Sub-Panel Sizing


Old 11-05-02, 12:38 PM
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Sub-Panel Sizing

I have a 200 Amp sub-panel I want to install in my basement prior to refinishing the basement. How do I determine the actual loading? I will be installing an electric furnace, and will have a workshop w/ radial arm saw and compressor, + the normal other areas ( TV area, office, playroom for the kids, sewing room for my wife, bathroom, small kitchenette ...) Do I nee the full 200 Amps, or can I get by with 100 or 150? What size wire will I need to tie the sub-panel into the main panel? Thanks
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Old 11-05-02, 01:33 PM
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One method is to consider the area to be served by the subpanel and perform a demand calculation. Below is a link for an entire home, but you may interpolate for your subpanel to establish some type of baseline.

Without knowing your home, 200A for a subpanel is probably excessive.
Old 11-06-02, 10:57 AM
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You mention an electric furnace and a kitchenette.We'll need to know the rating in kilowatts of the furnace and if the kitchenette will be equipped with electric appliances such as a range or oven.------I'm inclined to suggest two 100 amp feeders because you can insert 100 amp breakers into the Service panel.Connecting a 200 amp feeder breaker at the Service may be problematic.--Much depends on routing the feeders from the Service to the basement.The easiest Wiring Method would be Non-metallic cable. Two 100 amp feeders may be perceived as "over-kill",but the labor is the same for either 30,60,or 100 amp cables and the cost-difference between 60/100 amp cable is not excessive---One 100 amp feeder MIGHT be adequate, but we'll need an exact and accurate list of the total connected load to make that decision.---Good Luck!!!

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