are mccb trip units required

[blaggy]

Hi

i want to use a 250A nsx mccb for distribution. Am i right in thinking the trip units are only needed for adjustable requirements?

thanks

[RHH · Accepted solution]

Hello @blaggy ,

You are correct to say that with a micrologic you have way more input on the trip of the circuitbreaker.

The thing is there is also a difference in kind of protection.

With Micrologic you have electrical protection while when you use a TM-D for instance its only Thermal-Magnetic protection.
It totally depends on what you want to use it for. 

I found this little extra info online for you to get it a bit more understandable;
note: short circuit protection needs quick trip than
overload trip thats why thermal trip is used for Overload
Protection And Magnetic Property is used for shortcircuit
Protection.

In Microprocessor release, sensing and triping executed by
Micrprocessor in gives the very faster response than TMD
Release. Normally Microprocessor based release gives LSI
Protection

Hope this gives you a bit more insight.

[J_Travostino · Accepted solution]

Hello @blaggy ,

Considering Trip Units can be electronic (Micrologic) or Thermal Magnetic (TMD), they are anyway always necessary into circuit breakers.

Basically, they ensure protection again short circuits and overheating. 

If you don't have a trip unit, your circuit breaker main function (protecting humans and goods) is not achieved. 

[HelvinHermanT · Accepted solution]

Hi, 

If you use MCCB without Trip unit, then it will have fuction as Switch only to manualy ON & OFF. It will not trip unless you manually turn it ON or OFF.

Some application use MCCB as Manual Switch for Isolation purpose only (Not Protection purpose), so no need Trip unit.

But as other expert mentioned, if you need MCCB to work as protection such as Overload Protection and Short Circuit Protection, then you must use trip unit too.

[J_Travostino]

Hello @HelvinHermanT ,

Totally agree with you. 

To complement it: even if you need a Switch disconnector, you must have a "Trip unit-style" block as shown below (red circled).

It has not protection function but is mandatory to be assemblied.

 @blaggy ,

For more information about Switch-disconnectors MCCBs: ComPacT NSX NA, check out this link 👈