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Thread: Electricity for shop

  1. #1
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    Electricity for shop

    After figuring out the maximum load I plan to run at one time, how much extra should I add for what amperage sub panel to put in my new shop? The main house is 125 amp service, and I want to figure out if I really need a service upgrade.

    Thanks!

  2. #2
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    Oh, my. Most houses today have a 200 amp service, at least out here. All electric houses with AC can consume lots of electrons at one time. Even a non-all electric house has a greater constant load than we realize. I would want a 100 amp box for the shop if I could get it. Running a TS with dust collector, with overhead dust filter, lights, and an air compressor that can come on automatically presents quite a load in and of itself. If the house had 200 amp, running a sub panel for 100 amp might be doable.

    I can feed my shop trailer a 50 amp service. And I have to shift the motorhome to its generator to do that. I cannot allow the air compressor to be on unless it is the only thing I am using. I have to be careful running the TS or any other tool with DC and air filtering. The lights are all CFL's but divided into two circuits.

    You are wise to add up your loads, but it can be a daunting task.
    ++++++

    Some say the land of milk and honey; others say the land of fruits and nuts. All together my sort of heaven.

    Power is not taken. It is given. Who have you given yours to? Hmmmm?

    Carol Reed

  3. #3
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    Carol, are most of your big tools wired for 120 or 240? I have mine wired for 240 already and it halves the amp draw. This, was partly to me never getting around to running a sub panel to the attached garage at the old house and using temporary wiring from the dryer outlet.

    My compressor only gets turned on when I need it. I don't use air often enough to justify the energy cost of leaving it on auto.

    The stove, dryer, hot water and furnace are gas. Speaking of, I need to reelectrify the furnace, as the romex to it was cut.

  4. #4
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    The TS and the lathe are 220v. I had considered a bigger compressor at 220v but I am trying to downsize. Because the shop is now in a 24' cargo trailer I have had to make some defining decisions with regard to tools. I just finished the outlet wiring for both 110v and 220v. Lights are next but a move is coming up first. BTW, I have not in the past intentionally left the air on auto when not in the shop, but I do turn it on and work on something else while it fills the tank. That's where I have flipped breakers in the past. This new set-up will be educational. To say the least! LOL!
    ++++++

    Some say the land of milk and honey; others say the land of fruits and nuts. All together my sort of heaven.

    Power is not taken. It is given. Who have you given yours to? Hmmmm?

    Carol Reed

  5. #5
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    Mark, my house is 100 amp service.

    My machines are wired for 120, although I have one 220 line out there.(I run the TS off it with the DC)

    Forgetting about the costs, filing for a 200 amp service upgrade for me, was not a can of worms I cared to open.(my village frowns upon people working in their garage, so I decided no inspectors for me)

    My house was built in 1948, finished in 49 or 50, and from what my local electrician told me when he put in the other lines, they don't permit homes in my village to upgrade, unless its a commercial business.
    whatever, my point is that Ive been operating like this with full equipment since nov 2008, and yes, I blow fuses now and then, mostly in the summer with AC's running, but if I keep as much off in the house as possible, I have little problems.

    Id love to put in a larger jointer and planer, but I don't have the juice.

    you can run your shop on 120 power.
    Human Test Dummy

  6. #6
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    Allen is giving great advice. The secret is load management, don't try and run everything at once. The other thing is that your 220 service provides 2 110 circuits sharing a common neutral to the main lines. You need to be wired so you run off both sides of this. That is where many garage shops suffer. They have 1 110 line servicing the garage shop. You need at least 2 circuits and need to try and split your tools running at the same time between them. If you have a 110 dust collector that will be running when your table saw runs it may also run when your planer runs and your sander runs ect. But your TS and lathe or planer sander ect won't likely run at the same time. So your Ts, sander. lathe, planer ect can share a circuit as they will usually trun one at a time and you can make sure they do. So they can be on one circuit while your dust collector would be on another circuit and should be on the other side of the service line as well. Probably a good idea if you have a compressor it could share a line with the Dust collector. When the clothes dryer is running or an electric range is being used just do some hand work or clean up. And the other thing is if you can run tools off 220 they always run more efficiently off of 220 than they do 110. The current is cut in half and that cuts down on the line losses. Not that you can't run off 110 and I do except for my Air Compressor but if I was wiring from scratch it would be 220 all the way.

    Garry
    Last edited by Garry Foster; 08-26-2013 at 01:21 PM.

  7. #7
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    Mark, sounds like you're on the right track adding up all the scenarios of things that may run at the same time (lights/TS/DC, lights/compressor, lights/lathe/DC, etc...).

    If you were upgrading service at the house, I'd go with 200 amp at the house and 100 amp to the shop. If you're looking to stick with 125 amp at the house I'd still consider a 100 amp in the shop if you have room and code will allow. Now you may throw the main at the house if you have too much running between the two locations, but you'll learn when you can/can't draw more power. My thought is that you're paying for the service to the shop once and don't have to upgrade it again if you decide to replace the house with a 200 amp later.

    EDIT: I asked one of our electricians here at work. He said that your sub-panel size will depend on the rating of the breaker tab size of your existing main panel. The tab is the part that the breakers clip onto when snapped on to the main lug. It should list what the maximum size of breaker it will support, some older ones have a max of 70, but most newer ones are rated up to 100 amps or more. Check that and it will narrow down what you can do if you're going to use the existing main.
    Last edited by Darren Wright; 08-26-2013 at 03:40 PM.
    Darren

    To a small child, the perfect granddad is unafraid of big dogs and fierce storms but absolutely terrified of the word “boo.” – Robert Brault

  8. #8
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    Darren, great minds and all that. I'd decided to put in a 100 amp main breaker with 100 amp capable cable, but then put a smaller breaker supplying the shop from the service main. This way I don't take out the house, but am ready to go if I do upgrade service later.

    Now time for some code book reading and researching.

    Is it silly to get a box that uses breakers in common with the house service main? That takes Murray breakers available at Lowe's. I think thelabel says QP but I have to check.

  9. #9
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    Quote Originally Posted by Mark Kosmowski View Post
    Darren, great minds and all that. I'd decided to put in a 100 amp main breaker with 100 amp capable cable, but then put a smaller breaker supplying the shop from the service main. This way I don't take out the house, but am ready to go if I do upgrade service later.

    Now time for some code book reading and researching.

    Is it silly to get a box that uses breakers in common with the house service main? That takes Murray breakers available at Lowe's. I think thelabel says QP but I have to check.
    Nope, not silly at all, good to have a place to get spares in a pinch and don't have to remember what brand you need to get for one vs. the other.
    Darren

    To a small child, the perfect granddad is unafraid of big dogs and fierce storms but absolutely terrified of the word “boo.” – Robert Brault

  10. #10
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    Quote Originally Posted by Mark Kosmowski View Post
    Carol, are most of your big tools wired for 120 or 240? I have mine wired for 240 already and it halves the amp draw.
    Not exactly, you are effectively drawing half the amps on each leg - but you end up with about the same amp draw overall (i.e. you're drawing 2 * 5 amps instead of 1 * 10 amps). The motor might be slightly more efficient and there might be a smidge less loss but in the grand scheme of things its not really meaningfull (at our scales).

    As to your original question - agree that the best way to answer that is to sit down and add up all of your actual load. If you can get a clamp on ammeter that will remove a lot of the guessing from that process, especially if you can get one that can log load over a period of time or at least peak loads. Its worth checking what the burst load is when tools/etc.. turn on as pretty much all electrical equipment takes a lot more power on turn-on than under continuous load.

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