Replies

1. 
   BillHartmann | Feb 28, 2006 09:56pm | #1

   It is based not on the total of the breakers, but the "actual" electrical demand.

   And that is calculated based on the size of the house and the size of appliances and certain assumptions that you won't be ironing, using the oven, and the hot tub all at the same time along with every receptacle having a 15 amp load plugged in at the same time.

   Here is a worksheet for the calcualtions.

   http://www.taunton.com/finehomebuilding/pages/bh0019.asp

   Note - tell us if you have a home workshop as it does fit that worksheet.

2. 
   csnow | Feb 28, 2006 10:17pm | #2

   "If I have 200 Amp service, how can I have over 500 Amps worth of breakers in my panel?

   I know that everything doesn't operate at the same time, but it could."

   That's normal.  If you tried to exceed 200amps, the main would blow, as designed.

   Normally, it takes a bit of doing to to exceed 200amps in a residential case unless you have a lot of electric heat. 

   The largest common consumer would be an electric range, which could approach 50amps if you ran all of the elements at once.  Electric water heaters and electric clothes dryers will generally draw somewhat less than 30 amps each, so even with all of that going at once, you can still run the dishwasher, toaster, microwave, a hairdryer, lights, and not blow the main.

   Throw in a big arc welder and an air compressor, then maybe...

1. 
   NCtim | Mar 02, 2006 01:34am | #9

   Thanks, everyone. I imagined this is the case but thought I'd check because I just put a hot tub in @ 60 amps and I want to run 100 amps to a garage/workshop I'm building where I'll be using an arc welder occasionally, plus all my shop tools. I was getting concerned that I would have to get a dedicated transformer from my power supplier.

   I have 120 amps of electric resistance heat and recently added 30 amps of heat pump for zone heating/cooling for an addition, but my house pretty much heats itself because I built it passive solar. Also, the hot water is preheated via a solar capture system I'm still perfecting. So, I knew some of my circuits aren't even drawing a load.

   I do appreciate everyones' honest assessments and straight-forward answers, and not thinking I'm an idiot. Okay, you might think it, but you didn't say it. Ha!

   NCtim

    

3. 
   DanH | Feb 28, 2006 10:28pm | #3

   There are no stupid questions, just stupid questioners. :)

   If every circuit was loaded to the max, and all operated simultaneously, yes, the main breaker would trip. That's the main reason it's there.

   But your typical 15-20A lighting or receptacle circuit is rarely loaded to more than 5 amps. Dedicated circuits like for an AC likewise are set up for a worst-case (typically during startup) load, and include "safety" margins to allow for breaker inaccuracy and odd load variations.

   In a home environment it would be rare to have a total current demand larger than about 1/4 of the sum of the individual branch circuit breakers.

   If ignorance is bliss why aren't more people

   happy?

4. 
   Piffin | Feb 28, 2006 10:38pm | #4

   Using your financial comparison ...

   If I have ten credit cards in my wallet

   Each having a credit limit of ten grand

   I could concievable run up a CC debt of a hundred grand

   Unl;ess I were using that to build a real value asset, it would probably blow up my financial situation

   Compare that to each creduit card being a breaker in your ( wallet) service panel.

   You don't run a max all day long
   MOF you rarely run a max on any one circuit

    

    

   Welcome to the
   Taunton University of Knowledge FHB Campus at Breaktime.
    where ...
   Excellence is its own reward!

1. 
   DanH | Mar 01, 2006 02:55am | #5

   You don't know my brother.
   If ignorance is bliss why aren't more people

   happy?

1. 
   Piffin | Mar 01, 2006 03:34am | #6

   Hey - I got brothers! LOL 

    

   Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

1. 
   segundo | Mar 01, 2006 04:00am | #7

   i have heard of people building entire houses on credit cards, of course these are just job site rumors from construction types but hey its possible.

   i have even heard it used as a method of aquiring cash for business startup' if you apply for them all on the same day you could get over 100,000 in credit card limit then just keep transferring balances on convenience checks back and forth till house sells.

2. 
   NCtim | Mar 02, 2006 01:38am | #10

   Geez, man! I think I understand electricity better than the financial comparison. Hahaha! Thanks for the anecdote, though. Okay if I pass this on to some financially challenged folks?

1. 
   Piffin | Mar 02, 2006 03:54am | #11

   Sure, it'll improve the species, won't it? 

    

   Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

5. 
   pm22 | Mar 01, 2006 05:18am | #8

   There are a number of factors. Most everything is not used at once. You don't run air conditioning and heating at the same time although Richard Nixon liked fires in the White House fireplaces even during summer. The Code requires certain circuits whether they are used much or not. For instance, it requires a 20 amp circuit for the bathroom but if your wife is bald, then you don't have hair drier worries. And motor circuits, such as air conditioning compressors, are allowed larger breakers to deal with the high start up currents that can be six times running load but last only a second.

   Loads should be limited to 80% of the breaker rating.

   An important point is that the main 200 amp breaker is two pole. That means that each side can endure up to 200 amps. If you load each side up to 195 amps, it should not trip indefinately.

   ~Peter

   What can you do to help the survivors of the Seattle-Tacoma earthquake?