Increasing Electrical Capacity for CNC Setup

I just ordered the LongMill MK2 Beginners Kit - 48x30 and plan on building a basic work station in my garage, which also doubles as my current woodshop. When I work on simple projects in the winter, I can overload the circuit breakers and cause them to trip just from having the garage lights on, running a couple space heaters and powering up my miter saw for 5-10 seconds. Along with the CNC I’ll obviously have additional devices like my laptop, monitor, shop vac, garage lights, etc all running at the same time that will just add to the electrical load. My biggest concern is being able to rely on the circuit breakers not overloading in the middle of a running project. How big do I need to go here and is there anything you would recommend for increasing my power supply? From what I’m seeing online, adding an additional sub panel is all I can seem to find, but that looks like it can get pricey and my lack of overall electrical knowledge is really limiting me. Not sure if this info helps in any way, but my electrical panel for the entire house is located in my garage, about 10 feet from where I would have my CNC operation running. I don’t want to break the bank here, but I’m willing to spend a couple extra bucks as opposed to the cheapest DIY option possible, end up causing an electrical fire, and burning down the home my wife and children live in.

Appreciate any feedback, tips, or advice.


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Also, I sent the above message to the support team at Sienci and they responded with the following.

“You’ll want to make sure the controller and computer are on a separate circuit from the router and dust collection.”

They also pointed me to this community and the Facebook group, but I’ve got down that I need a separate circuit for the device combinations listed above.

@Tpoole1988 Welcome to the forum. Good folks, sound advice. I had some issue with the power brick from my MacBook Pro and my controller board. It would trip my GFCI outlet. As soon as I put the CNC with the router on a separate dedicated circuit, and the laptop on another circuit, the problem went away. I have yet to get dust collection running, although it runs on 240v on its own circuit. It wouldn’t be an issue.

To answer your question, I would use a dedicated circuit for the LongMill and a second circuit for your computer and possibly your shop vac.

From what you described, it sounds like you could use an upgrade for electrical in your shop. The space heaters take a lot of energy and blowing a breaker during a carve could be very problematic for you and your projects.

So the disclaimer: if you don’t feel safe and comfortable doing electrical installation on your own or if your local area requires licensed electrician to do the work, consider hiring the job out.

You will enjoy the heck out of your LongMill, I know I sure do. Again, welcome!



Has anyone set theirs up to run from a UPS system? Longmill would draw from the battery and leaving only the charging system to be vulnerable to the voltage dips and spikes. I am about to change my setup to run like this as I need to make my Longmill portable for this summer.

@Parrott You would need a pretty good size UPS to run a router for any length of time, UPS are good for low amp draw. $2500 UPS you would get about 5 min of run time. Small generator would be the best bet.

I will only be running the computer longmill board and motors from the UPS. Router will be seprated. Not trusting my power supply I want the computer cnc to be able to be on their own. I have 2 80lbs sealed agm UPS that should be more than enough to handle it.

Even if you’re not running the router, a UPS would be a short-lived option. 400w as picture will run a 110v computer for about 20-30 min. There is free online calculators to figure out your amp draw and that will tell you what size UPS you would need.

It would be running off a charging system. The ups is just to stop any power dips from a generator or other source that is not part of my tested plug in setup.

Your showing a battery not a UPS in your picture, if you are using an inverter generator then batteries will be a mute point. Inverter generators provide a clean sine of energy, keep it full of gas and you should have no issues.

A couple of space heaters are the source of your problem. Turn off the heaters while running your cnc, else find another type space heater like kerosene/alcohol etc…
Next and best solution is add an outlet next to your breaker panel and add its own breaker. An electrician will charge only the minimum billing for this if you are uncomfortable DIY.

@Tpoole1988 Welcome to the community. Where is your current panel located? Are you sure your maxed out on it? Might just need a small 20amp run for a couple new plugs. Sub panel would probably be 50amp min and the copper for that can get expensive depending on how far to run it.

Currently my setup is in my basement and everything is on the same 20amp circuit. Dust collector, Longmill (router,longboard, etc.), intel nuc (computer). I have had no issues. I understand this is not the case for most people, just happened to work for me.

I am in the garage. Had my buddy come over who is a jack of all trades and got me setup nicely. Put some split breakers in and all new outlets, updated to 20A and a couple USB outlets (he told me this was a major issue as most of them were in dire need of replacement and were borderline hazardous)