Sizing supplemental circuit breaker for 220v Power Feed

PreciseHack · May 2, 2021

I bought a Wen Ding 150lb torque 220v power feed for my mill table off ebay. Right now I only have a single 50A 220v circuit in my shop. But I'm building a box on the back of the mill to house the VFD and other electronics, and I would like to get a secondary circuit breaker that is sized appropriately for the power feed so I don't overdraw and damage it. Any ideas how I can figure out the right amperage to choose? I checked the manual and other sources and I can't seem to find one that specifies the current draw for these.

ignator · May 2, 2021

Is this 50amp circuit connected to wall outlets? Or is this just a power feed from a main breaker to the shop and connected to nothing right now?
Anything connected to this requires 6AWG copper to ensure circuit breaker trip in the event of a short.
What you need is a sub panel, that has 10 circuits or so of separate breakers that are sized for the machines, and wall outlets kept separate. Note wall outlets for 15amp require 14AWG copper, wall outlets 20amp require 12AWG copper. Note that the circuit breaker is to protect the wire not the load.
Your power feed should have a built in circuit breaker or fuse, to protect the motor, and electronic Thyristor circuit. But it will be plugged into a wall outlet of 14 or 20 amp capacity.
The USA has a code issue where extension cords of smaller wire gauge can be plugged into a circuit that can cause them to melt down. They are a major cause of fire. But we live with that design flaw.
Lastly, you must have purchased this from eBay or some other source, as they typically are 120VAC power feeds delivered to our market.
So if it is 220V, you need a dual pole 15 or 20 amp subcircuit from a sub panel you install in your shop.

PreciseHack · May 2, 2021

The 50 amp circuit is a single outlet to the panel in the garage with a 50 amp breaker. It was installed to run a welder. Thanks for the info on the sub panel. I'm admittedly not knowledgable on shop wiring, but trying to learn. That sounds like the right plan. I didn't know that the power feed itself had a fuse. In my head I was thinking I could just run the appropriate gauge wire to an enclosure on the mill and then split it up to power the VFD, DRO, and Power feed so I only had 1 cord running to an outlet. And then use some of those DIN rail mountable circuit breakers in the enclosure to make sure the individual components aren't being overloaded. But I don't know whether thats a bad idea or if there's a simpler way to set it all up. I appreciate the advice!

PreciseHack · May 2, 2021

Also yes I did buy it from ebay. I wasn't paying close enough attention otherwise I would have only gotten a 110v power feed since I only have 1 outlet of 220 right now and I'm using that to power the VFD. I know the way I have it setup right now is not safe and I make sure everything is disconnected when I'm not using the mill. Hence my post because I'm trying to research what I need to do in order to set it all up safely and correctly.

ignator · May 3, 2021

PreciseHack said:
The 50 amp circuit is a single outlet to the panel in the garage with a 50 amp breaker. It was installed to run a welder. Thanks for the info on the sub panel. I'm admittedly not knowledgable on shop wiring, but trying to learn. That sounds like the right plan. I didn't know that the power feed itself had a fuse. In my head I was thinking I could just run the appropriate gauge wire to an enclosure on the mill and then split it up to power the VFD, DRO, and Power feed so I only had 1 cord running to an outlet. And then use some of those DIN rail mountable circuit breakers in the enclosure to make sure the individual components aren't being overloaded. But I don't know whether thats a bad idea or if there's a simpler way to set it all up. I appreciate the advice!

That's a bad idea. You want a subpanel,
Menards have them, should be one close to you:
https://www.menards.com/main/electr...74-c-6438.htm?tid=1387889210693179313&ipos=16
The problem with a DIN rail mount how do you have the input wires sized for the 50 amp. A sub panel has large distribution connections so you don't have a fault that results in meltdown of the conductor feeding the smaller breakers.
So the linked Menard panel is 12 circuits, I would use 2 of them for a main disconnect, so a 50 amp dual pole breaker would be installed int he first two slots.
https://www.menards.com/main/electr...d-circuit-breaker/qo250cp/p-1444444035505.htm
And for your single pole 15 or 20 amp outlet connections:
https://www.menards.com/main/electr...d-circuit-breaker/qo120cp/p-1444444026633.htm
Me, I would only run 12AWG wire to the 120 volt outlets. But there must be some wiring in the first place. Is there a sub panel in your garage currently? If not how are you powering lights and such?

PreciseHack · May 3, 2021

Yes there is some existing wiring. 8 outlets of 110v running in conduit around the walls, and then 8 more outlets on the ceiling for some LED light panels. The panel in the garage is a sub panel being fed by the main panel inside the house. I was already planning on putting more 220v outlets around the shop because then I don't have to have all my machines clustered right next to the panel. Would you still put them all on separate circuits even if you're never going to be running more than 1 machine at a time?

1yesca · May 3, 2021

to start off with if you plan on having a big shop more machines then start off with exchanging that sub panel with one with a few more circuits or if you want more clutter just leave it be or put another one next to it but it sure looks like your out of room in that one

ignator · May 3, 2021

You can parallel many of the 20amp 240volt outlets off one breaker. Looks like that panel has no spare connections available for another 20amp 240V dual pole breaker. I would find the lowest cost panel at your local home store and feed that with the same 50 amp source, but since you're all ready using Square D panel, I would stay with that brand, that uses the same breakers (Memory is Square D has two types, and they are incompatible with each other from a panel insertion).

I have my shop wired that way as well (many outlets on the same breaker). I use VFDs to power individual machines (powered with a 20 amp breaker). I do have a dedicated VFD on each machine, so it is setup for the motor HP of the machine. This is to protect the motor from burn out overload. And VFDs are cheap in my mind.

So where are you in Iowa?

DDoug · May 3, 2021

I thought most of those have an onboard fuse in a panel mount holder ?

PreciseHack · May 3, 2021

ignator said:
So where are you in Iowa?

I'm in West Des Moines

ignator · May 3, 2021

I'm north of Cedar Rapids 8 miles, I'd help you out if I was closer. My sister lived in West Des Moines, just north of the Ballroom, back in 1992.

gustafson · May 3, 2021

IF your 240 outlet is a 4 wire, meaning it has a neutral, you can wire an outlet with a 15 or 20 amp fuse

If not you cannot wire to it.

Then just get a nice heavy gauge extension cord from your nearest outlet

PreciseHack · May 3, 2021

ignator said:
I'm north of Cedar Rapids 8 miles, I'd help you out if I was closer. My sister lived in West Des Moines, just north of the Ballroom, back in 1992.

Nice. I grew up in NEIA so familiar with that part of Iowa.

Pathogen · May 3, 2021

NEC, Tap rule

PreciseHack · May 3, 2021

Pathogen said:
NEC, Tap rule

Are you saying this in reference to running a single power source into the enclosure and then splitting it up?

ignator · May 3, 2021

Pathogen said:
NEC, Tap rule

What is that rule? All I know is the ampacity of the wire must stay to the size required to trip a breaker, so no 12AWG taps on 6AWG wire without a fuse stuck inline (and I'm not sure that's code, but I've done that with mini split installs where the outdoor system feeds power and control signal to the indoor unit, and the sellers provide 16AWG wire that is connected to a 20 amp circuit).

ignator · May 3, 2021

PreciseHack said:
Are you saying this in reference to running a single power source into the enclosure and then splitting it up?

Here you go;
Feeder and Secondary Tap Rules

If you read the text, It is for distributing the secondary of a transformer from the power company source. Or feeders sourced from a main panel to multiple subpanels. I don't think this applies to your situation.
And it requires overcurrent protection rated to protect the smaller wire. At least that's my interpretation.
How many more pieces of 240VAC equipment are you going to install in the future? Lathes, milling machines, wood working equipment.... A subpanel is the smartest solution, or replace the existing with a larger one with more circuits (get one to reuse your existing breakers).
But only you know what your trying to do. You probably just want to test the power feed at this point. You can do that with suicide alligator clips. Or wire a 240volt mating outlet and connect it to the 240 breaker in your existing panel. Did they give you the USA 240 volt power cord?

I have two of these Asian power feeds on my milling machine. The critical installation step is installing the right shims for the fit of the bevel gears. A very small amount of backlash is what your looking for.

SomeoneSomewhere · May 4, 2021

If the other equipment is integrated into the machine, IMHO it's very reasonable to put a few breakers inside and then feed pumps, lights, smaller drives etc. off those. Computers too, maybe. Anyone who's opened up a UL-compliant machine (NEC does not apply to appliances/machines) with a PLC and VFDs onboard has probably found a socket for a programmer's laptop, and various breakers for control transformers and the actual loads being controlled.

I would be more wary about putting general-purpose outlets on the outside of the machine.

FWIW I deal with machines built to UL specs with around a linear metre of DIN rail breakers for loads.

The reference to the tap rule is, I believe, that conductors can in some cases be protected from overload by downstream breakers/fuses, and short circuit protection either provided by the upstream device being suitable (a 50A breaker is still likely to trip immediately on a short in a #14 wire with low enough let-through energy to avoid damage), or omitted entirely if it's of a sufficiently short length and not likely to be damaged. It looks like the NEC version of this is substantially stricter than the AS/NZS one.

PreciseHack · May 4, 2021

ignator said:
Here you go;
How many more pieces of 240VAC equipment are you going to install in the future?

I have another mill and a surface grinder that are 220v. The rest of my power tools are all 110.

ignator said:
Here you go;
Did they give you the USA 240 volt power cord?

No just a standard 110v. Which is probably why i didn't notice it right away when i opened the box. I thought I had ordered a 110v one. The info boxes on those ebay listings definitely had 110v in there for the different ones, but it was totally my fault for not paying closer attention.

ignator said:
I have two of these Asian power feeds on my milling machine. The critical installation step is installing the right shims for the fit of the bevel gears. A very small amount of backlash is what your looking for.

Yeah I'm fairly new to machining, so it's hard to know how much is "very small" by feel but I did put it on and off about a dozen times with different shims until i couldn't hear a ratcheting sound when going forward or reverse and it didn't feel like it was binding just turning it by hand. I also had to mill a new key for the shaft because my old one didn't fit. From what i understand the amount of modifications I had to do was pretty low compared to a lot of people. If I was going off what my time was worth I would have come out miles ahead just buying the Servo 150 that's made for my mill, but I learned more this way. Lol.

PreciseHack · May 4, 2021

SomeoneSomewhere said:
If the other equipment is integrated into the machine, IMHO it's very reasonable to put a few breakers inside and then feed pumps, lights, smaller drives etc. off those. Computers too, maybe. Anyone who's opened up a UL-compliant machine (NEC does not apply to appliances/machines) with a PLC and VFDs onboard has probably found a socket for a programmer's laptop, and various breakers for control transformers and the actual loads being controlled.

I would be more wary about putting general-purpose outlets on the outside of the machine.

FWIW I deal with machines built to UL specs with around a linear metre of DIN rail breakers for loads.

The reference to the tap rule is, I believe, that conductors can in some cases be protected from overload by downstream breakers/fuses, and short circuit protection either provided by the upstream device being suitable (a 50A breaker is still likely to trip immediately on a short in a #14 wire with low enough let-through energy to avoid damage), or omitted entirely if it's of a sufficiently short length and not likely to be damaged. It looks like the NEC version of this is substantially stricter than the AS/NZS one.

This is pretty much what I was thinking when I posted originally. I work in software development for my job, and I did a contract with a client that made carwashes, and I saw what their panels looked like with the DIN rails and different breakers and power supplies distributing different voltages to the sub components. That's kinda what I was envisioning making. Not the cheapest way to go about it, but I think I would prefer doing it all self contained just from how it would look and the clutter factor.

Sizing supplemental circuit breaker for 220v Power Feed

Plastic

Cast Iron

Plastic

Plastic

Cast Iron

Plastic

Stainless

Cast Iron

Diamond

Plastic

Cast Iron

Diamond

Plastic

Hot Rolled

Plastic

Cast Iron

Cast Iron

Hot Rolled

Plastic

Plastic

Similar threads