Welding And Amperage Needed

[jonp]

The recent thread I posted for welding has me once again thinking of running power to the garage for a DC outlet. A few years ago I had an electrician put a 200 Amp box on the house with a 100 Amp sub-box in the house. This leaves 100Amps outside. My intention was to run a different sub to the garage and leave a 20 Amp open at the house to run a generator into and power my freezers and fridge if the power went out. I would use an automatic flip in case the power came back on when running the generator to prevent back feed.

The question is whether an 80 amp sub in the garage is enough to run a DC welder. I am not running a professional unit, just a small stick. My idea was to run a line into the garage and have one 40 Amp DC outlet for a welder and 2 20 Amp breakers for running other lines. Does that sound right? Would a 30 Amp DC outlet be enough leaving 50 Amps free? That would leave I could put in 1 20 Amp and 2 15 Amp breakers.

Any opinions?

[rancher1913]

a transfer panel would not need separate 20 amp circuit, it uses the same circuit as the main house, you do need a separate panel for the circuits the generator will run but when not being fed by the generator they are fed from the normal house panel. the jest is you will have 100 amp to the house and 100 amp to the shop. most big welders only use a 50 amp circuit.

[dangitgriff]

Consider installing an in-line fuse/fuses on the load side. We use them for 3-phase power to radars.
R/Griff

[Mal Paso]

There are single circuit transfer switches commonly used on wells that include a weather proof twist lock plug for your generator.

My 250A stick welder needs a 30 amp outlet

[MrWolf]

Whichever route you take please install the proper generator transfer switch so you don't accidentally electrocute someone working the line. Good luck

[corbinace]

Just a short PSA before I continue to add my opinion.

If you do have some sort of transfer switch for a backup generator, please have it blessed by your local inspection authority. There are Linemen killed and injured every year from unauthorized genset hookups back-feeding the system. Please do your part to save a life. A freezer full of food is not worth killing someones dad.

Now with that out of the way. The 100A sub in the garage can have many more circuits/breakers than what add up to 100. They are never all in use at one time in a residential setting, so do not actually add up to 100A of usage. Look at your house panel for example, way more than 100A worth of breakers.

The welder circuit is most generally 6ga wire protected by a 50A breaker in my area. The welder does not actually use this much.

These rules are spelled out in the National Electric Code (NEC) but are modified by local authorities all the time. So the advice you get here is only worth what you pay for it. Best to get local help, that knows the local codes.

Good luck.

[jonp]

I was instructed by the electrician on putting in the transfer switch. Before I get it done I'll most likely have an electrician (wife's dad is a commercial/industrial electrician) make sure it's being done right. That's in the future anyways.

My intention with the box on the outside of the house was always to run a sub box out in the garage for the garage. If a 250 Amp welder needs a 30 Amp circuit then that will work fine as my needs are less than that. Corbinace, I'm aware that you can have more but I don't need to do that. All I want is a DC for a welder and a line or two to run the tumbler, melting pot, table saw etc. Nothing heavier. The distance to the garage is about 75 ft. I'll over size the wire just in case. As for local codes, they don't have any. We follow state and National codes which I've looked up.

My house circuits add up to 100 Amps. I wired it myself with some advice and I did that on purpose just in case.

[JohnChrysostom]

husband? ............. 30 amp socket is serviceable but turned up it will kick every so often or if your stick an electrode real good to your work it will likely kick, 50 amp for welders is better because you almost never have to reset the breaker or heat up your electrical wiring. "Weldingweb" has lots of old posts about this you can just read but (their new websites on the frits and they are moving back to the old one soon)

[jonp]

husband? ............. 30 amp socket is serviceable but turned up it will kick every so often or if your stick an electrode real good to your work it will likely kick, 50 amp for welders is better because you almost never have to reset the breaker or heat up your electrical wiring. "Weldingweb" has lots of old posts about this you can just read but (their new websites on the frits and they are moving back to the old one soon)

Yeah, want to make something of it?

I typed that wrong, haha.. Wife's Dad.

[JM7.7x58]

A 30 amp clothes dryer circuit will be fine. In five different houses I've lived in over the last twenty-five years, that is what I have used. I have run SMAW, GTAW, and GMAW on a 30 amp circuit. I wouldn't try to run 5/32" stick. I wouldn't try to spray aluminum. And I wouldn't try to carbon arc. But for your average, run of the mill stuff, a 30 Amp circuit is gonna be fine. With a little preheat and the right wire you can weld up some pretty thick stuff if you needed to.

JM

[lightman]

Jon, most welders that I hooked up circuits for ask for a 50 or 60 amp circuit. That would require #6 copper wire. The welder won't pull near that except for a few seconds when you are striking an arc. So your 80amp panel is certainly adequate. The last book that I saw on a Lincoln welder ask for #10 wire and a 60amp breaker but thats against the code. A 60amp breaker needs 60amp wire.

Oh yeah, Jon your circuit will be AC. The DC part happens inside the welding machine.

[Mal Paso]

I totally agree with bigger wire, the better the power, the easier to weld. Most of the mid size welders seem have cord sets for 30 amp outlets. If you put in a 40 or 50 amp outlet you will need to change the welder's cord/plug. I would put in whatever size outlet that fits plug the welder came with and get a good electric panel like Square D QO or Semans so you're not dealing with cheap circuit breakers.

[DougGuy]

You could take the easy way out and pick out a welding machine, it will have the proper plug on it for the service needed, then you just wire up your AC power to suit. Most home/automotive garage units will have 30a plug like an RV has, different than a dryer plug but still the same amps. Industrial machines will use higher amperage, they will have a 50a plug, and will need the appropriate gauge wire to your garage.

If you want a machine that will run 1/8" 7018, .045" fluxcore mig and .035" hard wire mig, there are plenty to choose from that will be perfectly happy with a 30a service. I would suggest this route, it will allow you to do equipment repairs, weld muffler pipe, you could build a small trailer very easily. Many of these will have a TiG function as well as stick.

Welding aluminum is a whole nother ball game. You have to have a high frequency source if you TiG it, and a spool gun usually requires a fairly complex power source to run it, escalating the cost substantially.

You may want to add up the cost of the 230v service, labor, and the cost of the welding machine, then compare this figure to an engine driven welder. A Miller Trailblazer will do all of the welding mentioned here, plus provide a robust 230v service in times of power outtages. If you are going to build a decent sized trailer, a portable engine driven welder would make a LOT more sense than trying to use wall power. You can only draw so many welding amps out of a 230v source, I don't care how you do it or what machine you use.

I weld a lot of equipment buckets, excavator and skid steer, we get upwards of 2" plate on a 6' bucket and this requires a lot of welding current, more than even a Trailblazer will produce. I use a Miller Big 50 diesel, I run a lot of 1/16" fluxcore wire and crank it religiously. I can carbon arc with ease, it will run 3/8" carbon arc rods which will easily draw 400+ amps. We just went through this same thing at a shop locally that I mentor their welder. One of the greenies was about ready to spend $10k on a 230v machine and other tooling, not knowing the limitations.

I found them a Miller Big 50 out of Craigslist for less than $3k and this suits the needs of this shop MUCH better than wall power.

In fact, I found them a Miller 12VS wire feeder and a 15' Bernard mig gun from ebay, both new in box, two good torches, one for cutting and one for gouging, oxy/acet regulators, flowmeters, welding cables, ground and stinger, pretty much tooled up the entire welding shop for less than $5k, which will barely buy a decent 230v welder if you buy new.

Anything more than this needs 3 phase, which will run you a LOT to have it dropped into your location, and a LOT every billing cycle.

[Plate plinker]

^^^^3 phase billing is outrageous for a small scale operation.