have not had any problems for the 8 years this machine has been running, 3 shifts , five days a week. I need to relocate this machine within our factory. I’m stumped at finding a code allowace for under sizing a load, even though experience shows 30amps is more than enough. I hate to install a 200 amp service unnecessarily,but i dont want to be violating any codes at the same time. Any help would be greatly appreciated.
Maybe the poster meant 19.2 amps?
 

Mark1990

Member
Location
Rochester ny
A little more detail on the machine. The prints call out several options not installed, totaling 33hp. Motors that are utilized are 27.5 kw servo and a 7.2 kw servo, along with a 7.5 kva transformer, for some 120 v loads. Maybe the nameplate includes the never installed options? My main question is, does the code allow me to run a smaller feed than the nameplate calls for? I dont see this anywhere in article 670. Any help is appreciated . Thank you
 

retirede

Senior Member
Location
Illinois
Sizing loads to industrial machinery

I think if the conductors are properly protected, you’re fine code-wise.

I have had similar experiences. We had machine tools that were never loaded anywhere near capacity. A vertical turret lathe with an integral 100 A breaker that never drew more than 15A the way it was used. Not uncommon.

We never downsized the conductors, however. We never knew what kind of work it would be asked to do next month!
 

Mark1990

Member
Location
Rochester ny
I agree that practically speaking as long as conductors are properly protected there is not a fire hazard etc. my main sticking point is if the job were to be audited by our fire insurance company or corporate for some reason I would like a code to reference that allowed a smaller than nameplate service. As everything I read in the code points to sizing the conductors and over current protection based on machine nameplate FLA.
 
Maybe the poster meant 19.2 amps?
I agree that practically speaking as long as conductors are properly protected there is not a fire hazard etc. my main sticking point is if the job were to be audited by our fire insurance company or corporate for some reason I would like a code to reference that allowed a smaller than nameplate service. As everything I read in the code points to sizing the conductors and over current protection based on machine nameplate FLA.
Got a letter/number punch set with a "." in it ;)
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
Engineer
As everything I read in the code points to sizing the conductors and over current protection based on machine nameplate FLA.
I don't see a problem.

NEC 2017
670.3(A)(2) - nameplate must list the maximum possible overcurrent protective device.
670.4(A) - The conductor sizing shall take into account the loads that will be connected at one time based on their duty cycle.670.4(C) the overcurrent device is sized to handle the full load current connected at one time.
 

retirede

Senior Member
Location
Illinois
I don't see a problem.

NEC 2017
670.3(A)(2) - nameplate must list the maximum possible overcurrent protective device.
670.4(A) - The conductor sizing shall take into account the loads that will be connected at one time based on their duty cycle.670.4(C) the overcurrent device is sized to handle the full load current connected at one time.
And since it ran for 8 years without problems on a 30A ocpd, it will obviously handle the actual full load current.
 

myspark

Senior Member
Location
SCV Ca, USA
Occupation
Retired EE
A little more detail on the machine. The prints call out several options not installed, totaling 33hp. Motors that are utilized are 27.5 kw servo and a 7.2 kw servo, along with a 7.5 kva transformer, for some 120 v loads. Maybe the nameplate includes the never installed options? My main question is, does the code allow me to run a smaller feed than the nameplate calls for? I dont see this anywhere in article 670. Any help is appreciated . Thank you
This comment is based on your (purported) details notwithstanding other details you provided (eg) 192 FLA etc.
The 33 HP name plate does make sense for existing #10 wiring

I surmise this is a press trim guillotine type cutter?
Most of this type machines are based on the GENEVA mechanism (i.e.) only one motor is running all the time while other motors that comprise the whole unit like indexing servos--only operate when called for. And when they do--they only operate momentarily.
Typical machines found in book binding and CNC machines.

Using the as-built info would resolve your dilemma.

(Touring the Biomass Generating Plant in Norway)
 
Top