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woodman51jfk 12-16-2007 01:36 AM

Wiring New Shop, OK?
I have just put in a new shop building of 1000 sq. ft., and will be running a cabinet making business out of it. This is a one man, one woman operation so using multiple machines is not an issue. At the MOST, it would be a large power tool, and the intermittent compressor cycle. I ran 6/2 w/ground from the main house panel on a 100amp breaker, thru grey plastic 3/4" conduit, under the house, buried about 25 ft. and up into a panel in the run of right at 100 ft. I will be installing 40, 30, and 20 amp breakers for powering 220 shop tools, compressors, and a welder, along with 110 tools & lighting. With the exception of the compressor, all the tools pulling 220 were dual voltage, rewired from 110 to 220. My question for the pros here is: will this set-up suffice, under the parameters of operation I have outlined, or am I looking at needing to pony up for some high dollar heavier gauge wire for the main run........TIA for the input
BTW, we're out in the country, so we don't need no stinkin' inspectors:laughing:

Stubbie 12-16-2007 03:16 AM

6/2 with ground....was this uf-b or some other type cable?? Whatever it is it must be a wet location rated cable.

6/2 with ground will let you have 240 volts only or 120 volts only but not both.... Unless this cable feeder has three insulated wires, one to be used as a neutral, you can only get one voltage to the shop. You cannot use a bare wire for neutral in a sub-feeder. You need individual wires in conduit or a 6/3 G cable rated wet location or direct burial in order to have 120 volts and 240 volts at the shop.

Getting this clarified will lead to the next set of questions. Whether or not the cable is big enough will depend on the amperage of the bigger loads in your cabinet shop...specifically the compressor and welder.

NateHanson 12-16-2007 06:40 AM

If he means 6/2 plus ground, isn't that sufficient for a sub in a detached shop as long as there are no other metallic connections? H-H-G and bond the neutral to ground at the sub. Certainly it would be better to run it with 4 conductors, and float the neutral, but given that he's already done it this way, can't he keep it rather than replace the wire?

HouseHelper 12-16-2007 07:44 AM


Originally Posted by Stubbie (Post 80930)
... Unless this cable feeder has three insulated wires, one to be used as a neutral, you can only get one voltage to the shop. You cannot use a bare wire for neutral in a sub-feeder.

That says it all.

NateHanson 12-16-2007 08:20 AM

Of course. :) I think I skimmed Stubbie's post, and didn't notice that he covered that. I've never been accused of being a good listener.

woodman51jfk 12-16-2007 11:09 AM

Thanks for the response!
I have run just 6/2 w/ground, interior rated, totally enclosed in plastic/PVC conduit, joints glued with Carlon spray adhesive, from a 100amp double pole breaker in the main, 200amp, load center. when it enters the sub panel in the shop one leg ties to one buss, the other to the other, the bare ground attaches to the separate neutral bar, which also has a 6ft copper ground rod driven to 5"8" with 6ga bare copper clamped on. this sub panel in the shop does not have a main disconnect, but only has six breaker slots, maximum 12 120 circuits ( using single width double switch breakers ), 6 high draw circuits, or 3 220 circuits.
It is currently powering lights & small hand tools while I complete the interior, and the largest motor will be the compressor at 6hp, all other 220 are 3hp or lower. The welder is just a crackerbox, dual voltage converted to 220.

I certainly don't question your far advanced experience on this Stubbie, but I have always thought a double pole breaker, with 2 insulated and one bare ground, could provide 110 off of each leg, or 220 using both, and the ground would double as neutral for the 110 circuits. Is this just a "work around" that we 'ol country boys have been doing and gettin' by with??

Surely do appreciate the patience y'all show when someone wanders in here looking for help! I signed up & decided this is where I'd find my answers, after spending a couple of hours reading the "love story" of Andy & Honker!!

JGarth 12-16-2007 11:39 AM

Believe me ... I just had to jump in here....
Pony up son....get a licensed contracror to do that wiring.
YOU are in the category that needs an inspector.
You didn't do any aspect of this wiring correctly.
ie..., breaker size, wire size & configuration, super small conduit (cheap).
I'm Sure glad there are no children in that dwelling.
PS....Do NOT quit your day job.

NateHanson 12-16-2007 11:52 AM

Jeez. Take it easy on the guy. He's just asking for advice. :rolleyes:

Woodman, I think you should pull new cable through that conduit. The 6/2 romex isn't right for that application. I think 60A would be more than sufficient for your shop, so you could run #8 THWN, 4 conductors. It'll be easier to pull. What size conduit did you use?

Put a 60A feeder in your main panel, put a shut-off in the sub panel (unless you plan to have no more than 6 switches total in there), and then you can separate the ground and neutral.

If you don't have the space in the conduit, or you want to save a dime, you could run 3 THWN conductors.

woodman51jfk 12-16-2007 12:35 PM

Thanks Nate, constructive criticism and information is always appreciated. I'll follow along with the advice on the 60amp breaker in the main panel right away, and have to save up a bit for the new wire to pull to the shop thru the 3/4' conduit, ( assuming I can get the romex out! ) There's still quite a bit to do before I move the big machines in, rigid conduit for lights & receps, a separator wall for the finishing booth, and a 3/4" OSB overlay floor, along with fabricating a couple of 10ft. tall doors.

Unfortunately, my neanderthal woodworking budget does not allow for a contractor, and inspectors aren't required out here in the country, and the kids are grown with kids of their I can go about my day job.......which is building cabinetry & furniture...........the Neanderthal Woodworker is a reference to the fact that I still create heirloom pieces the old world way, with nothing but hand tools for sawing, moulding, assembling and finishing, some of my working tools dating back to the 1800's. The power is required for the "production" jobs that pay the bills, and of course lights, classical music on the radio & coffee pot,but I appreciate the input.
Y'all take Care, & thanks again for the constructive criticism & advice,

Stubbie 12-16-2007 12:38 PM

1 Attachment(s)
Hi Woodman

Well there is just so much to explain. First your cable isn't correct and it must come out. Buried conduit is a wet location... an interior rated cable cannot be put in a buried conduit. Conduits fill with water over time and yes I understand your thinking that it won't cause all the joints are glued but you are mistaken. Second you probably have the breaker right but the cable is way to small and its wrong so it must be removed from your conduit. Sorry that is just the way it is. Your running a cabinet making shop so I assume over time you will grow and frankly a 100 amp feeder is prudent in your case. Interior 6/2 cable is only rated for 55 amps so as you can see it is way undersized for 100 amps. A 60 amp feeder will possibly get you by temporarily as Nate has suggested but I doubt it will be good in the long run.
Next the feeder must be 4 wire (H-H-N-G) if you have any other metallic paths existing or being installed between the dwelling with the service equipment (200 amp Panel) and the shop building.

You should run individual wires in conduit but before we get into that we need to know what Nate asked and that is how big is your conduit?

So I am going to give you a list and attach a diagram of what needs to be done.

1) You should be sure that the demand of the shop will not "rob" too much power from the needs of the dwelling service equipment your feeding the shop from....this is called a demand load calculation and is prudent in your case because this isn't a garage it is a cabinet making shop. That coming out ok then proceed. But remember any additions to the dwelling with the service equipment like hot tubs or tankless water heaters becomes a big issue.
2) Individual wires in the correct size conduit sized for 100 amps these can be aluminum or copper wires but they must be insulated and wet rated.
3) Pvc conduit must be buried 18" deep it must be sch.80 where it is above ground and may be sch. 40 underground.

The attached diagram should explain the rest ask questions if needed but if this is in any way more than your wanting to tackle consult an electrical contractor. This diagram is my drawing and is not to be considered as a ' how to ' guide to your installation and should be verified by a knowledgeable person.

JGarth 12-16-2007 12:49 PM

Why didn't you get the proper info before doing this lame wiring installation on your own. The "neanderthal" reference ... I'd doubt that.
Budget is no excuse for lack of safety and rules .... Period.. the mark of lack of intelligence.
Your total lack of electrical knowledge, callous attitude, and poor actions are going to get someone hurt, possibly quite severly. People with this total lack of competance and this type of attitude .. don't deserve any break. They are incapable of understanding what is RIGHT.
Rationalizing these absurd actions is the basis of imcompetance.
Keep the day job .... I bet they wouldn't let you do any wiring in a legitimate shop. And I'm sure glad the kids are gone.
Have a nice day ....

woodman51jfk 12-16-2007 01:25 PM

Great info Stubbie, and many thanks......I'll be using the set up I have for the rest of the construction phase, then pull the romex out & go with the THWN before setting up for worst case I'll just have to un-bury about 40 ft. of conduit to enable a straight pull. If I need to increase the conduit size from 3/4", I can do it at that time, as its just laid on the ground under the house, then buried for about 40ft from house to shop. Again ,many thanks to you and Nate for the advice and information, it will be heeded.

J.........I really do not understand your attitude and confrontational demeanor........I was asking for advice once I found a site where I felt confident of receiving well thought out explanations, before I put my attempt at DIY wiring into operation......your anger, apparently at life in general, flows out through your words. Be glad you woke up breathing, and try to help with sage advice, not sarcastic belittlement, which is totally unproductive, and way less than informative.

Thanks again guys,
Merry and Safe Christmas and Holiday To All,

Stubbie 12-16-2007 01:51 PM

Hi Again Woodsman

I just now see your post about the 3/4 conduit. This will not allow wire the size needed for 100 isn't big enough. It will not even allow #4 for your application. So 60 amp and maybe 70 amp my be what your stuck with but 3/4" is still to small for a cable sized in #6 awg. So if you run #6 awg thwn individual copper insulated wires in conduit you will be ok and it will be good for 65 amps provided that the service equipment at the dwelling is listed for 75 C connections it most likely is unless it is very old. You can verify this by the spec sheet posted at the panel door location. The new panel you installed in the shop will be listed at 75 C connections. If all this checks out you can put the #6 thwn on a 70 amp breaker. Btw if you can go with the 70 amp and 6 awg copper you will only need a #8 ground... if you must go with a 60 amp breaker and 6 awg copper you will only need a #10 awg copper ground. a 70 amp breaker is not real common at the big box stores so you may have to get it from an electrical supply. I would try to go the 70 amp route if at all possible.
Below is a conduit fill table for pvc that will help you with the sizes... generally speaking for diy... use the size conduit that will let you put all the same size wire in the conduit. By this I mean if you have 3 #6 and 1 #8 use at least a conduit that will take 4 #6 wires.

Hope I havent confused you to death. Be careful this is serious stuff.


NateHanson 12-16-2007 03:34 PM

I'm a furniture maker myself, and for a one-man shop (if you're pretty sure it's always going to be a one-man shop), 60 amps is plenty. I've got a 12" 5hp jointer running off an 8 hp rotary phase converter, and I can run a few of the smaller machines in my shop at the same time as the jointer without tripping the breaker. I'd just keep the 3/4" conduit, and pull the THWN that these guys tell you can fit, and put the right breaker on it.

justdon 12-16-2007 05:59 PM

ONE thing to think about IS,,, gophers can and will bite thru 3/4 " conduit,,,the least size you can use without them being able to get their mouths around is 2". I have tried the 3/4 on an underground electric fence installatioon and learned the HARD way!!! BAD stuff happens when a pesky gopher bites into live wires,,,they LOVE to munch them!!

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