Is a 100 amp sub-panel enough for 220 welder

[jtaco1]

We are purchasing a new home to us, and there is a concrete block building on the property that I will be using as a shop. It currently has a 100 amp sub-panel installed, which will be replaced with a modern panel and wired to best utilize the circuits for recepticles and lighting.

My question is, is this enough of a power feed to install a 220 outlet for a 220 welder or plasma cutter? My building inspector said that it would not be enough for a bigger machine, but will be fine for my 110 welder, which I currently use in my single 30 amp breaker garage without issue.

Thoughts???

[demonranger]

technically yes you do have the amperage in the panel to supply the power

your welder requires 50A at max draw you figure you have lights that will run a total of 20A or so depending on the shop size so you still have plenty of extra but you're going to see a dimming of the lights when you start an arc.

[carwash]

if it's a 100 amp panel, then it's probably only 100 amp service coming into it. if you need to go higher on the inside panel, yer gonna have to run higher service into it as well.

I have 200 amp service into my home shop, but could prolly get by with 100 amp. I run a miller 251 on a 50 amp breaker, a monster plasma on a 40 amp breaker, lights totaling about 20 amps, and outlets, etc... I doubt i will ever run my welder at 50 amps, or any of the other equipment at its rated amerage breaker. So, i bet i have never been using 100 amps at once anyway. Now, if you plan on adding some big equipment later on, like a lathe or mill, and need to run a phase converter etc, yer gonnna run into issues. If you are just going to be smaller potatoes, and hobbyish, you should be fine.

[actionpaintball]

I originally only had a 30 amp panel and it ran my 180amp Lincoln MIG just fine at only 30 amps.

Check the wiring going into the panel. It should be appropriateley sized for your codes depending on length from the main panel, type of wire (cu or al) ect...lets say it happens to only be 4 gauge wire-you would want to drop down to the approriate sized subpanel main breaker size or run new service wire out to the panel to make sure its within code.

My subpanel was less than 100 feet so I had to use minimum 2 guage minimum (AL) and since it was greater than 50 feet-it had to have its own grounding rod. The ground and neutral bars had to be separated.

The 100 amp panel will be fine-you just need to size the specific breaker according to your max draw on your welder; which should be listed on the welder itself or online.

Here is a good quick reference on wire size:
http://electrical.about.com/od/wiringcircuitry/a/electwiresizes.htm

[jtaco1]

Thanks guys, yes the building has a 100 amp service, just that the current box is a Federal Pacific Panel, that the building inspector says should be replaced since they are known for fires and what not, plut it is not setup the best. They are currently running lights on a 50 amp breaker :shaking:

I would be looking to replace the panel and breakers with something better and giving me more options, probably run a 50 amp breaker just for a welder, which I don't have yet, only have a little 110 welder at the moment. Then put all the lights on one breaker and use another for the outlets. I will look inot the codes a little more and see what is required, I also know a very competent electrician that is a family friend that I will have do the major hookups, I can handle the wireing after that.

I don't plan on adding anything bigger than the welder really, the building is a little small for mills and lathes, plus I don't have the $$$ for those things.

Thanks

[PAToyota]

Depends on the welder. I've got a C320 service coming into the property split to a 200amp panel in the house and another 200amp panel in the shop. My MIG (MM250X) is on a 50amp 220V breakers, but the TIG (Syncrowave 250DX) is on its own 100amp 220V breaker. I also use the 50amp circuit for the plasma (Hypertherm PM1100), but the compressor is on another 30amp breaker. Then add in lighting and the possibility that my father is upstairs in the woodshop...

In your case, you'll probably be fine with a 220V MIG. The plasma/compressor combination could be the limiting factor depending on how big you go and how heavy of work you get into.

[jtaco1]

Plasma cutter is a bit down the road, will probably pickup a torch setup here soon, if I can find one for a decent price. This is mainly a small shop for working on my 88 4 Runner and some of my dads vehicles, may do a build up on one of his 37 Chevy pickups eventually.

[PAToyota]

Another thing to consider would be that if you're updating the panel anyway, go for a 200amp panel and just put a 100amp breaker in it for now. Then, if you outgrow the service and want to upgrade you're ready for it. A SquareD QO 200amp 40/40 panel is about $200 at Lowes and more of your cost is going to be in having the electrician install it.

[RustoleumWhite]

You'll be fine.

Like was said above, double check the wiring leading to the sub panel, make sure the [house] breaker feeding that sub-panel is sized right for the wiring.

FYI, if you only have, lets say and 80A circuit feeding the sub-panel, you can still run a "100A" sub-panel, heck you could run a 200A sub-panel, that doesn't mater since you'll only be able to draw out of it what the breaker (and the wire) feeding it are. The main breaker in the sup-panel however should be changed to match the feeder breaker.

As for a panel, by a name brand (Square D, GE, Siemans etc) that fits your budget (don't go super cheap) and readily available (i.e. you can get breakers and parts easily at Home Depot, your local friendly supply house etc). That way you have easy access to reconfigure the panel as need be.

FYI, code [IIRC] now requires that all Garage 15/20A 120V outlets be GFCI... this is of course if your getting a permit and doing it "right" :D The worlds not going to end if you put std receptacles in.

[Pook]

I personally prefer the Cutler Hammer Panels and is what I always buy when doing panel upgrades for myself or friends. The breakers have a nice positive lock on the bus rails.

Federal Pioneer like what you have currenly are garbage...the breakers wobbles around and can easily come loose on the rails.

[Mechanos]

...The main breaker in the sup-panel however should be changed to match the feeder breaker...

:confused:
The sub-panel shouldn't even have a main breaker.... it should be a main lug only type panel.

[Todd W]

Depends on what kind of welder and how thick you plan to weld.
I used my dryer plug at my old rental on my powermig 255 and tig 225... if i turned them up they could/would trip the breaker. I also ran my 5hp compressor it tripped the breaker only once or twice.

You can get by on it with 220 that's for sure.

My TIG and MIG donlt really come close to 100amp abd don't even need that (alone), the only time I need more is if I`m running my plasma (~70amps) compressor (~25) 2 fans (~20) and the lights. I plan to put in a 125 or 150 amp breaker in the garage/shop so if/when I run ALL of these at once I can... sometime next year :)

[jtaco1]

Thanks guys for the insight, all of my tools are 110 at the moment so it would be a bit until I get the bigger welder. I don't really see running a bunch of high load things at once while welding. Thanks

[RustoleumWhite]

:confused:
The sub-panel shouldn't even have a main breaker.... it should be a main lug only type panel.
If its not within sight of the panel feeding it, it needs some sort of local disconnect, typically that would be a main breaker or a back-fed main if you had a main-lug panel.


I'll need to double check on that though, my brain's not telling me 100% on that, but I'm pretty sure thats how its spelled out in the National Code.

edit: clarification.

NFPA 70 National Electrical Code (2008)
225.31 - Disconnecting Means [outside branch circuits and feeder]
short translation, a separate building needs a disconnecting means [225.32] either outside or inside the structure, close to the point were the wires enter the building.

However, 225.34 (six disconnects rule) basically allows you to have up to (6) circuits in your panel and get away without a main disconnect. Beyond that, you need one.

So if you put a 12-space sub panel in your detached shop, it needs to have a disconnect of some sort, easiest way is to get a main-breaker panel, or back feed a main.

If your sub-panel is in an attached garage (or other room) main lug is OK.



If someone translates this different, I'm usually willing to be corrected.

[Mechanos]

Thanks guys for the insight, all of my tools are 110 at the moment so it would be a bit until I get the bigger welder. I don't really see running a bunch of high load things at once while welding. Thanks

That's the whole deal.... how much stuff are you going to be running at once. I have a 100-amp main panel in the garage of my house. I filled it up and needed more room for additional circuits in my garage and basement, so I set a 60-amp subpanel right next to the main panel. Gave me the additional circuits I needed and has never been a problem since there is no way I will be using everything in the house at the same time.

[in4x4guy]

no matter what you do you need to replace that federal pacific box. I can't believe your inspector missed that one, they were recalled years ago and are prone to shorts at the breakers. also if you can find breakers for them they are real expensive it's cheaper to replace the whole box then buy two breakers.

[Nordic1]

100 Amp 220v?

30 amp 220 air compressor
50 amp 220 welder
20 amp 110 x2 for tools

[jasonmt]

100 Amp 220v?

30 amp 220 air compressor
50 amp 220 welder
20 amp 110 x2 for tools

An inductive load like a transformer in a welding machine or an air compressor motor generally requires a overcurrent protection device sized to take into account the inrush current. This means that unless you somehow manage to start up equipment with large draws at the same instant it will not be an issue.

So your true 5hp motor is only going to be drawing ~25A when the compressor is approaching maximum pressure.

A 300A GMAW welder like a Miller 252 that calls for a 50A circuit breaker when wired for 230V is going to be drawing ~28A when running at 150A/40% duty cycle. Conventional transformer based AC GTAW machines are one of the worst cases for inrush current, especially when running unbalanced AC output.

I would not worry about needing more than a 100A service until you get to the point where you are regularly blowing a 100A main breaker, ensuring that if you do buy a AC/DC GTAW machine that it is inverter based will certainly help.

[rock mafia]

Half my house runs off two sub panels fed by a 90 amp breaker. Everything in the kitchen, water heater, 1/2 the lights and all of the garage with 220 welder, comp, plasma and AC. Nothing dims the lights, nothing trips any breakers.

[jtaco1]

no matter what you do you need to replace that federal pacific box. I can't believe your inspector missed that one, they were recalled years ago and are prone to shorts at the breakers. also if you can find breakers for them they are real expensive it's cheaper to replace the whole box then buy two breakers.

Yep, he told me to replace it, so I am throwing it back on the current sellers to give me a credit for it so I can replace it, but will be replacing it anyways since it is setup a littlle wierd, 50 amp breaker to run lights that are screw in bulbs :eek: It is a neglected building that was used to store wood and a tractor, I will be rebuilding it to suite my needs as a shop until I build the new garage.

Thanks