New Addition Subpanel

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  #1  
Old 08-25-05, 11:27 AM
curlywiz
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New Addition Subpanel

I am converting an unfinished basement into a family room, bathroom and three bedrooms (that's the longterm goal after many phases). The service panel (200 amp) has three current breakers, one 100 amp to a subpanel, one 50 amp circuit to a hot tub and one 20 amp circuit to the existing lights in the basement. The 100 amp sub panel is full and services the main floor. In calculating the total load for the finished house I come up with less than 200 amps. Can I add only another 30 amps worth of circuits? Or can I add another 100 amp subpanel for the basement?
 
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  #2  
Old 08-25-05, 11:41 AM
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Assuming that when you calculated the load that you included the new load too, then you can do either.
 
  #3  
Old 08-26-05, 08:53 AM
rlrct
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Originally Posted by curlywiz
I am converting an unfinished basement into a family room, bathroom and three bedrooms (that's the longterm goal after many phases). The service panel (200 amp) has three current breakers, one 100 amp to a subpanel, one 50 amp circuit to a hot tub and one 20 amp circuit to the existing lights in the basement. The 100 amp sub panel is full and services the main floor. In calculating the total load for the finished house I come up with less than 200 amps. Can I add only another 30 amps worth of circuits? Or can I add another 100 amp subpanel for the basement?
This isn't an electrical code point, but to have a code-compliant bedroom, you've got to have an egress window (or 2 doors, I think). You might want to check with your town on the rules for that before you go down the path of finishing the basement to find out that you can't use the rooms as bedrooms.
 
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Old 08-26-05, 12:24 PM
curlywiz
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Thanks, we've got the bedroom egress covered. The house is on a hillside so the "basement" is actually a lower unfinished floor that daylights on three sides.
 
  #5  
Old 08-26-05, 12:42 PM
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Is this 200A panel readily acessable to add breakers to?
If so, add your 3 or 4 circuits there.

If not, I'd run a 40-60A sub from the 200A panel.

If they structrally pass as bedrooms, ALL openings need to be AFCI protected as well.
 
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Old 08-31-05, 05:37 PM
curlywiz
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What does AFCI stand for?
 
  #7  
Old 08-31-05, 05:43 PM
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AFCI stands for Arc Fault Circuit Interrupter. This protection is required for bedrooms.

One other point, your bathroom will require a dedicated 20 amp circuit. This, along with the AFCI required for the bedroom, is a minimum of two circuits. However, I certainly would not put three bedrooms and a den on one circuit.

I would probably go two 20 amp AFCI circuits for the three bedrooms, one 20 amp circuit for the bathroom, and another 20 amp circuit for the den.

Note that you may be able to reuse the 20 amp circuit for lighting that is presently there, since you will have to either remove it from the bedrooms or make it AFCI.
 
  #8  
Old 08-31-05, 06:55 PM
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I don't know how you added up all your loads but I have a feeling yo might have just added up the breaker values. That is not how you do it.
You said you would be adding 30 amps to the basement. Thnias makes me think you might be adding two 15 amp circuits. You will need one 20 amp circuit for the bathroom only.
 
  #9  
Old 09-01-05, 11:16 AM
curlywiz
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In calculating the household electrical load I added up all the building's electrical loads, existing and planned expansion, (using the load factors) and found the total was less than the current 200 amp service.

I plan on adding roughly six circuits in the downstairs. One 20 amp just for the bathroom (light, fan, GFCI outlets), one 15 amp for two kids/guest bedrooms, two 20 amps for the family room (its big and I might want to tap in for exterior lights someday), one 15 amp ground isolated for a computer and one 15 amp for the stairs/hallway. The third bedroom is a later phase so I wanted to leave space for it in the new sub panel. The current main service panel is quite far from the new space so I thought the sub panel, centrally located in the new space, would make the new circuits shorter, cleaner and easier to work on.

Are there any particularly good books out for home wiring because the ones I have don't cover AFCI protection of circuits (either the need or how to accomplish).

Thanks for all the advice so far!!
 
  #10  
Old 09-01-05, 11:27 AM
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Your plan sounds pretty good. I would recommend using all 20A circuits though; #12 NM is only marginally more expensive than #14, and the work required to install it is the same. It's worth it to have 25% more power available throughout the basement. 15A circuits are all but obsolete for receptacles and sometimes used for lighting.

Don't bother with an "isolated ground" receptacle for the computer. It's a waste of money in residential wiring, because it gains you absolutely nothing over a plain-old dedicated circuit.

AFCI protection is easy to implement. You buy special AFCI breakers for the circuits that have outlets (lights, receptacles, smoke detectors) in bedrooms. AFCI breakers are considerably more expensive, about $30-$40 each. If you have a relatively modern panel, most all of the home centers carry AFCI breakers to fit it.
 
  #11  
Old 09-01-05, 11:34 AM
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I agree with the advice in the above post to go only with 20 amp circuits, and to not bother with the isolated ground circuit.

Don't forget that everything in the bedrooms must be AFCI protected. This includes the smoke detectors, which must be interconnected. Local rules MAY allow the smoke detectors to be non-AFCI, so check before you start. Note also that all the smoke detectors for the basement will need to be interconnected. If the rest of the house has interconnected smoke detectors then add them to this same circuit.

While it was already stated, it bears repeating. Make certain that each bedroom has a separate means of egress other than the bedroom door (which probably is off the den or a small hallway. This other means of egress must be a door or large enough window that leads outside directly or indirectly, but via a different path than the main door.
 
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