Subpanel Addition Questions

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  #1  
Old 03-21-06, 05:28 PM
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Question Subpanel Addition Questions

We have a 100 Amp Main circuit breaker panel. There is a 60 amp 220 V breaker feeding a small 8 circuit breaker panel right next to it. Our home is gas. (No stove, water heater or dryer on the electrical). We do have a bunch of GFIs for the hot tub, whirlpool, main pool and baths. There is also a 220 feed for a compressor. What has happened is that a lot of breakers have been used. When an addition was put on, we ran 5 15 amp feeds over 75 feet. I want to fix that now. My plan is to add another subpanel about 40 feet from the main panel. I think a 50 amp should be enough as it is only for a garage and big family room. I will reroute the 15 amp feeds to the new subpanel. That way I can get rid of the "piggyback breakers" in the main panel. I also want to add some more circuits for outdoor lightning and the garage and some pool lights.
1. Can I add a 50 amp subpanel when there is already a 60 amp subpanel?
2. The box I was looking at says 8 positions, 16 circuits. Does that mean 16 single phase breakers?
3. What size wire, I assume 2 conductor with ground to feed the new 50 amp panel.
4. Is 50 the correct subpanel size? Should it be a 60 amp feed?
Thanks in advance.
Mark
 
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  #2  
Old 03-21-06, 05:33 PM
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Why not just replace the sub panel you have now, with one having more ckt capability?
You have most everything in place now, except for the new ckts.

Just a thought.
 
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Old 03-21-06, 05:51 PM
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I want to get rid of the multiple long, long 15 amp 14/3 feeds to the new addition. I also want to put the new gas stove on it's own circuit. It draws 15 amps to preheat with an electric element. I think that I can minimize the voltage drop by locating a panel at that end of the house.
 
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Old 03-21-06, 06:01 PM
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Thats fine, But something will have to give. If you just get a bigger(more ckts) 60 amp sub andlocate that where you want it, You just remove the 8 ckt can and run a new 60 amp feed to the new location. any of those existing 8 ckts that don't reach, extend them aswell to the new location. Then bring in your new ckts. In short enlarge the sub, eliminate the existing one. There is no need to add ANOTHER sub. I hope I got my thought across . If not,I'll try again.
 
  #5  
Old 03-21-06, 06:41 PM
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8 positions 16 circuits means just that. 8 positions for breakers, and you can use tandem breakers for a total of 16 individual circuits. Of course, if you are talking 240 volt circuits, that number will be less.
 
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Old 03-22-06, 07:08 AM
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Originally Posted by n1ml
I think a 50 amp should be enough as it is only for a garage and big family room.
Can you show your math?

> 1. Can I add a 50 amp subpanel when there is already a 60 amp subpanel?
Yes. (Doesn't mean that you can actually run everything at the same time.)

> 2. The box I was looking at says 8 positions, 16 circuits.
> Does that mean 16 single-pole breakers?
Yes.

> 3. What size wire, I assume 2 conductor with ground to feed the new 50 amp panel.
Wrong, three-conductor plus ground.

> 4. Is 50 the correct subpanel size? Should it be a 60 amp feed?
That depends. Do you want it to be fully loaded and out of space from the time it goes in?
Or would you like to plan ahead and leave some room for future expansion but pay a little more now?
 
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Old 03-22-06, 08:56 AM
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1. I was curious on how the NEC addresses subpanels. There must be a limit on how many can be added. My question was not as much load as to how many indidual circuits could be hung off a 100A main. For example, and I know this is way out there, but could I wire a house with a 100 A main that has 75 circuit breakers, 15 A each?

2. Why 3 wire with a ground? I thought that you run the 2 220 wires from the bi-phase 220Vac input to the main lugs and then a same size AWG to the ground bar. Thats 3 conductors total. Am I required to run two same size AWG from the main panel to the subpanel?

3. The 50 60 amp question relates to what is standard out there. If 60 is a standard, I will use 60.

Thanks
Mark
 
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Old 03-22-06, 09:12 AM
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Originally Posted by n1ml
1. I was curious on how the NEC addresses subpanels. There must be a limit on how many can be added. My question was not as much load as to how many indidual circuits could be hung off a 100A main. For example, and I know this is way out there, but could I wire a house with a 100 A main that has 75 circuit breakers, 15 A each?

2. Why 3 wire with a ground? I thought that you run the 2 220 wires from the bi-phase 220Vac input to the main lugs and then a same size AWG to the ground bar. Thats 3 conductors total. Am I required to run two same size AWG from the main panel to the subpanel?

3. The 50 60 amp question relates to what is standard out there. If 60 is a standard, I will use 60.

Thanks
Mark
1. No real limit. You can have each receptacle be it/s own circuit if you want. Each panel is limited, but you could keep adding panels.

2. Your electricity is not 2 phase or bi phase, It is single phase. For a sub panel in the same building as the pane feeding it the ground and neutral must be isolated. That means four wires from the main panel to the sub panel. Two hot wires, one neutral and one ground. Depending on the current you may be allowed a smaller neutral and/or a smaller ground.

3. To see what is standard, browse the home stores. They concentrate on standard items.
 
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Old 03-22-06, 10:06 AM
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You answered a lot in your response. Thanks
By biphase, I meant that there is 220 VAC single phase that has been split by a transformer to be two 120 VAC sources out of phase by 180 degrees and each referenced to a common ground.
I did notice that my main 100A panel has one big ground bar strip that has all the bare and white wires connected to it. I take it that the new sub panel will have one ground bar also. I wire the new feed to ground bar in the main with both a jacketed wire and the bare ground wire? Seems odd.
Is there a standard for these subpanels. Should I do 50 or 60 or is it up to me?
 
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Old 03-22-06, 10:42 AM
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Both the ground and the neutral will connect to the same place in the main panel, but must be separated in the sub panel. You will probably have to buy a ground bar kit for the sub panel, and you will have to make sure that the neutral bar does not get bonded to the panel.

I would buy at 100 amp panel for the sub panel, but only feed it with a 60 amp breaker. You could, if you want, buy a 60 amp sub panel.
 
  #11  
Old 03-22-06, 10:55 AM
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Originally Posted by n1ml
There must be a limit on how many can be added.
Till you run out of room or have bad workmanship.

> how many individual circuits could be hung off a 100A main.
No limit.

> could I wire a house with a 100 A main that has 75 circuit breakers, 15 A each?
Sure.

> Why 3 wire with a ground? I thought that you run the 2 220 wires from the bi-phase 220Vac

You thought wrong.

> Am I required to run two same size AWG from the main panel to the subpanel?
Three plus a ground.


> The 50-60 amp question relates to what is standard out there.
> If 60 is a standard, I will use 60.
100A is standard too.


> I take it that the new sub panel will have one ground bar also.
It probably has none.
It is up to you to purchase ground bars as needed.
I recommend two to reduce clutter.

> I wire the new feed to ground bar in the main with both a jacketed
> wire and the bare ground wire?

Yes.
One is a current-carrying conductor (neutral, grounded conductor) the other is a equipment safety ground (bonding conductor).
In normal operation, the safety ground does *not* carry current.

This is not odd. The two wires serve entirely different purposes.
 
  #12  
Old 03-22-06, 12:39 PM
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Talking

OK. I think I got it!
I understand the 3 conductor with ground and why the subpanel isolates the ground from the "neutral".
I will shop around for an 8 or 12 breaker panel. Maybe 12 is better, especially if it has a main breaker. Most likely will go with a 60 amp since that is more than enough for the demand on this panel.
Thanks for all the info.
I should be able to plan and execute the job based on the helpful assistance from the forum.
Thanks again,
Mark
 
  #13  
Old 03-23-06, 08:41 AM
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Mounting Subpanel New Question

I plan to locate the new subpanel in a basement workshop area. The walls are cement on 2 sides and are plaster walls on the other two sides. The area is about 24 x 16 feet. The ceiling is plaster. I plan to mount the new subpanel on one of the plaster (skim coat over blueboard) walls. I plan to run the feed to to main panel in the ceiling rafters and and then come out and run down the wall to the surface mounted box. The wall the box is on is an exterior wall with the garage on the other side of the wall. The feeds will be exposed on the walls since it is a basement area. Do I need to affix a plywood board, like 2'x4' to the plaster wall and mount the panel to it? Can I just mount the panel to the plastered wall? Should I space the plywood out using some 2x3s so I can run the wires behind it? I've never come across something like this so I surely don't want to have to redo it if it is wrong.
Thanks (I really got to get this going instead of asking so many questions!)
Mark
 
  #14  
Old 03-23-06, 09:59 AM
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> I will shop around for an 8 or 12 breaker panel. Maybe 12 is better,

In a few years the 12 will be full and you'll be wishing you had 16 or 20.

> especially if it has a main breaker.

Not likely.


> Most likely will go with a 60 amp since that is more than enough for the demand on this panel.

Come back in 6 to 10 years and let us know how that worked out for future demand.


> Do I need to affix a plywood board, like 2'x4' to the plaster wall and mount the panel to it?

You don't have to. But you have to fasten every cable coming out of the panel.
Wood makes this much easier.
Four lag bolts or Tap-Cons will secure the board (3' wide) to the wall.
Then you can use short screws to affix everything to that.


> Can I just mount the panel to the plastered wall?

Bad idea.


> Should I space the plywood out using some 2x3s so I can run the wires behind it?

I would not. But you should conside how you would want it if the basement were to be finished or insulated.
 
  #15  
Old 03-24-06, 08:10 AM
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Panel Mounting Detail Question

I decided that the best location was on a concrete wall in the basement. The wall is 8 feet tall. I want to mount a 2' x 4' piece of 1/2" plywood securely fastened to the concrete wall. The 12 position panel will then be securely mounted to it. BTW, I chose a 12 position panel, utilizing a 50 Amp main fed with 6 AWG, 3 conductor with ground cable. The panel says that the main lugs are 4 to 2/0 AWG, so the side fed main will accomodate the 6 AWG.
 
  #16  
Old 03-24-06, 01:50 PM
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> The panel says that the main lugs are 4 to 2/0 AWG,

Is this a 100+A panel?

> so the side fed main will accomodate the 6 AWG.

Please explain how you came up with this.
 
  #17  
Old 03-24-06, 03:55 PM
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It is explained inside the breaker panel and was explained to be by an electrician.
The first two 1" slots on the upper left hand part of the box is populated with a 50 Amp 220 volt breaker. This is the side fed breaker with the feed, 6 AWG, from the other main panel. There is a 50 Amp double pole breaker in the main panel also.
It seems to make a lot of sense to me.
 
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