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Old 12-22-2009, 08:27 AM   #1
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main circuit breaker amperage


The main circuit breaker of our house says 200, I'm assuming it's the maximum amperage. But when I calculated the total amperage of the individual circuit breakers (kitchen, laundry, master bedroom,foyer,etc), the total exceeded 200 amps. I'm assuming the 200 amps is 220V and not 120v. I'm adding 2 20-amp breakers for my basement and I want to make sure I'm not exceeding the limit.

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Old 12-22-2009, 08:30 AM   #2
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main circuit breaker amperage


I have a 200a service & over 850a of installed breakers
This is common
Installing another breaker does not cause a problem
It's the Load on the service that matters, not the breakers

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Old 12-22-2009, 09:24 AM   #3
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main circuit breaker amperage


ScubaDave thanks for the reply.

But I still would like to know that I'm not overloading the main circuit breaker.
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Old 12-22-2009, 09:28 AM   #4
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main circuit breaker amperage


Is your electric bill over $1000 a month ?
Electric heat ?
Large electric tankless water heater ?

If not then there really isn't much chance your are overloading the Main breaker
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Old 12-22-2009, 09:28 AM   #5
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main circuit breaker amperage


Use a load calculator like this:
http://www.zenfixit.com/load_calculations.shtml
http://www.mikeholt.com/technical.ph...lationformulas

Don't add up the breakers.

Last edited by jerryh3; 12-22-2009 at 09:33 AM.
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Old 12-22-2009, 09:29 AM   #6
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main circuit breaker amperage


Quote:
Originally Posted by kupalino View Post
ScubaDave thanks for the reply.

But I still would like to know that I'm not overloading the main circuit breaker.

has the breaker tripped?

If not, you can assume, in all cases except a federal pacific panel, that you are not over loading the main breaker.

if you want to check, you will need either a single channel recording ammeter and 48 hours or a 2 channel recording ammeter and 24 hours. You would record your usage over a days time and simply look at the results.


If you have a clamp on ammeter, you can take an instantaneous reading anytime.
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Old 12-22-2009, 09:36 AM   #7
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main circuit breaker amperage


Quote:
Originally Posted by nap View Post
has the breaker tripped?

If not, you can assume, in all cases except a federal pacific panel, that you are not over loading the main breaker.
I used to have a FP panel. The worst piece of electrical equipment (next to the X-10 system components<g>) I have ever seen.
It is a wonder anyone is allowed to have them today!

I totally agree with nap. If the mains don't trip, then you're OK. Doing a check with a clamp-on would help you to know if you are close to the breaker trip rating. If you are, then you need to upgrade your service.

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Old 12-22-2009, 10:52 AM   #8
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main circuit breaker amperage


You could have a duplex outlet where you can plug in two things...

And you can get a power strip from the store and this power strip would come with a 15 amp circuit breaker on it. You could plug this into one of the outlets and plug a 100 watt lamp into that.

Then you could get a second power strip, plug it into the second outlet, and plug another 100 watt light into that.

You would have 30 amps worth of circuit breakers on that circuit!

BUT you are only using 200 watts of electricity! (Or less than 2 amps!)

The circuit breaker on each power strip protects the power strip. You can only use a maximum of 15 amps on each power strip.

Same with all the breakers in your panel. This limits the maximum you can use on any one circuit. In reality you are using much less than the limit on most circuits.

Circuit breakers protect the wiring...
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Old 12-22-2009, 11:45 AM   #9
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Thanks for the replies.
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Old 12-22-2009, 02:20 PM   #10
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main circuit breaker amperage


Quote:
Originally Posted by kupalino View Post
Thanks for the replies.
Services are sized based on the calculated load per NEC 220. Adding up the breakers is pointless.

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Old 12-22-2009, 05:13 PM   #11
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main circuit breaker amperage


"The amount of energy represented by one revolution of the disc is denoted by the symbol Kh which is given in units of watt-hours per revolution. The value 7.2 is commonly seen. Using the value of Kh, one can determine their power consumption at any given time by timing the disc with a stopwatch. If the time in seconds taken by the disc to complete one revolution is t, then [the current in amps = 3600Kh/t(240)]"
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Old 12-22-2009, 05:42 PM   #12
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main circuit breaker amperage


Quote:
Originally Posted by Yoyizit View Post
"The amount of energy represented by one revolution of the disc is denoted by the symbol Kh which is given in units of watt-hours per revolution. The value 7.2 is commonly seen. Using the value of Kh, one can determine their power consumption at any given time by timing the disc with a stopwatch. If the time in seconds taken by the disc to complete one revolution is t, then [the current in amps = 3600Kh/t(240)]"


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Old 12-22-2009, 07:21 PM   #13
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Quote:
Originally Posted by Scuba_Dave View Post


http://en.wikipedia.org/wiki/Electricity_meter
used as an ammeter.
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Old 12-23-2009, 08:32 PM   #14
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main circuit breaker amperage


Quote:
But I still would like to know that I'm not overloading the main circuit breaker.
If you load all your circuits to their maximum amperage, you will overload the main.

Many of your 20 amp breaker draw nothing because there is nothing plugged in/turned on.


A typical house may draw 90-100 amps if everything is turned on. Range, AC, water heater, dryer and every light in the house.

Add ten space heaters to that and your main will trip.

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