Moeller NZM12-1000 (ZM12) MCCB 1

[ahhie]

Hi,

I have NZM12-1000 MCCB at site which I do not know much about. How to know the setting for overload time Tr is ON or OFF? This is a thermomagnetics type.

Thank you.

 

[ScottyUK]

I'm not familiar with this specific breaker type, but normally the ON or OFF option associated with the time setting allows the user to enable or disable an inverse time curve charateristic. This normally helps with discrimination and grading with other protective devices on the circuit.




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

 

[jraef]

You are not providing the complete part number, so it is difficult to explain all the issues, but here goes. The NZM 12 Series came in 3 versions (in N. America anyway): a Fixed Thermal Magetic breaker, and Adjustable Thermal Magnetic breaker, and a Magnetic Only Motor Circuit Protector. None of them had the ability to turn the i2t protection on or off, but it could be ordered with or without it.

If the full part number on the breaker has the letters "obi" near the end, that indicates that it is a Magnetic Trip Only breaker, there is NO thermal trip element. Its a Motor Circuit Protector intended to be used in a motor starter application where a thermal overlod is also present. You cannot use that as a general purpose circuit breaker.

If there is no "obi" in the part number, AND it ended in -CNA, it is a Thermal-Mag with an adjustable thermal trip, and the range of adjustment is shown elsewhere in the part number. There will also be a small round dial on the front below the handle shaft that shows a number range and scale. That is the adjustment for the thermal trip element.

If the number ended in -NA, it is a Thermal-Mag but the thermal trip setting is fixed, and the value is shown elsewhere in the part number. The small round dial for adjusting the trip element is still there, but it will be sealed or covered over by clear plastic or a paper sticker showing the setting, i.e. "1000A".

Hope that helps.

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