What Exactly Is A Low Voltage Power Circuit Breaker

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I can not seem to find any good articles. Google reverts to any circuit breaker that a homeowner would use to for "power" in their house. Whitepapers mostly are there to expound on that an insulated case breaker is technically a molded case breaker in the eyes of standards bodies. An insulated case breaker has a energy storage mechanism and may even have electric spring recharge. A low voltage power breaker has the same but may be available at higher amperage's than insulated case breakers. It may be available with higher short circuit withstand ratings. But what is really the difference? And why is "power" used in low voltage power breakers?
 
A low voltage power circuit breaker is mounted in switchgear and some switchboards. The smallest frame size is typically 1200A, although older designs included some 800A frame devices.

Decades ago these breakers were made with steel frames and were designed to be repaired and refurbished. About 40 years ago the insulated case designs started to appear and now are the only style available from most major manufacturers.

Molded case miniature circuit breakers, like those found in panelboards and switchboards, are not intended to be repaired or refurbished.
 
jim dungar said:
A low voltage power circuit breaker is mounted in switchgear and some switchboards. The smallest frame size is typically 1200A, although older designs included some 800A frame devices.

Decades ago these breakers were made with steel frames and were designed to be repaired and refurbished. About 40 years ago the insulated case designs started to appear and now are the only style available from most major manufacturers.

Molded case miniature circuit breakers, like those found in panelboards and switchboards, are not intended to be repaired or refurbished.
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Yes but how do I tell when I see one (other than maybe a label) whether it is an insulated case or power circuit breaker? They both have charging handles and can have motorized spring charging and can be racked/drawn out. I’ve seen power circuit breakers with plastic frames. They don’t look much different than insulated case. So they look similar.

Or if I were in the business of specifying things, when would I know that for sure you can’t use an insulated case breaker for this and you have to use a power circuit breaker; or when would I know that an insulated case breaker would be better than a power circuit breaker?
 
An insulated case breaker is a power circuit breaker.

These are not the miniature molded case circuit breakers covered by UL 489.
 
jim dungar said:
An insulated case breaker is a power circuit breaker.

These are not the miniature molded case circuit breakers covered by UL 489.
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I’m sorry but I don’t think this is correct. Insulated case circuit breakers are listed to UL489. Maybe I don’t have to feel so bad for not really knowing the difference very well.

Downloads for Data Bulletin | Schneider Electric USA

Downloads for Data Bulletin - Download
www.ascopower.com

 
I-learns said:
I’m sorry but I don’t think this is correct. Insulated case circuit breakers are listed to UL489. Maybe I don’t have to feel so bad for not really knowing the difference very well.

Downloads for Data Bulletin | Schneider Electric USA

Downloads for Data Bulletin - Download
www.ascopower.com

Click to expand...

Correct. Insulated case breakers start at 1000 A frames and ALWAYS have a charging mechanism. They are part of UL 489. They can be draw out but that’s not mandatory.. But one important relevant detail is that insulated case breakers like all UL 489 breakers contain no user serviceable parts. They aren’t as sealed as mold case breakers but they aren’t intended to be serviced except the minimal requirements in NEMA AB4.

UL 1077 defines power circuit breakers. They often do require a charging system but it’s not mandatory. In fact vacuum breakers don’t need it at all, especially magnetic actuator types. Old ITE breakers went down to 600 A frames and were more ir less just a heavier cast frame version of a molded case breaker. And they can be bolt in designs too.

But what sets UL 1077 apart is that the equipment is designed to be serviced routinely. The service schedule is very limited but even GIS gear thst is sealed for life has some maintenance. Second everything is designed for 30 cycle short circuit withstand instead of UL 489 3 cycles. This gives you time to coordinate feeders and not be stuck with series combination rules.
 
For many manufacturers there is little to no difference between their 'power breakers' tested to UL489, and those tested to UL1066.
Schneider Electric type NW uses the same maintenance procedures and parts
Siemens type WL literature says 'Common guide frames for the draw-out version make the breakers completely interchangeable between the UL 489 and ANSI / UL 1066 rated circuit breakers'
Eaton even uses the phrase insulated case when describing their Magnum line "Magnum SB are insulated-case power circuit breakers designed for the performance and economic requirements of UL 891".

As a designer the question should be do you want Switchboard standards (UL891 gear and UL489 breakers) or Switchgear (UL1066)?
 
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