INSTANTANEOUS ONLY MINIATURE CIRCUIT BREAKERS 1

AS ALWAYS ... More details = better answers. How miniature is miniature? What current and voltage ratings? What standards are the breakers expected to conform to? What part of the world are these to be installed in?

Conventionally, "miniature circuit breakers" are the type used in residential distribution panels (120/240V AC) and thus, they are everywhere - and that begs the question, what are you looking for, that you can't obtain in bulk and pretty cheaply from your local electrical-hardware retailer?

Uh Brian.
I have only started working on residential panels in about 1956 and I am still learning.
This is the first time I have heard residential breakers called miniature breakers.
The name miniature breaker brings to mind a much smaller device.

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Ohm's law
Not just a good idea;
It's the LAW!

Everyone around here just calls them "circuit breakers", too.


Hence, questioning what the original poster means by "miniature", and in what way that is expected to differ from stuff that's a dime a dozen at the hardware store.

Thank you for the comments and questions. When I refer to miniature, I jump on the colloquial bandwagon these devices are often referred - these are the DIN Rail mount circuit breakers still falling under UL489. My application is for a critical motor control circuit where the motor itself is also subject to Instantaneous only protection. An MPC device will do - but I looking for a din rail mount (miniature) version.

Here is a web string to Automation Direct showing their line of Miniature Circuit Breakers (MCBs)



Thanks

When you created the link the forum software doesn't recognize a ")" as part of the link because that's not a normal URL character. Anyone using the link needs to add the missing ")" at the end (not the quotes, just the close parenthesis.)

"...#1. When I refer to miniature, ... these are the DIN Rail mount circuit breakers still falling under UL489. #2. My application is for a critical motor control circuit where the motor itself is also subject to Instantaneous only protection. An MPC device will do - but I looking for a din rail mount (miniature) version".
I have the following opinion for your consideration
In general, the term miniature circuit breaker (MCB) is used in the IEC world, but NOT in US.
1. Almost ALL European (IEC) MCBs are designed for DIN rail mount. This is NOT the case in the US.
2. Almost ALL IEC MCBs are with thermal and magnetic trip to Class B,C, D....
2.1 There are also DIN rail mount MPC with thermal (close to motor thermal overload tripping characteristics) and with addition having short-circuit instant trip; in one body.
3. Suggestion: look into any IEC MCB manufacture's catalogue. These are very low cost and very useful items that are easily available in any hardware stores all over the IEC world; including Singapore.
3.1 Attention. IEC MCB are designed with rated current and with Class B,C,D... magnetic trip. The current rating and tripping class is (factory set) NOT adjustable.
Che Kuan Yau (Singapore)

I guess time is passing me by.
I come from an era when Molded Case Circuit breakers were called MCBs.
Trying hard to adjust.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

Nice info, che.

Muthu

BlackJackJacques said:

My application is for a critical motor control circuit where the motor itself is also subject to Instantaneous only protection.

Click to expand...

You are misinterpreting the need and use of instantaneous-only breakers. The ONLY valid use for them (in North America) is as a COMPONENT of a factory assembled, tested and listed combination starter. Period. End of story. You CANNOT use an instantaneous-only breaker for ANY other purpose. They are not UL listed, ever, they are only UL Recognized Components (backward UR symbol), because they must be used WITH something else, in this case a UL listed thermal overload relay. So you can’t possibly have a situation where a “motor itself is also subject to Instantaneous only protection” here in NA, there is no such rule or requirement. So because there is no such valid use scenario for an MCB with instantaneous-only trips, nobody makes one.

If you have a motor with built-in thermal trips, as I suspect, that’s fine, but you cannot apply an instantaneous-only breaker with that because it is never allowed to be used as a stand-alone device. Just use a regular thermal-mag UL 489 listed breaker. It CAN be an MCB style if you like, but keep in mind those are often listed with very low interrupt ratings and NO series combination ratings to help out, so often as low as 10kA, but I have never seen and MCB rated for MORE that 18kAIC.



" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

As a general information, the terminology used in the IEC world and throughout Europe:
1. moulded case circuit breaker is MCCB. Generally I_u up to 3.2kA and I_cu up to 120kA.
1.1. Reference IEC standard : IEC 60947-..
2. miniature circuit breaker is MCB. Generally up to 63A and up to 10kA.
2.1 Reference IEC standard : IEC 60898
Che Kuan Yau (Singapore)