# Proper wire gauge for subpanel



## rockgod (Aug 29, 2016)

Hi,
I have an old house with old electric. I replaced my downstairs already, which was fairly easy. My upstairs is a bigger question. 
I have 4 bedrooms, a kitchen (that will soon become a laundry room), full bath and hallway.
I'm thinking of putting a subpanel in the attic and running new electric from there. Just think it would be easier for running new outlets and switches.
It would probably be a 200 amp panel. 
My existing panel is 200 amp
I would run 15 amp breakers to the bedrooms, bath, laundry, and hallway.
Run a dedicated breaker for washer (20 amp) and dedicated for dryer (30 amp). Total 155 amps for subpanel.
I'd be removing 2 20 amp breakers that feed all my bedrooms and bath and a 15 amp that feeds the kitchen from main panel. 

Question 1) any problems so far? I haven't been able to find a 160 or 180 amp panel so I'm not sure they are made in that amperage. Which is why I choose 200 amp. That plus looking towards the future, I may need to add an extra breaker for something. Can I just buy an empty 20 space panel and a separate 175 amp dual pole breaker? I'm just not sure what happens when running a 200 amp breaker off a 200 amp breaker...if anything.
Would I need to upgrade the main panel to a higher amp?
2) What gauge wire should be used for feeding the sub from the main panel?
I've googled but it's hard to find a direct answer. I'd be using copper. Is there a site that explains proper gauge for certain scenarios. The run form main to sub panel would be roughly 30-35 feet. 

This is all still in planning stage so none of this is set in stone or any thing even bought yet.
thanks for any guidance...


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## nealtw (Aug 30, 2016)

If you are taking out a kitchen, is there an outlet for a stove there now? You could use that for a smaller panel and run a new line for the dryer.


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## Kabris (Aug 31, 2016)

First off, a 200 AMP sub panel for bedrooms and laundry is way larger than you need, a 60 AMP sub would be more than enough.  Second of all, there are many codes involved with properly installing a service. I would not recommend a DIYer without electrical training attempting this.


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## CallMeVilla (Sep 1, 2016)

Agree with KABRIS ....  unless you are highly experienced, this is not a DIY job.  Another point many people miss, without permitting your homeowner insurance would NOT cover a fire.  Your policy would be void.  Is it worth the risk?

Get a qualified guy in there.  He might let you help with grunt work and do all connections himself.  Get plans, even rudimentary, done.  Get inspections and pay the fee.  Its cheap insurance.

As the quote says:  "A mans gotta know his limitations."   [ame]https://www.youtube.com/watch?v=_VrFV5r8cs0[/ame]


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## afjes_2016 (Sep 2, 2016)

rockgod said:


> ...
> I would run 15 amp breakers to the bedrooms, bath, laundry, and hallway.
> Run a dedicated breaker for washer (20 amp) and dedicated for dryer (30 amp). Total 155 amps for subpanel.
> I'd be removing 2 20 amp breakers that feed all my bedrooms and bath and a 15 amp that feeds the kitchen from main panel...



It is apparent that you are not familiar with the basic NEC codes. Please study them and consult a licensed electrician if need be. It is highly recommended that you have this project done with a permit and then inspected. 

You can not run a 15amp circuit for a bath. It must be at least a 20 amp circuit and may not extend out of the bathroom area unless it goes to another bath etc. Laundry circuits must be dedicated 20 amp ( specific rules on this also). Then the bedrooms, other living inhabited areas must be protected by AFCI breakers so count your circuits carefully as AFCI breakers take up a full breaker position. Make sure your panel will contain sufficient quantity of breakers according to the manufacturer's recommendation for that panel.

Another thing I notice is that you state you will run "breakers". You should refer to them as circuits. Example: you will run a 20 amp circuit using 12 gauge Romex. Know what size conductor will be needed for your circuit and be use you use the proper breaker (15, 20amp etc) Study up on your terminology a bit more so that it will help you understand what you read.

You do not add up breakers to figure total size panel needed. You would do a "load demand" calculation. Your idea of a 200 amp sub panel is way over what you would need.

What size conductors, quantity and gauge do you plan on running to your sub panel from your main panel and do you know the proper way to hook up a sub panel in relation to a main panel.

I would hate to see you invest all your time and money to find out that you made numerous serious errors after all is said and done. Some of your errors could be hazardous. Please do not attempt this until you do more research. And even if you plan on having a licensed electrician do this still do more research so that when the electrician and you discuss your needs you can follow him. Now is the time to do the careful planning for your future needs.

Finally, do not go just by the most recent NEC edition. Your local authority (AHJ) will more than likely have additional requirements above and beyond the NEC. You could find yourself re-doing a lot of what you thought was correct.


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## rockgod (Sep 2, 2016)

Thanks...I appreciate all the info, guidance, tips and concern.
After more research, I have done a preliminary "load calculation" based on my square footage.
calculations give me ~40 amps...so ya, I guess I was way off.
I've looked up local codes for electric. Still am...there are a lot. 
Romex isn't allowed in my city (Chicago) at all. Everything is ran through conduit. 
Circuit, breaker, circuit breaker...all the same thing no? Isn't' the full term a circuit breaker?
I know the sub panel ground bus bar needs to be broke in order to be a proper sub panel.
I know the space requirements for a panel in gerneral...3 feet of spacing around all sides of panel, etc...
I did not know about the 20 amp requirement for a bath...so thanks for that.
My washer/dryer will have dedicated 20/30 amp (respectively) circuit breakers, same as they have now in my basement.
GFCI outlets through out and AFCI breakers in the panel.
This job will be permitted and inspected when done.
I've already re-wired my entire downstairs, ran a dedicated circuit for my window A/C unit, ran electric outside for lighting and outlets..so I'm familiar with electrical work and how to do it properly and safely. 
A sub panel though, this is new to me. And I'm really only concerned with the feed from panel to panel.
I'm not against hiring a pro, I just would like to do all this myself. I do everything myself.
One of my questions was the proper gauge wire to feed the sub panel. After my load calc, I think I would be using 6/4 for a ~35' run. That's 2 hot, ground and neutral right?
Like I said, this is still in planning stage, which is why I'm asking questions now before I spend money on equipment and time on installation.


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## JoeD (Sep 2, 2016)

#6 cable is good for a 60 amp sub panel. 6/4 is a cable. I don't think you can use cable in Chicago even for sub panel feed. You will need to check to be sure.


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## afjes_2016 (Sep 3, 2016)

OK, before you go any further be aware of one very important fact. You say you are not opposed to hiring a professional but you want to do the work yourself. If you are planning on doing all the grunt work and then hiring an electrician to do the connections etc mainly at the sub panel you need to understand that many electricians will not "continue" work that has already been started by anyone else, not only by a home owner but by another electrician. Mostly the reasoning for this is their liability insurance. They don't want to take on the liability of someone else' work. So before you start running anything or installing anything find an electrician that may be willing to let you assist them in running some of the lines, installing boxes etc to save some money. I have turned down many jobs because of this reason. Especially if the work is done and the walls are closed up and I can't see what has been done. I end up with overloaded device boxes (too many conductors for the size box), conductors that are too short, circuits that are causing a dead short because someone drove a screw into a conductor, back stabbing on receptacles causing the rest of the circuit to fail then spending my time trying to find the problem, Tight bends on conductors, wrong number of conductors on cables, conductors that end up at a dead end with no power to them; you name it i have found it.

What do you mean by this statement? -->"I know the sub panel ground bus bar needs to be broke in order to be a proper sub panel." I would assume you mean you understand that the ground must be separate from the neutral and the neutral must be isolated from the panel. You don't run a 6/4, terminology is 6/3 with ground. But as stated you need individual conductors in conduit. If all conductors must be in conduit then you absolutely must be very mindful of how many conductors you are allowed in a specific size conduit, based on size of conductor and type of conduit you are using.

Circuit, breaker and circuit breaker are not all the same. Breaker and circuit breaker are basically the same. Circuit is the line you run.

What do you mean by GFCI outlets throughout? Unless Chicago has this specifically written in the code GFCIs are not required throughout living areas (specific locations only required such as bath, laundry etc), they are receptacles, not outlets. AFCIs are though.

If this is going to be permitted and inspected you will have to submit a plan/layout of your proposed circuits, panel, conductors, conduit etc etc etc. This is not a simple task. It will more than likely require a rough inspection and then a final inspection.

Again, do not start any work or buy anything until you have presented your plans to your local authority and they have been approved. Then you will know exactly what you will need. Also, again, if you will be utilizing an electrician be sure you make it know to them that you will be doing some of the grunt work. You don't want this electrician to come in to start the job and find you have started running conduit etc and then tell you they won't do the job.

This type of work takes years to learn and understand. Reading a few days off the Internet will not provide you enough of what you need to complete this on your own. Take your time, read all of the requirements from the local authority, understand all the terminology, discuss and review plans with an electrician, prior to submitting the plans, he/she may be able to help you do the layout. Also, if you are applying for the permit prior to doing so understand what you are doing, learn the term etc so that when you speak with the electrical inspector and you are going over your proposed plans he/she has the sense that you know what you are talking about.


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