# Breaker panel capacity



## Rze (Aug 9, 2006)

It is my understanding that if the Breaker box is 200 amps, that technically, you can have up to 200 amps PER LEG, for a total of 400 amps in one box, as long as you keep the box balanced.

Can anyone address this?


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## jwhite (Mar 12, 2006)

This question usually gets a conversation going even among professionals. But I think that the way you worded your statement if fundimentally correct.

If you have a panel feed with 200 amps at 240 volts, then you could have up to 200 amps at 120 volts on each leg. Except that you cannot load the panel beyond 80 percent so it would be 160 amps not 200.

Another way to look at it is by converting the voltage and amperage into wattage.

160 A x 240 V = 38400 W That is 80 percent of 200 amps at 240 volts.

320 A x 120 V = 38400 W That is 80 percent of 400 amps at 120 volts.

Note that the total wattage is the same.


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## Speedy Petey (Feb 1, 2004)

Like JW said. 
A watt is a watt. Amperage moves around according to voltage.
Your 200 amp service is NOT 400 amps for both legs. It is 200 amps @ 240v.


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## joed (Mar 13, 2005)

And all this has NOTHING to do with adding up the numbers on all the breaker handles which most home owners seem to want to do.


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## RobertWilber (Mar 24, 2006)

80% is CONTINUOUS load rating [more than 4 hours]


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## jwhite (Mar 12, 2006)

a continuous load is three hours or more.

And loading of panels is not the same as loading of branch circuits.


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## Speedy Petey (Feb 1, 2004)

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## Rze (Aug 9, 2006)

When I piece everything together, it makes sense! Thanks to all for responding!

Dave:thumbsup:


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## hodgehj (Nov 20, 2007)

If it has nothing to do with adding up the breakers then what does it relate to? I realize the load should be something less than the breaker size and the breaker is a safety device. It would therefore be possible to run each branch circuit at 85% and exceed design. It should however give a good estimate. If the breakers total up to the 80% watermark certainly I would think you wouldn't want to go any higher???


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## 220/221 (Oct 9, 2007)

> It is my understanding that if the Breaker box is 200 amps, that technically, you can have up to 200 amps PER LEG


.......Yes



Edited to clarify,..... although you can have the 200 amps on each leg you will not have 400 amps....unless you add up the total number of amps allowed on each leg and there would be no reason for doing that.


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## RichyL (Nov 17, 2007)

Rze said:


> It is my understanding that if the Breaker box is 200 amps, that technically, you can have up to 200 amps PER LEG, for a total of 400 amps in one box, as long as you keep the box balanced.
> 
> Can anyone address this?


This is incorrect. If you have a 200 amp service, that is your max load. Your 200 amp service should not be exceeded by your total branch circuit calculated load.
Adding the denominations of breakers has nothing to do with it, since a 20 amp breaker may only be hooked to lets say a washing machine which might draw 12 amps and be on a 20 amp breaker but is not even used continuously. Your load calculations are based on demand factors. You add the washer, lighting , general receptacle and small appliance receptacle loads all of those together. The first 25 amps of those loads (3000 voltamperes) will be calculated at 100%. The remainder will be calculated at only 35% for this example. This is just an example of course. There are more calculations involved for range, furnace, etc etc. NEC article 220 explains the rest if you can understand Greek :huh: and have a codebook handy. Oh yeah and no more than 42 breakers per panel.

It is considered good practice to balance your loads out on each side of the panel. I hope this helps


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## Andy in ATL (Aug 28, 2007)

42 breaker limit goes away in '08. Just in time for house panels filled with HOT AFCI's.:thumbup:


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## RichyL (Nov 17, 2007)

Andy in ATL said:


> 42 breaker limit goes away in '08. Just in time for house panels filled with HOT AFCI's.:thumbup:


Are you referring to the combination type arc faults? Will they just be required for bedrooms? I hope so, those breakers are so expensive. And how many breakers will be allowed in the new panels in 08. I guess in the next addition of the NEC we'll have to erect perimeter fences around our panels with fire-rated emergency opening doors :laughing:


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## Andy in ATL (Aug 28, 2007)

Wait til you get a load of this....

'08 NEC 210.12(B) Dwelling units. All 12V, single phase, 15- and 20-ampere branch circuits supplying outlets installed in dwelling unit family rooms, living rooms, parlors, libraries, dens, bedrooms, sunrooms, recreation rooms, closets, hallways, or similiar rooms or areas shall be protected by a listed arc-fault circuit interrupter, combination-type, installed to provide protection of the branch circuit.

So tell me RichyL...Is a switch an outlet?:laughing:


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## RichyL (Nov 17, 2007)

Andy in ATL said:


> Wait til you get a load of this....
> 
> '08 NEC 210.12(B) Dwelling units. All 12V, single phase, 15- and 20-ampere branch circuits supplying outlets installed in dwelling unit family rooms, living rooms, parlors, libraries, dens, bedrooms, sunrooms, recreation rooms, closets, hallways, or similiar rooms or areas shall be protected by a listed arc-fault circuit interrupter, combination-type, installed to provide protection of the branch circuit.
> 
> So tell me RichyL...Is a switch an outlet?:laughing:


Lmao....Hell no. Closet? whatchatalkin bout willis, thats my hide n seek room. I bet half the states dont adopt the 08 for quite a while, if at all. Makes you wonder if the NEC board is sleeping with the afci manufacturers, Seems a little excessive imo.


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## Speedy Petey (Feb 1, 2004)

Guys, let's remember the original post is well over a year old and I think the OP has his answer by now.
Hodge brought it back up to the top with his post.


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## Speedy Petey (Feb 1, 2004)

RichyL said:


> Makes you wonder if the NEC board is sleeping with the afci manufacturers, Seems a little excessive imo.


Ya THINK!


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## 220/221 (Oct 9, 2007)

Didn't realize it was an old post....but while were on the subject....




> '08 NEC 210.12(B) Dwelling units. All 12V, single phase, 15- and 20-ampere branch circuits supplying outlets installed in dwelling unit family rooms, living rooms, parlors, libraries, dens, bedrooms, sunrooms, recreation rooms, closets, hallways, or similiar rooms or areas shall be protected by a listed arc-fault circuit interrupter, combination-type, installed to provide protection of the branch circuit.


 
Ive said it before and I'll say it again. The people who write crap like this are idiots. I'm not saying that the AFCI's should not be required but why do they have to use language like this. 

They list a bunch of rooms and then add "or similar rooms. Why don't the just say all 15/20 outlets" or "all 15/20 interior outlets". 

If they mean recepticales, why don't they say recepticales? They should KNOW the simple fact that receps are OFTEN referred to as outlets.

If they mean branch circuits why don't they say so?


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## Andy in ATL (Aug 28, 2007)

Similiar rooms and areas...Does that mean kitchen, bath, garage, or basement lights???:no:


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## goose134 (Nov 4, 2007)

Well gosh, if they made everything perfectly clear, then what would we talk about?:whistling2:


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## Andy in ATL (Aug 28, 2007)

goose134 said:


> Well gosh, if they made everything perfectly clear, then what would we talk about?:whistling2:


Very well said. Can I steal that?:huh:


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## Stubbie (Jan 7, 2007)

220/221


I fail to see the confusion......btw these people are not idiots, but I would say someone who would make this statement would be suspect.....:yes:

"these people" have already saved more lives than you will in your dreams.

Stubbie


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## Andy in ATL (Aug 28, 2007)

Stub, I've stated before that AFCI's will save lives. Similiar rooms and areas confuses me. But then again I often (daily)consider myself an IDIOT:yes: 

Andy


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## RichyL (Nov 17, 2007)

Anyone happen to know which states will be adopting the 08 code in 08?


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## Stubbie (Jan 7, 2007)

Andy..... my reply wasn't directed at you it was intended for 220/221


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## arichard21 (Oct 17, 2007)

just think how people felt when a ground was required in all branch circuits back in the day. people were probably swearing up and down because of the added expense.

if i had to upgrade my current house to AFCI on the above listed ccts, i would have to add 1...

bedrooms already have them, kitchen, dining and laundry wouldnt need them. i would have to add 1 to the living room, thats it.

in our new house that we are planning, i would need 7 @ $50. really, what is another $350 in a $100,000 house? sounds like cheap insurance to me.


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## LawnGuyLandSparky (Nov 18, 2007)

One code, covering one mechanical aspect - $350.00 in your situation. Now add a few bedrooms or sq. ft, and some recessed lighting, and now you're talking $1000.00 or more. Now add the beefed up requirements in the plumbing & drain, construction, HVAC, energy, window, etc and you're talking about some real money. 

The issue for many isn't about the money, it's about the process which is permeating into building codes. Manufacturers are inventing so-called "safer" products and getting them mandated into codes not for safety, but for their profit. Just make a new product, get it patented and get it injected as a requirement and you're an instant millionaire. 

When you look at the statistics and data regarding house fires and injury and loss of life and property - how many will be prevented by this $350.00 - $1000.00 additional expense? Most residential fires are not caused by electricity, though when no concrete cause can be found the fires are almost always blamed on "electrical." 

Of those that are electrical, how many of those electrical fires were caused by, or would have been prevented with an arc-fault breaker? Not too many fires I've read about where the cause was an actual sparking connection.


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## arichard21 (Oct 17, 2007)

LawnGuyLandSparky said:


> One code, covering one mechanical aspect - $350.00 in your situation. Now add a few bedrooms or sq. ft, and some recessed lighting, and now you're talking $1000.00 or more. Now add the beefed up requirements in the plumbing & drain, construction, HVAC, energy, window, etc and you're talking about some real money.
> 
> The issue for many isn't about the money, it's about the process which is permeating into building codes. Manufacturers are inventing so-called "safer" products and getting them mandated into codes not for safety, but for their profit. Just make a new product, get it patented and get it injected as a requirement and you're an instant millionaire.
> 
> ...


my post was specificly about AFCI breakers, and that $350 is going to cover ALL the AFCI breakers i will need for my new house under the 2008 NEC.

are you blind to the fact that there are hundres of thousands of ELECTRICAL house fires all around the world every year?

you dont think many are caused by sparking connections?


call up my father in law, and explain that to him. and he will explain to you how his barn burnt down in '93 and took 150 head of cattle with it.

when you are done, call a friend of my parents, who lost their twins back in the early 80's in a house fire that was electrical.


just because they are new doesnt mean they are a crock. i cant stand the people who think this stuff is all a conspiricy and that AFCI breakers do NO GOOD AT ALL.


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## spebby (Oct 24, 2007)

arichard21 said:


> call up my father in law, and explain that to him. and he will explain to you how his barn burnt down in '93 and took 150 head of cattle with it.


All I can say is that must have been a BIG barn.


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## arichard21 (Oct 17, 2007)

spebby said:


> All I can say is that must have been a BIG barn.


yes it was. ended up a total loss.


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## Speedy Petey (Feb 1, 2004)

arichard21 said:


> are you blind to the fact that there are hundres of thousands of ELECTRICAL house fires all around the world every year?


No. Are AFCIs going to prevent this??? Do you know this for sure? 
If you knew the facts, and not just the propaganda being shown to you, you'd be skeptical too. 

Fact is we went from never having heard of an AFCI, to requiring the whole house be covered by them in two code cycles. 1999 introduced them and now two cycles later they want them on EVERY 120v branch circuit. Hell, even GFIs are still being phased in since their inception. 
This is a corporate invasion plain and simple. This has FAR less to do with saving lives than with making $$$$$.

Look around. MANY municipalities are adopting the NEC with amendments relaxing the AFCI requirements.


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## Stubbie (Jan 7, 2007)

Speedy I disagee but my Dad retired from Square d...........


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## arichard21 (Oct 17, 2007)

Speedy Petey said:


> No. Are AFCIs going to prevent this??? Do you know this for sure?
> If you knew the facts, and not just the propaganda being shown to you, you'd be skeptical too.
> 
> Fact is we went from never having heard of an AFCI, to requiring the whole house be covered by them in two code cycles. 1999 introduced them and now two cycles later they want them on EVERY 120v branch circuit. Hell, even GFIs are still being phased in since their inception.
> ...


 
and many kids were affected by ADD and ADHD way before anyone diagnosed it and came up with a medication for it. does that mean that because kids survived for hundreds of thousands of years it is "made up" to benifet the drug companies?

maybe it is just that i am not a skeptical... and that i dont have a problem with doing something that could make me and my family safer, weather it is real or not. but the reality is that it IS code in many municipalities for them to be on bedroom branch ccts and soon on many more ccts. there isnt anything that can be done about it. the NEC isnt going to take them out of the code because people don't want them there...


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## LawnGuyLandSparky (Nov 18, 2007)

arichard21 said:


> my post was specificly about AFCI breakers, and that $350 is going to cover ALL the AFCI breakers i will need for my new house under the 2008 NEC.
> 
> are you blind to the fact that there are hundres of thousands of ELECTRICAL house fires all around the world every year?
> 
> you dont think many are caused by sparking connections?


I do not. When an electric heater is placed near combustable material - the cause of the fire is deemed "electrical." When an extention cord is overloaded and heats to the point where it can cause ignition - the cause is deemed electrical. Arc-fault breakers will not open in these situations.



> call up my father in law, and explain that to him. and he will explain to you how his barn burnt down in '93 and took 150 head of cattle with it.
> 
> when you are done, call a friend of my parents, who lost their twins back in the early 80's in a house fire that was electrical.
> 
> ...


I didn't say they'll do no good at all - but there is what as known as a cost-benefit. One does not require an escape ladder from EVERY 2nd story window, though you can do this as an option.

As for your fires - how would a BARN FIRE be prevented by a residential electrical code? And how do you know it was arcing that started it? 

Sorry for your parent's friend's loss, but I DIDN'T CAUSE THE FIRE so don't try to use guilt trip to prove your point.


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## LawnGuyLandSparky (Nov 18, 2007)

arichard21 said:


> maybe it is just that i am not a skeptical... and that i dont have a problem with doing something that could make me and my family safer, weather it is real or not. but the reality is that it IS code in many municipalities for them to be on bedroom branch ccts and soon on many more ccts. there isnt anything that can be done about it. the NEC isnt going to take them out of the code because people don't want them there...


Are you serious? You would have NO PROBLEM implementing a required item, costing whatever it costs, knowing that it is not real? You would just do it and not balk about it, and not say anything to anyone about it?


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## Speedy Petey (Feb 1, 2004)

arichard21 said:


> and that i dont have a problem with doing something that could make me and my family safer, *weather it is real or not*.


Many, MANY, large companies thank you for this! 
Yes, even drug companies.


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## arichard21 (Oct 17, 2007)

LawnGuyLandSparky said:


> Are you serious? You would have NO PROBLEM implementing a required item, costing whatever it costs, knowing that it is not real? *You would just do it and not balk about it, and not say anything to anyone about it?*


 
because i am a realist. i know that it wont make a lick of difference.


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## 220/221 (Oct 9, 2007)

> I fail to see the confusion......btw these people are not idiots


 
Are you trying to tell me that you or I couldn't have worded it better? Are you trying to tell me that there will be no confusion over this?


One simple question. What was the point of listing a few rooms (parlor is my favorite) and then adding "or similar rooms"?




This is only one example of hundreds of pages of poorly written code.

I would not argue that the intentions of the code are important. My only point is that the people that write this kind of crap aren't "smart" enough say what they mean.



PS. IMHO, AFCI = $$$ and ADD = $$$


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## Andy in ATL (Aug 28, 2007)

Let me stir the pot a little...Our friends in the UK have GFPE on the entire house. I think AFCI's will save lives. Speedy, I'm not some corporate loving zombie eyed patsy who only hears the propaganda. I actually research stuff and form my OPINIONS based on what I see. I was right in the mix along with everyone else when the AFCI's hit and spent my fair share of time replacing recalled breakers and pulling my hair out wondering if I screwed up or if it is another bad breaker. I HOPE the new round that comes out Jan 1 is an improvement that actually works. I think it will and I think it will save lives.


But really fellows, read the writing on the wall. We will have GFPE as well as AFCI as well as GFCI ON THE ENTIRE house within four code cycles. 

Katie bar the door and you heard it here first.:whistling2: CARRY ON.


Andy


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## RichyL (Nov 17, 2007)

If you ask me since the homeowners will be paying for all these expensive breakers that prevent fires, this should allow them to lower fire insurace costs within a home to help offset the costs.


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## Speedy Petey (Feb 1, 2004)

RichyL said:


> If you ask me since the homeowners will be paying for all these expensive breakers that prevent fires, this should allow them to lower fire insurace costs within a home to help offset the costs.


YEAH! Like that'll happen.


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## Speedy Petey (Feb 1, 2004)

arichard21 said:


> because i am a realist. i know that it wont make a lick of difference.


That's funny. I am also a realist.

I also know one person _can_ change the world.


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## Andy in ATL (Aug 28, 2007)

Speedy Petey said:


> That's funny. I am also a realist.
> 
> I also know one person _can_ change the world.


I agree SP. Have I ever mentioned that through fate and circumstance I was a registered voter AND participated in the '00 election in Palm Beach County, FL?:laughing: :yes: :huh: :whistling2:


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## LawnGuyLandSparky (Nov 18, 2007)

RichyL said:


> If you ask me since the homeowners will be paying for all these expensive breakers that prevent fires, this should allow them to lower fire insurace costs within a home to help offset the costs.


Right, and as we can see, homeowners insurance rates have just been plummeting. :laughing: 

Since the 80's, automobiles have become a lot safer. Automatic seatbelts, airbags, anti lock brakes, traction control, anti-theft , and the implementation of LoJack and on-star vehicle tracking, has broken up hundreds of multi-million dollar car theft rings and chop shops. Have car insurance rates declined?

Contrary to what we're told, everything you buy on the retail level has nothing to do with the cost to produce or provide it. Car insurance / homeowners insurance is more expensive where people have more money, and it's dirt cheap where people are dirt poor.


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## 220/221 (Oct 9, 2007)

I don't care WHAT kind of protection they require in the future as long as it's FIELD tested.

The first bunch of AFCI's we installed several years ago tripped because of toggle switches, fans, vacuum cleaners and low voltage cans.

The last few I have installed have worked on all the above items.


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## Andy in ATL (Aug 28, 2007)

Aww come on 220, The man. do an excellent job testing their stuff and they will be listed, right???:laughing: :laughing: 

Just kidding


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## BigJimmy (Jun 30, 2006)

220/221 said:


> I would not argue that the intentions of the code are important. My only point is that the people that write this kind of crap aren't "smart" enough say what they mean.


So I know that this is WAAY off the original topic, but while we're all talking so nicely...

I have spent many years working on power plant and railroad signaling systems. Both (with the exception of office and parking lot lighting in Power Plant installations) are exempt from the NEC. That being said, most engineers who work in these areas typically use the NEC where applicable as a minimum standard, myself included. Therein, I have spent countless years reading and re-reading the NEC and it seems like every time I pick it up, I finally figure out/understand some little tid-bit that has alluded me in prior readings because the wording was misleading, nebulous, vague, etc (or perhaps I'm just an idiot!). Often, following such a revelation, I usually think "why the hell didn't they just say the obvious?" (I will admit that the big code handbook is quite helpful).

Reading through trade magazines like EC&M, you constantly find advertisements for code training seminars (I must receive a half-dozen similar solicitations in the company mail each month). Mike Holt is making a mint demystifying the code for the gen-pop but why the need? If the NEC was written to be easily understood would so many people need this sort of training? And if the NEC is supposed to be "black and white," why are there so many people arguing over things that are suppose to be absolutes?

IMHO, I've always thought that it could be written in a more straighforward manner. 

TTFN,
Jimmy


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## BigJimmy (Jun 30, 2006)

Andy in ATL said:


> CARRY ON.
> 
> Andy


_Jim: Your panel wiring is well executed but your choice of wire colors was abysmal. And, you violated section 314.16 by overfilling your boxes. Jim....You are out._

_Andy: You can stay._


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## Andy in ATL (Aug 28, 2007)

BigJimmy said:


> _Jim: Your panel wiring is well executed but your choice of wire colors was abysmal. And, you violated section 314.16 by overfilling your boxes. Jim....You are out._
> 
> _Andy: You can stay._


Should I laugh or be offended? As if I could BE offended.


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## BigJimmy (Jun 30, 2006)

Andy in ATL said:


> Should I laugh or be offended? As if I could BE offended.


I thought that the "carry on" reference was a Tim Gunn thing. I was trying to do my best Heidi Klum!


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## Andy in ATL (Aug 28, 2007)

I get it now.:laughing:


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## pcampbell (Feb 7, 2008)

jwhite said:


> This question usually gets a conversation going even among professionals. But I think that the way you worded your statement if fundimentally correct.
> 
> If you have a panel feed with 200 amps at 240 volts, then you could have up to 200 amps at 120 volts on each leg. Except that you cannot load the panel beyond 80 percent so it would be 160 amps not 200.
> 
> ...


This is a great point. I think that most people look at things in 120v and amps. So I have 100 amp service (240v) and I buy a dishwasher at 10 amps, thinking WOW, this 10 amp appliance is 1/10th or even 1/8th of my capacity, when it is realy 1/16th (1200 watts / 19200 watts) of my resources, at worst (since really DW does not operate for 3 hours, it is more like 2-2.5 h), assuming the rest of the house is balanced?


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## LawnGuyLandSparky (Nov 18, 2007)

pcampbell said:


> This is a great point. I think that most people look at things in 120v and amps. So I have 100 amp service (240v) and I buy a dishwasher at 10 amps, thinking WOW, this 10 amp appliance is 1/10th or even 1/8th of my capacity, when it is realy 1/16th (1200 watts / 19200 watts) of my resources, at worst (since really DW does not operate for 3 hours, it is more like 2-2.5 h), assuming the rest of the house is balanced?


This is pretty much correct. You could have a 40 circuit panel, and 38 of the circuits could be 20 amp breakers, that doesn't mean each circuit is loaded to 20 amps. The panel would total 760 amps, or, 380 amps on each 100 amp leg. Perfectly complaint. Now assume the remaining 2 spaces are used to feed a 50a 2-pole breaker to feed ANOTHER subpanel. Also filled with breakers. Also perfectly compliant.

Individual circuit breakers are there to protect that individual circuit. So that you don't exceed the circuit cable's rating. The main is there to protect the service entrance cable to your home, so that your total house load doesn't exceed that cable's rating. (There are no fuses or breakers between your home's service and the utility's transformer feeding your house.)


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