# What gauge wire for 220 volt, three phase, 7 1/2 HP motor



## moxie (Jan 19, 2015)

Hi All,
I recently bought a used 15" LeBlond Regal servo shift.  I've spent the last few days cleaning and leveling the machine in my shop and am hoping to wire the machine tomorrow.  I think the electrical information plate is stating that it runs at 16.35 amps at 220 volt.  I say that "I think" because aside from the stamped in numbers all the painted on data is gone.  It will be a wire run of about 45' from the circuit breaker box to the lathe.  Do I need 10 gauge or heaver?  Will the breaker need to be a 20 amp three phase breaker? Thanks for your advise, Dave


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## JimDawson (Jan 19, 2015)

I'd use #10 wire with a 30 amp, 3 phase breaker


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## tbell (Jan 19, 2015)

JimDawson said:


> I'd use #10 wire with a 30 amp, 3 phase breaker



I agree single strand copper. #10 the way to go 30 amp breaker. #12 too small that long of a run. Bigger is better. Tom


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## Eddyde (Jan 19, 2015)

moxie said:


> Hi All,
> I recently bought a used 15" LeBlond Regal servo shift.  I've spent the last few days cleaning and leveling the machine in my shop and am hoping to wire the machine tomorrow.  I think the electrical information plate is stating that it runs at 16.35 amps at 220 volt.  I say that "I think" because aside from the stamped in numbers all the painted on data is gone.  It will be a wire run of about 45' from the circuit breaker box to the lathe.  Do I need 10 gauge or heaver?  Will the breaker need to be a 20 amp three phase breaker? Thanks for your advise, Dave



 Technically, 12 gauge  wire would suffice up to 20A However, motors have a high inrush current on startup so as Jim said, a 30A circuit (10 gauge wire 30a breaker) would be the safe minuminum . you may consider fuses as they handle start loads better than breakers. I would even up that wire to 8 gauge if the run to the panel is over 50ft. Do you have a starter?


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## moxie (Jan 19, 2015)

Eddyde said:


> Technically, 12 gauge  wire would suffice up to 20A However, motors have a high inrush current on startup so as Jim said, a 30A circuit (10 gauge wire 30a breaker) would be the safe minuminum . you may consider fuses as they handle start loads better than breakers. I would even up that wire to 8 gauge if the run to the panel is over 50ft. Do you have a starter?


Thanks for the information Jim, Eddye and Tom.  I think that built into the back wiring panel of the lathe there are starters as well as three big fuses.  Interesting that you suggested solid wire.  I'll get that but would have probably bought stranded just to have made it easier to get through the conduit.
I hope to make a run to the electrical store or Home Depot later to get the supplies.
Regards,
Dave


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## JimDawson (Jan 19, 2015)

I would recommend stranded wire, much easier to work with.  It also has slightly greater current carrying capability due to the larger total surface area of the strands vs. solid surface area.  Electrons flow on the surface of a conductor with very little flow in the center.  All of the high voltage power transmission lines are actually tubing.


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## cwalker1960 (Jan 19, 2015)

amps and length of run determine wire size. at 16.35 amps you would be fine with 12 gauge wire but if want a little extra security use 10 gauge.. the 20 amp breaker is going to trip long before you do any damage to 12 gauge wire at that short a run.




moxie said:


> Hi All,
> I recently bought a used 15" LeBlond Regal servo shift.  I've spent the last few days cleaning and leveling the machine in my shop and am hoping to wire the machine tomorrow.  I think the electrical information plate is stating that it runs at 16.35 amps at 220 volt.  I say that "I think" because aside from the stamped in numbers all the painted on data is gone.  It will be a wire run of about 45' from the circuit breaker box to the lathe.  Do I need 10 gauge or heaver?  Will the breaker need to be a 20 amp three phase breaker? Thanks for your advise, Dave
> 
> 
> ...


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## cwalker1960 (Jan 19, 2015)

I would agree with every one else about the inrush current and needing to oversize if it were on a machine that starts running when you turn it on ,, not the case lathes they have clutches, the motor ( if used properly) is already up to speed before you  load it ,,not quite the same as starting a milling machine swinging a 10" face cutter when you hit the button. even so to be on the extremely safe side use 30 amp breakers and 10 gauge wire.


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## Leitmotif (Jan 19, 2015)

moxie said:


> Hi All,
> I recently bought a used 15" LeBlond Regal servo shift.  I've spent the last few days cleaning and leveling the machine in my shop and am hoping to wire the machine tomorrow.  I think the electrical information plate is stating that it runs at 16.35 amps at 220 volt.  I say that "I think" because aside from the stamped in numbers all the painted on data is gone.  It will be a wire run of about 45' from the circuit breaker box to the lathe.  Do I need 10 gauge or heaver?  Will the breaker need to be a 20 amp three phase breaker? Thanks for your advise, Dave
> 
> 
> ...



Yes you will need a 3 phase breaker - it is a 3 phase motor.

At 16.4 amp full load in theory 20 amp should suffice.  However you have not adequately addressed starting current.  Thumbrule for 3 phase motors is start current 4 to 9 times run current.  
SO 
assume the old NEC rule of triple for the line conductors so that puts you in at nearly 50 amp for the conductor ampacity and the circuit breaker.  This will ensure minimal line voltage drop and your motor will be able to build up magnetic field quickly.  It will also ensure no nuisance tripping of the breaker.  You can go into NEC and look at the "new" methods for sizing conductors - they will come out for a smaller conductor.  Get the correct sized overloads - I would start at 110% of full load current.

Never NEVER skimp on wire size for motors.

Yes I understand copper (or aluminum) is expensive 
but 
if you cannot afford to do it right the first time how many more times can you afford to do it wrong?

Dan Bentler


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## WDG (Jan 19, 2015)

Jim said it best, use #10 stranded and a 30 AMP 3ph breaker.  Under _normal _circumstances #14 is good for 15 A, #12/ 20A, #10 / 30 A, #8 / 40 A.  I personally always use stranded unless it is house wiring like lighting, and recepticals.  I've installed 1600 A 3ph 480 VAC main service and I have always paralleled stranded copper wire. Solid wire in sizes of 500MCM is impossible to bend without hydraulic benders.  And probably hard to find too.


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## compressorguy (Jan 20, 2015)

moxie said:


> Hi All,
> I recently bought a used 15" LeBlond Regal servo shift.  I've spent the last few days cleaning and leveling the machine in my shop and am hoping to wire the machine tomorrow.  I think the electrical information plate is stating that it runs at 16.35 amps at 220 volt.  I say that "I think" because aside from the stamped in numbers all the painted on data is gone.  It will be a wire run of about 45' from the circuit breaker box to the lathe.  Do I need 10 gauge or heaver?  Will the breaker need to be a 20 amp three phase breaker? Thanks for your advise, Dave
> 
> 
> ...



From what I see, it looks like 3 phase is required.  Do you have 3 phase power available?  I would use  10 gauge and a 30 amp breaker although.....  Are you sure it is a 7 1/2 HP motor?  18.3 amps seems a little low on 230 volt for that big a motor.  My air compressor is 7 1/2 and draws 23 amps at that voltage.


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## moxie (Jan 21, 2015)

compressorguy said:


> From what I see, it looks like 3 phase is required.  Do you have 3 phase power available?  I would use  10 gauge and a 30 amp breaker although.....  Are you sure it is a 7 1/2 HP motor?  18.3 amps seems a little low on 230 volt for that big a motor.  My air compressor is 7 1/2 and draws 23 amps at that voltage.


Hi Gary,
I am going by the stamped in info on the data plate.  However all the printed on data has been wiped off over time.  There is still a data plate on the motor but it is aimed the wrong direction to read it in the cast iron base.  I will try getting in there with my cell phone to take a picture of its data plate to confirm the volts and amps.

I do have three phase in my shop.  When we bought the warehouse building 16 years ago it was in an industrial zone and when we had the building rewired it was not a problem to bring in three phase.  Nowadays the neighborhood has gone upscale residential and we are part of a dwindling group that still build things.

I went to a suburban Home Depot in NJ last night did not find the 30 amp, three phase breaker.  I'll have to go to a real electrical supply house here in Brooklyn.

I'm also still sorting out two other issues.  One is that the lathe was missing its leveling feet.  I tried to level it with shims but picking up a 3300 lb machine and getting the correct amount of shims under 7 pads was hard to do.  I learned that the base castings actually have threaded holes for the leveling feet.  Thats the good news, but the tough part is that the holes are 1"-16.
Thats not a size I can buy so I will try to make them on my 13" South Bend.  I ordered a length of 1" hex material and will try to leave the upper end with the hex and turn round and thread the lower half.

The other issue is that I received a beautiful reversible three jaw Bison chuck with the lathe but with a D-6 back rather then the L-1 mount this lathe uses.  The chuck looks great and I don't think it has ever been used.  However I'm being told that this particular Bison chuck does not allow for a back change.  Something to do with how the company machines this model.  (Model 3245-10) I'm going to try and sell it or swap it for a decent brand 10" with an L-1 back.

Dave
10" SouthBend, 13" SouthBend, MSC mill, Van Norman 16, Clausing small knee mill and now 15" x 54" LeBlond.


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