3 Pole & 4Pole MCCB which one is suitable

[Abdul Basit Khan]

sir,

i am a user, and i need to define difference between 3 pole & 4 pole MCCB for 200kVA transformer & 275kVA generator in main distribution panel, if we use common neutral, what is the advantages and disadvantages.

 

Regards,

ABdul Basit Khan

[Spir Georges GHALI]

Abdul Basit Khan said:

sir,

i am a user, and i need to define difference between 3 pole & 4 pole MCCB for 200kVA transformer & 275kVA generator in main distribution panel, if we use common neutral, what is the advantages and disadvantages.

 

Regards,

ABdul Basit Khan

---

Dear ;

 

The using of ” 3 Poles ” or ” 4 Poles ” MCCB either for transformers or generators, that means if the ” Neutral ” should be directly connected ” 3 poles ” or switched on & off with phases ” 4 Poles ” will be decided after knowing the ” Earthing System ” used in the project. So, if you know the Earthing System you can decide which MCCB should be used for your application.

 

Regarding the ” Earthing Systems “, we use as follow :

     – TT,  TN-S,  IT (with distributed neutral) : the ” Neutral ” should be switched on & off with phases.

     – IT (without distributed neutral ) : we don't need it as we haven't a neutral

     – TN-C : as the Protection line & the Neutral are combined ” PEN “, this line should be directly and all ways connected.

 

Regards.

[Abdul Basit Khan]

I am still don't understand the advantages and dis advantages between them in a power ditribution on 350 computers in a software house???

[Spir Georges GHALI]

Dear ;

 

I said before that the using of a special pole for Neutral is depending on the used Earthing System in your software house, as in some Earthing system the Neutral should be Switched-On & Off with the phases poles, so, the advantages and disadvantages are for the Earthing system and not for the Neutral pole. For exp. if you used ” TN-C ” you can't never use the 4th pole whatever the advantages. 

 

In your case, it will be better to ask any Electrical Engineer in your place about the used Earthing system, then will decide if you should use the 4th pole in the circuit breaker.

[admin]

Dear,

 

Thanks for your clarification but, on ATS panel we recommend to use 4P breaker to switch off the neutrel coming from the generator because, may be reverse current will pass on to the generator.

[Chris2011]

Dear sir, do you also need surge protection device? maybe you can find it in http://www.fatech-surge-protection.com.

[elec master]

i think this will depend if the electrical sources in your network will be considered as separately drived systems or not , for separately drived system , we must use 4 pole circuit breaker to disconnect the neutral of the two sources ( transformer and generators or 2 generators ) to prevent earth fault in the main switchgear.

 

you can digg the NEC code for the expression ”  separately drived systems” and you will find the answer or got to the following site which explain the NEC code by following the link:

 

Understanding NFPA 70 (National electrical code) course

[Author]

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