Is there such a thing as a weak breaker

paulengr

Senior Member
Why can't OCPD's make advancements using solid-state controls? Automotive brakes did, EFI fuel systems did, light bulbs did, but not OCPD's ? You could actually make one breaker that spans many many setpoints, like a single 15/20/25/30 120v where you select/set the trip setting before installation (dial wheel on side, front window showing setting, etc), hence one ocpd that can "do it all".
They exist now. However two problems exist. The cost of an electronic trip unit is almost constant where thermal magnetic trip units scale with the current. Right now the cheapest ones break even at about 400-600 A so at that size or bigger electronic is cheaper. The second is that the breaker mechanism grows massively in size and cost with current. So usually within a frame size it only makes sense to have a 2:1 ratio between the largest and smallest size.

On a related note at the larger sizes “rating plugs” are common even with thermal magnetic units. So I can buy a 1600 A frame and make it anything from say 800 A to 1600 A by changing the rating plug. The plug is actually just a set of precision resistors.
 

FionaZuppa

Senior Member
Location
AZ
They exist now. However two problems exist. The cost of an electronic trip unit is almost constant where thermal magnetic trip units scale with the current. Right now the cheapest ones break even at about 400-600 A so at that size or bigger electronic is cheaper. The second is that the breaker mechanism grows massively in size and cost with current. So usually within a frame size it only makes sense to have a 2:1 ratio between the largest and smallest size.

On a related note at the larger sizes “rating plugs” are common even with thermal magnetic units. So I can buy a 1600 A frame and make it anything from say 800 A to 1600 A by changing the rating plug. The plug is actually just a set of precision resistors.
In a few months it will be year 2021. ;)
 
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