Question about using 12 volt dc fans instead of 24.

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Message 1840694 - Posted: 7 Jan 2017, 20:35:16 UTC

I have a UPS with the cooling fan going bad. It is an APC su2200net and it uses an 80mm 24 volt DC fan. My question is can I somehow replace it with dual 12 volt fans of approximately the same current draw in series. This should look like a 24 volt device to the power supply in the UPS but would it cause me any electrical problems to do so? I would just stack the fans one on top of the other since I don't want to cut any holes into the UPS.
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Message 1840701 - Posted: 7 Jan 2017, 21:06:02 UTC - in response to Message 1840694.  
Last modified: 7 Jan 2017, 21:10:56 UTC

I have a UPS with the cooling fan going bad. It is an APC su2200net and it uses an 80mm 24 volt DC fan. My question is can I somehow replace it with dual 12 volt fans of approximately the same current draw in series. This should look like a 24 volt device to the power supply in the UPS but would it cause me any electrical problems to do so? I would just stack the fans one on top of the other since I don't want to cut any holes into the UPS.

It should work well enough so long as you have two matching fans. Two different fans would work but you'd have to some math to calculate the voltage that would be present for each fan. You can look up a voltage diver calculator to make it easier.
Since fans tend not to be precision engineered to be exactly the same one will likely run a slightly different speed and you may get some odd acoustical artifacts with the fans stacked
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Message 1840703 - Posted: 7 Jan 2017, 21:14:09 UTC
Last modified: 7 Jan 2017, 21:14:38 UTC

Not sure if it's a good idea to do that with fans as the impedance can change with air pressure and temperature. I think it would be a better idea to use a voltage regulator; you could still use more than one fan, but you wouldn't need to worry about over or under volting the fans. That should also give you more control over the fan speed. You just need to double check that there is enough amperage coming from the UPS to power two fans (probably fine).

Example regulator: https://www.amazon.com/DROK-Numerical-Switching-Regulator-Adjustable/dp/B00BYTEHQO/
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Message boards : Number crunching : Question about using 12 volt dc fans instead of 24.


 
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