60A Circuit Breaker/MCB

[weeliang82]

Is a 60A MCB enough given the spec of the equipment below:

Type: VRF
Capacity/HP: 32 HP
Running Current: 49.5A (3 phase)
Built in Starter: Yes

Your help on the above matter is greatly appreciated. Thank you.

[goshen]

Hi your running current as stated is 49.5 amp!a 60 amp mcb should be able to handle this load ,but u should check starting charecaristics of mcb so it could handle starting current.

[Brian_UK]

The rating of the MCB is to protect the electric cable.

[weeliang82]

If our equipment is a soft starter type (amp started gradually until it reaches full load), should be no problem right?

[stefs_cruiser]

You appear to be working back to front, as Frank indicated, the CB is just there to protect the cable.

You should decide on the cable, to maintain voltage drop and current rating within specifications, and then decide on the Circuit Breaker.

[frank]

You appear to be working back to front, as Frank indicated, the CB is just there to protect the cable.

I think you meant BRIAN

[freezetech]

a mcb is a overload protection device it is there to protect all items that are connect to it ie cable and machine if the running current is 49.5 amps with soft start then you should have no problem but if your start up current exceeds your mcb rating then this would cause the mcb to trip same goes for protecting your machine if for instance your compressor stuck this would increase ampage therefore trip before any other damage is caused this is why you should always select the right mcb for the equipment being installed

[frank]

The motor should be protected by an overload, set 10-20% above FLC.

The MCB is there to protect the cable.

The MCB should be rated as close to but higher than the load current, and the cable should be rated higher than the MCB.

Example:

Motor FLC 21A
Overload set at 24A
MCB (type 3) 32A
Cable rated 34A
When selecting a cable size, be sure to apply the de-rating factors to the equation

[sachin230]

The Fault current overloads and short circuits can be detected by circuit breakers like MCB’s MCCB’s & HRC Fuses etc. But, Circuit breakers don’t detect leakage currents, which are dangerous for humans and livestock and if not detected, can lead to fire hazards. We need a solution that detects such leakages currents and disconnects the circuits from the power Supply & The solution in the form of RCCB (Residual Current Circuit Breaker) also
Known as ELCB (Earth Leakage Circuit Breaker) which provides protection against Fault current overloads and short circuits & direct and indirect contact of personnel or livestock and against probable fires.
So you need to choose the proper rating of RCCB / RCBO by considering starting current, Required “No of pole”, Rated full load current & tripping time
For current rating selection, check the equipment rated full load current (Not the running current)