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#1
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Load capacity of 200-amp panel
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). |
#2
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Load capacity of 200-amp panel
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). It all depends on voltage. A 220 amp service can in theory (you are not supposed to use more than 80%) supply 200 amps at 240 volts OR 400 amps at 120 volts or any combination of the above. |
#3
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Load capacity of 200-amp panel
In article s.com, "EXT" wrote:
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). It all depends on voltage. A 220 amp service can in theory (you are not supposed to use more than 80%) Not so. You misunderstand the 80% rule. supply 200 amps at 240 volts OR 400 amps at 120 volts or any combination of the above. |
#4
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Load capacity of 200-amp panel
On Oct 22, 1:19�pm, (Doug Miller) wrote:
In article s.com, "EXT" wrote: 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). It all depends on voltage. A 220 amp service can in theory (you are not supposed to use more than 80%) Not so. You misunderstand the 80% rule. supply 200 amps at 240 volts OR 400 amps at 120 volts or any combination of the above.- Hide quoted text - - Show quoted text - plus the 200 amp dual breaker can and will carry a percentage more indefinetely I had a friend who had the largest outdoor light display in the area, the power company loved him checking the legs of his main service, it exceeded 200 amps on either side. he couldnt run his dishwasher, washer dryer, or even a hair dryer as his wife found out when the lights were on.......... her hair dryer blacked out the total home. when his kids got bigger he quit decorating......... but geez it was beautiful |
#5
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Load capacity of 200-amp panel
On Oct 22, 2:14*pm, " wrote:
On Oct 22, 1:19 pm, (Doug Miller) wrote: In article s.com, "EXT" wrote: 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). It all depends on voltage. A 220 amp service can in theory (you are not supposed to use more than 80%) Not so. You misunderstand the 80% rule. supply 200 amps at 240 volts OR 400 amps at 120 volts or any combination of the above.- Hide quoted text - - Show quoted text - plus the 200 amp dual breaker can and will carry a percentage more indefinetely I had a friend who had the largest outdoor light display in the area, the power company loved him checking the legs of his main service, it exceeded 200 amps on either side. he couldnt run his dishwasher, washer dryer, or even a hair dryer as his wife found out when the lights were on.......... her hair dryer blacked out the total home. when his kids got bigger he quit decorating......... but geez it was beautiful- Hide quoted text - - Show quoted text - Aside from the 80% rule, you can't get 400 amps out of a 200amp service. The service consists of two hots, and a neutral. That means with a 200 amp service you can get 200 amps at 240V flowing between the two hots. Or you could get say 150 amps at 240V plus 50 amps at 120V. /In the latter case you have 200 amps flowing on one hot, 150 on the other hot, and 50 on the neutral. |
#6
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Load capacity of 200-amp panel
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#7
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Load capacity of 200-amp panel
Doug Miller wrote:
In article , 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. The service consists of two hots, and a neutral. That means with a 200 amp service you can get 200 amps at 240V flowing between the two hots. Or you could get say 150 amps at 240V plus 50 amps at 120V. /In the latter case you have 200 amps flowing on one hot, 150 on the other hot, and 50 on the neutral. Ummm....no. You could have up to 150A at 240V plus *100A* at 120V -- and if the loads are distributed evenly across the two legs, the current in the neutral is zero. And, to make it perfectly clear, _only_ the two "hots" are on overcurrent protection; the neutral is not. -- |
#9
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Load capacity of 200-amp panel
JayTKR wrote: Thanks. That's what I thought -- that 200 amps at 240 volts is basically 400 amps available at 120 volts. Or, for example, if 50 of the 200 amps were for a 240 volt circuit, that would leave 150 amps at 240 which could be 300 amps at 120 volts. One other complicating factor is the 125A max branch circuit limitation. Not an issue in normal residential application of course as few people have single loads over 125A, but something to keep in mind when feeding subpanels. |
#10
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Load capacity of 200-amp panel
On 2009-10-23, Pete C. wrote:
JayTKR wrote: That's what I thought -- that 200 amps at 240 volts is basically 400 amps available at 120 volts. The difference is that you can't run a single 120V load at a full 400 amps. But you could run two different 120V loads at 200 amps. One other complicating factor is the 125A max branch circuit limitation. The only limitation here is in the breakers for your panel. Larger breakers may be available; they often take up more space than normal in the panel, so as to have multiple connections to the same busbar. Cheers, Wayne |
#11
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Load capacity of 200-amp panel
On Oct 23, 2:24*am, Wayne Whitney wrote:
On 2009-10-23, Pete C. wrote: JayTKR wrote: That's what I thought -- that 200 amps at 240 volts is basically 400 amps available at 120 volts. * The difference is that you can't run a single 120V load at a full 400 amps. *But you could run two different 120V loads at 200 amps. One other complicating factor is the 125A max branch circuit limitation. The only limitation here is in the breakers for your panel. *Larger breakers may be available; they often take up more space than normal in the panel, so as to have multiple connections to the same busbar. Cheers, Wayne People just playing with words! Since: Power = voltage multiplied by amperage. For example if one has individual 20 amp 115 volt circuits the maximum power each could carry is 115 x 20 = 2,300 watts. A 15 amp lighting circuit, 115 x 15 = 1725 watts. Similarly (ignoring the 80% rule for the moment) the maximum power that a 200 amp (Standard North American 115 - 0 - 115) domestic service can carry is 200 x 230 = 46,000 watts. It is not possible for all the power could be loaded 'all on one 115 volt leg/side', as 115 x 400 = 46,000 watts. This would be rather like saying one could put the total weight of a ten ton truck ALL on one set of wheels! Or hiring two taxis to carry ten passengers, but then putting all ten passengers in one taxi, with none in the other! That's also why domestic loads are 'supposed' to be balanced/ distributed' across both legs. In practice rarely operating in most situations at anything close to maximum loading. So balance not often an issue. A domestic service double pole main circuit protects both legs of the incoming service. Once the trip limit of the breaker (200 amps say) exceeded, on either leg it would operate thus disconnecting both 115 volt legs. |
#12
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Load capacity of 200-amp panel
On Oct 22, 12:02*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). You shouldnt have more than 160 amps on any one leg or 80% of 200.. Jimmie |
#13
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Load capacity of 200-amp panel
I havn't heard from Clark Griswold in a while, not since
they did the movie about him. http://www.youtube.com/watch?v=ian6NyXpszw -- Christopher A. Young Learn more about Jesus www.lds.org .. wrote in message ... I had a friend who had the largest outdoor light display in the area, the power company loved him checking the legs of his main service, it exceeded 200 amps on either side. he couldnt run his dishwasher, washer dryer, or even a hair dryer as his wife found out when the lights were on.......... her hair dryer blacked out the total home. when his kids got bigger he quit decorating......... but geez it was beautiful |
#14
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Load capacity of 200-amp panel
I havn't heard from Clark Griswold in a while, not since
they did the movie about him. http://www.youtube.com/watch?v=ian6NyXpszw http://www.youtube.com/watch?v=8qc_RYm0ylA&NR=1 -- Christopher A. Young Learn more about Jesus www.lds.org .. wrote in message ... I had a friend who had the largest outdoor light display in the area, the power company loved him checking the legs of his main service, it exceeded 200 amps on either side. he couldnt run his dishwasher, washer dryer, or even a hair dryer as his wife found out when the lights were on.......... her hair dryer blacked out the total home. when his kids got bigger he quit decorating......... but geez it was beautiful |
#15
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Load capacity of 200-amp panel
I havn't heard from Clark Griswold in a while, not since
they did the movie about him. http://www.youtube.com/watch?v=ian6NyXpszw http://www.youtube.com/watch?v=8qc_RYm0ylA&NR=1 -- Christopher A. Young Learn more about Jesus www.lds.org .. wrote in message ... I had a friend who had the largest outdoor light display in the area, the power company loved him checking the legs of his main service, it exceeded 200 amps on either side. he couldnt run his dishwasher, washer dryer, or even a hair dryer as his wife found out when the lights were on.......... her hair dryer blacked out the total home. when his kids got bigger he quit decorating......... but geez it was beautiful |
#16
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Load capacity of 200-amp panel
On Oct 23, 7:38�am, "Stormin Mormon"
wrote: I havn't heard from Clark Griswold in a while, not since they did the movie about him. �http://www.youtube.com/watch?v=ian6NyXpszw � �http://www.youtube.com/watch?v=8qc_RYm0ylA&NR=1 -- Christopher A. Young griswald is what my neighbor was called reportedly by everyone he knew. he lit up the neighborhood, and his power bill collected donations for salvation army and created sometimes massive traffic jams, after his display was featured on news. i alwasys expected him to blow the local transformer.......... |
#17
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Load capacity of 200-amp panel
On Oct 22, 4:10*pm, (Doug Miller) wrote:
In article , 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. What you are arguing is like saying a resistor that has 1 amp flowing in it is actually carrying 2 amps, because 1 amp goes in and one amp goes out. *The service consists of two hots, and a neutral. * That means with a 200 amp service you can get 200 amps at 240V flowing between the two hots. * Or you could get say 150 amps at 240V plus 50 amps at 120V. */In the latter case you have 200 amps flowing on one hot, 150 on the other hot, and 50 on the neutral. Ummm....no. You could have up to 150A at 240V plus *100A* at 120V -- and if the loads are distributed evenly across the two legs, the current in the neutral is zero. That is not true. If you have 150A running at 240V then you have 150A coming in on one hot, 150A going out on the other hot during each half cycle and zero flowing through the neutral. The next half cycle, it reverses. If you now add another 50 amps between one hot and neutral, you now have 200A running through one hot, `150 amps through the other hot, and 50 amps through the neutral. There is nowhere for your extra 50 amps to come from to give you 250amps The max current flowing is still limited to 200 amps. |
#18
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Load capacity of 200-amp panel
JIMMIE wrote:
On Oct 22, 12:02 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). 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. -- bud-- |
#19
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Load capacity of 200-amp panel
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). Do you expect to actually draw 200 amps at once, or are you adding up the amperage value of all the circuit breakers? |
#20
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Load capacity of 200-amp panel
In article , JIMMIE wrote:
You shouldnt have more than 160 amps on any one leg or 80% of 200.. Incorrect. You do not understand the "80% rule". The rule applies only to "continuous loads" which is defined by the Code as maximum current for a period of three hours or more. |
#21
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Load capacity of 200-amp panel
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#22
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Load capacity of 200-amp panel
Neat. Would have liked to see that, but it sounds dangerous.
-- Christopher A. Young Learn more about Jesus www.lds.org .. wrote in message ... griswald is what my neighbor was called reportedly by everyone he knew. he lit up the neighborhood, and his power bill collected donations for salvation army and created sometimes massive traffic jams, after his display was featured on news. i alwasys expected him to blow the local transformer.......... |
#23
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Load capacity of 200-amp panel
On Oct 23, 9:41*am, bud-- wrote:
JIMMIE wrote: On Oct 22, 12:02 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). 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. -- bud-- 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. Of course if wife and daughter are both doing their hair at the same time that may put me over the top. Jimmie |
#24
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Load capacity of 200-amp panel
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. |
#25
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Load capacity of 200-amp panel
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. |
#26
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Load capacity of 200-amp panel
In article , 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? 200A @ 120V on leg 1, 200A @ 120V on leg 2. Being able to add to numbers* doesn't mean reality works that way. Actually, it does. [snip] * - Actually, that's incorrect too. The addends are out of phase, so 200 + 200 = 0. 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. |
#27
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Load capacity of 200-amp panel
On Oct 23, 3:54*pm, (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. What you are arguing is like saying a resistor that has 1 amp flowing in it is actually carrying 2 amps, because 1 amp goes in and one amp goes out. It's not at all the same. You are failing to consider that the two legs of a residential service can be treated as two *separate* parallel 120V circuits. The service consists of two hots, and a neutral. That means with a 200 amp service you can get 200 amps at 240V flowing between the two hots. Or you could get say 150 amps at 240V plus 50 amps at 120V. In the latter case you have 200 amps flowing on one hot, 150 on the other hot, and 50 on the neutral. Ummm....no. You could have up to 150A at 240V plus *100A* at 120V -- and if the loads are distributed evenly across the two legs, the current in the neutral is zero. That is not true. * If you have 150A running at 240V then you have 150A coming in on one hot, 150A going out on the other hot during each half cycle and zero flowing through the neutral. * * *The next half cycle, it reverses. * * If you now add another 50 amps between one hot and neutral, you now have 200A running through one hot, `150 amps through the other hot, and 50 amps through the neutral. * * Right so far... There is nowhere for your extra 50 amps to come from Sure there is: the other hot leg still has an extra 50A capacity. Yes, you are right on that point and I was wrong. to give you 250amps * Ahh, _there_ is the source of your misconception. The neutral carries only the unbalanced current. When the other hot leg carries 200A as well, the current in the neutral _drops to zero_. The max current flowing is still limited to 200 amps. Suppose that the residence has no 240V loads of any sort -- gas furnace, gas WH, gas dryer, gas stove, no large power tools, no double-pole breakers, every circuit in the panel is a 120V circuit. Do you maintain that the maximum power that could be drawn from this service is 200A @ 120V = 24kVA?- Hide quoted text - - Show quoted text -- Hide quoted text - - Show quoted text - The issue here is what defines the current at the service. In a 200 amp service there is only 200 amps of actual physical current running through the service conductors. The conductors are sized for 200 amps, not 400 amps. 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. That's what I meant when I said a 200 amp service cannot supply 400 amps of current. |
#28
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Load capacity of 200-amp panel
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#29
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Load capacity of 200-amp panel
In article ,
(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? *Immediately* above your two questions, he answered them both, Doug. There isn't really so much disagreement going on, it's just that y'all aren't paying attention to what the others are saying. 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. Consider a house with only 120V loads, no 240V circuits anywhere, and 200A service. Suppose that one leg of the service is fully loaded, and the other leg is unloaded. I think we'd both agree that the power being drawn is 200A at 120V, right? Now fully load the other leg too. |
#30
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Load capacity of 200-amp panel
On Oct 24, 2:35*pm, Smitty Two wrote:
In article (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? *Immediately* above your two questions, he answered them both, Doug. There isn't really so much disagreement going on, it's just that y'all aren't paying attention to what the others are saying. I think the problem is that people aren't paying attention to what the other is saying. R |
#31
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Load capacity of 200-amp panel
In article , Smitty Two wrote:
In article , (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? *Immediately* above your two questions, he answered them both, Doug. He doesn't understand the implications of what he wrote, though, which is why I'm emphasizing it. There isn't really so much disagreement going on, it's just that y'all aren't paying attention to what the others are saying. Rather, vice versa. A 200A residential service supplies up to 200A _at 240V_. This is _exactly_ equivalent to 400A at 120V -- which is precisely what you have if each leg of the service is fully loaded at 120V. 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. Consider a house with only 120V loads, no 240V circuits anywhere, and 200A service. Suppose that one leg of the service is fully loaded, and the other leg is unloaded. I think we'd both agree that the power being drawn is 200A at 120V, right? Now fully load the other leg too. |
#32
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Load capacity of 200-amp panel
On 2009-10-24, Doug Miller wrote:
A 200A residential service supplies up to 200A _at 240V_. This is _exactly_ equivalent to 400A at 120V -- which is precisely what you have if each leg of the service is fully loaded at 120V. There are a couple small differences between 400A worth of 120V loads balanced on the two legs of a 240/120V supply, and 400A of loads on a 120V supply. First, in the former case the biggest 120V load you can handle (without a transformer) is 200A, while in the latter case you can handle a 400A 120V load. Second, the voltage drop on the supply is different. V = I^2 * R, where I is 200A in the first case, and 400A in the second case. Cheers, Wayne |
#33
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Load capacity of 200-amp panel
On Oct 24, 2:17*pm, (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? 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. 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. 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. If you want to get techical, since it's AC, the current direction switches each cycle. Kapisch? 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. They are NOT parallel circuits. That would imply that each has it's own seperate return path. They do not. The return path is through the other hot conductor for the balanced part of the load and through the shared neutral for the unbalanced portion. Again, at any point in time there is only 200 amps moving through that service going into the home, which is why it's called a 200 amp service. Consider a house with only 120V loads, no 240V circuits anywhere, and 200A service. Suppose that one leg of the service is fully loaded, and the other leg is unloaded. I think we'd both agree that the power being drawn is 200A at 120V, right? Yes Now fully load the other leg too.- Hide quoted text - And now you have 200 amps flowing from one hot and back on the other hot. Zero flows through the neutral. Hence, again, it's only a 200 amp total current moving through the service. |
#34
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Load capacity of 200-amp panel
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#35
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Load capacity of 200-amp panel
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. .....with a common neutral wire which must provide a return path for both circuits. 200A flowing in each of two parallel circuits is 400A total, not 200A. As long as the neutral wire is rated for an amperage capacity of 400A...if it's not, and you try feeding 400 amps through a wire only rated for 200A max, what do you think will happen? ;-) |
#36
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Load capacity of 200-amp panel
In article , propman wrote:
Doug Miller wrote: The two legs of a residential electrical service are, in effect, two parallel circuits. .....with a common neutral wire which must provide a return path for both circuits. 200A flowing in each of two parallel circuits is 400A total, not 200A. As long as the neutral wire is rated for an amperage capacity of 400A...if it's not, and you try feeding 400 amps through a wire only rated for 200A max, what do you think will happen? ;-) You badly misunderstand how this works. In a 240/120 residential service, the neutral carries only the unbalanced current (the difference between the currents in the hot legs, not their sum): if 50A is being drawn on one hot leg, and 90A on the other, the neutral carries only 40A. If one hot leg is carrying 200A, and the other 199A, the current in the neutral is *not* 399A -- it's 1A. And if both hot legs are loaded exactly equally, whether that's 1mA each or 200A each, the current in the neutral is zero. For 200A service, the neutral does *not* need to be rated for 400A. The most it can ever carry -- if one hot leg is fully loaded, and the other is unused -- is 200A, and if the loads are even halfway close to being balanced across the two legs, most of the time the current in the neutral is far less than that. |
#37
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Load capacity of 200-amp panel
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#38
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Load capacity of 200-amp panel
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. |
#39
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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. At the time I read it a continuous power situation is the only thing that made sense to me. Having the flu and taking codeine will change ones sense quite a bit. Sorry, you are correct. |
#40
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Load capacity of 200-amp panel
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. 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, in a series circuit, the current is the same throughout the circuit. You seem to be claiming otherwise. |
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