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Need New Sub-panel attached to existing 200 amp meter/main breaker service panel

Need New Sub-panel attached to existing 200 amp meter/main breaker service panel

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  #1  
Old 03-27-13, 06:48 PM
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Need New Sub-panel attached to existing 200 amp meter/main breaker service panel

Hi everyone,

This is my first post here so Iíll try not to step on anyoneís toes.

I state my background not to brag or blow my own horn, by my experience with forums is people can be pretty rough if they think youíre total dumb ass and in way over your head. Iím not a dumb ass but my expertise is not electrical other than around the edges observing professionals and my own fairly small DIY projects.

Background; I managed a large state facility maintenance department for several years with about 60 professional staff. Before that I worked for the Dept of transportation structures design unit (bridges, retaining walls, etc.), and prior to that I worked for my father for several years in new residential construction. He was a general contractor and I schedule the work, made job site inspections, drew construction plans, dealt with permitting agencies, etc. Iíve done some minor remodeling professionally working for another contractor, and as noted a number of DIY projects.

I have a fairly current copy of the NEC, UMC and I believe my community has adopted the California Building Code (not sure which version), but that requires verification. Lastly, I will be hiring a licensed electrician in some capacity - just not at this time since Iím in the planning stage.

OK, now the problem.

I want to expand my current circuit capacity. Currently I have a 12 slot, 200 amp meter/main breaker service panel - see photo. I was originally thinking of gutting the panel to use it as a j-box, but after review I think it would be better to yank 3 breakers, and set a 70 amp sub-panel next to the exiting one.

My biggest issue seems to be finding a suitable sub-panel box. The ones Iíve looked at in a few local builders supply seem to come in interior mount or surface exterior mount. I donít have room for an interior cabinet, and the exterior cabinets all seem to have the KOís in the bottom and lower back/sides. I want to insert it into the wall just like my existing panel and bring my 5 or 10 new runs down through the wall from the attic. See KOís diagrams. So far Iíve looked at Siemens/Murray, GE and Square ĎDí. They all seem to be configured the same way.

BTW - done some review of main feed and I promise I wonít try to overload it. For instance, I'm converting 240v 50 amp electric dryer to gas. I converted my 240v 20 amp water heater to gas and have 120v 30 amp air compressor breaker that can move over. My new circuits will be 2 interior lighting and 2 wall plug circuits. Eventually I need to run a line out to my detached garage to put a sub out there.

Again I donít pretend to be an electrician and I am sincerely asking for help here knowing there are many people here with far more experience in this area than me. Please offer suggestion.
 
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Last edited by teagueAMX; 03-27-13 at 07:20 PM.
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  #2  
Old 03-27-13, 07:15 PM
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Welcome to the forums! You will fine the people here are much more helpful than some of the "pro" forums.

Your plan to install a outdoor sub panel next to your current one is good. You just need an panel that is rated for outside. The surface ones you have seen would work for you, you just need to either mount it to the surface, or remove some of the stucco and mount the new panel the same as the old one.

Pro's will punch a KO if there is not one available in the location that is needed. In your case, I would just punch a hole in the sides of the panels, old and new, and run a short nipple between the two. Relocate two circuits from the old panel, to the new panel, to make room for the new breaker to feed your new panel.

It appears you already have a two pole breaker that is off. Is that being used? That might be your two spaces you need.

You might find a 100 amp panel is less expensive than a 70 amp rated one, and will give you more spaces available for future. You would still not have to feed it with 100 amps. That is dictated by the breaker you will put in the main panel.
 
  #3  
Old 03-27-13, 07:19 PM
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You should only need to pull two breakers, assuming 240V single phase service.

You'll need to decide on the capacity of the subpanel. Personally I would go with 100A service. that means a 100A double-pole breaker in the main, Qty three of 3AWG THHN/THWN wires, and one 8AWG for ground.

Two of the wires become hots. One becomes neutral and is connected to both panels' neutral bus bars. The ground connects to the two panels' ground bus bars.

The neutral in the subpanel does NOT get tied to ground. This is different than the main panel.

I am not an electrician. If someone else, especially an electrician contradicts me, go with their advice.
 
  #4  
Old 03-27-13, 07:29 PM
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Wow you guys are great.

I'm converting 240v 50 amp electric dryer to gas. The double pole mentioned is for my 240v 20 amp water heater that I already converted to gas, plus I have 120v 30 amp air compressor breaker that can move over. My new circuits will be 2 interior lighting and 2 wall plug circuits. Eventually I need to run a line out to my detached garage to put a sub out there.

I like the 100 amp better but I was being cautious to avoid getting beat up, and yes it would be 240V single phase service.

I didn't know if the doing my own KO's was proper but I can handle that.
 

Last edited by ray2047; 03-27-13 at 08:12 PM. Reason: Remove unnecessary refer.
  #5  
Old 03-27-13, 07:35 PM
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Punching your own holes is easy if you have the right tools. We use a hydraulic KO punch that is quite expensive, but I bet you could rent one, or just use a proper sized hole saw in a pinch.

I agree with TWX, feed it with 100 amps and call it good. (with a 100 amp breaker and panel of course )
 
  #6  
Old 03-27-13, 07:35 PM
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Thanks T-W-X for the tech info. I'm just leaning about neutrals, bonding and grounds so that really helps. Plus the wire size info is really great.
 

Last edited by teagueAMX; 03-27-13 at 07:58 PM.
  #7  
Old 03-27-13, 07:49 PM
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@ Tolyn Ironhand

I can rent a punch no problem. Got what you said about the side KO's for connection to my old and new panels, but do you suggest bringing my new home runs through the sides or the top? I assumed when insert the box in the wall I may not have room between the studs.

Also, I read somewhere on this forum that a person could run a one or two 3/4" FMC from the new sub to the attic and terminate them in a j-box, and then the new circuits then tie into the j-box. Each FMC could serve up to 8ea 15 amp circuits. I don't need that many but did I read that read that correctly?
 
  #8  
Old 03-27-13, 09:56 PM
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Home runs come down the wall and enter the top of the panel. Panel boxes can be bought wothout any KOs in them, from an electrical supply house.

I read somewhere on this forum that a person could run a one or two 3/4" FMC from the new sub to the attic and terminate them in a j-box, and then the new circuits then tie into the j-box. Each FMC could serve up to 8ea 15 amp circuits
OK, I'll bite. What is FMC? If it's some type of conduit, like EMT, you'll have to pull individual conductors through it and derate the wiring if you pull more than 3 current-carrying conductors in one. Pretty expensive way to do it.
 
  #9  
Old 03-27-13, 10:36 PM
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I'm going to hazard a guess that FMC is "Flexible metallic conduit". I've heard such referred to as "armor cable" before if that's so.
 
  #10  
Old 03-27-13, 11:01 PM
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Sorry guys. See what happens when I read something - I get dangerous

But seriously, TWX, you are correct. I didn't know the difference until I Googled it a minute ago "FMC "Flexible Metal Conduit" vs emt".

The funny thing is I never heard the term FMC until I read it here today in this forum reading through some of the other posts. Just shows it's best to keep things simple.

Can somebody tell how to quote messages in line with a response. I've done it before on other forums, but can't seem to figure it out here. Is it a setting because I looked all over and couldn't find it.

Thanks again. You all have been very helpful.
 
  #11  
Old 03-28-13, 05:01 AM
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At the top is a little icon that looks like a speech bubble in a cartoon. You use that to get the quote tags. You copy and paste the text you want inside the quote tags. Then delete the refer URL that comes at the end of text you copy and paste.

The quote button was removed because people were quoting whole posts instead of just what was needed.

Example: [QUOTE]Can somebody tell how to quote messages in line with a response.

Read more: http://www.doityourself.com/forum/electrical-c-d-c/491771-need-new-sub-panel-attached-existing-200-amp-meter-main-breaker-service-panel.html#ixzz2Opnq6iUN[/QUOTE]


The part that begins
"Read more..." is what you delete.

What you end up with is:
Can somebody tell how to quote messages in line with a response.
 

Last edited by ray2047; 03-28-13 at 05:17 AM.
  #12  
Old 03-28-13, 06:36 PM
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At the top is a little icon that looks like a speech bubble in a cartoon. You use that to get the quote tags. You copy and paste the text you want inside the quote tags. Then delete the refer URL that comes at the end of text you copy and paste.

The quote button was removed because people were quoting whole posts instead of just what was needed.
Thanks ray2047 . . . . .. . . .. . . . ..
 
  #13  
Old 03-28-13, 06:39 PM
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Looking at panels today and I'm wonder if it's critical to have a main breaker in the sub.

These two panels will be separated by 12 inches max, and just a couple of inches.

Open for suggestions.
 
  #14  
Old 03-28-13, 06:52 PM
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You will not need a main for the subpanel.
 
  #15  
Old 03-28-13, 06:58 PM
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You do not need a main in the sub panel as it is attached to the same building as the main panel. However, it may be less expensive to buy one off the shelf that has one installed, then one that is a main lug only (MLO).
 
  #16  
Old 03-28-13, 08:16 PM
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Surprisingly a 125 amp main breaker is less expensive than a 100 amp. Would the 25 capacity make much difference? I would also need a 125 amp breaker in my service panel, correct?

Also, I noticed the main lug panels are rated I assume the rating is a max capacity, which I assume is the buss bar capacity and total slots, correct?
 
  #17  
Old 03-28-13, 08:25 PM
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Would the 25 capacity make much difference?
No. You will only have the ampacity you supply. See below.

I would also need a 125 amp breaker in my service panel, correct?
No. If you want to put one there and supply the subpanel at 125A you can, but you will need to use 1/0 AWG copper or 3/0 AWG aluminum conductors to connect them.

If you only need 100A in your sub, install a 100A breaker in the main panel and the smaller wires. The size of the main breaker in the sub is immaterial, so long as it is 100A or more. It will only function as a convenience disconnect.
 

Last edited by ray2047; 03-28-13 at 08:52 PM. Reason: Changed 125V to 125A
  #18  
Old 03-29-13, 04:35 PM
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Just curious, where is the 200 amp main breaker. I don't see it in the picture. But, I do see what appears to be a 30 plus year old meter socket that has considerable rust. I believe I'd think about replacing the meter/main combo panel.
 
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