Hi,

I have a customer who is having problems starting a 3ph fan. The fan is rated at 5.5kw, 10a run current. They're running from a 16a socket. The fan is DOL started. It is tripping a D16 breaker on their board. With a D32 breaker the motor will run, but is underperforming. The fan runs fine at another location, so something is not quite right locally. The supply voltage is 415 between each pair.

My uninformed thinking is that, while their 16a socket is fine for the motor run current, the start current which is up in the 80a range is potentially too high for their wiring so the motor is never getting enough power to get up to speed. I suspect that uprating their socket to a 32a with a 4mm run will solve the problem. But I would like to have a sensible (standards based) reason for suggesting this - rather than just suggesting changing it and hoping.

I'm hoping for some expert input to steer the customers electrician in the right direction.  I'm just providing some informal input to help them track down the issue (and am not a sparks) but no one seems to be able to solve the problem at the moment so thought I'd put it out here. Any advice appreciated.

TIA!