[NQBQDY]

Hello all, I have what may be just a simple question but I'm having trouble finding the answer at my locale home improvement store. I am building a new workshop behind my house and I am trying to see what gauge wire I can get away with safely as wire is costly. My situation is this, My building will be about 50' from the main box location if that. I want to run the line from the box to a second box I will install in the shop, from there I will run 12-2 throughout. I only plan to have a small 70amp 110v welder, a bench grinder, a fridge, air compressor, a few florescent lights and 6 or 7 receptacles in all. One man told me to run 8-3, another 4-3, and another said run two 10-2's. I was looking to purchase a 100amp indoor box with a main along with my wire. Any and all advice is appreciated and I suppose my basic objective is to keep the cost down while still being safe. I know a fair amount of this but I would like a real pros advice.

p.s. I also realize the line should only carry 80% of the load.

Thank you.

 

[TTW]

First add up all of the wattages of your known equipment from the nameplates on the equipment and let us know what that number is.

The size of the wire needed will be determined by the size of the breaker feeding your sub panel.

If you can get away with less than a 100 amp feed, you can use a smaller wire.

I believe 100 amp feed will need a 2-3 + ground NM (copper) or size 1/0 aluminum (3+ground).

Someone will correct me if I'm wrong.

 

[Missouri Bound]

#4 wire will allow you a 80 amp. service. Can you bury conduit or are you hell bent on using cable? If you bury conduit you have a bit of flexibility in case your needs change. With the price of wire nowadays this isn't going to be a cheap install at any rate.:whistling2:

 

[NQBQDY]

Thank you both for the quick reply. My total wattage is about 5000 watts including lights. As far as cable vs. wire with conduit I have no preference and I can use either. I do realize the it isn't going to be cheap and I can and will spend the money, I am just trying to see what is the cheaper way to go, at the store I just felt like they were trying to sell it all to me.

 

[jlmran]

My total wattage is about 5000 watts including lights.

Your welder alone appears to exceed 5K watts...

 

[NQBQDY]

Oh sorry this is just what I was going by:

120 volt, 20 amp, single phase input
Thermal overload protection with indicator light
Welding current: 40-70 amps AC
Rated duty cycle: 20% @ 70 amps
Stepless current regulator
Input: 120 volts, 20 amps, single phase, 60 Hz
Welding current: 40-70 amps AC
Rated output voltage: 22
Max open circuit voltage: 42
Rated duty cycle: 20% @ 70 amps
Electrode capacity: 1/16" to 3/32"

 

[jlmran]

Ahhh...welding current. Thought that was a bit strange, the way you had it worded.

 

[k_buz]

I would suggest running PVC and individual (3) #6 THHN/THWN and a #10 CU ground on a 2 pole 60A breaker.

 

[NQBQDY]

to jlmran: yeah I didn't word it right but didn't realize until you said something, sorry.

to k_buz: thanks I never really thought of running them individually.

 

[Stubbie]

I'm going to ask you a few questions and post some diagrams for you to use as a guide line.

Is your homes service 100 amps and if it is what big electric appliances are you operating if any ...ie... electric stove, central ac, baseboard heat etc.

Based on your description disregarding the welder which I think is incorrect at 70 amps you would get by fine on a 60 amp feeder to your 100 amp shop panel. However it is prudent to determine how tasked your homes panel is before adding load to it from your shop.

Assuming you have 150 amp or bigger service my opinion would be to run a 70 amp 4 wire feeder using three 6 awg thhn/thwn individual wires and one #8 ground in 1 1/4 " PVC. Protect it with a 70 amp double pole breaker in your homes panel. The 100 amp main breaker panel for the shop is a good choice and will satisfy the requirement for a service rated disconnect located at the shop. The shop panel need to be mounted as close as possible to where your feeder enters .. also a code requirement. The pvc needs to be 18" deep measured to the top of the pipe. Your shop panel needs to have the neutral and ground separated. Study these drawings and if you have questions use them as reference.

 

[NQBQDY]

to k_buz: I was thinking of having 220v at first, but everything I have in there will be 110v, is it better to have it anyway just to carry a load?
this probably seems funny and foolish but originally I was just going to run a 10-2 line off of a 30 amp breaker from my supply box. I now am glad I sought out help.

 

[Stubbie]

to k_buz: I was thinking of having 220v at first, but everything I have in there will be 110v, is it better to have it anyway just to carry a load?
this probably seems funny and foolish but originally I was just going to run a 10-2 line off of a 30 amp breaker from my supply box. I now am glad I sought out help.

Not really foolish but if your going to weld and have a compressor I'd say the minimum would be 40 amps. After all this is a shop not a garage.

 

[Stubbie]

Oh sorry this is just what I was going by:

120 volt, 20 amp, single phase input
Thermal overload protection with indicator light
Welding current: 40-70 amps AC
Rated duty cycle: 20% @ 70 amps
Stepless current regulator
Input: 120 volts, 20 amps, single phase, 60 Hz
Welding current: 40-70 amps AC
Rated output voltage: 22
Max open circuit voltage: 42
Rated duty cycle: 20% @ 70 amps
Electrode capacity: 1/16" to 3/32"

The red high light is the one your interested in ...

 

[NQBQDY]

I first want to say thank you to everyone, secondly I want to apologize I feel my original post might be misleading and worded wrong. I would like to start over, I intend to build a 16' x 16' shop/shed and would like to add power to it. My home box is a 200 amp panel which will be roughly 50' from said shop. I will have 4 florescent hanging lights, say 8 2-plug receptacles, bench grinder, welder, a fridge, air compressor, and a battery charger for cordless tools. I'm not sure if this is any more helpful or just confusing.

 

[NQBQDY]

I only intended to add a box to allow me to split the load among a few breakers instead of one big breaker at the house panel.

 

[jbfan]

Follow stubies advice and you will be fine.

I think you could even run a 60 amp service and be fine.

 

[Stubbie]

I only intended to add a box to allow me to split the load among a few breakers instead of one big breaker at the house panel.

I'm sorry I do not understand what you mean by the above.. I gather though your not wanting to have that much power as suggested out at the shop. If you weld on a high output setting and run your air compressor that is going to be in the neigborhood of 30 to 35 amps on your feeder. It would be much better to run 240 volts and 120 volts using a 4 wire feeder so you can balance your loads better. You must have neutral to get 120 volts. You can't use multiple single pole breakers in your house panel to run circuits to your shop.

And I agree a 60 amp service would be fine I was just giving you the maximum bang for your buck with the 70 amp feeder.

 

[frenchelectrican]

NQBQDY.,

The set up as Stubie et few other suggest is very common pratice and I have done this all the time on either side of pond.

And this set up will have more than enough capacity for your system for your workshop and a big plus that you will have 240 volts avaiable there so it will not be a issue espcally with med to large compressour ( very common for many peoples to set this up on 240 volts for few good reasons )

But one thing when you plan to do the wiring are you plan to enclose the wall or what ?? That will make the differnce on methold on useing the conductors.

Basically everything on 120 volts will be protected by GFCI recepectale or breaker ( Cheaper use the GFCI receptale at first point then it will be protected downstream )

The 240 volts items do NOT need GFCI at all.

Make sure you get the permit for this one.

Merci,
Marc

 

[NQBQDY]

Ok that all sounds great, thanks again everyone. I will update when I have completed the project or if I hit a snag. Meanwhile have a Merry Christmas.

 

[frenchelectrican]

Ya are more than welcome and keep us posted how you got so far and if anymore issue you run into or need special tips just ask us we will help ya on that.

By the way Joyeux Noël to ya.


Merci,
Marc