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IEC 10A Breaker

IEC 10A Breaker

IEC 10A Breaker

(OP)
I know the minimum power breaker size in NEC is 15A. Is the minimum power breaker size in IEC equal to 10A?

RE: IEC 10A Breaker

What do you mean by 'power breaker'? Miniature circuit breakers are available down to 2A, maybe down to 1A although I haven't seen one.

The only time I've seen the term 'power circuit breaker' was in relation to what I know as an ACB, and they usually start at about 630A and go upward to about 6300A. Obviously a different animal!
  

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If we learn from our mistakes I'm getting a great education!
 

RE: IEC 10A Breaker

(OP)
By power circuit breaker I meant circuit breaker feeding to motors, lighting, heaters etc...The tradition in USA is that 15A breaker is used for all loads upto 15A. It means that 15A breaker is used for all loads like 1A, 5A, 10A, and 14A. (However 20A bvreaker is used for a load of 16A.) Is there some similar convention in IEC world?

RE: IEC 10A Breaker

From 2A up to about 50A or maybe 63A we tend to use minature circuit breakers (MCBs) for the heating and lighting type loads normally fed from a distribution board. Bigger circuits are usually protected by a moulded case circuit breaker (MCCB), and motors over about 20HP generally have a motor circuit protector (MCP), which is basically a MCCB with only a mag trip, as part of a combination starter.

Generally IEC breakers are sized for the loads: the standard series is, from memory: 2, 4, 6, 10, 16, 20, 25, 32, 40, 50, 63. For each rating there are sub-types B, C, and D which define the MCB's response to inrush current. B is least tolerant, while D is most tolerant of high inrush. They come in single, dual, triple and four-pole varieties.
 
  

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If we learn from our mistakes I'm getting a great education!
 

RE: IEC 10A Breaker

timm333,
The term "circuit breaker" has slightly different meanings outside of North America compared to inside.

The reason why traditional "circuit breakers" (as I interpret you are using the term) don't typically go below 15A in NA is because if you look at the NEC/CEC, you are not allowed to run less than 14ga wire for branch circuits, so there was no reason to have breakers smaller than 15A. That said, many of the CB mfrs do offer 10A load center type breakers by the way. And if you expand the use of the term, there are plenty of "circuit breakers" with much lower trip values on things like appliances, electronics etc. Think of those little pop-up red buttons on small appliances with something like a "3.5" engraved in the top; those are 3.5A circuit breakers.

In IEC world, what they call a Miniature Circuit Breaker (MCB) can be used on any system and the smallest trip unit I have seen on those is 0.3A. But I have no clue as to what their minimum house circuit wiring size may be. They use them for slightly different purposes, i.e. they get much closer to the actual load size as far as thermal trip settings. They also have several different "trip curves" based on the type of load you may be protecting and the type of service connection you have feeding the house (they have several more than we do). So for example, you may have 2 separate 6A MCBs in a panel, one with a "B" trip curve for a general household lighting circuit and a "D" curve on an HVAC motor. Another panel may need "C" curve breakers because they use a different service connection style with respect to grounding and neutral connections.

Those same devices if used in NA however are typically NOT classified as "circuit breakers" because they don't meet the requirements of UL489, so we call them "UL1077 Supplementary Protectors" and they have to technically be backed up BY a UL489 circuit breaker or fuse. Recently there are now a number of IEC manufacturers who have released UL489 listed versions of the IEC format MCB devices, so now they can in fact be called "circuit breakers" here, and those are offered in trip ranges down to 0.3A


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RE: IEC 10A Breaker

jraef,

Minimum wiring size in the UK is typically 1.0mm     ² for a lighting circuit or auxiliary circuit, although 1.5mm     ² was once common for this application before the copper price went through the roof.
  

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If we learn from our mistakes I'm getting a great education!
 

RE: IEC 10A Breaker

Thanks Scotty. 14ga is a little bigger than that, about 2mm2.


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RE: IEC 10A Breaker

(OP)
Does it mean that if there is a load of 4A, then 5A breaker can be used in IEC (as compared to 15A breaker in NEC)?

RE: IEC 10A Breaker

Breaker sizes are to protect the cable, so provided the cable is good for 5A and the loop impedance is such that the circuit disconnects in the required time (0.4s for sockets, 5s for fixed equipment) then yes you could do that. Just FYI, 5A isn't a standard size, but 4A and 6A are.
  

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If we learn from our mistakes I'm getting a great education!
 

RE: IEC 10A Breaker

(OP)
Can MCB (miniature circuit breakers) be used in MCC, or are they only used in panelboards?

RE: IEC 10A Breaker

Yes, but they are limited to about 10kA breaking capacity so you either use them on low power MCCs or have a type-tested series combination with an MCCB upstream.
  

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If we learn from our mistakes I'm getting a great education!
 

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