Workshop sub panel

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  #1  
Old 02-23-16, 09:38 PM
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Workshop sub panel

I would like to add a sub panel to an area where I am building a workshop in my basement. We have 200 amp service info the house with a 40 circuit main panel, which also feeds a sub panel (8 circuits, original power to house). There are numerous breakers open in main panel.
The sub will be approx 60 feet from main panel, running through unfinished basement. I would like to be able to run my tools (table saw, jointer, planer, dust collection) off the new sub panel. It appears my table saw and planer draw the most amps (15). But only 1 tool plus dust collection would be run at same time.
I was told to pick up a 125amp panel which I could feed from a 100 amp breaker. Does this sound right? Or should I use 100 amp panel?
What size wire do I need for this? I have attempted to read the NEC chart for wire size but it's made my head hurt.
Any and all information is greatly appreciated! Thanks for your time!
 
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  #2  
Old 02-23-16, 10:39 PM
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I was told to pick up a 125amp panel which I could feed from a 100 amp breaker. Does this sound right? Or should I use 100 amp panel?
A 100 amp panel is more common and probably a bit cheaper. The loads you have should be fine on a 50 or 60 amp feed. For that you can use 6-3 NM-b (Romex) or THHN/THWN in conduit (L1-L2-Neutral-Ground). Since the subpanel is in the same building you can use a main lug panel and will not need a ground rod.

Why the feed will be less than the panel rating a 100 amp panel is use so you have an adequate number of spaces.

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  #3  
Old 02-23-16, 10:40 PM
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Yes you can use 100A breaker to feed 125A panel. Breaker just needs to be smaller than what sub panel is rated for.

For wire between main and sub panel, you will need 3 AWG conductor.
You can run 3-3-3-5 SER cable or 3 AWG THHN in conduit.
THHN in conduit probably is cheaper as long as you don't have too many turns.


---- EDIT -----
As ray2047 said, 6-3 NM-b on 50A breaker will be enough for you are planning on running. It is also cheaper.
 
  #4  
Old 02-24-16, 07:03 AM
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Consider using aluminum SER, it's a lot cheaper than copper. You need #1 Al SER for 100A, #4 Al SER for 60A, #6 Al SER for 50A. SER is installed the same as NM-b (Romex). I suggest 60A is all you need.
 
  #5  
Old 02-24-16, 12:06 PM
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Thank you all for your help!
If I would like the option to run other circuits outside of my workshop to shorten the run from my main panel, is 60 amp still OK? Is there a benefit in this situation to run 100 amp vs 60 amp? Thanks again!
 
  #6  
Old 02-24-16, 12:19 PM
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If I would like the option to run other circuits outside of my workshop to shorten the run from my main panel, is 60 amp still OK?
Actual loads are the determining factor. Once up on a time the average house used a 60 amp circuit. As to shortening the run there is no need to do that for circuits already in place. Distances in an average home don't have a significant effect. You could use conduit instead of cable so the subpanel could be more easily upgrade but I doubt it is worth the extra work.
 
  #7  
Old 02-24-16, 04:40 PM
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Is there a benefit in this situation to run 100 amp vs 60 amp?
Not really. 100 amps is a huge amount of power especially in an existing house. Like Ray said, there was a time when entire houses only had a 60 amp service and some of those had electric ranges and water heaters.
 
  #8  
Old 02-25-16, 08:38 AM
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I've decided on a 60 amp breaker feeding a 125 amp panel with 6/3 Romex wiring. Does this sound right?
This is what Lowe's told me will work, I was just confused on the numbers. I can still wire my shop and any other new wires I need to add (outside lighting for example) and not overdraw? I'm going to have an electrician hook it up I just want to understand what is going on. Sorry for all of the questions.
Also, in the end should I put a 30 amp breaker in for my larger tools and 20 amp for hand tools and chargers or 20 across the board will be OK?
 
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Old 02-25-16, 09:46 AM
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Also, in the end should I put a 30 amp breaker
If that is a 120v circuit 20 amps is maximum for a general purpose receptacle.
 
  #10  
Old 02-25-16, 10:32 AM
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Dedicated tools can have breakers larger than 20A, but they would also have plugs larger than 20A. If you have tools in the 5HP range like a 20" bandsaw, they may need 30A circuits. The tool manufacturer will spec that. Other than that, standard workshop tools should not exceed 20A circuits. If you plan to use a welder that's a special case so post back for more info.
 
  #11  
Old 02-25-16, 10:44 AM
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No tools like that yet for me. All will work on 20 amp plugs. I had my numbers crossed. But the panel and wiring will work to that point?
 
  #12  
Old 02-25-16, 10:54 AM
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Yes the plan sounds OK as you described it.
 
  #13  
Old 02-25-16, 11:42 AM
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Larger tools such as table saws that would require higher amperage are usually 240V to keep the amperage below 20A. A tool that would pull 30A at 120V will pull 15A at 240V, so that's why you'll see larger power demanding tools be 240V.
 
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Old 02-25-16, 03:17 PM
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All will work on 20 amp plugs
The plugs come on the tools, what plugs do the tools have have, 15 or 20 amp? If they have 15 amp plugs, as I suspect they do, there is no need to use 20 amp receptacles.
 
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Old 02-25-16, 07:12 PM
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When you buy your stationary power tools (Table saw, dust collector) check the motors and see if they are duel voltage (120/240v) If they are run them on 240 volts. The motors will start faster, run better, and have more power.
 
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Old 02-25-16, 08:44 PM
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For the most part running your power tools at 240V vs. 120V is not worth the trouble if you have to add a 240V circuit to do so. There is little to no benefit.
 
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Old 02-26-16, 02:22 PM
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There is little to no benefit.
I disagree. As mentioned my table saw performs MUCH better running on 240 volts compared to 120 volts. It starts faster and has more cutting power. The only extra cost is a two pole breaker instead of a single pole and perhaps a bit more for the 240 volt receptacle and cord cap. Either way you are running two wires so that is the same.
 
  #18  
Old 02-26-16, 02:58 PM
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As mentioned my table saw performs MUCH better running on 240 volts compared to 120 volts. It starts faster and has more cutting power.
If that's the case then you must have been suffering from voltage drop when using 120V. With all things being equal you will not gain more power with 240V over 120V, a watt of power is a watt of power. The biggest advantage of using 240V over 120V is it reduces voltage drop which if exist then more power is realized. There are certain motors that do run better on 240V but those are not typically what you find in a consumer table saw. Your results should not be touted as to what the effect will be in every situation when converting a table saw from 120V to 240V.
 
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Old 02-26-16, 03:15 PM
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Other people I have talked to have experienced the same results, mainly with table saws. I agree a watt is a watt however the motor windings are wired differently for each voltage.

Just sharing my experience.
 
  #20  
Old 02-28-16, 10:15 AM
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Someone else brought up the idea to just run 12/2 Romex from my main panel into the workshop. They said the distance isn't a huge factor and since I have plenty of open breakers it's not a problem. 250 feet of Romex is 49 bucks while 6/3 is 1.79 per foot. Is there any pluses or minuses to doing this? Right now in my panel have a 40, 60, 4 20s, and 2 15s open. I'm just trying to determine my best option. Thanks!
 
  #21  
Old 02-28-16, 10:37 AM
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Yes, you can run individual branch circuits for each piece of equipment if you want.

Minuses would be not having enough available spaces for the basement finish if that ever happens, ease of added more circuits later if basement was finished, and not having to go to the basement if you ever tripped a breaker.

If you can, don't buy 6/3 by the foot, it is more expensive that way. My local Menards sells 75' lengths of 6/3 for $115
 
  #22  
Old 02-28-16, 03:58 PM
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If you use 2-2-2-4 Al SER it's less than $1.50 a foot and will give you the potential of having as much as 90A to the sub-panel. You can feed it with a 50A or a 60A, up to 90A breaker. I highly suggest a sub-panel over running individual circuits 60 ft. from the main panel.
 
  #23  
Old 02-28-16, 04:44 PM
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Is 2-2-2-4 jacketed and one complete wire or do I need to purchase 4 separate wires? I just looked on Lowes and it is 1.49 a foot which is well under what I thought it would be. What breaker would you put to feed a 100amp panel? With 60 I figured I was limited to (3) 20 amp breakers. Also, will the wire need to be run in conduit or can I just run it along the joists in the basement? It is all inside. Thanks for the info!
 
  #24  
Old 02-28-16, 05:03 PM
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SER is jacketed and is installed the same as NM-b. It can be run along the joist and does not need to be in conduit unless subject to damage. It's a complete cable with 4 conductors. You don't just add up the breakers. I have a 100A subpanel fed with 60A and have 125A of breakers installed.
 
  #25  
Old 02-28-16, 05:06 PM
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Thank you so much for the info! I will be heading to Lowes tomorrow!
 
  #26  
Old 02-28-16, 05:12 PM
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Buy some Noalox for the connections when aluminum wire is used. It's a paste in a tube to prevent oxidation. Reread my previous comment I added breaker comment.
 
  #27  
Old 02-28-16, 05:34 PM
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OK...thanks. I was under the impression that your panel breaker total is limited to the breaker that is feeding it?
 
  #28  
Old 02-28-16, 05:38 PM
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Nope, you have to consider the total of the loads used at same time to size the feeding breaker.
 

Last edited by pattenp; 02-28-16 at 06:17 PM.
  #29  
Old 02-28-16, 05:42 PM
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Got it, that makes sense. Thanks again for your help I really appreciate the info.
 
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