Need Info about "pump handle" on High Power Circuit Boxes 1

[nojopse]

Hi, everyone, and thanks in advance for your answer. I had someone ask me something recently, and I didn't have the exact answer for him, and it's driving me crazy, because a whole day of google and internet searching didn't help. The question is: On an Emergency Powercircuit box or standard High Power circuit box/breaker panel, is anyone familiar with a "handle" that you have to "pump up" 3 times, in order to build up a charge, BEFORE you throw the Main Switch? I'm trying to find out exactly WHAT this "pump" does, WHY it is there, what FUNCTION it serves. My guess was that it charges a capacitor, but I couldn't understand- why you would need to build up a charge, when you have 220 VAC, or 440, whatever, coming in, ready to flow?

 

[weh3]

Many breakers do not rely on electrical means for opening/closure, and are not connected to power if they are open or racked out. You are typically charging a spring or some other type of stored energy mechanism so that switch closure can be accomplished rapidly to avoid an arc. It also allows the electrician to stand aside while performing the operation.

William

 

[dpc]

As weh3 states, the handle probably charges a spring. On a low voltage breaker, once sufficient spring force is developed, the breaker will close. The closing mechanism charges the tripping spring as it closes.

 

[itsmoked]

I believe that occasionally once pumped up the electrician can hook a string to the trigger and leave the vault entirely to turn on the breaker.

 

[jraef]

It is a ratchet mechanism compressing a spring. Spring closing mechanisms are used on almost all circuit breakers because you don't want the contacts closing too slowly and drawing an arc. On low power breakers, that spring mechanism is small enough to be operated by the little plastic handle on the front of the breaker. As the power rating gets larger, that becomes impossible. I have trouble closing the handle on a 1200A low voltage breaker, and I am rather big and strong. Many times when I am in the field, I am with other people who are not strong enough to move that handle, and I am always elected to do it. The charging mechanism is then used to enable a single low-powered human to exchange mutliple easier strokes for one big stroke.

Watch the original Jurassic Park movie. Towards the end, Laura Dern's character is required to get to some maintenance building and reset the main circuit breaker for the entire island. She pumps the handle 3 times and pushes the "Close" button, bringing the power grid back on line. If it was feeding the whole island, that was probably a very high capacity breaker so it is unlikely that she could have closed it without that spring charge mechanism.

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