Dilbert asked:
And if most of your usage is at 120 volts, does that mean you actually have 200 amps, to divide up among your 120 volt appliances?
And if most of your usage is at 120 volts, does that mean you actually have 200 amps, to divide up among your 120 volt appliances?
Is it normal for the total of all the 120 volt circuits to add up to more than than 200 amps? Or should the total always be less than the main breaker?
appliance zone
January 30th, 2010 at 7:59 pm
appliance zone phone number
Yes, it means 100amp at 240volts. Your total of 120volt circuits can exceed the rated main breaker because you don’t pull a full load on all the circuits at the same time.
February 2nd, 2010 at 9:18 am
appliance zone
100 amps is the maximum amps that can be used at one time, regardless of voltage. if most usage is at 120 volts, NO it doesn’t mean you have 200 amps. you have a max of 100 amps. your ampage never changes, unless you physically change the box yourself to a higher ampage (and a licensed electrician would have to do that.) 99% of the time you wouldn’t exceed the maximum ampage for your house.
February 2nd, 2010 at 5:27 pm
appliance zone phone number
100a main breaker means 100a at 240v. I understand your logic of getting 200a at 120v, you are correct, BUT, this assumes that the load is evenly divided among the two incoming hot lines, each good for 100a.
In a typical breaker panel, if you could see the bussbars in the back, you would see that the breakers alternate between the two hot legs. A double-pole breaker takes up two positions and gives you 240v.
The total of the breakers in a residential installation is virtually always more than the main breaker rating. Think about it, most of these circuits are rarely loaded to capacity (if they were, you would be having breakers tripping) and many circuits have little or no load on them most of the time. Many of the circuits could never be loaded to the breaker rating anyway, the 30a breaker that feeds you electric water heater will never see more than 19amps (for a typical 4500w heater), the electric dryer on a 30a circuit only draws 21a, the circuit for your electric stove is rated 50a but even if you turned on all the elements, you couldn’t draw that much. The breaker for your furnace might be rated 15 or 20 amps but it probably draws 10a or less. Most of the receptacle circuits in your home have very little load on them most of the time.
You probably could not get the main to trip unless you had mostly electrical heating appliances and turned on all of them, along with all the lights, blow dryer, microwave and everything else you had.