Reddit reviews Little Giant 521259 VCMA-15ULS VCMA Series Automatic Condensate Removal Pump (115 volts), 1/50 horsepower

You need to find a condensate pump. It's basically a small little pump contained in a little container. When the container fills up, it pumps it out. The pump is fairly small and doesn't draw much power.

http://www.amazon.com/Little-Giant-VCMA-15ULS-Condensate-horsepower/dp/B000AHT78O/ref=sr_1_1?ie=UTF8&qid=1342628268&sr=8-1&keywords=condensate+pump

Well, I'm no HVAC expert, but here's an issue that keeps popping up for me because of my particular HVAC setup. This is a complete shot in the dark for you, because HVAC setups vary widely, but...

Do you have a condensate pump? Does it appear to be electrically wired to your furnace? Is the pump working? Is the drain line it's hooked up to blocked?

Some background: So, A/C units involve metal coils which sit in the middle of a furnace's airflow. These coils get cold, the furnace blows air over these cold coils so the air gets cold, then that now-cold air makes its way throughout the house through the ducts. Since the air being blown over the coils typically contains moisture, that water vapor hits the cold coils and condenses, forming water which then drips down into (hopefully) a pan. In some cases, the pan has a drain which leads outside. In my case, the furnace is in the basement, so the water drains into something called a condensate removal pump. This pump collects all the condensed water, then when the water level reaches a certain height inside the pump, it activates and with a buzzing sound pumps the water up through a flexible tube and out of the house.

Now, these condensate pumps contain a safety switch and are wired to the furnace by a couple of electrical leads. If the pump fails for whatever reason - it's not getting power, the motor is broken, the drain line is clogged, etc. - then the safety switch fails and the furnace consequently will not turn on. This happens to me on occasion, most often because the plastic tubing hooked up to the condensate pump gets clogged with sediment or algae or god knows what, and the pump therefore can't get rid of the condensation piling up inside it and trips the safety switch, thereby making the furnace unresponsive. In that case, unplug the drain tube from the pump, hook up a shop vac to the tube to suck out whatever's blocking it (I just use my hand to create a seal between the shop vac and the tube), then hook the drain tube back up to the pump. And for good measure, maybe pour a diluted bleach solution into the pump until the pump activates and flushes out the drain tube with the bleach solution. Assuming the pump is now running and draining fine, the furnace should now activate normally again.

http://www.amazon.com/Little-Giant-VCMA-15ULS-Condensate-Removal/dp/B000AHT78O/ref=sr_1_2?ie=UTF8&qid=1301598419&sr=8-2