Main Panel / New Sub Panel Questions

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Old 02-06-10, 03:26 PM
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Main Panel / New Sub Panel Questions

Hello,

I am in Douglasville, GA and I am planning some electrical upgrades in my basement. The upgrades will fill my current box, so I plan on instead adding a sub panel, using the diagrams on the sub-panel installation sticky here.

My current service is 200A. I have a 200A main breaker located outside at the service entrance. Also there is a 10 slot panel, that currently has nothing on it. From there the service comes into the house to a CH42NL225A main panel. Inside the panel, the neutral bars and the ground bars are separated from each other.

My plan is to add a 60A 2 pole breaker to the existing main panel, and connect it to a 20 slot (or so) sub panel using #6 THWN. I will then add the new basement circuits to the sub panel and save the 6 remaining slots on the main panel for the airconditioning I will have to add for the basement and eventually the attic.

My questions are:

1 - My current panel uses type CH breakers. I figured for consistency I would use a panel that accepts the same breakers, but HD doesn't carry Cutler Hammer panels, and Lowes only carries Cutler Hammer panels that take BR breakers. Are the type CH breaker panels still current technology and I simply have to go to an electrical supply house to find what I want? Or should I forget about using a type CH panel and go with something else?

2 - My current panel is mounted between the studs in my basement with good access. My plan is to mount the sub next to it. Do I need to leave an empty stud cavity between the 2 panels, or can I put them right next to each other?

3 - When I run the conduit between the two, should I come out the bottom of the existing panel, and in the bottom of the new panel, or can I come in from the studs that the panels butt directly up to?

4 - A general question about my current panel to expand my knowledge. The info on the existing CH42NL225A panel notes a max of 200A total breaker rating per stab. I'm not positive I completely understand what that means. I would assume it is the sum of the breaker amp ratings on each stab, but that doesn't make sense when you start adding those breakers up. Just with the existing circuits each side of the box is already a good bit above that. So, what does that limit mean? Also, is there a limit to how much cumulative amperage breakers you can install in the box? I wouldn't think so since a load greater than the box is rated for would trip the main breaker anyway, but I want to understand this as best I can before I dive in to keep things safe.

Thanks for your help,

Matt
 
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Old 02-06-10, 04:18 PM
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First of all the term "main panel" can be misleading. There is no such term in the National Electrical Code (NEC). I do think the term "sub panel" is defined in the NEC either but the term is so universally used that most people know it is a panel fed from another panel.

That stated, the outside panel you have is your SERVICE panel and any panel that is connected after that panel will be a sub panel and will have the neutral bus isolated from the metal case and all equipment grounding conductors. IF the 200 ampere circuit breaker in the service panel is so arranged so that any subsequent circuit breakers in this panel are powered through this 200 ampere circuit breaker then you can add to this panel and perhaps another (a third) panel will not be necessary. If you post a few pictures of this outside service panel there will be someone here that can advise you on that subject.

Cutler-Hammer type CH panels and circuit breakers is their premium line and the BR is the second tier line just like Square D has the QO for their premium line and the Homeline is the second tier product. I was in my local Lowes yesterday and they did carry both the CH panels and circuit breakers so I am quite sure that your Lowes can order the CH for you. While there is nothing wrong with the BR line your desire to keep the same line is a good one.

You do not need an empty stud bay between the panels as long as the covers fit without overlapping. If the existing panel has its box against one stud it is likely that having the adjacent panel against the opposite stud in the next bay will allow both covers to fit without interference. If the covers will interfere they you will need to have the bay in between the two panels. You might be able to do some creative framing (using appropriate headers and jack studs) and make a large bay that will encompass both panels. This, of course, depends on how the existing cables run.

Unless conduit is required by your local code it will be easier to use type NM cable to run from one panel to the next. Use appropriate cable clamps and nail plates over the holes drilled in the stud(s). If you use conduit any method that is acceptable under the rules for conduit is okay. Remember that if you include any conduit bodies (LB, LL or LR) You need to leave the covers permanently accessible.

A "stab" is the part of the bus bar that the circuit breaker pushes on to. What the 200 ampere per stab means that of the two breakers that connect to one stab, i.e. the left and right CB, their total amperage may not exceed 200 amps. I seriously doubt that you have a situation (or will ever even see one) where this rule would apply.
No, there is no limit to what the sum of the individual circuit breaker amperages may add up nto being.
 
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Old 02-06-10, 05:21 PM
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With complete answers like that one Furd you could put me out of a job here . Well done Beer 4U2
 
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Old 02-07-10, 02:32 PM
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The Neutral must be "Ground-Isolated" in the new SP, and you'll need as seperate terminal bar for the EGC's.


Good Luck
 
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Old 02-08-10, 04:07 PM
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furd - Thank you for the detailed response. Regarding the stab limitation, now that I know what it really means, you are correct. There are no stabs that even approach the limit, and it would be tough to do so. Thanks for the rest of the clarifications of my knowledge.

Here are some pictures of my current service panel and sub panel. The sub panel that all of my circuits are on now is about 40 feet from the service panel, in my basement's equipment room. This is the same location that I intend to place the new sub panel in.

Since it is pretty far from the service panel, my intent was to pull the new sub panel off the existing panel in my basement. I guess the question that leaves me with is can I pull a sub panel off the existing sub panel? Can a third panel be fed off a second panel that is fed from the service panel? Does that make sense?

I'll attach a couple of pictures so you can see exactly what I'm talking about.

Outside Service Panel -

IMG_2164 on Flickr - Photo Sharing!

Inside Panel W/ Existing Circuits -

IMG_2167 on Flickr - Photo Sharing!

Thanks,

Matt
 
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Old 02-08-10, 04:49 PM
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Originally Posted by sabreliner View Post
Since it is pretty far from the service panel, my intent was to pull the new sub panel off the existing panel in my basement. I guess the question that leaves me with is can I pull a sub panel off the existing sub panel? Can a third panel be fed off a second panel that is fed from the service panel? Does that make sense?
You could do a load calculation but at 200 amps I doubt you will have an issue. You can have sub panels after sub panels if you want. As long as they have the capacity to handle the load.
 
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Old 02-08-10, 07:34 PM
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Your service panel has what are called "feed through" lugs where the feeder to the subpanel are connected. This means that you can use the spare openings in this panel if you so desire. It may make some sense to do so for the condenser (outside unit) of the new air conditioner or for any outside receptacles you may desire.

As Tolyn stated, you can keep adding subpanels to subpanels as often as you want as long as you don't end up overloading the original feeder.

It appears that your existing subpanel has two type NM cables entering the bottom without the proper clamp. Please take care of this.
 
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Old 02-08-10, 07:43 PM
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Thanks furd. On closer inspection I see the missing clamp that you are referring to. Kind of annoying the more I look the more problems I find that the original electricians left me. You know, little things like 20A outlets on 15A circuits, ground wires not connected in fixtures, and now a missing clamp. Kind of annoying.

I'll get my books out and read up on how to do a proper load calc just to be on the safe side.

Thanks for everyone's replies.
 
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Old 02-08-10, 07:54 PM
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As long as there are at two places to plug in, 15 ampere receptacles on 20 ampere circuits are completely legal in the US. A standard duplex receptacle has two places to plug in.
 
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Old 02-09-10, 07:36 AM
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Yup, I know you can use a 15A outlet on a 20A circuit. What you cannot do, and what I found 2 examples of on my house, is use a 20A outlet on a 15A circuit. But, I guess what can you expect on lowest bidder residential construction.
 
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Old 02-09-10, 06:38 PM
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Yes, of course you are correct, I misread the initial statement. unish:
 
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Old 02-09-10, 06:50 PM
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Thanks again for taking the time to offer your advice and experience!
 
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