Understanding HVAC

• An HVAC system is a series of components interconnected by copper piping. Outside the home, a compressor pressurizes a gaseous refrigerant turning it to liquid. The transformation causes the liquid to get very cold. Cold refrigerant is then sent to the evaporator, located in the house (often in the attic) where it passes through a set of copper pipes known as the coil. Warm household air is pushed across the coil chilling the air. Warmth from the air is absorbed by the coil and the refrigerant heats up, turns back to a gas, and is then sent back to the compressor where the heat is pulled away as the process starts all over again.
  
  

HVAC Fluids

• There are only two fluids that could leak in an HVAC system. The first is condensation, that can leak from damaged drain pipes, backed up pipes or drip pans that overflow. Since condensation is normal, you can expect to see plenty of water draining from the primary drain located near the compressor. A typical HVAC system produces 5 to 20 gallons of condensate daily. The second fluid is refrigerant. Since the system is sealed, theoretically no refrigerant can escape. However, the copper pipe that transports the refrigerant it soft and can be damaged outside the home by children, pets and lawnmowers. Inside the wall, nails used to hand pictures or secure wallboard have been known to pierce the supply line. Leaking refrigerant has a chemical smell and is oily to the touch. It tends to evaporate quickly making it hard to find, but does leave a staining residue.
  
  

Drain Blockage

• Water leaking into a home due to an HVAC system is probably not coming from the outside, but wherever the evaporator is located. The evaporator, which produces large amounts of condensation, can usually be found in an attic. While this is a great space-saving location, the location is bad when leaks develop. The evaporator usually has two drains, a primary and a secondary. The primary drain deposits water outside the home near the compressor. The secondary drain is often over a door or window to alert you to a problem with the primary drain. Most drainage problems are due to blockage in the drain by algae, insect nests or a dead rodent. Using a wet/dry vacuum, most blockages can be cleaned out easily. If more suction is needed, pour water down the drain from the drain vent located near the evaporator.
  
  

Frozen Coil

• Low refrigerant can also lead to drainage problems. Without a full charge, refrigerant in the closed moves inefficiently. What little liquid coolant there is stalls out in the coils, and the temperature drops below freezing. The condensation freezes, and a block of ice forms in on the coil. The ice can then cause the drain to block, and any condensation that doesn't freeze will seek a way out. Evaporators are not watertight and will leak. A frozen coil needs professional attention.
  
  

DIY Fixes

• A clogged air filter can cause the coil to freeze over and cause water to leak from the evaporator. Fortunately, this is a very easy fix. Simply replace the air filter, usually located behind a vent in the wall or ceiling. Allow the ice to melt, then restart the system and check for freezing. Another easy fix is to clean the coil. Remove the evaporator cover, and use a commercially available cleaner to spray on and drip off the copper pipes. Dirty coils can collect dust and dirt, which creates sticky paste that can cause drainage clogs.