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Old 12-09-2010, 02:12 PM   #1
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Couple Main and sub panel questions

Ok, first off, my house is older and therefore has an older main panel. Thankfully it is 100am and working well. Right now I am looking at doing a couple of changes in my wiring to make my life easier.

Some background:

100am mail panel. Square D QO Load Center QO-18-410 Series 2
Box Cat. NO. QOB-20 (Other numbers: L1735, LSK62886C)

Right now all the spaces are full, but i would like to change that up a bit. My entire second floor, minus the bathroom, and the ceiling lights of the 1st floor are all on one Circuit. The bathroom and kitchen are both on their own. I 4 circuits in the basement/first floor; one for half the basement lights, and some of the 1st floor outlets, one for the other half of the basement lights and the other half of the 1st floor outlets, one for two basement plugs and the back enclosed porch, exterior outlet, and one for the washer/dryer. There is also one circuit to the garage for lights and 2 plugs.

Here is what I want to do:

I want to remove a 30 amp 220 outlet attached to the bottom of the box, and use this to run a 30-50amp sub panel in the garage. Can I use the current 30 amp to setup the sub panel and then replace it later with a 40-50 if my needs change? I know I will have to replace the wire, and will size it for the larger amp rating.

I want to split the basement circuits up better, as follows:

1 for washer, dryer, and 1/2 lights (2 plugs, 4 lights)
1 for remaining lights, and porch.
1 for basement outlets
1 for 1st floor outlets.

I also want to add/split two of the circuits so i can split out my 2nd floor power so that I have the lights on one circuit, the plugs on one circuit, and an extra circuit for my computer equipment in the 2nd bedroom/office.

Thanks for any help.


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Old 12-09-2010, 04:25 PM   #2
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You might be able to use the existing 30 amp wiring if it has 4 conductors. Less the 4 and you would need to run new cable.

The laundry circuit should not have lighting loads on it. It is reserved for the washing machine and dryer, if gas. An electric dryer would require its own 30 amp 240 volt circuit.

The receptacles in the basement will require GFI protection if the basement is unfinished. They would also require AFCI protection regardless of finished or unfinished.


Answers based on the National Electrical Code. Local amendments may apply. Check with your local building officials.
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Old 12-10-2010, 08:09 AM   #3
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Ok, so I contacted Square D for more information, and they sent me a scan of page 6 of their 1960 digest showing my panel QO-18-410S since mine is surface mount. According to this, the Mains Rating Amps is 125, Max Poles is 18, and here is the description:

"Split Bus - One Lighting main, Three additional two poles connected in parallel and 10 single poles"

And it was originally $31.10

Even though that says 125, I believe I only have 100 amp service. If I did upgrade, it would be to 200 most likely.

Right now, the 220 from the old dryer is in one of the two poles, so I should be fine running the sub-panel from that. Can't reuse the wiring since the 220 outlet is attached to the bottom of the box, so the wiring is only 12 inches long. If I do move the sub-panel and garage wiring to that one, that frees up one space from the current garage circuit.

I also picked up two QO2020CP tandem circuit breakers, and figure I will use those for some of the outlets (porch, first floor outlets, Computer plugs) since those will need the 20 amp rating, but don't have huge draws on them often.

And thanks for the tip on the laundry lighting. Currently that circuit is only two outlets, one behind the washer, and one behind the dryer (gas) It only has those and a dehumidifier plugged into it, and 12-2 wiring from both plugs to the box.

As for the Basement outlets, I was planning on GFI, but will look more closely at getting an AFCI breaker for them if one is available (QO Plug on style) The current basement outlets do not have them, but they are all over 5 feet off the ground or more. The basement was partially finished before (drywalled walls and ceiling in half, painted in the other) but it could use some re-doing to make it better.
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