Ballasts will be warm. Electronic ballasts will usually be only warm, but magnetic ballasts usually do get HOT. Nothing can really be done to prevent the temperature, only things can be done to deal with it. Having a fan on them to help them run cooler is a great idea! Not only does it prolong the life of your ballast, it also helps perform better. This is due to the increase in resistance with the increase in heat. Keeping it cooler helps to keep resistance lower, therefore causing it to run more efficiant