Adding circuits for unfinished basement

Old 12-01-02, 06:48 PM
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Question Adding circuits for unfinished basement

I am about to embark on finishing the remaining half of my basement, but my 30 circuit 200 amp breaker box is full, and the total of all the breakers adds up to ALOT more than 200 amps.

To add the additional circuits, I will either have to add buddy breakers or try to tap into existing circuits which I would rather not have to do.

Is there a practical or code limit on the total number of circuits in a 200 amp breaker panel?
Old 12-01-02, 06:58 PM
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First of all, completely ignore what your existing breakers add up to. That sum is totally irrelevant.

Depending on how many square feet you are finishing, I suggest you consider a subpanel for your basement. It might be the right answer. However, you might also be able to do it with the tandem (aka twin, skinny) breakers. Is your main panel already in the basement?

But you'll need to figure out how many circuits you need in your basement. Modern homes are required to have two spare circuits already run to the basement, so you might check to see if your builder provided for this (depending on how old your house is).

I suggest about one circuit per 100-150 finished square feet. This is more than required by code, but it will offer you good flexibility.

If you will have a bathroom down there, you'll want to dedicated one 20-amp circuit for that. The rest depends on whether you'll need supplemental electric heat, how big your home theater is, how much computer equipment you will put down there, etc.

Don't just tap into existing circuits. The result will not be satisfying.
Old 12-01-02, 07:04 PM
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Your existing panel is UL listed with certain parameters regarding breaker quanity. Whether you can install buddy or twin mounted breakers will be documented on the instructions on the panel's door.
If the panel is listed to accept twin breakers, it might indicate on the circuit directory with a number and a or b next to it. Please keep in mind that no panel can contain more than 42 breaker positions, where a two pole 20A is two breaker positions.
Old 12-01-02, 08:16 PM
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Wow, two replies within 10 minutes of the original posting. Thanks guys!

There were two empty spots in the box when we moved in but I quickly filled those with a 220 volt circuit for the dryer. The box is in the currently unfinished area of the basement

Half the basement ( around 500 sq ft ) is finished and is on 2 20 Amp circuits and a 15 amp lighting circuit. This has proved to be too little when the home theater, a space heater, and the vacuum cleaner get going at the same time.

The remainder of the basement includes a laundry with a dedicated outlet for the washer and another 15 amp lighting circuit. I will be adding a 200 sq ft bedroom, a bath, and leaving the rest for storage.

My plan is to add a total of 5 20 amp circuits, one each for the bedroom, storage area, laundry, computer area, and home theater area, and to leave the lighting on the existing 15 amp lighting circuit.

That plan means I will replace 5 breakers with slender or buddy breakers, bringing the total to 35 circuits in the box, or 32 if if get credit for the 3 220 volt circuits.

My garage is on one 20 amp circuit, which is woefully little for my budding woodshop. Can I add another 30, 40, or 50 amp 220 V Breaker and run that line to a sub-panel in the garage?
Old 12-01-02, 08:51 PM
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Given your expanding needs, I suggest you add a subpanel right next to the main panel. You will need to move two of the current 120-volt circuits, or one 240-volt circuit, from the main panel to the subpanel. This will make room for the breaker that connects the two. A 12-space SquareD subpanel with five 20-amp breakers thrown in can be had for as little as $37.

You could add another subpanel in the garage, or simply run new garage circuits off the new basement subpanel.
Old 12-02-02, 05:22 AM
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Since the panel has a two hundred ampere main breaker I suspect you will find that it is a thirty by forty breaker panel in that ten of the slots are intended to accept half width or tandem breakers. Which one they accept will depend on the brand name. As HandyRon has already suggested if slots 21 through 30 have a,b markings in the panel directory that is a dead give away. If my suspicion pans out the only place you will need a sub panel is in the garage. Since you plan to have a wood shop out there the sub panel should be at least twelve slots and be supplied from at least a sixty ampere feeder.

One thing to be aware of is that all of your double pole breakers should be in the portion of your panel that will not accept the compact breakers. This keeps them from using up four slots worth of compact breaker space. If you arrange the panel differently then it is now you must be very careful about the arrangement of any circuit that has three insulated wires rather than just two. Those are multi wire branch circuits and the red and black wires from those circuits must be supplied from the opposing poles of the panel so that the output of the two breakers will have 240 volts across them and 120 volts between each breaker and the bonded buss bar of the panel. If you disarrange one of those circuits so that both the black and red wire come from the same pole of the panel the neutral of the multi wire branch circuit will be overloaded and a fire could result.

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