Advice on adding sub panel

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  #1  
Old 11-13-12, 01:14 PM
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Advice on adding sub panel

Hi, I want to add a small sub panel in my attic. the house we just moved into does not have any lights in the ceilings on the second floor only outlets controlled by wall switches. My wife and I both Prefer to install ceiling fans with lights in each bed room. the house currently has aluminum branch wiring through out. it has been checked and appears to be fine, but I will eventually replace it. for now though I want to run a good copper branch from my main panel in the basement to a small panel in the attic so when we start adding lights and fans it will be an easy job to just tie into the new copper wire and never splice into the old aluminum. While I don't plan on running a lot on this branch right now I want to semi future proof the job and go heavier then I currently need but not overkill. currently the branch would only need to support 4 fans with lights, and maybe some Christmas lights at the roof line. how ever when I start replacing some of the aluminum with copper it might be easier to tie into this for some of the rooms. I was originally going to run 10/2 to the sub panel with a 30 amp breaker in the main, and 2 or 3 15 amp breakers in the sub panel. then I got to thinking maybe it would be better to use 10/3 and run 220v to the sub panel. I did not want to spend a lot on wire but if there is reason I should go with heavier gauge then I am open. thanks
 
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  #2  
Old 11-13-12, 01:53 PM
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First the panel would need a refrigerator sized box in front of it to allow for the proper workspace. You also need headroom of at least 6.5'.

If you only ran xx-2 cable you would only be able to use 1/2 the breaker spaces in the panel. Every other leg would be dead.

The loads you are talking about adding are negible. I would either run the home runs now or add a conduit to the basement.
 
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Old 11-13-12, 02:14 PM
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just curious is there any reason I should not buy this wire for the job? it is cheaper then the 10/2 I have purchased...

Amazon.com: WIRE 8/3 NM-WG 50' [Misc.]: Sports & Outdoors
 
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Old 11-13-12, 02:27 PM
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That cable would allow you to install a 40 amp 240 subpanel.
 
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Old 11-13-12, 02:58 PM
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thanks. I see though I can not get that wire before saturday which is when I will have the help to do this job. I can go with my local lowes. but the 10/3 is cheaper then 8/3 obviously. shouldn't 10/3 be enough for what I need? I only need 40-50 feet of wire. also I would need a dual 30 amp breaker correct? thanks for the advice. I have a tendency to way over spend and oversize my projects that's why I am asking for advice. my first thought was run 6/3 wire lol like I said I don't want to waste money on this though.
 
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Old 11-13-12, 06:20 PM
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For the purposes you suggest, I'd use the 8-3 NM-B cable. Where in MO are you located? There may be a supply house near you that will be cheaper than Lowes. Let us try to help you on this now and we can talk about aluminum branch circuit wiring later.
 
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Old 11-13-12, 06:34 PM
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thanks for the advise. I live in St. Charles Mo... I can get 8/3 from lowes but it is about $115 for 50' vs 10/3 that is $75...
 
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Old 11-13-12, 06:52 PM
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Try Home Depot, they are generally less expensive than Lowes. The new Menards in St. Peters won't be finished for a while yet, so forget that. You could also try Butler Supply. They'll sell to the general public if you go to the counter and talk to them nicely. There is always SC Electric on Raymond too, but I think Home Depot would be cheaper.

Get through this project now and later talk to me about your aluminum branch circuit wiring, I can help you.
 
  #9  
Old 11-16-12, 11:46 AM
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Ok I have another question. It would be much easier to run some pvc conduit on the outside of the house from the basement to the attic, instead of going through the walls. At first I didn't want to go this rout as I did not want an eye swore. However when I started looking there is already some conduit ran up the house and since the house is almost the same color I hadn't noticed. I know for underground conduit you have to be careful what type wire you run, but since this will be sealed and dry can I use indoor wire or do i need something special. I read else where that wire can over heat in conduit and you should run thhn wiring. Also I would like to do the conduit since I can have the help I need this weekend then run the wire easy later when I get some in. thanks for the help guys
 
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Old 11-16-12, 12:25 PM
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but since this will be sealed and dry can I use indoor wire or do i need something special.
Outside is outside. Conduit is not expected to stay dry inside and usually doesn't if for no other reason then condensation. Be it wire or cable it must be outside rated after it leaves the house.

I read else where that wire can over heat in conduit and you should run thhn wiring.
You are confusing cable and wire. Best practice, though not required, is to use individual wires. THHN is not rated for outside use. It would need to be THWN.

Also I would like to do the conduit since I can have the help I need this weekend then run the wire easy later when I get some in.
I would suggest starting and ending the conduit in a weather proof single gang Jbox mounted on the outside wall at the bottom and top. You can use a pre-bent offset coupling at each box so the conduit lies flat against the wall. In the house you can run indoor cable or wire in to the box and transition to the outside cable or wire for the conduit in the box. While 1/2" conduit would work I'd suggest 3/4" in case you ever want to up size the feed.
 
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Old 11-16-12, 01:01 PM
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would 8/3 SOOW be fine in the conduit? I ask because there is some local for sale
 
  #12  
Old 11-16-12, 02:09 PM
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Are you still thinking of installing and feeding a subpanel? Or just adding a couple of new circuits into your panel?

Do you have the needed clearance to install a subpanel?
 
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Old 11-16-12, 02:09 PM
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never mind, whiles I could get 90ft 8/3 SOOW for $100 it is 8/3 without ground so it will not work for what I am doing....
 
  #14  
Old 11-16-12, 02:13 PM
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I would like to add a sub panel just so it will be easier to add more fans later. right now I only have 1 fan installed but will add 2 more maybe next year.

Yes I have enough clearance for the panel.
 
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Old 11-16-12, 03:43 PM
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I would like to add a sub panel just so it will be easier to add more fans later. right now I only have 1 fan installed but will add 2 more maybe next year.
You can add whatever you like. The three fans, with lights, should require one circuit - possibly a 15A circuit. What else?

Is your attic accessible? Does it have stairs leading to it?

If you want to feed the attic through conduit outside, you need to pull individual THWN conductors through the conduit. Since you can get those cut to length, that wire may cost you less than a coil of cable that is longer than you need.

If the conduit starts in your panel and ends in the subpanel, then you can pull those all the way. If not, you will need to mount a J-box at the end of the conduit and splice over to cable there.
 
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Old 11-16-12, 05:38 PM
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never mind, whiles I could get 90ft 8/3 SOOW for $100 it is 8/3 without ground so it will not work for what I am doing....
No, you wouldn't want to use that even if it did have a ground. I like ray's suggestion better.

I would suggest starting and ending the conduit in a weather proof single gang Jbox mounted on the outside wall at the bottom and top. You can use a pre-bent offset coupling at each box so the conduit lies flat against the wall. In the house you can run indoor cable or wire in to the box and transition to the outside cable or wire for the conduit in the box.
How many amps do you need to take to the subpanel? Is 40 enough or do you need 50 or 60? The advantage to ray's suggestion is that you can use romex (NM-B cable) at both ends and just use the conduit with THHN/THWN wire on the vertical run outside the house. If you use 8-3 NM-B cable you would have wiring good for 40 amps. If you use 6-3 NM-B cable you have 60 amps.
 
  #17  
Old 11-17-12, 06:29 AM
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Personally, if it's just for a few bedrooms, I would run 2 or 3 (or 4) cables from the main panel to the attic. It would probably be cheaper and all the breakers would be at the main panel. I think it would be annoying to have 4 breakers in the attic whenever you need to get to them.

Alternatively, you could run a PVC conduit from the panel to a junction box in the attic and pull wire as needed. Again, pulling 12 or 14ga wire as needed.

Just my opinion.
 
  #18  
Old 11-17-12, 07:44 AM
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There is definitely more than one way to do this and stay code compliant. I also don't like the idea of a subpanel in an attic, but I don't know of any code that would prohibit it. I am actually more concerned with the aluminum wiring in your home.

it has been checked and appears to be fine
There are a lot of qualified electricians on the street, but not that many of them have the knowledge and experience necessary to inspect and/or work on aluminum wiring properly (although most think they do!).
 
  #19  
Old 11-19-12, 05:26 PM
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the house currently has aluminum branch wiring through out. it has been checked and appears to be fine, but I will eventually replace it.
The aluminum wiring in your house may, in fact, be fine. There may be no need to replace it.

The problem with aluminum wiring is that when it is connected directly to copper wiring - when the two metals are in direct physical contact with each other - galvanic corrosion can and will occur. In most, if not all, cases, the home fires that have been blamed didn't start in side the walls or the ceiling, they started in a junction box - often a fixture box - where the aluminum was spliced to copper. At least as far as I know.

An effective and relatively easy way to correct the problem is to trim the aluminum wire back a bit and add a copper extension to it, using a connector that electrically connects the two pieces of wire without having them touch each other. AlumiConn connectors are one way to do that. You can get a free sample from them and start right away, without having to save up for a major investment or do a lot of workarounds in the meantime

And I don't see why ordinary push-in connectors, which you should be able to buy at the big box store, wouldn't achieve the same goal of creating an electrical connection without a physical connection.
 
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Old 11-19-12, 06:40 PM
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You will not find a push-in style of connector listed for use with AL.
 
  #21  
Old 11-19-12, 06:50 PM
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There are actually many problems with aluminum wiring and all those problems have one thing in common, oxidation. When aluminum wiring was installed originally, it wasn't direct connected to copper wire, it was direct connected to other aluminum wires with wire connectors that had zinc plated steel springs (generic wire nut). Aluminum wire starts to oxidize the moment the insulation is stripped off the conductor. Back in the day, just typical wire nuts were used for connections and many of those connections soon overheated due to the poor connection between the two conductors that developed surface oxidation. The path the current would follow eventually was from one conductor, through the zinc plated steel spring and then to the other conductor. The steel spring couldn't handle the amperage and would get hot. The wire nut would get hot and the plastic shell would start turning colors and showing evidence of burning and eventually the connection burned in two. Aluminum wire direct connected to copper wire is another problem just as aluminum direct connected to devices with brass backing plates and brass screws, but this is how it was done back in the day of aluminum wiring. This is the short version. I would NEVER KNOWINGLY buy a house with aluminum wiring.
 
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