Load capacity of 200-amp panel
In article , Smitty Two wrote:
In article , (Doug Miller) wrote: In article , Smitty Two wrote: In article , (Doug Miller) wrote: Umm, no, actually, that's *my* point: it's counted twice. *Two* amps at 120V. Doug, you know what you know, and you don't know what you don't know. Evidently there's a few gaping holes in your understanding of ohm's law. I'd have to speculate that you've never had an electronics course in your life, because you're making some erroneous statements about some pretty basic principles of circuit analysis. I understand Ohm's law much better than the folks who apparently believe that 200A at 240V is the same thing as 200A at 120V. I haven't seen anyone here claiming to believe that. Perhaps you should read more carefully, then. Several posters in this thread have insisted that the maximum capacity is 200A, period -- while ignoring the voltage. It's 200A on *each*leg* of the service. That's 200A @ 240V, or 400A @ 120V. A wire capable of carrying 200 amps is capable of carrying 200 amps, period. It doesn't matter whether it's 1 volt or 1,000,000 volts. An ampere is defined as a given number of electrons per second. And *two* wires capable of carrying 200 amps *each* are capable of carrying *400* amps. What's so hard to understand? And, in a series circuit, the current is the same throughout the circuit. You seem to be claiming otherwise. No, I've never claimed that. Rather, I've said several times that the two legs of a residential electrical service are, in effect, two parallel circuits. Yes, it can also be considered as a single series circuit -- IF the loads are exactly balanced. Any unbalanced loads are parallel. Let's try going at this from the opposite direction. Consider a single-pole 20A circuit breaker supplying a branch circuit. I believe we'd both agree that circuit can supply a maximum of 20A at 120V. Now consider a double-pole 20A breaker supplying a 240V circuit. I believe we'd both agree that circuit can supply a maximum of 20A at 240V. Re-wire that double-pole 20A breaker with two separate 12-2 cables, so that it's supplying two 120V circuits. How many amps can that supply at 120V? 20, or 40? Now re-wire it with 3-wire cable, making it instead a multiwire ("Edison") circuit supplying 120V loads instead of 240V. How many amps can that supply at 120V? 20, or 40? |
Load capacity of 200-amp panel
On Oct 25, 7:51*am, (Doug Miller) wrote:
In article , Smitty Two wrote: In article , (Doug Miller) wrote: In article , Smitty Two wrote: In article , (Doug Miller) wrote: Umm, no, actually, that's *my* point: it's counted twice. *Two* amps at 120V. Doug, you know what you know, and you don't know what you don't know. Evidently there's a few gaping holes in your understanding of ohm's law. I'd have to speculate that you've never had an electronics course in your life, because you're making some erroneous statements about some pretty basic principles of circuit analysis. I understand Ohm's law much better than the folks who apparently believe that 200A at 240V is the same thing as 200A at 120V. I haven't seen anyone here claiming to believe that. Perhaps you should read more carefully, then. Several posters in this thread have insisted that the maximum capacity is 200A, period -- while ignoring the voltage. It's 200A on *each*leg* of the service. That's 200A @ 240V, or 400A @ 120V. The maximum capacity of the service is 200Amps period. As Smitty pointed out, the current is determined by the amount of electrons passing through a wire each second and is independent of voltage. You are of the belief that the second hot leg carries an additional CURRENT, which it does not. In the case of a balanced load, it only carries the exact SAME current which is flowing in the other hot. As I said before, the current comes in on one hot while simultaneously exiting on the other hot. Let's say it's 150 amps. That 150 amps is coming in on one hot and going out on the other. It reverses each cycle. That is just like current flowing through a resistor. You wouldn't count the current in a resistor twice would you? Now let's add an additional 50amp unbalanced 120Volt load. Now 200 amps comes in on one hot, 150 goes back out as before on the other hot, and 50 amps goes back via the neutral. Add that up and you have 200 amps coming into the house and 200 amps leaving the house. For it to work any other way, current would be piling up or disappearing somewhere, which is a violation of Kirchoff's law. A wire capable of carrying 200 amps is capable of carrying 200 amps, period. It doesn't matter whether it's 1 volt or 1,000,000 volts. An ampere is defined as a given number of electrons per second. And *two* wires capable of carrying 200 amps *each* are capable of carrying *400* amps. What's so hard to understand? Again, this is like saying a resistor that has 1 amp flowing in it is carrying 2 amps because 1 amp is coming in and 1 amp is leaving. Would you say that 14 gauge wire running to an outlet is capable of carrying 30 amps? These two examples are the same as what is happening with the service coming into the house. And, in a series circuit, the current is the same throughout the circuit. You seem to be claiming otherwise. No, I've never claimed that. Rather, I've said several times that the two legs of a residential electrical service are, in effect, two parallel circuits.. They are not simply parallel circuits which would require they have seperate return paths. Yes, it can also be considered as a single series circuit -- IF the loads are exactly balanced. Any unbalanced loads are parallel. Let's try going at this from the opposite direction. Consider a single-pole 20A circuit breaker supplying a branch circuit. I believe we'd both agree that circuit can supply a maximum of 20A at 120V. Now consider a double-pole 20A breaker supplying a 240V circuit. I believe we'd both agree that circuit can supply a maximum of 20A at 240V. Re-wire that double-pole 20A breaker with two separate 12-2 cables, so that it's supplying two 120V circuits. How many amps can that supply at 120V? 20, or 40? It's still physically supplying 20 amps because as Smitty pointed out, that is determined by the number of electrons passing each second. That hasn't changed. More current doesn't come out of thin air. But what you have now is that same 20 amps passing through two circuits. Let's hook up a 6 ohm resistor to each of the new circuits. You now have 120V across each load, so as far as each load is concerned, they have 120Volts and 20 amps each. Count that twice and you have 40 amps of load at 120V driven by the same 20 amps flowing in the circuit. Look at it at the breaker which is analogous to the sevice point discussion and you still have 20A flowing, not 40. Now re-wire it with 3-wire cable, making it instead a multiwire ("Edison") circuit supplying 120V loads instead of 240V. How many amps can that supply at 120V? 20, or 40?- Hide quoted text - - Show quoted text - Here's another example. Take a cardboard box that will be our "house". Take an extension cord, put a 120Watt bulb on the end of it, plug it in to a 120V outlet and put the bulb in the box. You now have a 120volt, 1amp service to the box. 1 amp is flowing in the circuit. Now replace the bulb with two 60Watt bulbs in series. Across each bulb you will have 60 volts and 1 amp will be flowing in each of them. So, you are supporting two 1 amp loads at 60volts, But what is flowing in that extension cord? It's still 1 amp, not 2. The exact same scenario plays out in the 200 amp service coming into the house, which is why only 200 amps of actual current is ever flowing. |
Load capacity of 200-amp panel
[snip]
Oh, you mean that if both legs are fully loaded, there's no current being drawn at all? Sorry, but you don't understand. The current in the neutral is in fact zero, if both legs are loaded exactly equally -- and if all the loads supplied are 120V loads, then it is in fact drawing 400A @ 120V. That current is 200A. That 400A is obviously not in the neutral. WHERE is it? |
Load capacity of 200-amp panel
On Sat, 24 Oct 2009 23:55:15 GMT, (Doug Miller)
wrote: In article , wrote: On Oct 24, 2:17=A0pm, (Doug Miller) wrote: In article = ..com, wrote: [...] What voltage do you measure between a and b? Between c and b? 120 Volts 120 Volts What current do you measure between a and b? Between c and b? 1 amp and it's THE SAME 1 AMP current. It just gets counted twice. Which once again is my point. Umm, no, actually, that's *my* point: it's counted twice. *Two* amps at 120V. That makes no sense. 1A counted twice is 1A. No amount of counting changes what exists. I'm alone in my room. Therefore, counting the number of people in the room shows 1. Now, I look in a mirror and count again. Now there's TWO people in the room. You have ONE 50-foot rope. Every time you see rope count it. Now you have 10 ropes. There is only 1 amp flowing in the actual complete circuit, just like there is only a maximum of 200 physical amps flowing in a 200 amp service. OK, so there's 120V @ 1A flowing between a and b = 120W. And there's 120V @ 1A flowing between b and c = 120W. Total = 240W. 240W / 120V = 2A In a house, here's how the same thing happens. I hook a 120Volt light bulb that draws 1 amp on one hot leg and a 120volt fan that draws one amp on the other hot leg. The 1 amp current comes in one leg, goes through the bulb, through the fan and out the other hot leg. That's still an actual current of only 1 amp, though it runs through two 1 amp loads. Wrong. Two 1 amp loads = *two* amps, not one. You still haven't shown where that TWO amp current is. Is it in the first load? There's just 1A there. Is it in the second load? There's just 1A there. Is it in the first supply wire? There's just 1A there. Is it in the second supply wire? There's just 1A there. Is it in the neutral wire? There's ZERO current there. Is it in the air? There's heat there, but no current. WHERE is it? [snip] |
Load capacity of 200-amp panel
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Load capacity of 200-amp panel
In article , Sam E wrote:
[snip] Oh, you mean that if both legs are fully loaded, there's no current being drawn at all? Sorry, but you don't understand. The current in the neutral is in fact zero, if both legs are loaded exactly equally -- and if all the loads supplied are 120V loads, then it is in fact drawing 400A @ 120V. That current is 200A. That 400A is obviously not in the neutral. WHERE is it? There's no current in the neutral if the loads are balanced. |
Load capacity of 200-amp panel
In article , Sam E wrote:
On Sat, 24 Oct 2009 18:17:14 GMT, (Doug Miller) wrote: In article , wrote: Consider this simple circuit analogy which is exactly what you would have with a balanced load on a 240V service. It's a 240V voltage source powering two 120ohm resistors. ____________ 240V___________ I I I I I I ---------120ohm---------120ohm--------- a b c There is only 1 amp of actual current flowing in the circuit. Across each resistor there is 120Volts and 1 amp of current flowing. So, yes you have 1 amp flowing in EACH load, it is supporting two 1 amp loads, but it's the same physical current flowing through each load. The "service" is only supplying 1 amp of actual current, not 2. What voltage do you measure between a and b? Between c and b? What current do you measure between a and b? Between c and b? That's what I meant when I said a 200 amp service cannot supply 400 amps of current. But it can. 200A at 120V on each leg is a total of 400A at 120V. The two legs of a residential electrical service are, in effect, two parallel circuits. 200A flowing in each of two parallel circuits is 400A total, not 200A. You have a SERIES circuit (considering that the neutral is effectively disconnected). [snip] Wrong. The neutral is "effectively disconnected" *only* if the loads on the two legs are exactly the same. The two legs function as two parallel circuits with respect to 120V loads. Obviously they are indeed in series WRT 240V loads. |
Load capacity of 200-amp panel
In article , Gary H wrote:
On Sat, 24 Oct 2009 23:55:15 GMT, (Doug Miller) wrote: In article , wrote: On Oct 24, 2:17=A0pm, (Doug Miller) wrote: In article = ..com, wrote: [...] What voltage do you measure between a and b? Between c and b? 120 Volts 120 Volts What current do you measure between a and b? Between c and b? 1 amp and it's THE SAME 1 AMP current. It just gets counted twice. Which once again is my point. Umm, no, actually, that's *my* point: it's counted twice. *Two* amps at 120V. That makes no sense. 1A counted twice is 1A. No amount of counting changes what exists. 1A in _each of two parallel circuits_ is a total of 2A. [...] You still haven't shown where that TWO amp current is. Is it in the first load? There's just 1A there. Is it in the second load? There's just 1A there. The two loads are in parallel, not in series. 1 + 1 = 2. Is it in the first supply wire? There's just 1A there. Is it in the second supply wire? There's just 1A there. Two parallel circuits, 1A in each. 1 + 1 = 2. Is it in the neutral wire? There's ZERO current there. Is it in the air? There's heat there, but no current. WHERE is it? 1 amp in each of the two hot legs -- which with respect to 120V loads, are effectively two separate parallel circuits. |
Load capacity of 200-amp panel
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Load capacity of 200-amp panel
[snip]
WHERE is it? 1 amp in each of the two hot legs -- Of course. The problem is WHERE is the 2A. which with respect to 120V loads, are effectively two separate parallel circuits. No. That would require identical sources. These sources are not identical, but opposite. The difference can be up to 339V (the peak value for 240V RMS). In the circuit you describe there is ZERO current in the neutral. This is the same as the neutral not being there (current in that wire is 0A in either case). What you have is a SERIES circuit. It is the same current going through both resistors, therefore addition is not appropriate here. This reminds me of a story I heard a few years ago. Three 12-year-old boys wished they could vote. Since the voting age was 18, the boys decided that if they went together they'd get 2 votes. 12 + 12 + 12 = 18 * 2 The fact that you can do arithmetic doesn't mean it's appropriate to do so. -- 61 days until the winter solstice celebration Mark Lloyd http://notstupid.us "How could you ask me to believe in God when there's absolutely no evidence that I can see?" -- Jodie Foster |
Load capacity of 200-amp panel
[snip]
You have a SERIES circuit (considering that the neutral is effectively disconnected). [snip] Wrong. The neutral is "effectively disconnected" *only* if the loads on the two legs are exactly the same. Which they are (either in the 200A+200A example or the 1A+1A one). The two legs function as two parallel circuits with respect to 120V loads. In a parallel circuit BOTH ends of the loads are connected together (or at least to identical voltages). Neither is true here. Obviously they are indeed in series WRT 240V loads. Strangely, I get the idea that you actually know this stuff. In this 200A service there are THREE current-carrying conductors. Each of these conductors is of the proper size to carry 200A. OK so far? You say (when this service is fully loaded) that two of these conductors is carrying 200A (for a total of 400A, as you say). Then where is that 400A going? The only remaining conductor is the neutral, a big enough conductor for 200A (yes, this 400A was at 120V but current is still current and voltage doesn't change the conductor's current capacity). Somehow I'm imagining a bridge that can handle 200 cars per minute, but that can be 400 if half the cars are blue :-) |
Load capacity of 200-amp panel
In article , Sam E wrote:
[snip] You have a SERIES circuit (considering that the neutral is effectively disconnected). [snip] Wrong. The neutral is "effectively disconnected" *only* if the loads on the two legs are exactly the same. Which they are (either in the 200A+200A example or the 1A+1A one). And that almost never happens in real life, either.... The two legs function as two parallel circuits with respect to 120V loads. In a parallel circuit BOTH ends of the loads are connected together (or at least to identical voltages). Neither is true here. Wrong -- both are true. Obviously they are indeed in series WRT 240V loads. Strangely, I get the idea that you actually know this stuff. In this 200A service there are THREE current-carrying conductors. Each of these conductors is of the proper size to carry 200A. OK so far? OK You say (when this service is fully loaded) that two of these conductors is carrying 200A (for a total of 400A, as you say). 400A @ 120V, or 200A @ 240V, yes. Then where is that 400A going? The only remaining conductor is the neutral, a big enough conductor for 200A (yes, this 400A was at 120V but current is still current and voltage doesn't change the conductor's current capacity). Somehow I'm imagining a bridge that can handle 200 cars per minute, but that can be 400 if half the cars are blue :-) Cute. Just answer these questions; assume a 240V 200A service. What is the maximum power that service can provide? If all the loads supplied by that service are 120V loads (e.g. blender, toaster, light bulbs, range hood, stereo, TV, computer, etc.) what do you get when you divide that maximum power by 120V? |
Load capacity of 200-amp panel
On Oct 24, 10:11*am, Gary H wrote:
On Fri, 23 Oct 2009 19:54:26 GMT, (Doug Miller) wrote: In article , wrote: On Oct 22, 4:10=A0pm, (Doug Miller) wrote: In article = ..com, wrote: Aside from the 80% rule, Which doesn't apply... you can't get 400 amps out of a 200amp service. Of course you can; it just depends on which circuits are in use. If you're using only 120V circuits, you can get 200A on *each* leg. 200A @ 240V is the same power as 400A @120V. Yes but physically, a current of 200 amps is all that is actually flowing. * Put a meter on it and you will measure 200 amps, not 400. It's a simple matter of Kirchoffs law. 200 amps on _each leg_. It's a total of (up to) 400 amps at 120V. 200A on each leg. Where's the 400A? Being able to add to numbers* doesn't mean reality works that way. [snip] * - Actually, that's incorrect too. The addends are out of phase, so 200 + 200 = 0. Assume you are using one leg at 200 amps, that is all the breaker will handle that is 120 volts X 200 amps or 24,000 watts. If you again max out the breaker with 200 amps flowing on both sides that is 240 volts x 200 amps or 48000 watts. Thats the same as 120 X 400 amps. I think the OP wanted to know if he could get a total of 400 amps at 120VAC. Lets rephrase that to could he power 400 individual 1 amp 120 VAC loads from this box under residential conditions. The answer is yes but that sounds a lot like a commercial installation to me where the answer would be NO. I think this is a case of getting the right answers to the wrong question. Jimmie |
Load capacity of 200-amp panel
On Oct 25, 9:15*pm, Sam E wrote:
On Sun, 25 Oct 2009 18:46:17 GMT, (Doug Miller) wrote: In article , Sam E wrote: [snip] Oh, you mean that if both legs are fully loaded, there's no current being drawn at all? Sorry, but you don't understand. The current in the neutral is in fact zero, if both legs are loaded exactly equally -- and if all the loads supplied are 120V loads, then it is in fact drawing 400A @ 120V. That current is 200A. That 400A is obviously not in the neutral. WHERE is it? There's no current in the neutral if the loads are balanced. No current. I was replying to the person who claimed 400A. Assume you are using one leg at 200 amps, that is all the breaker will handle that is 120 volts X 200 amps or 24,000 watts. If you again max out the breaker with 200 amps flowing on both sides that is 240 volts x 200 amps or 48000 watts. Thats the same as 120 X 400 amps. I think the OP wanted to know if he could get a total of 400 amps at 120VAC. Lets rephrase that to could he power 400 1 amp 120 VAC loads from this box under residential conditions. The answer is yes but that sounds a lot like a commercial installation to me where the answer would be NO. I think this is a case of getting the right answers to the wrong question. |
Load capacity of 200-amp panel
On Oct 25, 2:45*pm, (Doug Miller) wrote:
In article , wrote: On Oct 25, 7:51=A0am, (Doug Miller) wrote: In article -media= ..com, Smitty Two wrote: In article , (Doug Miller) wrote: In article , S= mitty Two wrote: In article , (Doug Miller) wrote: Umm, no, actually, that's *my* point: it's counted twice. *Two* amp= s at 120V. Doug, you know what you know, and you don't know what you don't know. Evidently there's a few gaping holes in your understanding of ohm's l= aw. I'd have to speculate that you've never had an electronics course in your life, because you're making some erroneous statements about some pretty basic principles of circuit analysis. I understand Ohm's law much better than the folks who apparently belie= ve that 200A at 240V is the same thing as 200A at 120V. I haven't seen anyone here claiming to believe that. Perhaps you should read more carefully, then. Several posters in this thr= ead have insisted that the maximum capacity is 200A, period -- while ignoring the voltage. It's 200A on *each*leg* of the service. That's 200A @ 240V, or 400A @ 120V. The maximum capacity of the service is 200Amps period. * *As Smitty pointed out, the current is determined by the amount of electrons passing through a wire each second and is independent of voltage. You are of the belief that the second hot leg carries an additional CURRENT, which it does not. * You are wrong. It does -- in the case of 120V loads. Here we go again..... In the case of a balanced load, it only carries the exact SAME current which is flowing in the other hot. * As I said before, the current comes in on one hot while simultaneously exiting on the other hot. IF it's supplying a 240V load, yes. If it's supplying a 120V load, then it exits on the neutral. False. I clearly stated here that it's a balanced load. With a balanced 120V load, the exact same current comes in on one hot and exists on the other. In the case of a 200 amp service, that current is a max of 200 amps. Let's say it's 150 amps. * That 150 amps is coming in on one hot and going out on the other. * *It reverses each cycle. * *That is just like current flowing through a resistor. * You wouldn't count the current in a resistor twice would you? So is it your position that a 200A 240V service is incapable of supplying more than 200A at 120V = 24kVA? No and I and everyone else have tried to explain that to you. Go back many posts to the simple circuit diagram I drew: .. ____________ 240V___________ I I I I I I ---------120ohm---------120ohm--------- a b c You have a 240 volt voltage source as our "service" connected to two 120 ohm resistors in SERIES. How much current is flowing in that circuit? 1 amp How much current is flowing in the first resistor? 1 amp How much current is flowing in the second resistor? 1 amp What is the voltage across each resistor? 120V What is the power in each resistor? 120W So, you have 1 amp flowing in SERIES through each load, so you do have two loads of 1 amp at 120V, but only 1 amp of current is actually flowing in the circuit which comprises the "service" Capishe? Now let's add an additional 50amp unbalanced 120Volt load. * Now 200 amps comes in on one hot, 150 goes back out as before on the other hot, and 50 amps goes back via the neutral. * * Add that up and you have 200 amps coming into the house and 200 amps leaving the house. At 240V. Now we're back to what Smitty tried to explain to you. Current has nothing to do with voltage. It's based on the amount of charge, ie electrons, passing a point per second. 200 amps is still exactly 200 amps whether it's at a potential of 240V, 120V or a million volts. And btw, the voltage is not entirely 240V in the above example I gave either. 150amps is flowing at 240V and 50 is flowing at 120V. If it were simply all at 240V, you'd have 48KW of power here. Actually it's 150X240+50*120=42KW For it to work any other way, current would be piling up or disappearing somewhere, which is a violation of Kirchoff's law. How much power can be supplied by a 200A, 240V service? 24kVa, or 48kVA? That's been asked an answered many times in this thread. It's 48, Now answer my question. What is the maximum current that is actually flowing in the 3 wire cable of a 200 amp service? If you say it's more than 200 amps, outline an example and using Kirchoff's law, trace for us the current flowing in all 3 conductors. A wire capable of carrying 200 amps is capable of carrying 200 amps, period. It doesn't matter whether it's 1 volt or 1,000,000 volts. An ampere is defined as a given number of electrons per second. And *two* wires capable of carrying 200 amps *each* are capable of carrying *400* amps. What's so hard to understand? Again, this is like saying a resistor that has 1 amp flowing in it is carrying 2 amps because 1 amp is coming in and 1 amp is leaving. No, it's not. It's like saying that *two* resistors IN PARALLEL with 1 amp flowing through each have a total current of two amps. Do you disagree? Absolutely disagree. I gave you an example before. Take a 120W, 120V light bulb and place it between one hot leg and neutral. Take a 120V fan drawing 1 amp and place it between the other hot leg and neutral. You now have a balanced load drawing 1 amp. There is 1 amp flowing in one hot and out the other. The neutral is carrying 0 amps. You are supporting two 1 amp, 120V loads. Total amps flowing in the service: 1 amp. Those two loads appear in SERIES across the two hots. Would you say that 14 gauge wire running to an outlet is capable of carrying 30 amps? *These two examples are the same as what is happening with the service coming into the house. No, they are not. Keep thinking about it until you realize why those two examples are not the same, and then you'll understand where you've made your mistake. Several people in this thread say I'm right. No one is saying you are right. So, maybe it's time that you did some more thinking. And, in a series circuit, the current is the same throughout the circuit. You seem to be claiming otherwise. No, I've never claimed that. Rather, I've said several times that the two legs of a residential electrical service are, in effect, two parallel circuits .. They are not simply parallel circuits which would require they have seperate return paths. Wrong again. Sigh Yes, it can also be considered as a single series circuit -- IF the loads are exactly balanced. Any unbalanced loads are parallel. Let's try going at this from the opposite direction. Consider a single-pole 20A circuit breaker supplying a branch circuit. I believe we'd both agree that circuit can supply a maximum of 20A at 120V. Now consider a double-pole 20A breaker supplying a 240V circuit. I believe we'd both agree that circuit can supply a maximum of 20A at 240V. Re-wire that double-pole 20A breaker with two separate 12-2 cables, so that it's supplying two 120V circuits. How many amps can that supply at 120V? 20, or 40? It's still physically supplying 20 amps ON EACH CIRCUIT because as Smitty pointed out, that is determined by the number of electrons passing each second. That hasn't changed. *More current doesn't come out of thin air. You've just made current *disappear* into thin air: supplying a single 240V circuit, it's supplying 4800W of power -- but now you claim it's supplying only 2400W when connected to two 120V circuits. Where did that other 2400W go to? Again, you are somehow trying to mix current, which is measured in amps with power and voltage. But what you have now is that same 20 amps passing through two circuits. * 20 amps through each of two circuits = 40 amps. Yes, 20 amps through two loads in series. Yes it's supporting two 20 amp loads. But what current is passing through the breaker? 20 amps Let's hook up a 6 ohm resistor to each of the new circuits. *You now have 120V across each load, so as far as each load is concerned, they have 120Volts and 20 amps each. * Count that twice and you have 40 amps of load at 120V THANK YOU. Discussion over. That's what I've been trying to tell you for three days now. No, for 3 days you've been telling everyone here that in the case of a service, you get more amps because there is a second hot conductor. That is flat out wrong. Refer again to the box example later in the thread, where there is no second hot. driven by the same 20 amps flowing in the circuit. * Look at it at the breaker which is analogous to the sevice point discussion and you still have 20A flowing, not 40. 20A in each of two parallel legs = 40 amps total. Note that these do have separate returns... Oh no, there you go again. Counting current twice. If that breaker had 20 amps flowing through it at 240V, then it had a 12 ohm load on it. So, now to make it into a 120V circuit, we just remove the 12 ohm load, put two 6 ohm loads in series on it. Now across each 6 ohm resistor you have 120V, with the same 20 amps flowing sequentially through both and suddenly the breaker is now magically carrying 40 amps? Now re-wire it with 3-wire cable, making it instead a multiwire ("Edison") circuit supplying 120V loads instead of 240V. How many amps can that supply at 120V? 20, or 40? Here's another example. * Take a cardboard box that will be our "house". * *Take an extension cord, put a 120Watt bulb on the end of it, plug it in to a 120V outlet and put the bulb in the box. * *You now have a 120volt, 1amp service to the box. * 1 amp is flowing in the circuit. Now replace the bulb with two 60Watt bulbs in series. * Across each bulb you will have 60 volts and 1 amp will be flowing in each of them. * So, you are supporting two 1 amp loads at 60volts, * *But what is flowing in that extension cord? * *It's still 1 amp, not 2. * Measured at 120V, yes. Again, per Smitty and the rest of the world, measuring current has nothing to do with measuring voltage. But this isn't the same situation, quite, as a residential service. It is EXACTLY analogous to a residential service with a balanced 120V load. You have a 120V, 1 amp "service" supplying two 60W, 60volt loads. You have 1 amp flowing in series through the two loads, but ONLY 1 AMP IS FLOWING IN THE SERVICE. If it is not the same as a residential service, tell us exactly what the difference is and why the exact same principles do not apply. Keep the two ends of that circuit at a potential difference of 120V, and *ground* the point in between the two light bulbs.. Then you have 60V flowing through each 60W light bulb = 1 amp *each* = 2 amps *total* in the parallel circuits. Good grief. If you did provide an alternative "neutral" return path at the point between the bulbs, it would matter not a wit. Just as in the actual residential service, the load is balanced and zero current would flow in the neutral. That is why I left it out as I wanted to keep it as simple as possible. If you like, I can draw you the circuit diagram that represents a center tap 240V service, but it doesn't change how current is counted. The exact same scenario plays out in the 200 amp service coming into the house, which is why only 200 amps of actual current is ever flowing. So you still contend that a 200A 240V service cannot supply more than 24kVA at 120V?- Hide quoted text - Again, please stop misquoting me. Neither I nor anyone else here ever said any such thing. Let me restate what I've said all along: In a 200 amp service entering a house, there is a max of 200 amps of actual current flowing. You don't count current twice on a service cable anymore than you would on an extension cord. Here's a simple series of questions: 1 I have a big 240V water heater that draws 200 amps and is connected to a 200amp service via the two hot legs. How much current is flowing in a - Hot leg 1 b - hot leg 2 c - neutral d - the service cable entering the house 2 Now instead of the single 240V water heater, I have two 120V water heaters that draw 200 amps each. One is connected between hot leg 1 and neutral, the other between hot leg 2 and neutral. How much current is flowing in: a - Hot leg 1 b - hot leg 2 c - neutral d - the service cable entering the house 3 Is the situation in #2 above an example of a parallel circuit or a series circuit? 4 I now disconnect the water heater that was connected to leg 2 in the previous example. You now have one 120V, 200 amp water heater connected to leg 1 and neutral. How much current is flowing in: a - Hot leg 1 b - hot leg 2 c - neutral d - the service cable entering the house |
Load capacity of 200-amp panel
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Load capacity of 200-amp panel
On Oct 25, 11:08*pm, (Doug Miller) wrote:
In article , Sam E wrote: [snip] You have a SERIES circuit (considering that the neutral is effectively disconnected). [snip] Wrong. The neutral is "effectively disconnected" *only* if the loads on the two legs are exactly the same. But a balanced load is exactly what was shown in the simple circuit example above that he understood and is discussing. Which they are (either in the 200A+200A example or the 1A+1A one). And that almost never happens in real life, either.... Which matters not a wit. Unless of course you are trying to get close to the maximum capacity of the service. If it's totally unbalanced, guess what? You get 200 amps at 120V, or exactly half the power capacity of the service. Gee, I wonder why? Could it be that it's because the service can only handle 200AMPS? And that with a 200 amp unbalanced load at 120V, 200 amps is coming in on one hot and it's all going back on the neutral? The two legs function as two parallel circuits with respect to 120V loads. In a parallel circuit BOTH ends of the loads are connected together (or at least to identical voltages). Neither is true here. Wrong -- both are true. Wow, it's getting really strange here. Of course, by definition, a parallel circuit is one where the ends of the individual elements are connected together. A series circuit is one where elements are connected one after the other, in series. Obviously they are indeed in series WRT 240V loads. Strangely, I get the idea that you actually know this stuff. In this 200A *service there are THREE current-carrying conductors. Each of these conductors is of the proper size to carry 200A. OK so far? OK You say (when this service is fully loaded) that two of these conductors is carrying 200A (for a total of 400A, as you say). 400A @ 120V, or 200A @ 240V, yes. And there you go again, inserting voltage into a question of amperage. Amperage is a measure of the charge, ie electrons passing through the conductor and IS NOT LINKED TO VOLTAGE. Then where is that 400A going? The only remaining conductor is the neutral, a big enough conductor for 200A (yes, this 400A was at 120V but current is still current and voltage doesn't change the conductor's current capacity). Somehow I'm imagining a bridge that can handle 200 cars per minute, but that can be 400 if half the cars are blue :-) Cute. Just answer these questions; assume a 240V 200A service. What is the maximum power that service can provide? You;ve asked that question multiple times and it's always been answered the same: 48KVA Now answer his question that you avoided. Apply Kirchoff's law and tell us where current is flowing in a 200 amp service cable that totals up to 400 amps. All of us here agree and can account for 200amps. So explaing the missing 200. If all the loads supplied by that service are 120V loads (e.g. blender, toaster, light bulbs, range hood, stereo, TV, computer, etc.) what do you get when you divide that maximum power by 120V? If it's a balanced load, you get 400 amps because half the load is in SERIES with the other half. As I've outlined about 6 times now, you have 200 amps coming in on one hot, going through the loads in series and then out the other hot. 200 amps is flowing in the service. If you say it's 400, then why isn't it 2 amps that flows in a 120watt light bulb plugged into an outlet? 1 amp comes in one wire, 1 amp goes out the other wire. Yet the world agrees that only 1 amp is flowing, not 2. If it's a totally unbalanced 120V load, then you can't just divide the power by 120 as youu imply, because you have 200 amps flowing in on one hot, and 200 amps flowing out on the neutral. So you have a 120V, 200 amp load and only a power of 24KVA. No matter how you slice and dice it, there is a max of 200 amps flowing in the service. Since you believe otherwise, outline the current flows as I have here and how it adds up to greater than 200 amps flowing in the service conductors. |
Load capacity of 200-amp panel
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Load capacity of 200-amp panel
On Oct 26, 12:45*pm, bud-- wrote:
wrote: On Oct 25, 2:45 pm, (Doug Miller) wrote: * .... Now re-wire it with 3-wire cable, making it instead a multiwire ("Edison") circuit supplying 120V loads instead of 240V. How many amps can that supply at 120V? 20, or 40? Here's another example. * Take a cardboard box that will be our "house". * *Take an extension cord, put a 120Watt bulb on the end of it, plug it in to a 120V outlet and put the bulb in the box. * *You now have a 120volt, 1amp service to the box. * 1 amp is flowing in the circuit. Now replace the bulb with two 60Watt bulbs in series. * Across each bulb you will have 60 volts and 1 amp will be flowing in each of them. * So, you are supporting two 1 amp loads at 60volts, * *But what is flowing in that extension cord? * *It's still 1 amp, not 2. * This is the only error I picked up. The supply voltage, as stated, is 120V in both cases. In the second case the 2 *60W bulbs would have to be in parallel to give a load of 120W and 1A. Assuming the light bulbs are linear resistances, with 60V across a 120V bulb you would get 1/2 the rated current, or 1/4A which gives an effective wattage in the 2nd case of 30W. That isn't what you intended. Yes, I agree. good catch. 120W bulb - 120 ohms 60 W bulb - 240 ohms 240W bulb - 60 ohms So, in my example I should have used two 240 watt bulbs in series which would be the same resistance as the 120watt bulb. Actuallly, I should have used a simple resistor or similar, because the resistance of light bulbs is not a constant, temp dependent, etc. But the example, corrected, still holds. You would have 60 volts and 1 amp flowing across each bulb. *.... Let me restate what I've said all along: The arguments have gotten so twisted let me start here. In a 200 amp service entering a house, there is a max of 200 amps of actual current flowing. *You don't count current twice on a service cable anymore than you would on an extension cord. Here's a simple series of questions: 1 * I have a big 240V water heater that draws 200 amps and is connected to a 200amp service via the two hot legs. How much current is flowing in a - Hot leg 1 b - hot leg 2 c - neutral d - the service cable entering the house 2 *Now instead of the single 240V water heater, I have two 120V water heaters that draw 200 amps each. * *One is connected between hot leg 1 and neutral, the other between hot leg 2 and neutral. How much current is flowing in: a - Hot leg 1 b - hot leg 2 c - neutral d - the service cable entering the house 3 *Is the situation in #2 above an example of a parallel circuit or a series circuit? 4 *I now disconnect the water heater that was connected to leg 2 in the previous example. *You now have one 120V, 200 amp water heater connected to leg 1 and neutral. How much current is flowing in: a - Hot leg 1 b - hot leg 2 c - neutral d - the service cable entering the house Everyone, I believe, has the same the answers (though I'm not sure what "d" is). I'm not so sure there is agreement as to the answers. And if there is agreement, then I don't see how there can be disagreement on how many amps are flowing on the service cable. If you have X amps coming in and X amps going out in a circuit, then that means X amps, no? The question from the OP, as I understand it, is with a panel feed at 200A 240V can you supply 200A of 120V load or 400A of 120V load. It is case #2 above. You can supply 400A of 120V load. You can't supply a 400A 120V load, but with the load split between the legs you can supply a total of 400A of 120V load, half of it from each leg. In that case the hot legs run at 200A and the neutral is zero. You don't have 400A on any wire. I assume that is not a problem for you. That is all I read Doug as saying. I agree. Its gotta be a point-of-view problem. -- I don;t see it as a point of view problem at all. How many amps are actually flowing in a 200 amp service to a house? You draw an imaginary plane and answer the question of how many amps are flowing in and how many are flowing out. If it is indeed 200 in, 200 out, then that is 200 amps period. You can have 200 amps flowing between the two hots. You can have 200 amps flowing between hot 1 and the neutral. You can have 200 amps flowing between hot 2 hot and the neutral, Any way you slice and dice it, it's still 200 amps. If you can really have 400 amps of real current flow in the service, then maybe Doug can answer this. Suppose I have a 120 volt load that takes 400 amps. I connect it as a single 120V load to a 200 amp service. What happens? A - Eveything works peechy keen, because 120V* 400amps = 48KVA, at the service limit, so 400 amps flows just fine. B - The service cable burns up, because the only way you can supply that 400amps is by the load being balanced, in which case it appears as a series load and the service is actually pulling 200amps through one hot and back the other. Which means that it would ONLY work if you had two 200 amp, 120V loads connected to OPPOSIITE legs, and hence acting as a SERIES circuit. bud--- Hide quoted text - - Show quoted text -- Hide quoted text - - Show quoted text - |
Load capacity of 200-amp panel
On Oct 26, 1:44*pm, wrote:
On Oct 26, 12:45*pm, bud-- wrote: wrote: On Oct 25, 2:45 pm, (Doug Miller) wrote: * .... Now re-wire it with 3-wire cable, making it instead a multiwire ("Edison") circuit supplying 120V loads instead of 240V. How many amps can that supply at 120V? 20, or 40? Here's another example. * Take a cardboard box that will be our "house". * *Take an extension cord, put a 120Watt bulb on the end of it, plug it in to a 120V outlet and put the bulb in the box. * *You now have a 120volt, 1amp service to the box. * 1 amp is flowing in the circuit. Now replace the bulb with two 60Watt bulbs in series. * Across each bulb you will have 60 volts and 1 amp will be flowing in each of them. * So, you are supporting two 1 amp loads at 60volts, * *But what is flowing in that extension cord? * *It's still 1 amp, not 2. * This is the only error I picked up. The supply voltage, as stated, is 120V in both cases. In the second case the 2 *60W bulbs would have to be in parallel to give a load of 120W and 1A. Assuming the light bulbs are linear resistances, with 60V across a 120V bulb you would get 1/2 the rated current, or 1/4A which gives an effective wattage in the 2nd case of 30W. That isn't what you intended. Yes, I agree. *good catch. 120W bulb - *120 ohms 60 W bulb *- 240 ohms 240W bulb - 60 ohms So, in my example I should have used two 240 watt bulbs in series which would be the same resistance as the 120watt bulb. * Actuallly, I should have used a simple resistor or similar, because the resistance of light bulbs is not a constant, temp dependent, etc. But the example, corrected, still holds. * You would have 60 volts and 1 amp flowing across each bulb. *.... Let me restate what I've said all along: The arguments have gotten so twisted let me start here. In a 200 amp service entering a house, there is a max of 200 amps of actual current flowing. *You don't count current twice on a service cable anymore than you would on an extension cord. Here's a simple series of questions: 1 * I have a big 240V water heater that draws 200 amps and is connected to a 200amp service via the two hot legs. How much current is flowing in a - Hot leg 1 b - hot leg 2 c - neutral d - the service cable entering the house 2 *Now instead of the single 240V water heater, I have two 120V water heaters that draw 200 amps each. * *One is connected between hot leg 1 and neutral, the other between hot leg 2 and neutral. How much current is flowing in: a - Hot leg 1 b - hot leg 2 c - neutral d - the service cable entering the house 3 *Is the situation in #2 above an example of a parallel circuit or a series circuit? 4 *I now disconnect the water heater that was connected to leg 2 in the previous example. *You now have one 120V, 200 amp water heater connected to leg 1 and neutral. How much current is flowing in: a - Hot leg 1 b - hot leg 2 c - neutral d - the service cable entering the house Everyone, I believe, has the same the answers (though I'm not sure what "d" is). I'm not so sure there is agreement as to the answers. * And if there is agreement, then I don't see how there can be disagreement on how many amps are flowing on the service cable. * *If you have X amps coming in and X amps going out in a circuit, then that means X amps, no? The question from the OP, as I understand it, is with a panel feed at 200A 240V can you supply 200A of 120V load or 400A of 120V load. It is case #2 above. You can supply 400A of 120V load. You can't supply a 400A 120V load, but with the load split between the legs you can supply a total of 400A of 120V load, half of it from each leg. In that case the hot legs run at 200A and the neutral is zero. You don't have 400A on any wire. I assume that is not a problem for you. That is all I read Doug as saying. I agree. Its gotta be a point-of-view problem. -- I don;t see it as a point of view problem at all. * How many amps are actually flowing in a 200 amp service to a house? * You draw an imaginary plane and answer the question of how many amps are flowing in and how many are flowing out. *If it is indeed 200 in, 200 out, then that is 200 amps period. * You can have 200 amps flowing between the two hots. * You can have 200 amps flowing between hot 1 and the neutral. * You can have 200 amps flowing between hot 2 hot and *the neutral, * *Any way you slice and dice it, it's still 200 amps. If you can really have 400 amps of real current flow in the service, then maybe Doug can answer this. * Suppose I have a 120 volt load that takes 400 amps. * I connect it as a single 120V load to a 200 amp service. *What happens? A - Eveything works peechy keen, because 120V* 400amps = 48KVA, at the service limit, so 400 amps flows just fine. B - The service cable burns up, because the only way you can supply that 400amps is by the load being balanced, in which case it appears as a series load and the service is actually pulling 200amps through one hot and back the other. * Which means that it would ONLY work if you had two 200 amp, 120V loads connected to OPPOSIITE legs, and hence acting as a SERIES circuit. bud--- Hide quoted text - - Show quoted text -- Hide quoted text - - Show quoted text -- Hide quoted text - - Show quoted text -- Hide quoted text - - Show quoted text -- Hide quoted text - - Show quoted text - QUESTION... In a service rated as a "200 Amp service".. What are the numbers printed on the TWO main breakers? Are they A) 200/200? or B)100/100? That is really the only question that needs to be answered ..... The rest should be obvious. Mark |
Load capacity of 200-amp panel
On Oct 26, 1:53*pm, Mark wrote:
On Oct 26, 1:44*pm, wrote: On Oct 26, 12:45*pm, bud-- wrote: wrote: On Oct 25, 2:45 pm, (Doug Miller) wrote: * .... Now re-wire it with 3-wire cable, making it instead a multiwire ("Edison") circuit supplying 120V loads instead of 240V. How many amps can that supply at 120V? 20, or 40? Here's another example. * Take a cardboard box that will be our "house". * *Take an extension cord, put a 120Watt bulb on the end of it, plug it in to a 120V outlet and put the bulb in the box. * *You now have a 120volt, 1amp service to the box. * 1 amp is flowing in the circuit. Now replace the bulb with two 60Watt bulbs in series. * Across each bulb you will have 60 volts and 1 amp will be flowing in each of them. * So, you are supporting two 1 amp loads at 60volts, * *But what is flowing in that extension cord? * *It's still 1 amp, not 2.. * This is the only error I picked up. The supply voltage, as stated, is 120V in both cases. In the second case the 2 *60W bulbs would have to be in parallel to give a load of 120W and 1A. Assuming the light bulbs are linear resistances, with 60V across a 120V bulb you would get 1/2 the rated current, or 1/4A which gives an effective wattage in the 2nd case of 30W. That isn't what you intended. Yes, I agree. *good catch. 120W bulb - *120 ohms 60 W bulb *- 240 ohms 240W bulb - 60 ohms So, in my example I should have used two 240 watt bulbs in series which would be the same resistance as the 120watt bulb. * Actuallly, I should have used a simple resistor or similar, because the resistance of light bulbs is not a constant, temp dependent, etc. But the example, corrected, still holds. * You would have 60 volts and 1 amp flowing across each bulb. *.... Let me restate what I've said all along: The arguments have gotten so twisted let me start here. In a 200 amp service entering a house, there is a max of 200 amps of actual current flowing. *You don't count current twice on a service cable anymore than you would on an extension cord. Here's a simple series of questions: 1 * I have a big 240V water heater that draws 200 amps and is connected to a 200amp service via the two hot legs. How much current is flowing in a - Hot leg 1 b - hot leg 2 c - neutral d - the service cable entering the house 2 *Now instead of the single 240V water heater, I have two 120V water heaters that draw 200 amps each. * *One is connected between hot leg 1 and neutral, the other between hot leg 2 and neutral. How much current is flowing in: a - Hot leg 1 b - hot leg 2 c - neutral d - the service cable entering the house 3 *Is the situation in #2 above an example of a parallel circuit or a series circuit? 4 *I now disconnect the water heater that was connected to leg 2 in the previous example. *You now have one 120V, 200 amp water heater connected to leg 1 and neutral. How much current is flowing in: a - Hot leg 1 b - hot leg 2 c - neutral d - the service cable entering the house Everyone, I believe, has the same the answers (though I'm not sure what "d" is). I'm not so sure there is agreement as to the answers. * And if there is agreement, then I don't see how there can be disagreement on how many amps are flowing on the service cable. * *If you have X amps coming in and X amps going out in a circuit, then that means X amps, no? The question from the OP, as I understand it, is with a panel feed at 200A 240V can you supply 200A of 120V load or 400A of 120V load. It is case #2 above. You can supply 400A of 120V load. You can't supply a 400A 120V load, but with the load split between the legs you can supply a total of 400A of 120V load, half of it from each leg. In that case the hot legs run at 200A and the neutral is zero. You don't have 400A on any wire. I assume that is not a problem for you. That is all I read Doug as saying. I agree. Its gotta be a point-of-view problem. -- I don;t see it as a point of view problem at all. * How many amps are actually flowing in a 200 amp service to a house? * You draw an imaginary plane and answer the question of how many amps are flowing in and how many are flowing out. *If it is indeed 200 in, 200 out, then that is 200 amps period. * You can have 200 amps flowing between the two hots. * You can have 200 amps flowing between hot 1 and the neutral. * You can have 200 amps flowing between hot 2 hot and *the neutral, * *Any way you slice and dice it, it's still 200 amps. If you can really have 400 amps of real current flow in the service, then maybe Doug can answer this. * Suppose I have a 120 volt load that takes 400 amps. * I connect it as a single 120V load to a 200 amp service. *What happens? A - Eveything works peechy keen, because 120V* 400amps = 48KVA, at the service limit, so 400 amps flows just fine. B - The service cable burns up, because the only way you can supply that 400amps is by the load being balanced, in which case it appears as a series load and the service is actually pulling 200amps through one hot and back the other. * Which means that it would ONLY work if you had two 200 amp, 120V loads connected to OPPOSIITE legs, and hence acting as a SERIES circuit. bud--- Hide quoted text - - Show quoted text -- Hide quoted text - - Show quoted text -- Hide quoted text - - Show quoted text -- Hide quoted text - - Show quoted text -- Hide quoted text - - Show quoted text - QUESTION... In a service rated as a "200 Amp service".. What are the numbers printed on the TWO main breakers? Are they A) 200/200? or B)100/100? That is really the only question that needs to be answered ..... The rest should be obvious. Mark- Hide quoted text - - Show quoted text - in other words, is this: http://homerepair.about.com/od/elect...elec_pnl_4.htm considered to be a "100 amp service" or a "200 amp service? Mark |
Load capacity of 200-amp panel
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Load capacity of 200-amp panel
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Load capacity of 200-amp panel
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Load capacity of 200-amp panel
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Load capacity of 200-amp panel
In article , Sam E wrote:
If all the loads supplied by that service are 120V loads (e.g. blender, toaster, light bulbs, range hood, stereo, TV, computer, etc.) what do you get when you divide that maximum power by 120V? That would be 400A. Exactly so. Of course that's only in your imagination since the math is invalid (120V is obtained by splitting the service into 2 separate halves, each of which is only 24KW). 200A each. Total of 400A of 120V loads -- as you said. |
Load capacity of 200-amp panel
On Oct 23, 10:34*pm, (Doug Miller) wrote:
In article , JIMMIE wrote: On Oct 23, 9:41=A0am, bud-- wrote: JIMMIE wrote: You shouldnt have more than 160 amps on any one leg or 80% of 200.. As Doug has probably been saying, the 80% limit is for continuous loads (over 3 hours). Major loads in a house are not likely continuous. A circuit breaker can operate at its full capacity, but may trip if at full capacity for over 3 hours. Its doubtfull you would ever pull more than 100 amps on a house wired with a 200 amp panel. Worse case in my house would be WELDER, HVAC, OVEN, and SPA running all at once. Exactly. So why do you keep talking about the 80% rule? It doesn't apply. Of course if wife and daughter are both doing their hair at the same time that may put me over the top. Do they take three hours to dry their hair? While the welder, HVAC, oven and spa are all running? For three hours? The 80% rule applies _only_ to continuous loads -- which is clearly and specifically defined in the Code. It seemed like it should in this case per the OP's description . What's he doing, growing pot in his attic? Even if technically an installation is residential commercial rules should apply if the situation warrants it. I would say the described situation could fit such a case. Jimmie |
Load capacity of 200-amp panel
On Oct 26, 10:37*pm, (Doug Miller) wrote:
In article , Sam E wrote: If all the loads supplied by that service are 120V loads (e.g. blender, toaster, light bulbs, range hood, stereo, TV, computer, etc.) what do you get when you divide that maximum power by 120V? That would be 400A. Exactly so. Of course that's only in your imagination since the math is invalid (120V is obtained by splitting the service into 2 separate halves, each of which is only 24KW). 200A each. Total of 400A of 120V loads -- as you said. Where in the box can you measure 400 amps? If the panel is controlling 48KW there will be no current on the neutral because the currents will be balanced. The current that flows through one half of the breaker is the same current that flows through the other half of the breaker. In this case what you have is two 200 amp breakers in series. Doug you have more current coming into the box than going out and that shouldnt happen. |
Load capacity of 200-amp panel
"JIMMIE" wrote in message ... On Oct 26, 10:37 pm, (Doug Miller) wrote: In article , Sam E wrote: If all the loads supplied by that service are 120V loads (e.g. blender, toaster, light bulbs, range hood, stereo, TV, computer, etc.) what do you get when you divide that maximum power by 120V? That would be 400A. Exactly so. Of course that's only in your imagination since the math is invalid (120V is obtained by splitting the service into 2 separate halves, each of which is only 24KW). 200A each. Total of 400A of 120V loads -- as you said. Where in the box can you measure 400 amps? If the panel is controlling 48KW there will be no current on the neutral because the currents will be balanced. The current that flows through one half of the breaker is the same current that flows through the other half of the breaker. In this case what you have is two 200 amp breakers in series. Doug you have more current coming into the box than going out and that shouldnt happen. The power is coming in from a transformer secondary winding that is center-tapped. Let's call the 3 wires Line 1, the neutral & Line 2 (seee the link below that shows a transformer secondary at the bottom of the page). When you put 120V loads across Line 1 & neutral, they are independent of Line 2. In effect, you're only using half of the transformer secondary, so you're only going thru the Line 1 half of the main breaker. The current path is from the Line 1 side of the secondary winding, thru the Line 1 side of the main breaker, thru the load, and back thru the neutral to the Line 1 half of the secondary winding. If you also put a 120V load across Line 2 and the neutral, then the current path is from the Line 2 side of the secondary winding thru the Line 2 side of the main breaker, thru the load, and back thru the neutral (in the opposite direction of current flow of the Line 1 current thru the neutral) and back to the Line 2 side of the secondary winding. Both loads form their own circular loops that are independent of each other, except for sharing the neutral (in opposite directions) to complete their separate circuits. Here is a great explanation of the transformer secondary, using the battery analogy which the author (not me) originally designed to show balanced loads, but is also useful in showing how 120V loads form independent circuits on each side of the secondary. You can even close the various switchs and see the effect. http://home.comcast.net/~ronaldrc/wsb/ax.htm |
Load capacity of 200-amp panel
On Oct 22, 1:02*pm, "JayB" wrote:
This came up elsewhere and I am just curious about what the answer is. If someone has a main service panel with a 200-amp main breaker, how many amps of service can that panel actually service? I am probably not wording this correctly, but I thought that I remember something about a 200-amp main breaker actually being okay for 400 amps of service since there are two separate circuits coming in (a 240-volt service split into two 120-volt circuits in the panel box). The answer is obvious; 200 amps. Although one working current recommendation is to not exceed (I guess that's at any one time) some 80% of the maximum capacity. So say 160 amps. It's rather like saying how many passengers can a 60 seater bus carry (seated of course)! The wire connections, bus bars (to which the individual circuit breakers attach) are rated for 200 amps. Do not exceed. BTW 200 amps at 230 volts is 230 x 200 = 46,000 watts (46 kilowatts).And 80% of that is about 37 kilowatts. That's usually plenty for all but the biggest homes. To get maximum capability that load should be balanced over the two 115 volt legs. Because if all the loads were on only one leg the maximum capacity would be 115 x 200 = 23,000 watts (23 kilowatts) and 80% of that is about 18 -19 kilowatts. |
Load capacity of 200-amp panel
"Steve N." wrote in message ... "JIMMIE" wrote in message ... On Oct 26, 10:37 pm, (Doug Miller) wrote: In article , Sam E wrote: If all the loads supplied by that service are 120V loads (e.g. blender, toaster, light bulbs, range hood, stereo, TV, computer, etc.) what do you get when you divide that maximum power by 120V? That would be 400A. Exactly so. Of course that's only in your imagination since the math is invalid (120V is obtained by splitting the service into 2 separate halves, each of which is only 24KW). 200A each. Total of 400A of 120V loads -- as you said. Where in the box can you measure 400 amps? If the panel is controlling 48KW there will be no current on the neutral because the currents will be balanced. The current that flows through one half of the breaker is the same current that flows through the other half of the breaker. In this case what you have is two 200 amp breakers in series. Doug you have more current coming into the box than going out and that shouldnt happen. The power is coming in from a transformer secondary winding that is center-tapped. Let's call the 3 wires Line 1, the neutral & Line 2 (seee the link below that shows a transformer secondary at the bottom of the page). When you put 120V loads across Line 1 & neutral, they are independent of Line 2. In effect, you're only using half of the transformer secondary, so you're only going thru the Line 1 half of the main breaker. The current path is from the Line 1 side of the secondary winding, thru the Line 1 side of the main breaker, thru the load, and back thru the neutral to the Line 1 half of the secondary winding. If you also put a 120V load across Line 2 and the neutral, then the current path is from the Line 2 side of the secondary winding thru the Line 2 side of the main breaker, thru the load, and back thru the neutral (in the opposite direction of current flow of the Line 1 current thru the neutral) and back to the Line 2 side of the secondary winding. Both loads form their own circular loops that are independent of each other, except for sharing the neutral (in opposite directions) to complete their separate circuits. Here is a great explanation of the transformer secondary, using the battery analogy which the author (not me) originally designed to show balanced loads, but is also useful in showing how 120V loads form independent circuits on each side of the secondary. You can even close the various switchs and see the effect. http://home.comcast.net/~ronaldrc/wsb/ax.htm I need to make a correction - the Line 2 current flow would be down the neutral, thru the load, up thru the Line 2 half of the breaker, back to the Line 2 side of the transformer. The currents flow in the same direction thru the transformer secondary "halves", and in opposite directions thru the neutral. |
Load capacity of 200-amp panel
JIMMIE wrote:
Where in the box can you measure 400 amps? If the panel is controlling 48KW there will be no current on the neutral because the currents will be balanced. The current that flows through one half of the breaker is the same current that flows through the other half of the breaker. In this case what you have is two 200 amp breakers in series. Doug you have more current coming into the box than going out and that shouldnt happen. Think heat. |
Load capacity of 200-amp panel
On Oct 27, 7:46*am, "HeyBub" wrote:
JIMMIE wrote: Where in the box can you measure 400 amps? If the panel is controlling 48KW there will be no current on the neutral because the currents will be balanced. The current that flows through one half of the breaker is the same current that flows through the other half of the breaker. In this case what you have is two 200 amp breakers in series. Doug you have more current coming into the box than going out and that shouldn't happen. Think heat. LOL |
Load capacity of 200-amp panel
On Oct 26, 7:18*pm, (Doug Miller) wrote:
In article , wrote: On Oct 25, 2:45=A0pm, (Doug Miller) wrote: How much power can be supplied by a 200A, 240V service? 24kVa, or 48kVA? That's been asked an answered many times in this thread. *It's 48, Very good. Now divide 48kVA by 120V and tell me what you get. Again, this has been answered here repeatedl, so I don't see why you keep asking.. One more time, it's obviously 400 amps. Also, you only get those 400 amps if the load is balanced so that it appears as a series load. The 200 amp current flows in one hot and out the other. If you had a single 120V 400 amp load, it would sit between one hot leg and neutral, where the capacity is limited to 200 amps and the cables would melt. Gee, I wonder why? Could it be because the actual current in a 200 amp service circuit is only 200 amps? You can divide and get any answer you want. I could divide 48KVA by 10volts and get 4800 amps. So a 200 amp service could support a total 4800 amp, 10 volt load too. But how much max current is actually flowing in the service cable entering the house? Exactly the same as always, 200 amps. If you believe otherwise, please tell us what currents are flowing in each of the three conductors. |
Load capacity of 200-amp panel
On Oct 27, 9:03*am, JIMMIE wrote:
On Oct 27, 7:46*am, "HeyBub" wrote: JIMMIE wrote: Where in the box can you measure 400 amps? If the panel is controlling 48KW there will be no current on the neutral because the currents will be balanced. The current that flows through one half of the breaker is the same current that flows through the other half of the breaker. In this case what you have is two 200 amp breakers in series. Doug you have more current coming into the box than going out and that shouldn't happen. Think heat. LOL Jimmie: I think the reason this thread has gone so long is that some do not really understand current flow, especially AC (Alternating Current) single phase and may be confusing current flow (amperes) with power (watts/kilowatts). In some countries also they have only two wires coming into a domestic service (plus ground/earth). So they have a concept of only the two wires of a single phase 230 volt service. One of which is neutral (essentially at zero volts!) and the other at 230 volts (often 50 hertz) to neutral and ground. the size of those dermines the ampere capacity of the service. Was looking at distribution along a street in Malta; which was attached to the face of the buildings. It comprised four wires. One of which was ground/earth. I think it was green? One of the remaining three was neutral. The other two were most likely 230+ and 230- as it were of a single phase. Or they might have been two phases of a a 3 phase delta/star transformer sub-station secondary at end of the street. The house services along the street were connected alternately to these last two. In other words all services were two wire single phase 230 volt, plus a ground/earth. Again in one of the Gulf States it was also essentially 230 volts 50 hertz. BUT; in that instance there were the three phases and neutral etc. coming into every residence unit and the circuit breaker panel or CU (Consumer Unit) had three sections one for each phase. The fact that there were some seven large 230 volt 50 hertz AC units in each unit probaly required a heavy service! Residentially didn't see any 3 phase equipment although it could have been hooked up. It was mainly UG. Other areas of the world may vary; in Sri Lanka for example it was hard to tell what was going on viewing some of the lash-ups on some of the service poles! Anyway the point of all this is that it's best to understand, no matter where one is, what the electrical service arrangement is. Also that with two wires (plus ground) there can be no doubt .................. a 200 amp service (or whatever it's rated) is just that, 200 amps. No more (unless overloaded) no less (subject to the recommended 80% rule for prolonged use). Nothing magic about it! |
Load capacity of 200-amp panel
On Oct 26, 4:36*pm, bud-- wrote:
*Suppose I have a 120 volt load that takes 400 amps. * I connect it as a single 120V load to a 200 amp service. *What happens? You don't connect it to one leg. You split the load in half and connect one half leg 1 to neutral. You connect the other half from leg 2 to neutral. (In this case you reconnect the single 400A 120V load as a 200A 240V load.) That was precisely my point. That to support a 400 amp 120V load, the load must be perfectly balanced. And that is because only a max of 200 amps is flowing in the service cable and the 400 amp, 120V load must appear as two 200 amp, 120V loads in SERIES. It's a very basic and simple electrical question as to how many amps are flowing in that 200 amp service cable and it's 200 amps. You could support all kinds of loads of varying voltages off it, including 400 amps at 120V, provided the load is perfectly balanced. I could further break it down to support a total load of 800 amps at 60volts, etc. That doesn't change the physical current in the service cable from being limited to 200 amps? If you put a current meter on it you would measure 200 amps flowing into the house, 200 amps flowing out. Do we agree? And none of that has anything to do with claims that were made here that you get 400 amps because there is a second conductor. Or that the service is a parallel circuit. I showed in the box with light bulbs how the exact same thing can be done running various loads/ voltages off just a 2 wire 120V outlet. If you have 40 - 10A 120V loads (400A total at 120V) you connect 20 of them to leg 1 (200A). You connect the other 20 to leg 2 (200A). The neutral current is zero. You have supplied 400A of 120V loads by splitting it and connecting half to each leg. A - Eveything works peechy keen, because 120V* 400amps = 48KVA, at the service limit, so 400 amps flows just fine. B - The service cable burns up, because the only way you can supply that 400amps is by the load being balanced, in which case it appears as a series load and the service is actually pulling 200amps through one hot and back the other. * Which means that it would ONLY work if you had two 200 amp, 120V loads connected to OPPOSIITE legs, and hence acting as a SERIES circuit. Which is how you connect it. I don't want to go back and reread the thread - Doug's use of parallel may have not been the best. But I always understood he was saying that half of a 400A load (200A) was connected to leg 1 and the other half (200A) was connected to leg 2. In answer to the OP's question - with a panel feed at 200A 240V can you supply 400A of 120V load - the answer is yes. I still think it is a point-of-view problem. You and Doug (and Smitty and others?) all understand the underlying electrical. -- bud--- Hide quoted text - I'm not so sure, as I have yet to hear Doug acknowledge that there is actually only a 200 amp current flowing in that service cable. When asked that by others he has replied with answers that try to link it to voltage, ie 200 amps at 240V or 400 amps at 120V. And that is simply wrong. Amps and voltage are two different things. There is never more than 200 amps flowing in that service cable circuit. |
Load capacity of 200-amp panel
On Oct 27, 2:37*am, "Steve N." wrote:
"Steve N." wrote in message ... "JIMMIE" wrote in message ... On Oct 26, 10:37 pm, (Doug Miller) wrote: In article , Sam E wrote: If all the loads supplied by that service are 120V loads (e.g. blender, toaster, light bulbs, range hood, stereo, TV, computer, etc.) what do you get when you divide that maximum power by 120V? That would be 400A. Exactly so. Of course that's only in your imagination since the math is invalid (120V is obtained by splitting the service into 2 separate halves, each of which is only 24KW). 200A each. Total of 400A of 120V loads -- as you said. Where in the box can you measure 400 amps? If the panel is controlling 48KW there will be no current on the neutral because the currents will be balanced. The current that flows through one half of the breaker is the same current that flows through the other half of the breaker. In this case what you have is two 200 amp breakers in series. Doug you have more current coming into the box than going out and that shouldnt happen. The power is coming in from a transformer secondary winding that is center-tapped. Let's call the 3 wires Line 1, the neutral & Line 2 (seee the link below that shows a transformer secondary at the bottom of the page). When you put 120V loads across Line 1 & neutral, they are independent of Line 2. In effect, you're only using half of the transformer secondary, so you're only going thru the Line 1 half of the main breaker. The current path is from the Line 1 side of the secondary winding, thru the Line 1 side of the main breaker, thru the load, and back thru the neutral to the Line 1 half of the secondary winding. Agree. If you also put a 120V load across Line 2 and the neutral, then the current path is from the Line 2 side of the secondary winding thru the Line 2 side of the main breaker, thru the load, and back thru the neutral (in the opposite direction of current flow of the Line 1 current thru the neutral) and back to the Line 2 side of the secondary winding. Both loads form their own circular loops that are independent of each other, except for sharing the neutral (in opposite directions) to complete their separate circuits. Don't agree with this. If the second load on line 2 is equal to the load already on line 1, then the current flow is in on line 1 and back out on line 2. No current flows in the neutral. If the second load on line 2 were half the size of the load on line 1, then half the current from line 1 would flow back out on line 2 and half the current from line 1 would flow back out the neutral. The key here is look at that service cable coming from the transformer and you have a circuit running a max of 200 amps. Agree? |
Load capacity of 200-amp panel
terry wrote:
On Oct 22, 1:02 pm, "JayB" wrote: This came up elsewhere and I am just curious about what the answer is. If someone has a main service panel with a 200-amp main breaker, how many amps of service can that panel actually service? I am probably not wording this correctly, but I thought that I remember something about a 200-amp main breaker actually being okay for 400 amps of service since there are two separate circuits coming in (a 240-volt service split into two 120-volt circuits in the panel box). The answer is obvious; 200 amps. The answer is obvious; 400 amps. Although one working current recommendation is to not exceed (I guess that's at any one time) some 80% of the maximum capacity. So say 160 amps. Don't know about Canada, but in the US 80% only applies to "continuous loads" (over 3 hours). In a house service, if you could get a 200 amp peak it wouldn't last long. Loads cycle on and off. It is called "diversity". Because of diversity the service wires (in the US) can usually be 'undersized' with a residential derate. Can't do that in commercial, where you turn on lights and they are on all day long ("continuous"). The wire connections, bus bars (to which the individual circuit breakers attach) are rated for 200 amps. Do not exceed. BTW 200 amps at 230 volts is 230 x 200 = 46,000 watts (46 kilowatts).And 80% of that is about 37 kilowatts. That's usually plenty for all but the biggest homes. To get maximum capability that load should be balanced over the two 115 volt legs. And when you balance the load over the two 115 volt legs you get - lets see - 46,000 watts divided by 115 volts - um - 400 amps of 115 volt load. Even in Canada. That is what the OP asked. -- bud-- |
Load capacity of 200-amp panel
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