Running electric to garage

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  #1  
Old 05-21-07, 11:41 AM
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Running electric to garage

I need to run some electric to a detached garage. I was thinking 3 lines as opposed to trying to put a sub-panel in. Anyway, what is the longest distance I can run the line or as I assume, it doens't matter.

I'm looking to run two 15 amp and one 20 amp breaker (for a table saw an air compressor). I have the underground conduit already.

Any input or suggestions are appreciated.
 
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Old 05-21-07, 11:46 AM
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> thinking 3 lines as opposed to trying to put a sub-panel in

If you need multiple circuits in the garage, then you'll need to install a subpanel. Code allows for only one circuit to outbuildings which can either be a typical lights and receptacles circuit or a subpanel feeder.

> what is the longest distance I can run the line or as I assume,
> it doens't matter

It does matter. You can run long distances, but you need to install larger wires to accommodate the voltage drop over the distance. Usually anything beyond about 150' requires some upsizing of the conductors.

> I'm looking to run two 15 amp and one 20 amp breaker
> (for a table saw an air compressor).

What are the horsepower of these tools? Are they wired for 120V or 240V?

> I have the underground conduit already.

What size, type and buried depth?
 
  #3  
Old 05-21-07, 11:59 AM
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The runs hould be well less than 150 feet. The tools are likely 120, it's portable table saw and a 5 gallon compressor, we're not talking major tools here.

The conduit it 2-inch, the grey PVC and it's not installed yet.

We'll see about a subpanel. The cost is ridiculous these days to go that route so if anything, I'll run one big line with receptacle and lights and be done with it.

I work in the development field and over the years one thing I've found is that codes are usually overkill when taken as a whole and they're developed by govt agencies looking to justify their jobs and create business for the people who pay their campaigns.

Cynical I know.
 
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Old 05-21-07, 12:04 PM
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Your entire project likely requires inspection, which will ensure that you don't do something stupid like "run one big line".

No, sub-panels are not expensive. You will likely find that a sub panel is cheaper than multiple lines. You will also find that it give you more flexibility.

No, electrical codes are no overkill and they are not developed by government agencies. If you think so, you will likely end up dead wrong. And dead is permanent.
 
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Old 05-21-07, 12:06 PM
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Since your needs aren't really that great, I can make a suggestion which is both inexpensive and legal. You can install a 20A multiwire circuit to the garage instead of a subpanel. This provides you with the equivalent power of (2) 20A 120V circuits and limited use of 240V.

Through the conduit, you would pull (4) #12 THWN wires in black, red, white and green. In the main panel the hots are fed with a 20A double pole breaker and the neutral is shared between each leg of the circuit. After the circuit enters the garage, install a junction box with two toggle switches as disconnects and split off as if you have two separate circuits.

> I'll run one big line with receptacle and lights and be done with it.

If you mean install a circuit with a breaker larger than 20A, don't. This method would really be unsafe (not a technicality).

> codes are usually overkill when taken as a whole and they're developed by govt agencies

The National Electric Code is developed by the National Fire Protection Association which is not a governmental body.
 
  #6  
Old 05-21-07, 01:06 PM
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Price out small subpanels. I think you'll find them reasonable. And the subpanel route gives you 100% more power for 33% more wire. Seems like a bargain to me.

Or, you can certainly use Ben's multiwire suggestion if you think that will be enough power for you.

Half the people think the code is too strict (when they are the ones doing the work) and half think the code is too lenient (when they inherit the work of others). Go figure.
 
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