I’d like to build a shed for my workshop, but at this time, I don’t want to go through the hassle and expense of wiring it back to my house through underground lines and such (I have a concrete pad and lots of big rocks in the way). I would, however, like to run a fat extension cable to a big outlet in my house so that I can power my table saw (15 amp) and dust collector (11 amp) and lights, as well as other power tools as needed. I list the saw and DC because they’d be my biggest concurrent power draws at any one time.
I think the best solution would be something like a generator transfer switch in a breaker box in the shed. Then I can run a 40amp 240v extension cable from a home outlet (e.g. a to-be-installed car charger) to the shed breaker box when in use.
Thoughts and other ideas?
Replies
See if you can get the electric company to run a line and put a meter on it. thats what I did. Back then it was free and it costs 5 per month plus elec. used. The run was 1/3 the distance than from my house. Times have changed since then but take a look and don't assume they won't.
We need more info to give good advice.
How far is the shed from the house? The farther, the bigger wire you will need to prevent significant voltage drop at the shed when the motors start up. There are tables that give the voltage drop for the size wire, the distance, and the voltage/current draw. Inadequate wire size risks burning out your motors when they try to start, or get heavily loaded.
Are you running the table saw and DC on 220 or 110? Mixing 220 and 110 usage requires 4 wires: 2 hots, a 220 common, and a ground wire. Without the 4th wire, you will have unbalanced loads on the two hot wires, leading to possible voltage on your one common wire. Not a good idea, as that puts a voltage on the chassis of all your 110 power tools.
Once you have determined the wire size you need, you will need to find out if there is a pre-made extension cord of that size. And the price. I don't know if they exist in larger wire sizes.
I would consult with a knowledgeable electrician before making any firm decisions.
The house is about 15 ft from shed. To be clear, I'm thinking of running a 240v electrical extension cable to a sub panel in the shed, and then the sub panel will distribute the 120v like normal.
So in short, I'd do the following
Main panel 40amp breaker --> 240v Outlet --> 40 amp 240v extension --> generator transfer switch in shed --> 40amp shed sub panel with two 20 amp breakers --> 120v circuits to receptacles (lights, tools)
My tools are all 120 v, and I don't plan on rewiring to 240v
See if the electric company will run a line. Or do it properly, underground. I would not, in any event, run a "permanent" extension cord on the ground.
Do it right. If anything happens you will be liable, and your insurance company will run the other way.
I definitely would not use the extension cord for anything more than short-term use. As in, I am not intending to bury it or leave it out when not actively using the workshop.
As VESPID mentioned above - call the electric company and get them to tell you what you need and how much it will cost (if anything). Mention to them your idea(s). Then call an electrician. You probably know one or know someone who does know one. Have them go through the same procedure - tell them what the electric company told you. They may have a different approach or a better way to do things. If the two differ wildly, get a third electrician to come out.
The point is to get several ideas/concepts/costs and then decide if you want to proceed with your concept or have a separate line installed. The best advice will usually come from the pros.
I followed this procedure when I built a 2 car garage in the back of my house several years ago. I ended up hiring an electrician - worked out for the best.
Good luck!
At 15 feet apart I would consider going overhead. It's a low cost alternative to cutting and patching the driveway.
In conduit you don't have to bury it. But sure you can run an extension cord. I have sheds and I run extension cords but it's a bit of a PIA dealing with cords that way and 40Amp 220 is a bit of a safety issue. Personally, since this is a permanent setup, I'd get a concrete saw ,cut a channel and run my wires through conduit below the slab. Grout the groove when your done.. 15' you could cut the slab with a diamond blade and a circular saw in a couple of hours!
Conduit absolutely does need to be burried. Usually conduit allows a shallower depth, as little as 6 in for steel in many situations.
You'll be fine with the extension cord.
I recommend that you wire the shed up properly internally and run a nice robust cord to a waterproof external port.
Don't forget the length of the wire indoors, but if you think about it, it is more than 15' from the power distribution board to most garages or cookers so such short distances are not a problem.
You can calculate the voltage drop easily enough with a simple online calculator - https://www.rapidtables.com/calc/wire/voltage-drop-calculator.html 2.5mm cross-section wire should be ample.
I used an extension cord from the house to an unpowered garage - would have been about that distance. I just used a standard cheap 10 amp 240V cord and it was fine - when I powered up my jointer (2Kw) the lights would dim briefly but otherwise everything ran fine.
Just one final thing - if you use a reel type extension lead, ensure it is fully extended before use, otherwise it will melt.
I never had a reel for extension cords so I never thought about heat and melting. I just trip over wires. When I fly I always carry an extension cord with me.. if I start to fallout the cord is quaranteed to get caught on something! Anyway, melting cords in reels--- and they sell them? Any giant notices plastered on them? I have my air hose on a reel and have considered doing the same for extension cords...but maybe not.
They do have notices on to extend fully before use. My mother ignored it one day running a line to a tumble drier. The whole thing became a molten mess.
You should consult the National Electrical Code for requirements for running power to outbuildings. Link below, you can sign up to get free access to read thru it. Or hire an electrician who knows the code. The code is there for several reasons: 1. to keep you from killing yourself or others. 2. To keep you from burning down your own or others property. Basically to preserve life and limb! Also as previously mentioned it allows your insurance company to pay for accidents without an easy out. Really not worth saving a couple bucks.
https://www.nfpa.org/codes-and-standards/all-codes-and-standards/list-of-codes-and-standards/detail?code=70
Lord Ulrich, no , both ridged and flexible conduit are approved for above ground application -but if you do bury it there are requirements for depth that changes depending on what materials you use. The requirements have to do with shovels mostly.
I have a scary story that involves a shovel ,6" of dirt and a power company SERVICE DROP in direct burial cable! Needless to say PG&E owes me a shovel! But then they owe a bunch of people whole towns!
As to wire reels --then if you have to fully extend it everytime you use it your not any better off than just using an extension cord. I can use a 12ft extension cord if I need 12' or a 100' extension cord if I need 100' but on a reel I have to use 100'( if it's 100') when I need 12'. Seems dumb!
I think Mom did what many people would do- extract the amount of wire they required and leave the rest on the reel. I don't really want to go all Nader on this but if they can't properly insulate the wire then they shouldn't sell them.
On another note was the wire rated to handle 40 Amp 220 v and had a 3 or 4 prong dryer plug on the end? Seems implausible!
To the op ,Yes, consult code, why not? But if you do consult the power company on this then you will probably end up being involved in pulling permits! Scary prospect where I live!
Pantalones868
I might be a little less definitive with electrical advice since local municipalities adopt and interpret the NEC differently and sometimes you will find variances between inspectors. As far as conduit being allowed to be used above ground the NEC is as usual vague and subject to interpretation. The NEC does state it must be SCH 80 PVC not the more common SCH 40 or threaded steel and states NEC Article 352.30 "Securing and supporting" states PVC and steel conduit must be supported and secured. How would you support and secure it to the ground? NEC Article 352.10 "Uses not permitted" (C) Where subject to physical damage. I would think that if the conduit was lying on grass subject to mowing or across a driveway where it could be run over by a car it would fail inspection 99 times out of 100. I know it would where I live.
As for wire reels; the Ampacity of cables is rated by the ability of a certain cable to disapate the heat that flowing electrons generate to insure that the insulation doesn't melt or start burning. These tests are conducted in open air not with cables wound tightly together with other hot wires, if they tested that way our cords would all be 8GA monsters. Since we all know all orange extension cords are the same and voltage drop is a myth go ahead and load that 100ft 14GA Chinese cord on your reel and run your 15 A load through it, what can go wrong? For me there is a reason all my cords are 10GA and not longer than 50 ft.
NEC states that cord shall not be used as a substitute for fixed wiring methods. Some will note that manufactured structures, mobile homes, etc. cord connect to a feeder or service. Your shop is in a grey area. In cases where cord is permitted it must be protected from physical damage--vehicles, lawn mowers, etc. Cord for a 40A circuit would require #6 conductors, pretty fat, almost an inch. #8 conductors in rigid conduit only 4 or 6 inches under the slab is a much better permanent solution. 1/2 inch rigid conduit is surprisingly easy to work with. Hiring a qualified electrician is your best choice for a safe, reliable installation.
Regarding a cable reel. The product must be used according to the manufacturers' instructions. Assuming it was a listed reel I doubt it was ever tested (listed) for use in the wound up state.
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