Enough power from subpanel?


Old 01-18-05, 02:02 PM
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Enough power from subpanel?

Last year, knowing I'd be finishing my basement in the future, I had an electrician add a sub-panel to my basement. My wife and I gave the electrician a guess about what kind of things we'd need to power in the basement, then he added the sub-panel.

Now I'm in the process of planning the circuits for the basement and I'm wondering if the sub-panel connection will be adequate. It's connected to the main panel by a double-pole 50 amp breaker. I've added up the power requirements of the things we want in the basement, which is more than we originally expected when the sub-panel was installed (big surprise), and I'm coming up with nearly 8,000 watts.

I'll only need 120 volt circuits for lighting, home theater setup, several small appliances, etc. (no 240 volt appliances). With the current sub-panel, am I limited to 6,000 watts (50 amp breaker * 120 volts)? If so, I assume the fix is to have the electrician install a higher amp breaker (likely requiring new wiring to the sub-panel).


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Old 01-18-05, 02:16 PM
Join Date: Jan 2002
Location: Chicago
Posts: 1,915
You don't just add all of the circuits, you need to add what's actually running in the circuit. For example, you may run a 20A circuit for 10 outlets, but you don't just say that circuit will use 20Ax120V. You need to only take into account the actual current draw of the devices plugged in. At the same time, the chance of running all circuits at full capacity at any one time is very remote in most cases. It's not uncommon to have a 200A panel with 500A of "actual" breakers in there.

Also, a 50A 240V panel is capable of 11,000VA at 110V. It's basically 50A at 220V or 100A at 110V.
Old 01-18-05, 02:55 PM
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Thanks, trinitro

My wattage estimate includes lighting, electronics, and appliances that might easily all be running at the same time (except for a small dishwasher and a microwave), plus one extra circuit for mostly-unused outlets. I'll re-do the estimate and make sure I have it right.

But, if the panel is basically 100A at 110V, then it's a moot point - I shouldn't have anything to worry about.

Thanks for your reply!


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