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stqevo 09-02-2009 01:59 AM

Wiring shop need advice
I am wiring a new shop building and need some advice. I have a couple of electrician friends helping but just want to make sure we are doing this job correctly.
Firstly we are running the wire out to the shop from the elec box on my house. There are 3 empty slots and I am told the box will handle the load. The shop is aprox 90 feet away. We have run 2 conduit1.5inch buried underground. The conduit is aprox 90 feet in length to the building. We are going to put a sub panel out in the shop.
Now for what I will be using in the shop. I have your standard air conpressor 110v, maybe a 110v bandsaw and miter saw also. I want to have the standard wall sockets for general use. I also have a new Inverter tig welder that runs single phaze 230v, and I know it has a 50amp plug. Also
  • 230 V, 1-Phase Power
Rated Output
  • DC: 150 A at 16 VDC, 20% Duty Cycle
  • AC: 150 A at 16 VAC, 20% Duty Cycle
Welding Amperage Range
  • 10 - 165 A
Max. Open-Circuit voltage
  • 80
Basically knowing little about electrical I am depending on my friends for help. I just want to be sure they are wiring the shop up to what my needs are. I guess if someone could give me some advice as to what size wiring, breaker, etc. for this setup that would be such a huge relief.
I've spent a ton of $$ on this building so far, about $20,000. It is almost 1000sq/ft, with metal roof and hardie paneling. I've graded and leveled and also poured the concrete and put the building up myself. This electrical is out of my league so far. Any and all help will be greatly appreciated..thnxx..

oilseal 09-02-2009 05:56 AM

stqevo: You haven't indicated the wire sizes running to the shop. For serving the welder, I'd use a 6AWG line. For the rest a 12AWG should suffice.

stqevo 09-02-2009 11:43 AM

That's what I was asking what size wire to run to the building. I was thinking 6awg and was told this. anyone else?

J. V. 09-02-2009 12:12 PM

Hold on a minute. How can you already have a box as you call it with "3 empty slots" but are now running a 1.5 inch conduit and want to know what size wire you need? This makes no sense. Do you have a temporary power source?
First, you should have posted before you poured that slab. You could have saved yourself some work. Second, if you already have a panel why do you need another one. (It's a code violation by the way).

I suggest you take a step back and tell us what you have and what you want to do.

stqevo 09-02-2009 12:25 PM

I am running off of the house box, through 100foot of conduit to the shop. When I poured the slab I went ahead and ran the conduit up through the concrete bed. I went ahead and ran 2 pieces of conduit and we have run 2 pieces all the way from the house box. We are planning on having a sub panel out in the shop. I meant to say that there are 3 empty slots in the house box, I was told the house box was adequate to run what I need out in the shop. thnxx

Scuba_Dave 09-02-2009 01:25 PM

Nice - planning ahead

Will multiple people be working in the shop at once?
IE you might be welding & a friend mught be there working on something else

What size Service Feed to the Main house?
What size sub are you thinking of running to the shop?
Any heating/AC in the shop?

I don't know anything about welders, despite what you posted :(
But the Panel power has to be greater then what the Mig uses

Stubbie 09-02-2009 02:44 PM

We definitely need the info Scuba asked for.....:)

As for the welder let the cord be your guide to the branch circuit. I wouldn't play around with downsizing the wiring to the 50 amp cord and plug welder. It is likely you could but we need the welder model number and manufacturer. We often can go to the website and pull the breaker and wire size recommendations from the owners manual if you give us that information..

Not having that then wire the welder for a 50 amp branch circuit. You have two choices. If you supply the welder with a cable like NM-B (romex) then you will need 6 awg copper. That would be 6/2 with ground since the tig would likely be 240 volts.

If you run thhn in conduit (like emt) then you can supply the welder with 2 #8 awg and one #10 green ground or the emt for ground. Better I think to run the ground wire over the emt ground in your case.

Reason for the difference is that NM-b is required to use a different ampacity column than wires in conduit.

FWIW...I much prefer emt and individual wires for the shop equipment finished walls or not.

I dislike PVC looks like crap IMO. Use it for underground wiring runs or exposed outside.

stqevo 09-02-2009 11:42 PM

This is my plan so far with my friend that is the electrician. Run two 6 awg conductors with a 8 awg ground from your main panel. That should be good for a 60 amp breaker in your main panel. Then we'll want to run a sub panel in your shop itself, and yes we'll need to drive a ground rod and ground the panel so that way if it gets struck by lightning we'll be well protected. From there we will need a 30 amp two pole breaker that will be exclusively for the welder. We'll use a 20 amp single pole breaker for the receptacles and a 10 amp single pole for the lighting circuit.
The welder is a Miller Diversion 165. I will not be running any AC/Heat at this point. At this point these are my plans for starting off, I need to grow my business then I can also upgrade my equipment and electrical to fi the demands of the new equipment. This should however get me through the next year or so with no problems.
The air compressor that I will be using is a 110v general output, small to medium sized unit. Nothing big at this point, your standard buy it at Home Depot special. The other equipment will also be standard light duty semi professional 110v, such as Bandsaw and bencktop grinder, standup drill press, miter saw, etc. This is a 1 man operation and more times than none I will be the only one operating this equipment. So no double duty at this point. The welder and air compressor will not be run at the same time, not at this point in time.
In setting this up I have found there are countless ways to accomplish the same electrical design. Depending on what area of the country you could get many typical answers as to handle my needs for this particular shop setup.
You guys in the know , take a look at my electrical plan. Any help, info will go to reassure me that my electrician friend is leading me in the right direction. As I have stated my budget is limited. I've spent upwards of $20,000 at this point, so I have to be careful to watch my spending. However; I am Not one to cut corners or spend money to down the road in a few months have to spend more $$ to FIX a problem that could have been avoided in the original design plan. Thanxx to everyone for your input, I do appreciate it very much. Tell me what you think of what we are planning on doing.

Stubbie 09-02-2009 11:58 PM

You have a 200 amp service to the house?

stqevo 09-03-2009 12:17 AM

I'm pretty sure it is, my main concern was if it was ok to run off my home box. Granted this is a rural area but I don't want to overburden the system in my home. Explain your concerns. As I have stated previously my electrical knowledge is not what it should be. I have through the years obfuscated and relied upon skilled elec tradesmen.

Stubbie 09-03-2009 12:42 AM

1 Attachment(s)
Here is a link to your owners manual

This is the specification to your diversion 165...give this to your electrician. Your minimum wire size is 14 awg AC or DC mode so 12 awg is all you really need to upsize to using conduit and thhn. If cable I'd go with 10 awg as you plan. 30 amp breaker. Welders because of duty cycle allow larger breakers than what the wires size may imply. But your plan of 30 amp breaker on 10 awg is fine if that is what your electricians wants.

Here are the electrical requirememts for the branch circuit. It is always nice to have a wall mounted disconnect right above the receptacle but you can use the circuit breaker if you like as the disconnect. The manual shows the wall disconnect as a recommendation.

stqevo 09-03-2009 12:47 AM

Thnxx stubbie..I know I looked all over that manual both the copy I have and the online version. I definitely missed this electrical chart for the wiring and the conduit. Thnxx again...I just went right by it I guess when looking through the pages. See it never hurts to eyes are better than 2

Stubbie 09-03-2009 01:05 AM

2 Attachment(s)
Sure supplying the sub-panel from the house is fine. I'd say a 60 amp sub panel is good for your present needs and you have a 1.5" conduit (2 of them) out to the shop so you can always pull in a bigger wire if you want to upgrade someday. For the money and to get enough breaker space get a 100 amp sub panel. And feed it 60 amps using 6 awg thwn or thwn-2 in conduit for the conductors and 60 amp breaker in the house panel. I prefer the kind that take full size breakers not the 1/2 size ones.

If you run any metal paths like water pipes or data/ coax/ phone/cables to the shop you must run 4 wires (H-H-N-Grd) for your feeder and not bond neutral and ground. If your on the 2008 code cycle at your local jurisdiction you must run 4 wires or your local jurisdiction codes may require it. I'm going to attach two drawings one is a 3 wire feeder to a detched building from a house panel (service equipment ) and one is a 4 wire you will notice that in the 3 wire like you are doing now you bond neutral and ground and in the 4 wire you do not bond them. Show these to your electician but he likely already knows this.

The shop must have a building disconnect the easiest way to do that is get a main breaker sub-panel. It must be mounted very near where the feeder enters your shop. If you don't want it there then buy a disconnect in a seperate enclosure and put it where the feeder enters then buy a main lug only panel and put it where ever you want.

Your ground wire for 60 amps feeder can be #10 awg but a #8 is fine and is good for 100 amps. Good luck

Here are the drawings....

Stubbie 09-03-2009 01:18 AM

Just as a side note to avoid any argument with your electrician. 6 awg thwn or thwn-2 in conduit has a 65 amp ampacity. There is no 65 amp breaker so you are allowed to protect it with the next size up standard breaker which is 70 amps. Your choice... 60 or a 70... either is fine.

J. V. 09-03-2009 12:18 PM


Originally Posted by stqevo (Post 322862)
I am running off of the house box, through 100foot of conduit to the shop. When I poured the slab I went ahead and ran the conduit up through the concrete bed. I went ahead and ran 2 pieces of conduit and we have run 2 pieces all the way from the house box. We are planning on having a sub panel out in the shop. I meant to say that there are 3 empty slots in the house box, I was told the house box was adequate to run what I need out in the shop. thnxx

Excellent planning. You did everything I was going to tell you, you should have done. :yes:
It looks like Stubbie has you fixed up. Good Luck and Good Job.

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