Molded Case Circuit Breakers

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JayOlivo

Member
Can someone please explain the difference between a molded case circuit breaker and a normal cirucit breaker. Why would I use a molded case circuit breaker over another in a control panel? There is some controversy at my job over this issue and I can't find any information that will support the benefits or the justification of using one.

Thanks in advance.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
The "everyday" circuit breakers you see in a residential panel are one variety of molded case circuit breakers. The 2000 amp breaker at a mall might indeed be another variety.
You just need to select the model that provides you with the correct amperage, voltage, AIC rating, trip curve and other characteristics suitable for your application.
 

GeorgeB

ElectroHydraulics engineer (retired)
Location
Greenville SC
Occupation
Retired
Can someone please explain the difference between a molded case circuit breaker and a normal circuit breaker. Why would I use a molded case circuit breaker over another in a control panel? There is some controversy at my job over this issue and I can't find any information that will support the benefits or the justification of using one.

Thanks in advance.
One's definition of normal matters. I always considered molded case the small end ... even at 2000 amp, 600V. I distinguished them from OCBs, ACBs, and SF6 breakers (O=oil, A=air) where relaying caused the trip instead of built-in "stuff". I've not thought about the 4160 and 7200 stuff and have never had any experience with it.
 

wireguru

Senior Member
look at what the manufacturers call them. they usually refer to breakers such as din rail, QO/QOB, and other small branch breakers as 'miniature circuit breakers'
Larger breakers in ratings from 15 amps to 3000 amps such as the various sqd power pact breakers, FA / LA series etc as 'molded case circuit breakers' and the
large draw out types as 'circuit breakers'
 

zog

Senior Member
Location
Charlotte, NC
No idea what a "normal" circuit breakr is.

MCCB - Molded case - from the tiny ones in your house to 4000A ones in switch boards - all LV

ICCB - Insulated case - mostly 480V, 400-4000, all LV. Masterpact, SACE, Spectra are examples

ACB - Air breakers, LV-MV class - open air frame most common type in power distribution

VCB - Vacuum CB, LV and MV (Mostly used in MV), contacts contained in a vacuum bottle

OCB - Oil breaker (LV-HV) - older technology, being replaced by GCB's - cpntacts immersed in an insulating oil

GCB - Gas breaker - MV-EHV - contacts in a tank filled with a gas, usually SF6
 

broadgage

Senior Member
Location
London, England
Here in the UK a moulded case circuit breaker is generally understood to mean a larger and more sophisticated unit than those used for small branch circuit protection.

MCB= miniture circuit breaker, a small relatively cheap unit primarily intended for protection of subcircuits (branch circuits) or for building into equipment.
Not adjustable, has fixed and often rather crude settings.
Cant be maintained, a disposable product.

MCCB=moulded case circuit breaker, larger than the above in both dimensions and electrical ratings. Primarily intended for the protection of submains (feeders) large loads, utility scale transformers and the like.
Has adjustable trip settings, often for both thermal and magnetic trip.
Often equiped with auxillary contacts for remote indication, warning of tripping etc.
Case is moulded together, not intended to be dismantled, requires complete replacement if defective.
Self contained, no external battery required.

ACB/OCB/VCB etc. larger types of circuit breaker intended primarily for substation and utility scale applications.
Often with sophisticated adjustable features.
May be equiped with remote tripping and setting, therefore useful for remote control, not just fault protection.
Not normally self contained, usually requires an external battery for tripping.
Requires specialist maintenance.
 
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