Sub Panel load calc

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Old 01-24-10, 06:05 AM
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Sub Panel load calc

WHere would I find the calculation for the maximum load from a 50A feed to a subpanel in a remodel basement? thanks
 
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Old 01-24-10, 06:19 AM
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Without sounding like a smart butt, it would be 50 amps wouldn't it?
 
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Old 01-24-10, 07:10 AM
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Sorry. I meant how much in face value breakers (15,20A) can go into a sub panel where the subpanel is fed from a 50A from the main panel 30 feet away.
 
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Old 01-24-10, 07:28 AM
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I think what you would want to do is a load calculation. By doing so, you can see what load is going to be on your panel. The number or sizes of breakers really have no bearing on the actual load. Your main panel may have breakers that add up to 400 amps.

You could have 100 amps worth of breakers but the actual load may be 40.

Go here and open the residential load calculation worksheet and see what the amount of load you're adding.

Mike Holt
 
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Old 01-24-10, 07:41 AM
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OK thanks. It is just a couple dozen convenience plugs, 20 can lights and a steam room unit (29Amp). So at .625A per canlight, I think it's OK. The problem is I'm not certain of the exact wire spec on the line between the main and the sub, so am hesitant to change anything. If breakers in the sub trip in service, I'll have to dig deeper into the feed to the sub, and call a pro.
 
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Old 01-26-10, 08:25 AM
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Here's how I would break it down:

general-purpose receptacles @ 3W/ft^2 (guessing 1000 ft^2): 3000W
can lights: 20 @ 65W = 1300W
steam unit (you didn't say 240V or 120V. I'm guessing 240V) 29A * 240V = 7000W

total: 11300W

A 50A panel can supply (50A * 240V) 12000 watts. That means you're just within the range of this panel.
 
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