Star/Delta, but not as I know it.

[ref717]

Nike, I think there is a "typo error" on the drawing within the motor's symbol. U2 should be W2, V2 should be U2 and W2 should be V2. In the Delta connection, as you can see L1 voltage is on the same motor winding leads(U1 & U2) w/c is abnormal in any 3 phase motor configuration,likewise with L2 and L3 line voltages.
For a constant supply line voltage, you can never alter the speed of a 3-phase motor unless we have a VFD control or dual voltage motor.

[nike123]

For a constant supply line voltage, you can never alter the speed of a 3-phase motor unless we have a VFD control or dual voltage motor.

That is different than what you said here:

You can never change the speed of any 3-phase motors unless you vary the line voltage frequency or the no. of poles of the motor.

Any asynchronous motor have slip. That slip varies with motor power and required power for synchronous speed. If we aply power regulation to motor(by varying voltage or by pulse with modulation) we vary actual speed of rotation of fan no matter if it is 3 phase or single phase.

[Tayters]

Thanks again chaps for your input.

I'll try and get hold of the control diagram also but there may be some delay on this.

Didn't mention before so as not to add unnessesary info but the first chiller I looked at would start with star contactor first then delta (thats what made me assume star/delta).
The second chiller would start on the delta for a few seconds, then star for about 20secs then back to delta. Now there could be a fault but after turning the unit on/off to put the electric panel back on (which had the isolator on the front of it, hence all the on/off) it would do the same thing. Note the HP alarm was on a this chiller but another circuit which wouldn't run due to the alarm.
Why the first one worked different, beats me.
It's a not a massive fan by any means, no bigger than DOL ones I've seen.
Mr Steinmetz is a new one on me which I'll look into.

That'll please the wife.

Cheers,

Andy