Anyone can shown me how to install a 12VDc FAN into Uninterruptible Power Supply (UPS)? Is it I need to connect the FAN Positive Supply to the UPS Switch? Or some others else...
You can connect the 12-V fan to the battery terminal, but make sure that you connect only to 12-V not the whole battery because some UPS use series battery connection (to achieve more than 12V, e.g.: 24V or 48V).
And, don't forget to interconnect it to the UPS switch so that the fan will not run when you turn off the UPS.
Wear safety glasses. Working on the inside of a big UPS is dangerous. 50V or more from a battery stack can hurt you even when the mains is off.
Do not wear a metal watch or finger rings. If your watch or ring shorts circuits the DC supply you will be badly burned.
The battery negative may be connected to earth. If you touch a soldering iron to battery DC with the mains cable connected, even with the mains switch off there can be a big bang.
If you short circuit somthing inside the UPS there can be smoke, fire and flying metal.
The correct answer is either
a) using your knowlege of electronics identify a suitable place where mains power is converted to 12V in the UPS
b)Get a suitable small mains to 12V power supply and put it inside the ups wired to the ups mains power.
or c) throw away the 12V fan and get a mains fan or a fan of a suitable voltage.