Running a Fadal on an 'undersized' breaker?

Hey guys,
I am selling one of my machines (Fadal VMC15) and have had a few questions regarding power. The plate on this machine says full load amps is 40A (at 220V). Is anyone running one of these on an undersized breaker? I know people do this all the time with HAAS mills, and I'm pretty sure I've heard of people doing it without issue for Fadals but I wanted to check.

Anyone running a VMC15 or similar with a 30A breaker (on 220/208V)?

Thanks!
-Aaron

aarongough said:

Hey guys,
I am selling one of my machines (Fadal VMC15) and have had a few questions regarding power. The plate on this machine says full load amps is 40A (at 220V). Is anyone running one of these on an undersized breaker? I know people do this all the time with HAAS mills, and I'm pretty sure I've heard of people doing it without issue for Fadals but I wanted to check.

Anyone running a VMC15 or similar with a 30A breaker (on 220/208V)?

Thanks!
-Aaron

Click to expand...

You could run with a 20A breaker and it would be fine.

A 4020 calls for a 70A breaker. I put a clamp on meter on one the incoming legs and it uses 2.5A at idle, and cutting aluminum I was seeing 6-10A so it will be fine

Sometimes, the size wire the machine is plumbed with can give a fair indicator the MTB was full of shit. Little Haas's say 30 amps and they have 14 gauge wire feeding the entire machine. Servos are like RC car motors. I had a little Fadal, don't recall the model, and it had tiny little wire inside.

Check the wire AWG inside and look at an AWG amp chart.

It would probably run fine on 20 amp fuses. I have a couple pretty powerful machines running on 30 amp 240V 3 phase disconnects without any problem. In my shop, most things with a ramped spindle speed or a clutch and 15HP or less are on 30 amp fuses. Lathes with DC spindles need way more though. They draw some extra juice.

aarongough said:

Hey guys,
I am selling one of my machines (Fadal VMC15) and have had a few questions regarding power. The plate on this machine says full load amps is 40A (at 220V). Is anyone running one of these on an undersized breaker? I know people do this all the time with HAAS mills, and I'm pretty sure I've heard of people doing it without issue for Fadals but I wanted to check.

Anyone running a VMC15 or similar with a 30A breaker (on 220/208V)?

Thanks!
-Aaron

Click to expand...

The VMC 15 claims a 7.5 HP spindle motor ≈ 5.6 KW.

@208 V equates to 29.91 Amps (single phase) with a power factor of 0.9 for "Syncronous(sp) motors" .

@220 V equates to 28.21 Amps (single phase) with a power factor of 0.9 for "Syncronous(sp) motors" .


Three phase you get very little current draw.

for example

220 V (line to line three phase) [power factor 0.9] ---> (16 Amps).

220 V ( line to neutral three phase) [powerfactor 0.9] ---> (9 Amps).


Kilowatts to amps (A) conversion calculator

double check with on line embedded app. ^^^

Fadal VMC 15 CNC Milling Machine Model# 914-15 Serial# 012000020244 -- Claims

Volts 230/440 3 Phase 40/20 Amps Travel X 20" x Y 16" x Z 20" Table Size 29.5" x 16" Spindle RPM 7,500 Spindle Motor 7.5 HP Cat 40 tapered spindle 21 tool Automatic Tool Changer Coolant

dum de dum de dum. [Probably unlikely all servos will be energized all at the same time at maximum draw.].


For your future buyer or client can you wire it into a 30Amp single phase breaker (at the box) to see if to goes OK ? (before hand, 208V versus 220 is only slight difference of about a single Amp at single phase.).

^^^ This seems to fit what folks have said so far in this thread also.

The "Power factor" is a bit of a fudge / fiddle factor on other motors at maximum draw with zero resistance theoretically the spike could be as high as 70 Amps (on a power factor of 0.35 ).

The "spike " maximum draw may be so quick / short that it doesn't have enough time to really trip a breaker (maybe) other wise it's probably running / coasting along much like what triumph406 has indicated.

_______________________________________________________________________________________________

Just some extra butt covering / won't catch fire etc.

Just to clarify, the official docs for the VMC15 'claims' 15HP (11.2KW), but they have 10HP motors in them and are run by an oversized spindle drive. I believe the 15HP rating is a 'limited time' rating.

Reference: http://www.ssi-made.com/wp-content/uploads/2017/06/FADAL-Specifications.pdf

But yes I agree with all above that the machines will likely run just fine on a 30A breaker and possibly smaller, glad that I remembered this correctly! Thanks all!

Funny thing:
I could have answered my own question by checking my panel. Apparently my electrician re-used an existing breaker so my VMC15 is already running on a 30A breaker with no issues!

Side note: the electrician for this building is a total pain, and I'm glad I won't be using him again... Nothing gets done as I ask...

On a mill, the only time you are going to draw anywhere near close to max
current is when you are in a huge full HP cut. And lets be real here,
its not a 4020, its a VMC15, odds are you are never going to be able to
use all the power that spindle has, even though it is only 7.5hp (thats
at 100% duty cycle isn't it?).

I'm sure on some higher end machines, the axis motors might give you
a significant draw with some crazy accelerations, but this is a Fadal,
it just kind of gets up to speed when it feels like it.

Accelerating the spindle on a lathe, you have a big giant draw tube,
big giant bearings and a big ass heavy, large diameter chuck. That
can need some serious juice to get going. A Cat40, there is almost
nothing there for mass to begin rotating, so you aren't going to see
a big draw there either.

30amp breaker. I'd have no problem doing that myself. I ran a 4020
on a 30amp for a few years (un-knowingly) and never had a problem, and
there were some pretty big cuts in that time frame.

I can just hear the buyer now, "Man that sounds like just what I am looking for, but I only have a 30 amp circuit", like you should be feel sorry for them because they are too cheap to put the manufacturers required circuit to the machine. There are so many things to go wrong by telling the customer to do something that doesn't meet the recommended requirement of the Machine Manufacturer. There is no reason to add to your liabilities, just to make a sale.

Many if not most anything electrical device manufacturers use smaller wires than the NEC recommended size for supplying it. Each gauge wire can carry more current than NEC supply standards safely, as long as the circuit is properly designed. That is up to the design engineers to make those determinations.

tmt said:

I can just hear the buyer now, "Man that sounds like just what I am looking for, but I only have a 30 amp circuit", like you should be feel sorry for them because they are too cheap to put the manufacturers required circuit to the machine. There are so many things to go wrong by telling the customer to do something that doesn't meet the recommended requirement of the Machine Manufacturer. There is no reason to add to your liabilities, just to make a sale.

Many if not most anything electrical device manufacturers use smaller wires than the NEC recommended size for supplying it. Each gauge wire can carry more current than NEC supply standards safely, as long as the circuit is properly designed. That is up to the design engineers to make those determinations.

Click to expand...

Yeah that's fair. I will certainly couch it in the terms that I have heard it can be done, but it's not what the electrical plate says to do... I am glad that the installation in my new shop is done 1000%

Also to be clear: I am not talking about running an under-sized circuit, but an undersized breaker. The breaker obviously needs to be the weak point in any circuit otherwise there is a lot of risk. With a machine like this if you pull wire for 40A and then only run a 30A breaker because you're lean on power I don't see how you're going to cause a dangerous situation, more likely the worst case is a nuisance trip sometime silly like in the middle of a tool change or something.

You can put the breaker at whatever you please, but don't skimp on the wire

I wire all my smallish machines with 10/4 SO.

Current draw may not pop the breaker but it will cause voltage drop with too thin a wire. i think startup is probably peak current, motor start and all 3 axis rapid to a start position

I mean I ran a whole shop on a 70 amp single phase breaker for years, 2 knee mill CNC, 12CK lathe,3hp manual mill, 5hp cold saw, tumbler...and that is just the 3 phase stuff running on a pair of converters.

aarongough said:

Yeah that's fair. I will certainly couch it in the terms that I have heard it can be done, but it's not what the electrical plate says to do... I am glad that the installation in my new shop is done 1000%

Also to be clear: I am not talking about running an under-sized circuit, but an undersized breaker. The breaker obviously needs to be the weak point in any circuit otherwise there is a lot of risk. With a machine like this if you pull wire for 40A and then only run a 30A breaker because you're lean on power I don't see how you're going to cause a dangerous situation, more likely the worst case is a nuisance trip sometime silly like in the middle of a tool change or something.

Click to expand...

I was assuming that this was a question from a buyer to you since your original statement you said you were selling a Fadal. What I would do and what I would tell a buyer are two different things. I can control what I do but, I cannot control what a buyer might try or do.

I think they may just put whatever numbers they want on the plate
Here’s my VMC20. I believe the same motor



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