3 phase motor does not change direction when phases are reversed

[Marvo]

The best you could do is to check the run current in both directions and wire it which ever way the run current is the lowest. As long as that run current is < the FLA stated on the motor you should be fine.

 

[Deleted member 72666]

Caution here, if this fan was once part of a ducted system then it may have been designed/spec'd for that particular ducting arrangement, taking or altering ducting can have massive effects on the load demand of the motor. EG ... opening or removing the inlet duct from a designed system can ramp the motor current up beyond FLC of the motor, it may sound counter-intuative but is down to controlled vortices complementing air flow and reducing motor demand.

I've experienced something similar on a Parks Cramer 'travelling cleaner' you maybe familiar with these as they were used in the textile industry, basically they were fan motors mounted on a track (powered via overhead busbars, 3phase, 110 volts) with 'dangling' 'blow' legs with nozzels placed strategically to blow 'fly' (cotton/woollen dust) from vital m/c components and yarn. Anyway someone decided they wanted the floor cleaning at the same time to avoid sweeping up and they removed the stop ends in the legs...........It worked all right but the fan motors kept getting hot and started to trip, the fan motors drew excessive current due to there being no restriction on the outlet.

 

[Marvo]

Same with centrifugal fluid movement as well. Many pumps have a minimum required head pressure, with lower pressures they overload the motor.

 

[vitoboy]

Thanks for the input stantheman.

we have now moved the fan unit to a suitable orientation...we will run it up today and check the load and start current to see if it likes where it is.
its running now in a very short duct run..about 4m in total...im sure theres not much in the way of air resistance to hold it back...
if it runs at greater than flc then i guess it will have to go back to ebay..!.....cheap deals often end up this way.

thanks again

vito