If there is water in your emergency drain pan most likely your primary drain line is stopped up, and the water is overflowing into your emergency drain pan. If your system is older you could have a rusted out primary drain pan or cracked drain pan. This is less likely. Your first step should be to try to unstop your primary drain and remove the water from your emergency pan if it doesnt have an emergency drain. See the unstopping drain faq.
Tags: drain, float switch