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Breaker panels and how much load they can have

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#1 Ravn

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Posted 02 March 2013 - 07:03 PM

Hello all,


This is Mike, Peg's husband. I have a question for any electricians on the board. I have a 200 Amp service with 30 breaker slots in it. Because I have a heat pump, and because everything in the house is electric, I have most of them taken up by big double-pole breakers. I'm putting new living space in my garage, and I decided to add a subpanel rather than use the half-wide breakers, as I heard they overheat. I have done house wiring before, but this is something I'm inexperienced with. So I have some questions.


I have looked at Lowe's and Home Depot, but it looks like the smallest 6-slot subpanel available is 100 Amp. Do I need that much capacity? And can my main panel handle it? Here is what I am trying to power with it.


1. Ceiling Fan and light and closet light in the new bedroom.

2. Ceiling light in my office

3. Ceiling light in the new laundry area.

4. Ceiling light in storage closet

5. Bedroom outlets (arc-faullt protected

6. Office outlets

7. Dedicated 20-amp outlet in bedroom for air conditioner

8. Dedicated bedroom outlet in office for air conditioner.(5000 btu units with heater - 15 amp circuit rated)

9. Smoke alarms.


Everything else already has breakers in the main panel.I am adding two breakers to the main panel - one for a freezer outlet and one GFI protected circuit that feeds an outlet in the laundry room and two others in a hallway area.


It seems like an awful lot.I know some of these can be on one circuit.Here, they make you put smoke alarms that are interlocked on their own circuit.


#2 TheDHJ

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Posted 02 March 2013 - 10:55 PM

Hey it's Mungo! :lol:

The one person who may be able to help you is banned. Don't know if there are any other electricians here.

#3 Lostsailr

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Posted 03 March 2013 - 12:23 AM

A1 - I am not an electrician, nor do I play one on TV:


It does depend on a few things.... mostly, how many amps are already provided in your old box...not the 200 amp service rating, but add up all the breaker totals in the box and get your number.

You will need to have enough amps left to cover the amps your sub box will provide, I believe.


Here's a link to a thread on that topic...  http://www.garagejou...ad.php?t=111720


hope it helps (guess I AM here to do google searches for you, Baller!)  :wink:

#4 Ravn

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Posted 03 March 2013 - 05:03 PM

he can't remember his board password :lol:



Thanks y'all <3

#5 MeOmYo

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Posted 03 March 2013 - 10:09 PM

I am not an electrician but have done a fair bit of it.

You may not need it but if that is the smallest panel you can find, so be it. You are needing breaker slots after all, not a perfectly designed electrical circuit. If you don't want to send 100 amps to the sub panel, size your wire to a reduced breaker in your main panel and save $ on wire. So, if you only need 60 amps in the sub panel, size the wire to the sub for 60 and use a 60 amp breaker in the main panel for that circuit.

If you overdraw the main panel,you should have a main breaker so no worries there. If it happens often, you may need to upgrade the main panel or put another meter for the garage.

Of course, check local codes to see if you can create a panel like that.