MCCB in parallel, from vendor neutral perspective

Thread Starter

meowsoft

Joined Feb 27, 2021
494
Do you think it is good idea for 4 pole MCCB to be used in parallel condutor, wich conductor amperage is 2x each pole of MCCB and use two pole in parallel for each conductor ?, do you think is there a problem ?, example : use 4p 50a MCCB, for single phase 100a load, with 4 core wire (each core ampacity by local code is 50a maximum), and then use two pole in parallel for MCCB ?

By local code, is allowed to use parallel conductor, but each wire needs to be same sectional area, and same type, also same raceway/conduit (if applicable), and each wire needs to be protected by circuit breaker sized for each wire maximum ampacity, example : use 2 wire with 50a capacity for 100a is allowed, but each wire needs to be protected by 50a circuit breaker
 

Ramussons

Joined May 3, 2013
1,098
I believe that paralleling contacts for higher current capacity is fundamentally incorrect.
All the contacts will not "make" or "break" simultaneously and this will result the last "break" to burn off first. and the others to follow.
 

MisterBill2

Joined Jan 23, 2018
9,776
I believe that paralleling contacts for higher current capacity is fundamentally incorrect.
All the contacts will not "make" or "break" simultaneously and this will result the last "break" to burn off first. and the others to follow.
Certainly this is true, AND, In Addition, probably most electrical codes will not allow circuit breakers or fuses in parallel. Aside from unpredictable operation it could leave a circuit live when one circuit breaker was on, and the others were off.
You might be able to get away with using ganged breakers intended to trip at the same time. But that still might not satisfy the electrical code requirements.
 

Thread Starter

meowsoft

Joined Feb 27, 2021
494
O
Certainly this is true, AND, In Addition, probably most electrical codes will not allow circuit breakers or fuses in parallel. Aside from unpredictable operation it could leave a circuit live when one circuit breaker was on, and the others were off.
You might be able to get away with using ganged breakers intended to trip at the same time. But that still might not satisfy the electrical code requirements.
It is allowed by local electric code to run wire in parallel, NOT run breaker in parallel

Parallel conductor is allowed in any size more than 16mm2 for copper and 25mm2 for aluminium, and only with same conductor type and size

Example :
Is allowed by local code to run two 50a wire in parallel, and each wire is protected with 50a circuit breaker
Is prohibited by local code to run two 25a MCB with 50a wire in incoming nor outgoing wire
 

MisterBill2

Joined Jan 23, 2018
9,776
O

It is allowed by local electric code to run wire in parallel, NOT run breaker in parallel

Parallel conductor is allowed in any size more than 16mm2 for copper and 25mm2 for aluminium, and only with same conductor type and size

Example :
Is allowed by local code to run two 50a wire in parallel, and each wire is protected with 50a circuit breaker
Is prohibited by local code to run two 25a MCB with 50a wire in incoming nor outgoing wire
OK, it is clear that I did not understand post #1 correctly. Parallel conductors are certainly OK for the application.
It might be a problem getting all of the conductors into the terminal at the circuit breaker, or that part may not be a problem at all. And it is very reasonable to do that. It will be important to assure that all of the conductors are connected correctly at the load end of the wires.
 
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