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#1
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Double Pole Circuit Breakers
I understand that double pole circuit breakers feed 240v (two120's) to
water heaters, stoves, ect... But, Im confused about the amperage marking on the middle tab; I see that most say 30A. Does that mean the each pole from that circuit breaker can handle up to 30A each pole? 30 + 30 = 60A total? or is the amps on each hot leg split into two; 15 amps each pole; 15 + 15 = 30A? I never worked with 240V circuits before, obviosly. I just need to install a small baseboard heater in my shop for the upcoming winters; it calls for a 20A 240v breaker. Another quick question, but off topic: Why don't wire manufactures insulate the bare ground wire inside romex cables? |
#2
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Double Pole Circuit Breakers
Each pole of a breaker, single, double or triple, provides the amperage
marked on the breaker. Double pole 20 amp gives you 20 amps on each legs or 20 amps @240 volts I too, would like the ground wires to be insulated for my own safety wrote in message ups.com... I understand that double pole circuit breakers feed 240v (two120's) to water heaters, stoves, ect... But, Im confused about the amperage marking on the middle tab; I see that most say 30A. Does that mean the each pole from that circuit breaker can handle up to 30A each pole? 30 + 30 = 60A total? or is the amps on each hot leg split into two; 15 amps each pole; 15 + 15 = 30A? I never worked with 240V circuits before, obviosly. I just need to install a small baseboard heater in my shop for the upcoming winters; it calls for a 20A 240v breaker. Another quick question, but off topic: Why don't wire manufactures insulate the bare ground wire inside romex cables? |
#3
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Double Pole Circuit Breakers
In article , "RBM" rbm2(remove wrote:
Each pole of a breaker, single, double or triple, provides the amperage marked on the breaker. Double pole 20 amp gives you 20 amps on each legs or 20 amps @240 volts I too, would like the ground wires to be insulated for my own safety How would insulating the ground wire improve safety? -- Regards, Doug Miller (alphageek at milmac dot com) It's time to throw all their damned tea in the harbor again. |
#4
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Double Pole Circuit Breakers
If they were insulated, I wouldn't have to be so careful while flailing them
around inside panel boxes "Doug Miller" wrote in message y.net... In article , "RBM" rbm2(remove wrote: Each pole of a breaker, single, double or triple, provides the amperage marked on the breaker. Double pole 20 amp gives you 20 amps on each legs or 20 amps @240 volts I too, would like the ground wires to be insulated for my own safety How would insulating the ground wire improve safety? -- Regards, Doug Miller (alphageek at milmac dot com) It's time to throw all their damned tea in the harbor again. |
#5
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Double Pole Circuit Breakers
On Mon, 12 Jun 2006 07:09:40 -0400, "RBM" rbm2(remove
wrote: Each pole of a breaker, single, double or triple, provides the amperage marked on the breaker. Double pole 20 amp gives you 20 amps on each legs or 20 amps @240 volts I too, would like the ground wires to be insulated for my own safety imho: Ground Wires 'do not' carry current except under ground fault conditions. In that case, the breaker/fuse will break the circuit asap(by design). So it normally carries 0 voltage, 0 current. hth, tom wrote in message oups.com... I understand that double pole circuit breakers feed 240v (two120's) to water heaters, stoves, ect... But, Im confused about the amperage marking on the middle tab; I see that most say 30A. Does that mean the each pole from that circuit breaker can handle up to 30A each pole? 30 + 30 = 60A total? or is the amps on each hot leg split into two; 15 amps each pole; 15 + 15 = 30A? I never worked with 240V circuits before, obviosly. I just need to install a small baseboard heater in my shop for the upcoming winters; it calls for a 20A 240v breaker. Another quick question, but off topic: Why don't wire manufactures insulate the bare ground wire inside romex cables? |
#6
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Double Pole Circuit Breakers
"Tom The Great" wrote in message ... On Mon, 12 Jun 2006 07:09:40 -0400, "RBM" rbm2(remove wrote: Each pole of a breaker, single, double or triple, provides the amperage marked on the breaker. Double pole 20 amp gives you 20 amps on each legs or 20 amps @240 volts I too, would like the ground wires to be insulated for my own safety imho: Ground Wires 'do not' carry current except under ground fault conditions. In that case, the breaker/fuse will break the circuit asap(by design). So it normally carries 0 voltage, 0 current. You are correct that it normally carries nothing, but why would a breaker open on a ground fault? (unless it is a gfci...) |
#7
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Double Pole Circuit Breakers
According to Toller :
You are correct that it normally carries nothing, but why would a breaker open on a ground fault? (unless it is a gfci...) A ground fault is simply a leak to the grounding conductor - it could be a few milliamps, or many amps. Breakers trip on big ones. GFCIs trip on small ones. -- Chris Lewis, Una confibula non set est It's not just anyone who gets a Starship Cruiser class named after them. |
#8
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Double Pole Circuit Breakers
Chris Lewis wrote:
According to Toller : You are correct that it normally carries nothing, but why would a breaker open on a ground fault? (unless it is a gfci...) A ground fault is simply a leak to the grounding conductor - it could be a few milliamps, or many amps. A ground fault is a leak to ground. It may or may not pass through the grounding conductor. Breakers trip on big ones. GFCIs trip on small ones. Breakers trip on excessive current regardless of the path that it takes. GFCIs trip on an unbalance between the two wires that compose the active circuit. -- --John to email, dial "usenet" and validate (was jclarke at eye bee em dot net) |
#9
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Double Pole Circuit Breakers
On Mon, 12 Jun 2006 13:34:31 GMT, "Toller" wrote:
"Tom The Great" wrote in message .. . On Mon, 12 Jun 2006 07:09:40 -0400, "RBM" rbm2(remove wrote: Each pole of a breaker, single, double or triple, provides the amperage marked on the breaker. Double pole 20 amp gives you 20 amps on each legs or 20 amps @240 volts I too, would like the ground wires to be insulated for my own safety imho: Ground Wires 'do not' carry current except under ground fault conditions. In that case, the breaker/fuse will break the circuit asap(by design). So it normally carries 0 voltage, 0 current. You are correct that it normally carries nothing, but why would a breaker open on a ground fault? (unless it is a gfci...) If a hot comes in contact with a metal casing, that is grounded, it is called a ground fault. Following the NEC all grounded equipment conductors (the ground wire) have to have as lose impedance to electricy back to the source. So using ohms law E=IR E is electrical potencial, or Voltage I is current R is resistance. Solve for I (current) results in I = E/R substitute numbers for lowest norm voltage. I = 120 / ~0 *Note: Used 0 since a small house has almost 0 ohms back to the panel on the ground wires. So calc Current, and you have an almost infinite amount of current, a short, and the breaker will open on this ground. A normal breaker should open on any ground fault over thier set points. Meaning a 15 amp breaker should open on any ground faults over 15 amps, on over current protection. Ofcourse an almost infinite current, should trip the breaker on short circuit protection. hth, (please ignore spelling errors) tom |
#12
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Double Pole Circuit Breakers
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#13
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Double Pole Circuit Breakers
In article , ~^Johnny^~ wrote:
On Mon, 12 Jun 2006 08:34:35 -0500, wrote: That's one thing people often do not understand. If you have a 100A service and only use 120V items in the house, you can actually draw 200A. No way. Your total load calc may be 200 A at 120 V, but you are still pulling 100 amps. You've got two 120 volt loads in series, that's all. You are STILl pulling 100 amps at 240 volts. Which is exactly the same electrical power as 200A at 120V. Since the individual loads are in series/parallel, they share half teh voltage, so the total load calc comes out to 200 amps, but only 100 amps are flowing through the service. Really. 100A at 240V -- and, as noted above, if only 120V loads are in use, the total current draw is (up to) 200A at 120V. -- Regards, Doug Miller (alphageek at milmac dot com) It's time to throw all their damned tea in the harbor again. |
#14
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Double Pole Circuit Breakers
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#16
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Double Pole Circuit Breakers
) said...
But, Im confused about the amperage marking on the middle tab; I see that most say 30A. Does that mean the each pole from that circuit breaker can handle up to 30A each pole? 30 + 30 = 60A total? or is the amps on each hot leg split into two; 15 amps each pole; 15 + 15 = 30A? Overcurrent protection is placed on the hot side of a circuit, so with 120V circuits, there is only a single pole breaker for the single hot. On a 240V circuit, you get 120 volts (relative to the neutral) per hot (from separate legs). The current that goes through one returns through the other. Overcurrent protection is needed on BOTH hots and must be rated the same because it is the SAME current that passes through both. Since the voltage is doubled, even though the current is the same, the POWER that can be provided by the circuit is doubled. A neutral conductor is only needed on a 240V circuit if there are loads that require only 120V on the circuit. In those cases, the neutral will carry the DIFFERENCE between the current in each hot. (e.g.: if one hot had a current of 10A and the other had 9A, the neutral would be carrying the 1A difference). Why don't wire manufactures insulate the bare ground wire inside romex cables? Why bother? There is really no safety issue as it only serves to bond metal chassis and boxes to ground. It will carry a current in fault situations, but no greater than the overcurrent protection on the circuit. However, in the case of those ORANGE outlets, the ground pin on the receptacle is ISOLATED from the bare ground that the box is bonded by. A separate INSULATED ground conductor is needed to bond the ground pin to the grounding bus in the panel. Often the red conductor of a 3-wire cable is used for this purpose. -- Calvin Henry-Cotnam "I really think Canada should get over to Iraq as quickly as possible" - Paul Martin - April 30, 2003 ------------------------------------------------------------------------- NOTE: if replying by email, remove "remove." and ".invalid" -- Posted via a free Usenet account from http://www.teranews.com |
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