Running 220v/100a to my Detached Garage/Future Shop - Woodworking Talk - Woodworkers Forum
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post #1 of 82 Old 09-22-2018, 12:12 PM Thread Starter
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Running 220v/100a to my Detached Garage/Future Shop

Aside from recovery from a broken wrist, the biggest hurdle to me setting up my shop and getting back to serious woodworking at the new house is the inadequate electrical power in the 20x24 detached garage.

My old shop was in my basement right near the main breaker box, so running 220v service for my Unisaw was trivial. Now, I'm looking to set up shop in a detached garage about 45 feet away from the main house. The plan is to set-aside 10x20 feet of space for my 1967 Volvo (plus space for spare parts & automotive tools) and use the rest of the space as my new woodshop.

The garage has a little power already... one 15amp circuit for the garage door opener, lights, and a single GFCI outlet. Period. The power runs from the house in a PVC conduit, under an asphalt driveway, and surfaces at an elbow before entering the garage on the side wall. There's no sub-panel, just a master flip switch for the whole place. Not at all adequate for much anything.

Between my Tablesaw, Radial Arm Saw, Air Compressor, Dust Collector (and eventual Mig welder), I know that I need two or more 220v circuits, plus a couple dedicated circuits for lights, chargers, and smaller power tools. From other threads on this forum, and some web searching, I know that I'll need at least 60 amp service to the garage - probably 100 amp, just to be sure.

I've read up and watched a few videos on the topic and I realize that I've got more factors here than just the breaker size, wire gauge, and outlets per line.

I'm not afraid of doing my own electrical work, but I expect that I'll need to contract this out due to the complexity with wire depths, grounding, code-compliance, and general safety. I've never wired anything larger than 20 amps by myself, and 60 amps with knowledgeable direction.

That said, I was hoping for some opinions on how to tackle this project, even if I pay someone else to actually do the work. If I do pay someone to do this, I want to have the right information available. What sort of key information items do I need to establish (e.g. existing wire depth, total amps needed, etc.)?

I think what needs to happen is this:
1) add a service panel in the garage
2) replace the 40-50ft of wires in the buried pvc conduit with 100 amp appropriate gauge wires
3) add 100 amp breaker to my indoor panel (there's plenty of space for one)
4) hook up everything (use anti-corrosion paste if aluminum wire is used for the run)
5) add supplemental ground rod by garage..?

Whether I do this myself or contract it out, does it appear that I am in possession of the relevant key bits of information? Am I overlooking anything really important with this sort of upgrade. If I do contract this out, is there anything else I should be asking about?

My deceased father-in-law generally advised me on electrical matters, but that's no longer possible w/o a Ouija board.

Thanks for any thoughts and advice.

Last edited by RepairmanJack; 09-22-2018 at 12:16 PM.
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post #2 of 82 Old 09-22-2018, 12:41 PM
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First question -what size is the conduit?
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post #3 of 82 Old 09-22-2018, 12:50 PM
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how big and deep is the current pvc conduit?
is it continuous under the drive or just stubbed up at each end?

if you have 3/4'' pvc conduit already under the driveway at least 18'' deep, consider running a 60 amp sub-panel
you should be able to run four #6 thhn/thwn copper thru 3/4 pvc conduit, #6 is good for 60 amps
60 amps will run a lot of equipment in a one man shop
even if the pvc is not deep enough, while not to code, you will probably be safe enough under asphalt

100 amp, 240 volt circuit needs to be 24 inches deep for direct burial
if you come out of the existing house panel you will need 4 wires to connect a sub-panel
if you come out of the meter base it is considered a panel and you can use 3 wires
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post #4 of 82 Old 09-22-2018, 01:31 PM
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Go with 100 AMPs

If you go big now, then you're all set for later... for just a few dollars more. It ain't the cost of the parts, it's the digging and running the conduit. Do use conduit! Leave the smaller conduit there for phone lines, alarms whatever.

I use Square D QO breakers and panels all through the garage, shops and house. The main panel has a 100 AMP breakers to supply the sub panels in the garage and shops.

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #5 of 82 Old 09-22-2018, 02:25 PM
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Quote:
Originally Posted by woodnthings View Post
If you go big now, then you're all set for later... for just a few dollars more. It ain't the cost of the parts, it's the digging and running the conduit. Do use conduit! Leave the smaller conduit there for phone lines, alarms whatever.

I use Square D QO breakers and panels all through the garage, shops and house. The main panel has a 100 AMP breakers to supply the sub panels in the garage and shops.
Second the Square D QO advice.

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post #6 of 82 Old 09-22-2018, 04:45 PM Thread Starter
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The grey PVC Conduit is 1-1/8" OD and I have to assume that it was installed to code as the garage itself was built between 2002-2007 in a town where building something this big requires permits - or else. Heck, they want a me to get a permit to assemble my HF 10x12 greenhouse. The asphalt went in over gravel about the same time. It's over the top of the conduit and I would not look forward to lifting and smashing that much material. I busted up and lifted about 200 sq feet of the stuff so I could squeeze in a garden back in spring.

I guess (aside from safe wiring) my big concern is the sufficiency of the existing conduit. Is it deep-enough and big enough for the wiring? Code seems to state that even a 15 amp line has to be 18" down


I could live with 60 amp service if that's what would fit. 100 amps would be worth the extra expense, as long as I didn't have to go through all that asphalt and lay new PVC. However, it sounds like it's probably not deep enough for 100 amp, and I'm not planning to replace the asphalt for a couple years - if ever.


Here's the space in question. The line leaves the house (right side of photo just in front of the concrete pad) and runs to the left side of the garage door - in the breezeway where it goes through the siding.

Last edited by RepairmanJack; 09-22-2018 at 04:48 PM.
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post #7 of 82 Old 09-22-2018, 06:30 PM
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time for some professional advice

An electrician would know what size 3 separate conductors will fit inside the 1 1/4" OD conduit. That's an important question and will determine which size panel you can use. Romex is flat and may be wider than 3 individual conductors, so it won't work as well. Nice looking site and building!

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #8 of 82 Old 09-22-2018, 06:57 PM
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Just because you move into a larger shop doesn't mean you would be using very much more power. I have a 6000sq. ft. building with mostly industrial equipment and I run it off a 60 amp circuit. The biggest difference is lighting since you still would only run one machine at a time.

Since it is a separate building your additional service panel needs to be a sub-panel and they are wired different than you main breaker box. You isolate the neutral and ground wiring plus install a ground rod just for the sub-panel.
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post #9 of 82 Old 09-22-2018, 07:23 PM
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Contact some electricians and let them bid on the job. Our city/county would require something like to have a building permit and be inspected at the beginning and the end of the job. Plus, if they mess up, the liability is on them and the inspector. Then you call a lawyer.

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post #10 of 82 Old 09-22-2018, 08:05 PM Thread Starter
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Thanks, that's been my thinking. This is probably not the time to stretch my skill set and luck and risk burning up my car and all my tools.

I'm dealing with some existing stuff installed by the previous owners. Over 14 years the previous folks seem to have done very little to the house and garage and they contracted out of what they did actually do - not very handy people. I'm pretty confident that the garage was done professionally - it has a truss roof and the limited wiring looks to be code.

I'm glad for the advice. I'm still got months of wrist healing and physical therapy ahead of me, before I'll be wanting to do anything major, but if a professional electrician's touch is needed, at least I have the time and luxury of shopping around.

I wanted to have a realistic sense of what I could do with the existing conduit and generally meeting my shop needs.You;ve help me get there.


I ran my old basement shop off a 20 amp tool circuit, 15 am lighting/air cleaner circuit, and a 20 amp/220v circuit for the unisaw. I'm adding a dust collection system this time, so that's the main change. It's a one-man shop, so I'd never be running more than two 220 machines at any time (dust collector, table saw).

I guess, I'll be looking for some skilled professionals. Very much appreciate the thoughts and suggestions!

Last edited by RepairmanJack; 09-22-2018 at 08:07 PM.
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post #11 of 82 Old 09-22-2018, 09:18 PM
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Hey there Jack ...

You can go with a 60 AMP panel, but here's why I like a 100 AMP.
You can leave all your major stationary tools plugged in. No need to swap out cord and plugs in the middle of typical operations. You can run several separate 20 AMP circuits for the hand held power tools and bench top tools. You will want to have 2 lighting circuits. You may want ceiling fans for comfort cooling and exhaust fans for air fums and dust extraction. Gonna do some welding? Gonna have a hard wired air compressor? All this adds up fairly quickly. My 100 AMP wood shop panel is FULL. Remember, 240 V machines require 2 slots per breaker and the 100 AMP gives you lots of slots.

Ya can't go back and make it right afterwards. FWI, I have 4 - 100 AMP panels, a 175 AMP Main and a 225 AMP Main with 400 AMP service. OK, that's a bit much for a typical house. But, add in a garage and two shops and I'm glad I went "overkill".

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #12 of 82 Old 09-23-2018, 10:59 PM
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Since I don't see it discussed here yet I'll ask: what is the amperage of the breaker panel you want to feed this subpanel from? The NEC states that each overcurrent protection device should be half(or less) of the upstream device feeding it. So if you don't have at least a 200 amp service, 100 amp is too big to feed from that panel.

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post #13 of 82 Old 09-24-2018, 09:36 AM
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+1 on hiring an electrician to at least install the service - too many factors for us to evaluate and offer advice on from here. most are glad to let you help and learn. have him install the minimum box, and he may guide you on the box install and rough wiring, and come back later to check it out. if you are intent on DIY.
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post #14 of 82 Old 09-24-2018, 12:06 PM
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+1 on hiring an electrician to at least install the service - too many factors for us to evaluate and offer advice on from here. most are glad to let you help and learn. have him install the minimum box, and he may guide you on the box install and rough wiring, and come back later to check it out. if you are intent on DIY.
Excellent advice, just bear in mind that a lot of the people offering solutions in forums like this have actually no idea what the code calls for, and it sounds like the local inspectors are on the ball, which in the long run is a good thing.

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post #15 of 82 Old 09-26-2018, 11:31 AM
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Quote:
Originally Posted by RepairmanJack View Post
I ran my old basement shop off a 20 amp tool circuit, 15 am lighting/air cleaner circuit, and a 20 amp/220v circuit for the unisaw. I'm adding a dust collection system this time, so that's the main change. It's a one-man shop, so I'd never be running more than two 220 machines at any time (dust collector, table saw).
"It's a one-man shop" you'll be fine with 60 amps run in the existing 3/4" conduit. if you ran your old shop on those 3 circuits, you could double the load and still be fine with 60 amps. the more 240 volt tools you have the better as the load is half the amps split between 2 legs. the total breakers you have, has nothing to do with the load your using. you could have a 40 space panel with a 60 amp sub panel and still be code compliant, even though the breakers add up to 200 amps or more.

my 50x50 barn/shop had an existing 30 amp 240 service going to it when i bought the property. always figured i'd upgrade to 100 amp but i've managed for the past 20 years. the 240 volt compressor is always on when i'm out there, i also have a 120 volt mig, table saw, band saw, lathe, drill press, radial arm saw, drum sander, delta air cleaner and a plethora of hand power tools. led lighting has really helped reduce the problems i had vs the old 12t florescent bulbs, turning on the table saw in cold weather, use to put me in the dark for a few seconds

imo, once you have healed up this is definitely a diy project. getting the inspector involve would only cost you more money and you'd be at the mercy of the inspector and his mood of the day. inspectors are under paid civil servant wanna be electricians that never had the skill set or smarts to actually get an electrical license, they enjoy making a point of their lack of knowledge. i know, i was a licensed electrical contractor for 25 years

if you wanted to upgrade to 100 amp later, all you'd need to do is run the underground service to the sub panel, though i guarantee you'd never do it.
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post #16 of 82 Old 09-26-2018, 11:43 AM
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You can go with a 60 AMP panel, but here's why I like a 100 AMP.
You can leave all your major stationary tools plugged in. No need to swap out cord and plugs in the middle of typical operations.
i don't get this. what does having a tool plugged in have anything to do with load? i have 8 stationary tools plugged in and a direct wired compressor. a tool plugged in has no load until you turn it on. a one man shop can only have so many tools on at one time
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post #17 of 82 Old 09-26-2018, 01:08 PM
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i don't get this. what does having a tool plugged in have anything to do with load? i have 8 stationary tools plugged in and a direct wired compressor. a tool plugged in has no load until you turn it on. a one man shop can only have so many tools on at one time

Very true. However, I would not use that as an argument against putting in a 100 amp circuit. I would always go with the most capacity that was practicable/affordable.


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post #18 of 82 Old 09-26-2018, 02:10 PM
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Did I mention load?

Quote:
Originally Posted by _Ogre View Post
i don't get this. what does having a tool plugged in have anything to do with load? i have 8 stationary tools plugged in and a direct wired compressor. a tool plugged in has no load until you turn it on. a one man shop can only have so many tools on at one time
It is a "convenience" to not have to swap cords and plugs in the middle of an operation. That has nothing to do with the loads on each tool or the total load. I could easily draw 100 AMPs by turning on all my tools, air compressor and wall heater at the same time, buy why would I do that?

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #19 of 82 Old 09-27-2018, 01:54 AM
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Long story /short version

When an addition was added to the house a 100 Amp sub-panel was added to the shop, er garage. All shop wiring is via conduit. While running power to the various tools I noticed that the ground (green) and neutral (white) bus bars were not connected in the sub panel. Odd I thought and a simple fix.

WRONG

As soon as I connected the cable to the TV in the garage we started getting occasional pixelation on all the TVs along with other annoyances. It took me awhile to realize that the cable is basically an analog device and the extra wire in the sub-panel was creating a ground loop. Removing the extra jumper solved the problem.

There are some anal retentive inspectors that will require the jumper in the sub-panel. Pit it in to make them happy. Just remove it before you put cable TV in the shop.

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post #20 of 82 Old 09-27-2018, 06:52 AM
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neutral and earth ground are tied at one location in a residential service, in the MAIN panel only, and should be electrically isolated from there on out. subpanels included - not connected - ever. very surprised that an inspector made you install a jumper!!!!
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