MCB RATING

Please turn off Caps Lock; there is no need to SHOUT.

The current in the neutral will never be greater than the largest of the currents in any of the three phases, as it is the vector sum of them.

Installing a circuit overcurrent protection device in the neutral conductor is a practice that falls outside British Standard 7671 and can lead to potentially lethal results.

If you want to have a "break" in the Neutral Pole too, then you must go for either a TPN or a four-pole MCB. In a TPN or four-pole MCB, the continuous current carrying capacity or the rating of the neutral is the same as that of the phase.

However, in a triplen harmonic rich environment you may have to double-size the neutral for which you may need five pole MCBs. But, I doubt, any such product is available in the market today.

Triplen harmonics cancel each other out in 3 phase, as do even orders. It's the non- triplen odd order harmonics you need to worry about. But I have no advice on sizing a CB for that, we are not alowed to switch the neutral here in the USA.

I am surprised at such a grossly "incorrect" comment. The definition for triplen harmonics is "odd multiples of three". And, it is a globally well-known fact that triplen harmonics have zero phase sequence, and thus add up in the neutral as neutral current. This being so, your statement that triplen harmonics "cancel out" each other in the three phases is WRONG, WRONG and WRONG. Also, please note that even the even order harmonics don't 'cancel' out each other, but only their effects are nullified due to what is called "half wave symmetry" effect. And, the non-triplen odd order harmonics, like 5th, 7th, 11th, 13th, etc. have no business with neutral whatsoever. I fear that you yourself first need a thorough learning about harmonics, before posting such incorrect answers here in this forum.

While I agree that in US, neutral switching is not allowed, as the network is TN-C, here in India, we generally follow a TN-S system and hence, neutral switching is very much permitted.

I am deeply worried about such wrong and dangerous advices being posted here in this elite forum.