Water leaking from air handler

[alroadking]

I have a great deal of water leaking out of my air handler. I have replaced my fan motor and thermostat. I have also checked and made sure that the drain pipe coming off the drip pan is free of obstruction. I have not seen it leaking, only found the water on the floor. It seems that what could be happening is that the core is developing a great deal of frost around it (it is a 5 ton unit) because the fan is not always coming on before the core gets cold. When the fan comes on to start moving air through the frost melts off the core and generates a good bit of water that overflows the drip pan faster than it can drain. Is this possible? If so, what else could it be?
Thanks, Mike

[frigetater]

low charge, dirty filter, dirty coil/blower, fan speed, just to name a few....if the drain is overflowing it is more than "frost", make the call