Replies

1. 
   saschafer | Jun 17, 2009 11:55pm | #1

   I think a 100 A subpanel is a better choice. It's surprising how those amps add up...

   -Steve

2. 
   stevemorris | Jun 18, 2009 12:03am | #2

   how much will you run at once? that ac unit may draw 4 or 5 amps, fridge a couple, tablesaw saw up to 10 or 12, dc maybe 5 or 6, 50 amps is pushing the limit when you add lighting, a fan, and few battery chargers, stereo etc etc and if its a garage what happens if somebody decides to open the garage door?

   without the ac and fridge you'd be ok but otherwise go for the 100, the cost over the 60 amp is way less than doing it twice

1. 
   highflyercool | Jun 18, 2009 12:51am | #3

   Well, it'll just be me in the workshop.  There is no Garage door.  And one tool at a time will be run ofcourse.  Not real sure bout the fridge, but deffinately a small refrigerated A/C Unit.  I was going to go with a 100 AMP Box but ran into a buddy of mine who works as an A/C istalation/Carpenter and he told me that 50 AMPs would be plenty exspecially if its just me.  And besides I ran 8 guage wire for my subpanel and he said the max for 8 guage is 50 AMPs. 

1. 
   Eef | Jun 18, 2009 01:10am | #4

   high,
   "...not sure bout the fridg...how, pray tell, do you keep your beer cold?
   eef

1. 
   RalphBarker | Jun 18, 2009 01:14am | #5

   Not to mention "freezing" the vodka! ;-)

2. 
   forestgirl | Jun 19, 2009 08:05am | #7

   "...tablesaw saw up to 10 or 12, dc maybe 5 or 6,...."  Those numbers seem pretty low to me.  I know my old Jet 1.5HP contractor saw drew more than that, especially on start-up, and I think the DC does also.  Our OP hasn't said whether his saw is 120V or 240V, missing some data.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-) 

3. 
   northhouguy | Jun 18, 2009 02:02am | #6

   A non-adjustable molded case circuit breaker will only continuously carry 80% of its rating.  So your "50 A" circuit is really a 40 A circuit.  Feeder wires must be sized for 125% of the breaker rating, so your # 8 AWG wire is undersized.  Make sure you don't bond the neutral and ground bars together in the subpanel.  They should only be connected at the main panel. 

   If you haven't already finished this project, or want to re-visit your new supply, I recommend a 100 A, 24 circuit panel.  That way you have room for growth and for just $100 or $200 more you are "set for life."

    

4. 
   BrianDerr | Jun 19, 2009 08:19am | #8

   Even for one man shop, 50 seems pretty limiting. I'm planning on 240v TS and DC--almost 50A right there, not to mention lighting, fridge, stereo . . . even if all 120V, its easy to bust 50A. Is there a a good reason for cutting it this close? If not, go 100A. Tell us more about your tools and shop.

   Brian

1. 
   saschafer | Jun 19, 2009 04:36pm | #9

   If you read between the lines, I think what the OP actual wants is validation for his decision to run AWG 8 for the subpanel...

   -Steve

    

5. 
   JohnWW | Jun 19, 2009 05:08pm | #10

   I would go with a larger box just to have room for more circuits even if I only had a 50 amp feed. It is nice to be able to isolate circuits to the machines and the lighting and refrigerator from each other.

   The circuit breaker that counts for the 8 gauge wire is not the main breaker in the new sub panel. The breaker in the main panel that your shop feed comes off of is the one that has to be sized for the 8 gauge.

   John White
   Shop Manager for FWW Magazine, 1998-2007

6. 
   DougAA | Jun 20, 2009 04:05am | #11

   If you are running normal 3 wire (hot/hot/neutral/ground) supply and using a two pole main breaker then you may have more power than you think available. 

   Assuming you are running all 120v tools (DC /TS/airCond + other stuff)  then you have up to 50amps on each hot to work with.  If you set up your circuits correctly in a balanced way then you are in good shape.
   eg
   on black (hot)  --> lights, fridge, a/c, DC    (maybe 25 amp total)
   on red (hot) --> TS, portable tools, garage door opener (maybe 25amp total)

   You still have another 25amps on each side (or 15 amps if using an 80% loading factor).

   If you have a 240v A/C and 240v TS then it might look like:
   240v(Red+black) --> TS, AC (maybe 20a total)
   120v on black (hot)  --> lights, fridge, DC    (maybe 15 amp total)
   120v on red (hot) --> portable tools, garage door opener (maybe 15amp total)
   With everything running, each leg (red+black) is at about 35amp - well under 50amp per leg (and still under the 40amp 80% factor). 

    

    

   DA

   The goal is not to

   look professional but to be professional.

7. 
   mr_kramer | Jun 21, 2009 03:19am | #12

   I have to agree with saschafer. Murphy's Law says that you will have several things going on with a helper, in the middle of August, and when you least expect it, the fridge will hit. Go a 100 amps and you wont occasionally pull your hair out.

1. 
   wannabeknot | Jun 21, 2009 04:44pm | #13

   Going with a 100 amp panel now would be better than trying to upgrade the wiring for the panel for future growth.  You may want to consider running a dust collector and air cleaner, especially if you work in an enclosed space (I work in my basement). 

   -Tom

    

1. 
   highflyercool | Jun 22, 2009 06:03pm | #14

   Now to clear some things up I will admit I'm a little ignorant when it comes to electricity as far as the amps and what guage wire to run, but as far as the mechanics of it all no sweat.  At first the plan was to put in a 100 amp box but like I said a buddy talked me into 50 amps being enough but I should have went with my instincs.  So if i have to redue my wire job what gauge would I have to use and if so could i keep my neutral/ground at 8 awg?

    

   From the labels on my equipment:  The table saw is a 1 1/2 horsepower 110/220 volt contractor table saw, the band saw is a 1 horsepower 110/220 volt which says it only uses 10 amps,  the jointer is a bench top model which is a 2 horsepower 110 volt, the planer is is also a bench top model which is a 2 horsepower 110 volt at 15 amps, the drill press which is a bench top model which is a 1/2 horsepower 110 volt.  Also I plan to install one maybe two lights.  I even have a 10 gallon shop vac that will help me in cleaning up my saw dust. Now the fridge was a second thought but not for sure.  And now that I think about it a radio would be a must. 

1. 
   saschafer | Jun 22, 2009 06:45pm | #15

   The required wire gauge will depend on the distance from the main panel to the subpanel, and also the type of wire that you use, although I would always recommend SE cable for a subpanel unless it has an underground run. Typically, the number will come out to be between AWG 4 and AWG 2 for copper, and a couple of notches larger for aluminum, but don't just pick a number out of the air. Find someone local (so that they can inspect the actual situation) who knows how to do the measurements and calculations.

   You will need a 4-wire cable (SER, three insulated conductors plus ground, hard to find in copper). Using a 3-wire cable (bonding together the neutral and ground) would make the subpanel a service entrance, and you can't do that without satisfying a bunch of other requirements that are more trouble than they are worth in this kind of situation (and is not allowed at all by some codes). If the shop is in a separate building, you may need to provide a separate earth ground, too.

   -Steve

    

2. 
   DougAA | Jun 22, 2009 11:53pm | #16

   If your big tools (120/240v) are wired for 240v then the amperage will be 1/2.  eg 15A at 120v  will be 7.5A at 240v. DA

   The goal is not to

   look professional but to be professional.<!----><!---->

8. 
   twotowers | Jun 23, 2009 12:30am | #17

   Highflyer/

   I put in a 100 amp service for my shop and recommend it. I run electric heat that can chew through 30 amps in the winter, so I really didn't have an option. I can say that I have never tripped the breaker running heat, stereo, table saw dust collection and may be the jointer at the same time  oh and lights - plenty of lights.

   Here are two really important suggestions. Get a much bigger box than you need. The upgrade is a hand full of dollars, but you will be suprised on how many circuts you will add. I added a new 220 volt Band saw and lathe.....each is wired with separate dedicated circuits  as per the manufacturer instructions.

   The other suggestion is spend a little bit more and make sure your  box has an on/off switch. This allows you to shut off all power in the box when you are installing new lines. By shutting power off inside the box you don't have to run back to the home's main circuit box to turn off the power. This will save you time and end the lazy temptation to work on a box that is live.

   Finally your wiring will determine ultimately what service wire you will end up with and not the circuit breaker. It the wire and the breaker is not matched you run the risk of a fire. What ever you do make sure your safe by having an electrician do the actual hook up of the two boxes....he doesn't have to run the wire in between, or wire the circuits, but he should make sure you basic system is solid to begin with.

   Best & enjoy your new set-up!

   TT