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Using a breaker as a 2 or 3 conductor switch?

rons

Diamond
Joined
Mar 5, 2009
Location
California, USA
20 or 30 amp circuit with breaker up stream.

Would using a 40 amp breaker as a switch in a enclosure be ok? To function as a safety disconnect for the particular enclosure.
 
To answer your immediate question, yes, you can use a breaker as a switch. Any switch or breaker is only to used in an enclosure.

I am not sure what your mean by your second statement. Are you thinking of bringing a circuit into an enclosure and using a breaker to disconnect the circuitry in the enclosure? If yes, its done all the time.

Tom
 
If the concern is about operating the circuit breaker frequently, that is not a concern unless you're talking about hundreds of thousands of cycles. The opposite is actually more of an issue - circuit breakers that are not mechanically operated periodically are more likely to operate slowly or fail to operate when they should trip.

Are you going to switch a load directly with the circuit breaker, or will it be operated so it is not making or breaking any load? Some loads have high current inrush (like lighting ballasts) so breakers that will be used as switches to energize those loads must be designed accordingly.

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I have already used this handle in another box. The surplus price at one place was $15. After I decided to use it I found another one for $5 at a second store.
They are designed to operate Fuji breakers. So I made a fixture to mate the breaker to the handle.

https://www.globalmachineparts.com/...ories&appname=Store&PartNumber=BZ-V40C-EUL|01

I might be using a Allen Bradley breaker with the Fuji handle to switching on/off a VFD in a enclosure. Wow, the price on my box is $15. New electrical
prices are a rip-off. (Link shows a 50A not a 40A breaker).

140U-G2C3-C50 by ALLEN BRADLEY - Buy or Repair at Radwell

- Radwell.com
 
Switch how?

Breakers usually are not "control" devices.

They are not designed for making and breaking contact under load.

Some are but most are not.

The contacts will wear out and the load point will change.

Last we seen this was one of our agency patrol boats where they used the main breaker as disconnect instead of battery switch.

The 60 amp breaker would trip at about 20 or so.

When they lit up the bad guys the motor would stall...

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A interlock safety switch could switch out a VFD when driving a motor. But the point of the interlock is that you want to remove power before opening a door.
 
Breakers UL listed for "Switching Duty" are designed for that use
About 10 years ago (maybe more), UL changed to require "switching duty" on all UL489 listed breakers, whether they say it on the label or not. Many manufacturers still show the "SWD" on the label out of force of habit and customer expectations, but it actually is no longer necessary, it's inherent if the breaker is UL listed under UL489.

Of note that however, many of the IEC "MCB" style breakers are NOT listed under UL489, they are listed under UL1077, which is not legal as a Branch Over Current Protective Device in the US, so be careful..
 








 
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