New outlet, breaker and wire size?


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Old 05-05-10, 08:33 PM
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New outlet, breaker and wire size?

I'm putting in a new outlet in my unfinished basement for some computer equipment and want to make sure I don't run into problems or do anything not up to code or unsafe. There will be two computers, one with a 400 Watt power supply that says it runs at 10 amps, and one with a 1050 Watt power supply that says it runs from 5.5 to 11 amps. Assuming both will be running at near max capacity what size breaker and wire should I use? Also, there is a possibility that another 1050 Watt computer will be added at a later time so I had considered having two outlets on the same run. Is it possible to put all that on one run/breaker safely or should I split it to two?
 
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Old 05-05-10, 09:29 PM
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You could run a multi wire circuit just to be sure. You would run 3-conductor with ground from a 240 volt 20 amp breaker. You could use a 2-gang box with two duplex receptacle. The neutral would be shared between the two duplex receptacles. Red would go to one receptacle and black to the other receptacle. Depending on location GFCI receptacles may be required. I really think one 20a circuit would be enough but this would give you an extra margin.
 
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Old 05-06-10, 04:52 AM
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As long as you are unobstructed for wiring at this time, why not simply run two 20a lines for the computer location. This will be adequate for now and for the future. Use 12awg with 20a CB. The cost between a 15a line and 20a line is no big deal.
 
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Old 05-06-10, 06:58 AM
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Originally Posted by ray2047 View Post
You could run a multi wire circuit just to be sure. You would run 3-conductor with ground from a 240 volt 20 amp breaker. You could use a 2-gang box with two duplex receptacle. The neutral would be shared between the two duplex receptacles. Red would go to one receptacle and black to the other receptacle. Depending on location GFCI receptacles may be required. I really think one 20a circuit would be enough but this would give you an extra margin.
I would not recommend a multiwire dedicated for computer equipment. If your only load is computer equipment, it's better that each circuit have it's own neutral. Computers are part of the "harmonic loads category" that don't do well with a shared neutral.

If your basement is unfinished, the receptacles must be GFCI.

I would recommend two 20A circuits. Depending on what you're using these computers for, if you put them through a lot of work all at once a single circuit could be undersized and cause your breaker to trip particularly if you add the third unit.
 
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Old 05-06-10, 08:26 AM
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I agree that two separate 20A GFCI circuits are indicated.

Ray, normally the MWC would be the way to go but computer power supplies produce harmonic frequencies in the neutral that can actually cause the current to add rather than cancel out like a normal multiwire would. You can get "computer room rated" MC cable for shared neutral circuits that has #12 hots and a #10 neutral to alleviate this problem, but it's probably not worth the special order for a small project.
 
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Old 05-06-10, 09:13 AM
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Thank you both for the correction. I didn't know about the harmonics problem. Mods please delete my original post.
 
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Old 05-06-10, 06:55 PM
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I agree with the two circuits. You could use one run of 12-2/2 romex to a 4 inch box with two GFI receptacles with each circuit on a single pole 20 amp breaker.

http://www.southwire.com/flashapps/E...talogPage.html
 
 

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