should i use the fan on my power supply?

[shiznut123]

i have an old power supply that is 200watts. it has a verrrrryyyyy quiet fan on it. i only have two computers and each one has a 250watt ps. should i leave the fan on in case i need to use the ps as a backup or should i use the quiet fan on it

 

[fondoo]

yes, it sucks the hot air out.