220 house pump on two (2) SEPARATE breakers??
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220 house pump on two (2) SEPARATE breakers??
Wayne Whitney wrote:
On 2008-08-25, wrote: Sorry if this is a dumb question: if they are physically tied together with a tie bar, and (somehow) a single breaker trips, will the trip throw the switch hard enough to force the other breaker to switch off together with it?? No, not always. There's a difference between a double pole breaker, where the two sides are internally connected, and two single pole breakers with a handle tie. In both cases, if you manually turn off the breaker (you are using it as a disconnect), you will turn off both sides. But as far as automatic operation (its job as an overcurrent protection device), only the double pole breaker will reliably shut off both sides. What breakers, other than a main, are 'tied' internally? I've never seen one. For the OP, you need at a minimum to have the proper handle tie (no nails!), and you may need to have a double pole breaker. I believe that if the pump uses the neutral, you need a double pole breaker; if it is a pure 240V load without using the neutral, then a handle tie is sufficient. I've quoted the appropriate parts of the NEC below (2002 version). I'd just put in a double pole breaker, anyway, as it seems safer. Whats the electrical difference between a double pole breaker and 2 breakers with the handles tied together? We are not talking about a double pole switch where the hots and neutral are all switched are we? Kevin Cheers, Wayne 240.20(B) "Circuit Breaker as Overcurrent Device." Circuit breakers shall open all ungrounded conductors of the circuit unless otherwise permitted in 240.20(B)(1), (B)(2), and (B)(3). 240.20(B)(2) "Grounded Single-Phase and 3-wire dc Circuits." In grounded systems, individual single pole circuit breakers with approved handle ties shall be permitted as the protection for each ungrounded conductor for line-to-line connected loads for single-phase circuits or 3-wire, direct current circuits. |
220 house pump on two (2) SEPARATE breakers??
On 2008-08-26, Kevin Ricks wrote:
Whats the electrical difference between a double pole breaker and 2 breakers with the handles tied together? The difference is that in a 2 pole breaker, the trip mechanisms are tied together internally and will both trip if the unit sense an overcurrent. For two single breakers with a handle tie, this is not reliably true. Wayne |
220 house pump on two (2) SEPARATE breakers??
In article ,
Wayne Whitney wrote: On 2008-08-26, Kevin Ricks wrote: Whats the electrical difference between a double pole breaker and 2 breakers with the handles tied together? The difference is that in a 2 pole breaker, the trip mechanisms are tied together internally and will both trip if the unit sense an overcurrent. For two single breakers with a handle tie, this is not reliably true. Wayne Curious minds want to know why tying the trip mechanisms together internally is intrinsically safer or more reliable than tying them together externally. |
220 house pump on two (2) SEPARATE breakers??
On 2008-08-26, Smitty Two wrote:
Curious minds want to know why tying the trip mechanisms together internally is intrinsically safer or more reliable than tying them together externally. Have you used a handle tie? There's some give. Wayne |
220 house pump on two (2) SEPARATE breakers??
In article ,
Wayne Whitney wrote: On 2008-08-26, Smitty Two wrote: Curious minds want to know why tying the trip mechanisms together internally is intrinsically safer or more reliable than tying them together externally. Have you used a handle tie? There's some give. Wayne I've not used them. Odd that they would make them poorly. Good to note that it's the execution and not the theory that's at fault, then. |
220 house pump on two (2) SEPARATE breakers??
On 2008-08-26, Smitty Two wrote:
Have you used a handle tie? There's some give. Wayne I've not used them. Odd that they would make them poorly. Good to note that it's the execution and not the theory that's at fault, then. It's not that handle ties are made poorly, it is that circuit breakers have two (or more) functions: they can serve as a manual disconnect and they can serve as an overcurrent protection device. Handle ties only have to do with the function as a manual disconnect. If you think about it, a circuit breaker has three states: on, off, and tripped. Often to reset a circuit breaker you need to go from tripped to off to on. As a result, the handle isn't rigidly connected to the internal trip mechanism. So the handle tie can't rigidly connect the trip mechanisms. Cheers, Wayne |
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