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Is a 200 amp Panel only allowed 200 amps of loading
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That is to say, 400amps is flowing, just not in service conductors.

Originally posted by rjniles View Postif the sum of each side sees more than the breaker rating it will trip.
It's not determined by the sum of each side.

Bob: while I don't disagree, it depends on how you define the panel loading.
The original post wasOriginally posted by Galmagie View PostIs a 200 amp residential panel only allowed 200 amps of loading?
Often what is trying to be asked is "How much current can be put on a panel using 120v loads?"
The answer is 200 amps on each side or effectively 400a. I agree 400amps doesn't actually flow at once, but practically speaking that's how its loaded and how many determine panel loading.
A better way is to calculate the power and avoid confusion is to calculate loading in VA.
240v x 200a= 48kva of power. And
120v x 400a= 48kva.
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By your explanation you are never drawing 400A, but 200A on Phase A or 200A on Phase B which are 180 degrees out of phase in time so the most you will ever draw through the main breaker (with out tripping it) is 200A at any instant in time. Yes you can draw 200A on each phase but never at the same time so you will never draw more than 200A without tripping the breaker.
An Amp is a measurement frozen in time. If a full cycle is 1/60 of a second, then the 200A load on Phase A exists for half that cycle or 1/120 of a second, and the 200A load on Phase B for the second half of the cycle. But it's never at the same time so the load is never more than 200A.
So I think saying 400A at 120V is incorrect, as it never happens. And if both legs of the breaker are tied together such that a load >200A on either leg will trip the breaker, then the that is all you can ever load the breaker to without tripping it.
These small breakers have no current measuring capabilities, they work by heating a bimetallic strip that flexes when it heats up from increasing current, letting a spring trip the breaker open. The breaker reacts to a short circuit in a different manner. There is so much current flowing through the breaker in such a short time span that it creates a magnetic field which causes the breaker to trip, watch the short video below to see it happen in slow motion. Once the current is interrupted and the metal cools off it regains it's original shape and can resist the force of the spring, so when the breaker is reset it will remain closed until the breaker is manually opened or an overload or short circuit condition exists again.
As far as I know a double pole breaker is basically the same construction, it's just a pair of single pole breakers tied together. There is no capability to add the loads from Phase A and B together to arrive at a combined load greater than the rating of the breaker.
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CWS, Your correct that amps are amps but your understanding is lacking. How current flows is just as important as amperage.
It helps to understand what is actually happening in a split phase system.
The transformer secondary winding is single phase 240 volts. That 240v is center tapped and intentionally grounded which derives 120v on each leg to ground.
If you look at that 240v AC sine wave, you will see that the current alternatives + and  each cycle (60 times per second) 360 degrees back and forth. As current is flowing in one direction on one leg, it's flowing in the opposite direction on the other leg.
The next cycle it flows in the other direction.
So yes, the panel is limited to 200 amps but this is a 240v system. Those two poles of the 200 amp breaker are in a series circuit at 240v.
Now take just one hot leg with respect to ground. It is only half of a cycle because of the midtap or 180degrees. Now that leg can draw 200amps on that side and current returns on the mid tapped neutral for half the cycle and 200 amps can be drawn on the other leg similarly. So both sides are drawing 200 amps but 180 degrees apart from each other, or a half cycle apart.
So effectively it is drawing 400 amps at 120v (just not at the exact time). This 400 amps at 120v, is actually the same thing as 200 amps at 240v which happens in a full cycle.
This is why you can load both sides of the panel with a 200amp breaker.
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John,
I think I have to disagreed with you on that. Amps are amps and Voltage does not influence the singular value of an Ampere. There's no difference between a 120 Volt ampere or a 440 Volt ampere, is there? When a wire conductor, or in this case a circuit breaker, is rated for a particular Current, that is all that it will safely take because of the resistance of that particular circuit without overheating or respectively tripping.
While I could be wrong about this, I don't think so. I looked on the internet to see if my presumptions were wrong and frankly I think there's a lot of confusion everywhere. One Google group went on for an extremely long back and forth and never did reach a consensus that I could find. It appears that much revolves around the fact that when a requirement of amperes at 120 Volts can max out a circuit, moving to 240 Volts, almost cuts those amperes in half. However the inverse of thinking that 200 amperes at 240 Volts allows for 400 amperes at 120 Volts is simply not true! An 'ampere' is a defined value of 'current', and applying a voltage change does not effect that value. What does change with a voltage difference is simply the value in the number of amperes, going down as the voltage goes up, and increasing as the voltage goes down.
In other words, 200 amperes is 200 amperes, regardless of voltage!
I've looked at a couple of manufacturer's web sites, my copy of an older NEC, as well as a couple of books here, and I have found nowhere that states or gives any explanation that a specificvalue can be exceeded when it comes to the amperevalues of a circuit breaker Main. With that in mind, I still am concluding that a panel with a 200amp Main is limited to 200 amps in total of service. Voltages may differ of course, but it is still a matter of current allowed (actually, it's more a matter of restricted) by the conductor. A conductor will only tolerate a current flow to the point where the conductor's resistance is surpassed and as it approaches that point the conductor will heat, and once surpassed will overheat causing the conductor to breakdown and possibly melt.
But, as I stated earlier, if anyone could point me to a manufacturer or regulatory statement I would greatly appreciate furthering my education.
CWS
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A ton of misinformation here.
A 200amp panel is rated for 200amps @ 240volts.
Theoretically, each half of a 2pole 200a breaker can see up to 200amps independently, or a total of 400a @ 120v without tripping.
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Originally posted by Bob D. View PostI think it depends on the construction of the breaker. If it's two individual breakers physically tied together so you can't open/close one without the other then an overload
( >200A ) on one side will cause it to trip BUT as I asked if 190A on one side AND 40A on the other side WILL NOT cause a trip because neither breaker has reached an overload condition.
But, if the breaker design is a single breaker with double pole, double throw contacts THEN yes I believe exceeding 200A in any combination would trip the breaker.
I don't know enough about these small MCCBs (Molded Case Circuit Breakers) and haven't taken the time to research it, because I don't have a need to know. But the originator of this thread might want to do the research if they truly want to know the answer because they are not getting a clear answer here as I stated in my previous post. The answers that have appeared in this thread so far are not clear to me which is why I asked (and worded) my question the way I did in post #7.
A 2 pole main breaker is common trip (internally tied such that if either side sees an excess current both side will trip). And if the sum of each side sees more than the breaker rating it will trip.
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I think it depends on the construction of the breaker. If it's two individual breakers physically tied together so you can't open/close one without the other then an overload
( >200A ) on one side will cause it to trip BUT as I asked if 190A on one side AND 40A on the other side WILL NOT cause a trip because neither breaker has reached an overload condition.
But, if the breaker design is a single breaker with double pole, double throw contacts THEN yes I believe exceeding 200A in any combination would trip the breaker.
I don't know enough about these small MCCBs (Molded Case Circuit Breakers) and haven't taken the time to research it, because I don't have a need to know. But the originator of this thread might want to do the research if they truly want to know the answer because they are not getting a clear answer here as I stated in my previous post. The answers that have appeared in this thread so far are not clear to me which is why I asked (and worded) my question the way I did in post #7.Last edited by Bob D.; 10092019, 05:35 AM.
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I believe it will trip at greater than 200 amps, regardless of which phase or combined. The main breaker is as RJNiles described in post #2, in that it is basically two 200 amp breakers that are joined. So if either side exceeds 200 amps, it will trip and bring the other side with it, effectively terminating all power to the panel circuits. So, either side or both sides combined, the maximum load on that panel is 200 amps.
CWS
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Does the main breaker trip when it sees >200A on either phase or does it trip when the combined load of both phases is >200A, say 190 + 40 ?
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Originally posted by Galmagie View PostAgain, my main question is when the Electrical Authority states that a 200 amp residential house panel is only good for 200 amps of loading max. Is that 200 amps total of the panel or is that 200 amps per each side of the panel?
As the 200 amp breaker is 2  200 amp breakers tied internally. The electrical service has 2 service conductors coming into the panel, so why can't they each see 200 amps (max).
I know this question has been asked many times but it seems there is still questions.
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Okay, so I'm NOT an electrician; but, the "panel", beyond the design of the overall contacts, plates, etc. IS defined by the main circuit breaker, is it not?
Providing the incoming power lines is adequately sized to carry the load, here where I live the "panel" maximum is controlled by the Main or Master circuit breaker. The voltages of 220 or 110 are not the defining factor, it's the maximum rated Amperage of the Main breaker and of course the individual circuits are designed for the maximum amperage of the individual circuit breakers.
So, you can have a number of circuits that, added up, may well exceed 200 amps. (For example, a dozen 15 amp breakers and five or so 20 amp breakers. Let's say they total to 250 amps in our example. However, all those circuits are not on at the same time and most likely no circuit is running at their maximum load.
We all know that if you exceed the maximum load of an individual circuit you will have a problem. The primary concern is the wire ampacity (amperage capacity); a 14 ga wire will handle a maximum amperage of 15 amps/120 Volts; 12 ga, 20 amps/120 Volts; 10 ga, 30 amps/240 Volts... etc. The larger the wire gauge (smaller number) the more amps and volts it can handle.
So, to keep from over maxing the particular wire used in the circuit, the panel MUST have the rightsized circuit breaker. You can't use 14 ga wire for a 15 amp circuit and then one day decide to 'upgrade' the circuit by popping a 20 amp breaker in the panel.... you'll over heat the wire and maybe burn your house down. (Personally, I've never used 14 ga wire, ever; instead prefer 20 ga.)
When you have a 20 ga wired circuit, and then decide that your power tool or appliance is drawing too many amps so that the tool isn't running efficiently or you're continually popping the breaker, THEN you might consider fixing the machine to run on 220 Volts (not all motors can do this). The purpose of running 240 Volts is because the amperage is cut in half. For example, if you're Saw is drawing 18 amps/120 Volts on run it may well pull 20 or more Amps on startup. That would of course trip a 20 amp breaker. Switch the Saw's circuit to run on 240 Volts, and now that saw will run at 9 or 10 amps with a maximum startup of 12 amps; wellwithin the ampacity of the wire and below the trip of the breaker.
The main breaker in the panel doesn't care what the voltage is AS LONG AS you're not going to exceed the breaker's rated amperage. So you can run almost every circuit you have in the panel as long as you don't exceed the Main Breaker.
So, as I understand it, you can only run a maximum of 200 amps in a house with a 200 amp panel. NO that doesn't mean 200 amps per side! That total, is both sides together! As I understand it, those two service wires at the top each carry 120 Volts, generally running down each side of of the panel or parallel to each other down the middle of the panel. A third wire coming from with the service pair is the neutral, which completes the circuit of one or both 120 volt service lines through each circuit breaker. When 220 Volts are used, a proper Circuit Breaker is installed so that it uses both incoming 120 Volt lines, thus providing 240 Volts.
So, regardless of whether the circuit is 240 or 120 Volts, it is the amperage that is the main concern. You cannot exceed the rated amperage of a particular gauge wire, nor can you exceed that of the particular circuits Breaker. That also applies the incoming service and of course the the panels Main Breaker.
When I upgraded my last house from a 70 amp fuse box to a 150 amp CB panel, it wasn't just a matter of changing the panel. The incoming service line was old (about 1indh in diameter) and I had to have a new line (like 2plus inch diameter) put in by the power company. It required new ground rods, service line, panel, meter, weatherhead, etc.) When I upgraded the house here, it already had the newer service line and all I had to do was upgrade the CB panel. It presently has a 200 amp Main, and I understand it can be upgraded further by just replacing the Main Breaker.... THAT OF COURSE would be the sole job of a qualified electrician!!!
So, is my summary on target OR do I too have a misconception? (Hey, I'm always up to being educated!)
CWS
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