Subpanel Amperage

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  #1  
Old 06-18-05, 09:37 AM
ajpeters
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Subpanel Amperage

Hello - I'm finishing my 800sf basement and am putting together my electrical plan. I'm not sure what size of subpanel my basement requires... I'm planning on wiring a theatre (dedicated 20-12/2 circuit), a wet bar, a bathroom, a work-out room, an open area for a pool table, and a few outdoor lights. I'd just assume over-wire now while there is no drywall... I was hoping to get some expert input on:

1. What size of subpanel shoudl I get?
2. What size wire should I use from my main breaker?

Thank you!
 
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  #2  
Old 06-18-05, 11:58 AM
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ajpeters,

I guess the question that needs to be asked is...Why a Sub-Panel?

Is the existing panel in the house upstairs inside a wall meaning you are not able to get to it....since you will need to in order to run the cable for a sub-panel anyway.

Is your panel in the basement area of this house...which in this case why even do a sub panel...or is your existing panel already full..?

I think answering your question depends on the following things:

1.) What size EXISTING service panel do you already have in your house.
2.) Where is it located?
3.) Sizing the sub-panel is going to depend on the load you intend to put in the basement.

From the loads you have listed I do not see a large amount of load so curious on why you would want to sub-panel this. Again is your panel already full with no space left.....what loads do you have in your existing finished area of the house and what size is the service....answers those and we should be able to assist you.
 
  #3  
Old 06-18-05, 12:23 PM
ajpeters
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Subpanel Amperage

Here goes:

1) My main panel is 200A and there are 5 slots open.

2) My basement is under half of my 1st story and my garage is adjacent to the half of the house w/ no basement. My main panel is on the far wall of the garage. Thus, to string wire to the basement, I'll go over the garage ceiling, down the wall, thru the crawl space, and into the basement... ~60 feet.

3) The basement loads include:
- Home theatre
- Recessed lighting & outlets (800sf space)
- Full bath
- Fitness room
- Wet bar (i.e. small fridge)
- Some outdoor lighting & an outlet

Thanks.
 
  #4  
Old 06-18-05, 06:06 PM
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ajpeters,

OK Aj....we are halfway their.....so now tell me this...

Go to your panel and tell me WHAT are the largest loads in your house right now....in other words are all your major applicances electric or are any GAS and in your panel...list how many double pole breakers you have and amp rating on them.

Bascially you should be fine for what you are trying to do as I do not see any major loads here. However, I would run a 100A Main Lug (8) circuit panel because they are quite cheap.....no need to size it for 100A but would suggest you get that size for the actual panel.

In your main panel the OCPD for the Main Lug panel personally without more data on whats in your house I would put a 80A breaker to feed the main lug sub-panel...However, the SER I would run would be # 1 Al SER which should be fine.....it has a rating of 100A but you will not need that much but on the wire you can be larger and it may be easier to find than running a # 2 AL SER or so on.....in our area they only carry # 1 SER and # 4/0 SER so it depends on your electrical supply house. Now if you wanna SPLURDGE you can ask about copper in # 3 CU......rated at 100A but again at the price of copper I would stick to the aluminum...

Now again...all this is said WITHOUT knowing the other loads in your house so I would not go any furthur on this until we know this information. Also remember if you did get the main lug panel you are also going to need a grounding bar kit as well....just so you know that.

Let us know the major details of the other items in your house...are any of your applicances GAS.....and list all the major appliances you have and peek in your existing panel and let us know the breakers you have and their ratings.
 
  #5  
Old 06-19-05, 09:02 AM
ajpeters
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Subpanel Amperage

Ok, here are the major appliances on my main breaker (my furnace, water heater, & stove are gas):

200 Amp Main Panel
- 30A, 2-pole: Dryer
- 30A, 2-pole: Oven#1
- 30A, 2-pole: Oven#2
- 40A, 2-pole: AC
- Other: 18 other 15 or 20A circuits supporting outlets & lighting

So you're recommending that I put a 80A breaker to a 100A main panel? Thus, the 100A panel would really only be able to provide 80A (this should be plenty!) to the basement, correct? If this is the case, do I need wire to support a 100A panel or 80A panel? I'll browse around the site for some details on the grounding bar kit.

Thanks!
 
  #6  
Old 06-19-05, 03:14 PM
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ajpeters,

Ok...here is the complex way I like to think when I am telling novices how to do something. 1.) Keep the circuit potential protection at 80% of what the actual panel load is......so that worse case senerio you can ALWAYS replace the 80A with a 100A if you ever feel you need it...which I doubt it.

The reason I like the 80A on this theory is because I like to feel it limits you and bring the DIYer into reality so they dont get carried away so to speak...but if you find the 80A is more costly than the 100A you can certainly put a 100A in if you wish.....

Just what I would do is all I am saying. Now, rating with wire for the PANEL max which is 100A leaves you ROOM to move...if you wired if for 80A or less you are STUCK.......no room to grow even if you dont have an intention to...funny how things change like that.

As for the load.....sounds like your main items are GAS so you should be fine even if you wanted to put a 100A in........the 80A was only my suggestion for the OCPD on the 100A panel.......since you are going to get away CHEAP with a main lug 100A panel.....if anything I would splurge on the wire itself and make sure it is rated to handle 100A.....even if the circuit never has that on it....always fine to have the wire larger than the OCPD...just not the other way around....
 
  #7  
Old 06-19-05, 08:32 PM
ajpeters
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Subpanel Amperage

Great - thanks for your help!
 
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