Help on UPS fan modding

[bitwelder]

I recently got a new UPS for home, Eaton 5SC750i.
The problem that I have is that relatively noisy, due to the fan that *never* stops.
The fan is a 60mm, high speed (4500 rpm), ~36 dB type and as wrote, even when battery is fully charged it doesn't stop spinning, although it goes into 'low speed' mode, but for a relatively silent home it is still quite noisy.

So I wonder if it would be possible to mod the unit and put a slow-speed silent 100-120 mm fan.
The issue that I see is that the UPS logic detects and alerts if the fan is malfunctional, so I would need to make some kind of converter from the 'low rate' signaling that the low speed fan offers to the 'high rate' that the UPS logic expects (the fan is a F-type).
Any suggestions how to do that?

[Seekonk]

Not familiar with that unit but at my camp I removed the fans form my inverters and allowed better ventilation.  That may not be practical for you but adding a temp control might be the solution.  I have a half dozen of these and I love them, only $3.65.   Place the sensor on a heat sink and let the fan cycle when it needs to.   http://www.ebay.com/itm/141442045768?_trksid=p2060778.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

[bitwelder]

at my camp I removed the fans form my inverters and allowed better ventilation.  That may not be practical for you but adding a temp control might be the solution.

How would a temp control system solve the problem that the fan is monitored by the UPS controller and so it would trigger the UPS alarm when it sense the fan is not spinning?

[Seekonk]

I doubt the fan itself is monitored.  These three wire fans generally attach to some temperature sensor or more likely just go to a higher speed when when the microprocessor knows it is doing something that will cause heat.