Shop Wiring

Morning my YT friends. I'm moving out to my property finally and getting ready to wire my shop. I've got a couple of questions for the brain trust. I'm getting one of those 100 amp shop boxes from Lowe's. The 30 amp breaker will be for my welder which the plug will be right below the box. Will 10/2 be big enough for that 1 foot run? Also I got some 4 tube drop in ceiling fixtures that use F32T8 tubes. How many of those can I daisy chain together on one 15 amp breaker? Also how many single recepticles can I put on one? And I'm assuming 12/2 will be good for all of that. Thanks for your help

I'll get flamed for this. I would put at least 30 amp on the light lines and depending on the size of the building and the number of plugs would probably only put about 3 boxes on each side for a 20x30 building. And I would go with 8 wire and a 50 amp plug for the welder. I tend to do over kill for wire and breakers on things. No fires nor non tripped breakers if shorted.

Most welders use a 50 amp plug. I would wire it for 50 amps (AWG 6) regardless of what the welder requires. That way it's good to go if you get a bigger welder.

You can run a LOT of T8 bulbs on a 15 amp circuit, although if I was installing new fixtures I'd go straight to LED. Assuming 40 watt bulbs, 15 amps at 120 volts should power 45 four foot T8s. Actually, the number is a bit less due to power lost in the ballast and non-unity power factor. But you should be good with 32 bulbs, or 8 eight-foot fixtures.

Don't use a 15 amp breaker for your wall outlets. Use a 20 amp GFCI breaker. One circuit is probably enough for all your outlets, since you seldom will run more than one big 120V tool at a time. But feel free to have more circuits; more is better.

Don't forget you'll need a separate circuit for your (presumably 240V) air compressor.

The 30 amp breaker will be for my welder which the plug will be right below the box. Will 10/2 be big enough for that 1 foot run?

Yes, for a wire welder that will work. If you plan on ever using a stick welder, they want a 50 amp circuit on #6.

Also I got some 4 tube drop in ceiling fixtures that use F32T8 tubes. How many of those can I daisy chain together on one 15 amp breaker?

Those pull about 1 amp each. You want to max out a circuit at about 80% of it's rating, so about 12-13 on a 15 amp circuit.

Also how many single recepticles can I put on one? And I'm assuming 12/2 will be good for all of that.

Yes, #12 wire for a 20a breaker. Also consider any outlet near a sink or outdoors needs to be on a GFIC outlet or breaker. How many depends on the load. Resistive loads, like electric heaters, pull a lot! One plug in heater will max out a circuit. So will a compressor or anything with a 3HP motor. Consider putting that on a 240v circuit if possible. Other hand tools, and such draw much less, but consider how many people will be working at one time. If only you, then the load drops.

Overkill is good, better to over build now than to have to come back later and redo!

Danny, run a 50 amp for your welder and 8 AWG wire.

> I would put at least 30 amp on the light lines

If you had that many fixtures, it would make more sense to split them between two 15 amp circuits. Not only is it a lot cheaper and easier to run 14 gauge than 10, if one lighting circuit breaker trips you won't be left in the dark.

> depending on the size of the building and the number of plugs would probably only put about 3 boxes on each side for a 20x30 building.

My 30x40 shop has five quad outlets on one side wall and four on the other. And that's barely enough.

Thanks for the replies and help! I should have said it's a stick welder so I'll go 50 amp #6 and the compressor is a 110v. Steve when you say 12-15 are you talking about individual tubes or fixtures?

Don't waste your time with fluorescent. Go straight to LEDs. You can put at least twice as many LED fixtures on a circuit, still pull a fraction of the Amps, and have way more light.

x10000. Use the same fixtures if you want, but rewire them to LED tubes. Get single-ended plastic tubes. Bypass or remove the ballast. Please.

Agreed. Having had both, I wouldn't put fluorescent up if they were given to me.

Give the 110V air compressor to your brother-in-law and buy a new 240V compressor. You deserve it!

when I wired my shop I mounted 5 screw in porcelain bases and used the screw in 3 panel LED fixtures, plenty bright and cheaper.

That's per fixture. If you convert to LED you can have more.

My Lincoln buzz box requires a 50 amp breaker which means nothing less the 8 gauge wire as per code

Thanks but I don't use it that often it works fine for what I need.

Two Stage.

For a shop I use the actual 20-amp duplex receptacles, the ones rated for a house are actually 15-amp. The commercial heavy-duty receptacles are actually worth the extra money they never ware out.

Hi Danny, good questions, I will answer and provide my comments BUT NO WARRANTY IM LONG RETIRED FROM POWER DISTRIBUTION ENGINEERING and rusty as an old nail lol:

QUESTION 1 The 30 amp breaker will be for my welder which the plug will be right below the box. Will 10/2 be big enough for that 1 foot run?

If you run a 30 Amp branch circuit (if that suffices for your welder????) especially such a short distance, 10/2 Copper with Ground will suffice. Assuming its 240 Volt (requires a TWO Pole Circuit Breaker) that's Two Hots L1 & L2 and one Equipment GroundING Conductor. If it were 120V which I doubt, that's One Hot, One Neutral, One Equipment GroundING Conductor still 10 Gauge for 30 Amps.

NOTE if you ever want to allow for expansion, say you used an AC 200 or so Amp Buzz Box stick welder, most require a 50 Amp 240 Volt service, which requires 6 Gauge Copper Conductors and of course a Two Pole 50 Amp Circuit Breaker.

QUESTION 2

Also I got some 4 tube drop in ceiling fixtures that use F32T8 tubes. How many of those can I daisy chain together on one 15 amp breaker.

I do not know how many watts (bulbs plus ballast) those individual fixtures require, so I cant say. HOWEVER here are some basics: If you were to use a 15 Amp Lighting Branch Circuit (14 Gauge wire protected with a 15 Amp Circuit Breaker) do NOT use more fixtures that in total draw over 80% or 12 Amps of current, which equates to a total of 1440 Watts for ALL fixtures combined. If you used a 20 Amp Branch Lighting Circuit, that could total a maximum 80% of 20 = 16 Amps or 1920 Watts total. NOTE FWIW I NEVER SPECIFIED AND DESIGNED THAT CLOSE TO THE LIMITS IN ALL MY YEARS OF PRACTICE EVEN IF PERMITTED BY THE NEC NOTE I would consider LED instead for sure to get more Lumens per watt (more fixtures allowed per branch circuit) and longevity YOUR CHOICE NONE OF OURS

QUESTION 3 Also how many single recepticles can I put on one? And I'm assuming 12/2 will be good for all of that.

SAME AS ABOVE for a 20 Amp Convenience Outlet Branch Circuit (12 Gauge wire and 20 Amp Breaker) the MAXIMUM Continuous Current would be 80% of 20 or 16 Amps. HOWEVER its good engineering and practice to run more than one branch circuit, perhaps 2 or 3 so receptacles are staggered around fed by different circuits. Typically I never placed many more than 8 duplex receptacles on a 20 Amp Branch Circuit even if more were allowed, BUT THAT DEPENDED ON THE APPLICATION.....

NOTES A garage/shop type structure with a concrete floor typicaly requires GFCI protection on convenience outlets. That can consist of GFCI receptacles orrrrrrrr the use of GFCI Circuit Breakers in the panel. I would ONLY use Spec Construction Grade receptacles not cheap big box store grade.

NOTES Assuming this is fed from a home panel ??? it needs to be configured as a SUB PANEL which means it has Separate Isolated and Insulated Neutral and Ground Busses, and for 120/240 Volt service, that requites FOUR Conductors, Two Hots L1 & L2, One Neutral, One Equipment GroundING Conductor plus the buildings electrical service (last time and jurisdictions where I practiced at least) requires bonding to a proper Grounding Electrode(s).......

Hope this helps, post back any questions. As always where fire and life safety are concerned if in doubt consider consulting the NEC if and where applicable and professional electricians or engineers DO NOT TAKE MY WORD FOR ANY OF THIS.....

John T

I would convert the light fixtures over to direct wire LEDs, no ballast, and be done. Less amps, more light. When I convert my two tube fixtures over to LED I am able to get the equivalent light form only one LED bulb. Instead of 80 watts, (two 40 watt bulbs) one, I think, 18 watt LED, so I am only drawing about 1/4 the watts for the same light.

My Lincoln buzz box requires a 50 amp breaker which means nothing less the 8 gauge wire as per code.

I wired My 220 a Lincoln buzz box with 50 ft of 10-2 with ground.
For the past 30 years, I've yet to trip the 30 amp breaker.

Breakers protect the wire not the welder.
I already had 10g wire at the time and I'm too cheap to buy 8g and a 50g breaker if I didn't have to.

That said if you want to spend exra $ buy 8g and a 50a breaker,
I use 12-2 with ground to my 220v mig welder.

Get yourself an Ugly's Electrical manual. For about $20 you will find the answer to nearly every electrical question you have. Even a used one will work for most jobs.

Was that a typing mistake or did you really mean to say that 12-2 will work for a welder?

I had my old buzz box wired with 10 gauge and smoke test it more then once

Ive had one for years great reference. It and the NEC were my bibles when I was practicing.

John T

Thats right the current drawn from the primary (your 240 volt input source) depends on the secondary welding current, I don't doubt your experience one bit !!!!!! As long as you weld at low enough current so will the primary current draw be low HOWEVER if you need to weld at high current for a long enough time YOU WILL LIKELY EVENTUALLY TRIP A 30 AMP THERMAL MAGNETIC CIRCUIT BREAKER on a typical 50 Amp input welder Well DUH lol

But if you dont weld at max high current a real long time, you can get by with ONLY a 30 Amp Branch Circuit and NEVER cause a trip WELL DUH

Every time I designed or installed a branch circuit for a welder, I specified adequate capacity to match the welders max welding capacity, I nor my boss nor the NEC as I best recall, would allow anything less BUT HEY THATS JUST ME AND HOW I UNDERSTOOD THE NEC even if sure less will work if you dont weld at high current for long enough times TO EACH THEIR OWN WIRING CHOICES is fine by me. Connect your 240 Volt 50 Amp welders with 30 amp service and you can for sure get by just fine SUBJECT TO WHAT YOURE WELDING for how long

John T Long retired n rusty power distribution engineer so no warranty things change

George, I'm pretty sure your welder has a 50 amp plug on it, even though it never draws 50 amps. My opinion (and code as well, I think) is that a 50 amp receptacle should be wired for 50 amps. If you don't, sooner or later someone will plug a 50 amp load into it and it's not going to work. In the case of the OP installation where the run is very short, the cost difference between 30 amps and 50 amps is negligible.

Mark,
The 10g wire doesn't get warm.
The 30 amp breaker has never tripped.
I'm sure my welder has never used more than 30 amps..
The 225 amp lincoln isn't designed to well at 225 amps full time. I rarely use more than 120-150 amps.

Use an amprobe and measure the actual current.
I can't read amprobe and weld at the same time.

I don't care if it has a 100 amp plug.
Circuit breakers are designed to protect the wire, not the welder, agree?
Why would I change to 8g wire when 10g wire has served me well for 30 years? Code or no code!

10-2 30a breaker for lincoln, 50 ft
12-2 20a breaker for 220v mig welder, 50 ft.

Mark is correct, 630.11(A) of the NEC code states that The ampacity of the supply conductors shall not be less than the I value on the rating plate. Just because something works and you've done it does not mean that you should recommend it to others. I personally want to do everything I can to ensure that any electric work is safe for myself, my family, and any future buyers/users. I don't see the point in skimping to save a couple bucks when a home or county inspector down the road may catch it and cause you to spend more time and money than you'd have spent doing it right the first time.

he NEC code states that The ampacity of the supply conductors shall not be less than the I value on the rating plate.

WORKED FOR ME When I practiced in our jurisdiction I never specified less ampacity than the device and recall that to be NEC at the time.

John T BSEE,JD

We take down perfectly good fluorescents all the time and they go directly to the garbage

> I don't care if it has a 100 amp plug.
> Circuit breakers are designed to protect the wire, not the welder, agree?
> Why would I change to 8g wire when 10g wire has served me well for 30 years? Code or no code!

George, what you do in your own shop is your business. But when you're handing out advice to others, it's best to be conservative in your recommendations. The OP may have a puny welder now, but he just might buy a 300 amp TIG welder tomorrow. If you're putting in a 50 amp outlet, it ought to be good for 50 amps.

30 amp and 50 amp double-pole circuit breakers of the same brand and type typically cost the same. And with a short run, he's only buying a few dollars worth of wire either way. There's no good reason for him to wire the circuit for 30 amps rather than 50.

The 10/2 will be fine for a 30A breaker, but will your welder need more than a 30A outlet/breaker. Most stick welders need 50 amp.

The four tube fixtures will work on one 15 amp breaker, and 12/2 will be fine. 14/2 will comply with code, if the shop is not too big and voltage drop is not an issue. Make sure your local inspector will let you use Romex exposed and above a drop ceiling though.

John,
If I paid someone to wire something critical, I would want them to wire to code.

Has anyone looked inside a 225 lincoln to see the size of wires they used?

Sometimes companies play a numbers game.
Remember when B&S got into trouble overrating their motors..

When it comes to rating electronic power
You have RMS Watts, Peak Watts, and Peak to peak watts..
Same with amps. Please check my numbers below.
Example;
1 watt rms = 1.414 peak watts = 2.828 peak to peak watts.

Same with amps.
1 amp rms = 1.141 peak amps = 2.828 peak to peak amps.

Are welders playing the same numbers game with amps? Using the larger numbers?
100 amps rms = 141 peak amps = 282 peak to peak amps?

I know the welding leads can no way handle 225 amps, too small.
They look like they may be able to handle 100 amps.

What size wire is used to make the transformer?
Is the primary made of 8g copper?
Is the secondary wire capable of 225 amps.

Has anyone measured the actual primary and secondary amps?

Don't always believe what you read.

What about the wire size for the Lincoln 225 welder?
Now that we have decided 60A is an ideal circuit breaker for this welder, choosing the right size of wire should not be a big issue. The #10 wires are mostly recommended for the welder.

However, there is a small chance that you will need to buy #8 wires. This is only because the manufacturer recommends a 60A circuit breaker with a #10 wire and not #8. So, if it happens that you need to buy #8 wires for your welder, then by all means go for it.

Don't believe what you read.
60 amp breaker on a 30 amp 10g wire.

Has anyone put an amprobe on their 225 lincoln?
Has anyone looked inside their lincoln welder?
Are the people making welders playing a numbers gain?
I don't know.

Do places over rate horsepower?
I have a 4 hp craftsman electric chainsaw that uses 15 amps.
How did they cook those numbers?? 4 peak to peak HORSEPOWER?
I think my shop vac hp may be overrated.
I dont believe everything I read. Please measure amps.

Better check the amperage draw on that welder .

Good Neighbor George, Believe whatever YOU choose,,,,,,,,Wire however YOU please,,,,,,,, Im for you, you will get no argument from me. You will have take up your arguments with the NEC if you know better than they do NOT ME Im your friend and support your right to wire as you please GO FOR IT IM NOT STOPPING YOU

HOWEVER as a trained and experienced Power Distribution Design Engineer,,,,,Having attended NEC seminars and workshops over many years in my practice I CHOOSE TO FOLLOW THE NEC GUIDELINES NOT YOU and prefer to do it RIGHT not half or possibly unsafe, ones life or property is NOT worth the risk in my opinion

To each their own George, where fire and life safety are at risk its YOUR choice to do it per the NEC or per George if you know better than they do...Maybe you do ?? If so and you convinced the NEC to change the rules then I will follow, until then I will follow the NEC because I trust their expertise over you. Thats NOT an attack on you as a friend

Best wishes George, please do as you like and let the NEC and others do as they believe can better save a life or a fire....

John T

> Has anyone put an amprobe on their 225 lincoln?
> Has anyone looked inside their lincoln welder?
> Are the people making welders playing a numbers gain?

George, I don't think anyone is saying a 30 amp circuit is inadequate for your welder. Or for the OP's CURRENT welder. But we can't say 30 amps is adequate to handle whatever the OP might plug into that 50 amp outlet in the future.

When you plug a 15 amp 120 volt plug into a 15 amp 120 volt outlet, you don't worry about whether the circuit behind the outlet is adequate to handle whatever you're plugging in. You know there's at least a 15 amp circuit behind the outlet, or possibly a 20 amp circuit. Same thing when you plug a 50 amp plut into a 50 amp outlet: You expect you can run the device you're plugging in without it blowing the circuit breaker.