Guide
Frozen coil or dripping drain line
These two summer problems look different but often share a cause. A coil that freezes will flood its pan once it thaws, and a blocked drain will put that water somewhere you do not want it.
Why a coil turns to ice
The indoor coil runs below the freezing point of water on purpose; warm house air passing over it keeps the surface just above. Cut the airflow or the refrigerant charge and the surface drops further, moisture freezes on the fins, and the ice blocks even more air.
Clogged filters, closed supply registers, a slow blower and a low charge from a leak are the common starting points. Running the system at very low setpoints on cool nights can contribute too.
- Frost or ice on the larger, insulated copper line at the outdoor unit.
- Weak airflow from the vents even with the fan on high.
- Water around the furnace once the system has been off a while.
What to do when you see ice
Switch to fan only
Set the thermostat to off for cooling and the fan to on. Moving air thaws the coil faster.
Check the filter
Replace it if it is dirty. Then give the coil a few hours to thaw fully.
Watch the pan
Meltwater is heavy. Check the drain pan and the area below the unit while it thaws.
Call if it returns
Ice that comes back after a clean filter points to a refrigerant or blower problem.
Where the water is supposed to go
On a humid day the coil pulls a steady stream of water out of the air. It collects in a primary pan and runs out through a drain pipe. Attic units add a secondary pan beneath the whole cabinet, and many have a float switch that cuts the cooling when water rises in a pan.
Algae and dust build up in the drain over a season. When it clogs, the float switch shuts the system off, which looks like a failed AC but is really a full pan.
What Garland's code says about condensate
The City of Garland's guidance for AC work says water from every cooling coil must travel from the drain pan outlet to an approved disposal location. It may not run into a street, alley or anywhere it becomes a nuisance.
That matters when a contractor reroutes a drain line during repairs or a replacement. Ask where the new line will end before the work starts.
Common questions
Water is dripping from the ceiling under the attic unit. What first?
Turn the cooling off at the thermostat, put a container under the drip and check whether the secondary pan is full. Then call, because a full secondary pan usually means the primary drain is blocked.
Can I clear the drain myself?
Some homeowners flush the line through its access cap. If you cannot find the cap or the clog sits inside the coil cabinet, leave it to the contractor.
Does a frozen coil damage the compressor?
It can. Liquid refrigerant returning to the compressor is hard on it, which is why the system should stay off for cooling until the coil thaws.
Where these facts come from
Talk it over with an independent HVAC contractor
Say what the equipment is doing and where it sits in the house. The contractor on the call can tell you what a visit would involve and whether the work needs a city permit.