Hi feets, I did read your earlier observations and this contributed to my choice of fan. I was not thinking of the amount of air being moved, more about longevity of the fan motor.
I had actually thought about just leaving as is in fact, it may be possible that the 850 watt motor may spin the same speed, and the wattage increase made to cope with the extra amount of air the larger fan will be moving, so only extra life expectancy.
It also crossed my mind that if the 850 watt unit did spin faster, the pitch of the 600 watt fan blades may not be suited to the extra speed, much in the same way that a boat propeller can be optimised for 'X'revolutions.
Given the abundance of these fans, and assuming it works ok I may fit and leave as is.
