Home HVAC Evaporator coils icing up

[pdharrin]

No air was coming through the registers, so I opened up the HVAC closet "box" and the evaporator coils have ~1" thick ice completely covering them. Also, I can hear the flow of freon through the lines. Had the freon topped off last year because we have a small leak and it worked fine then. I am not very familiar with AC, does anyone have any ideas what is causing the icing? Thanks

 

[PETEY]

your condensor might be be clogged up with debris. bad filtration possible cause. no airflow through it will cause it to ice up.

 

[Tom R.]

Yeah, the most common reason for that in my experience is a dirty filter.

 

[Ed A. Stevens]

#1 typical problem is low air flow, due to a dirty filter (Change the filter and brush off the dry evaporator coil).

Dirt on the blower can also reduce airflow (clean the cupped blades of the blower with a brush).

Did the refrigerant leak ever get identified and fixed (sealed)? Low refrigerant will eventually lower the pressure in the evaporator, lowering the temperature if the condenser temperature is also low (on a cold morning). Good airflow will still move heat from the house into the evaporator and refrigerant, usually keeping it frost free, but this condition combined with even a slight reduction in airflow can produce the icing you experience.

The last simple thing to look for is closed vent grilles and registers. Winter heating tends to make some people close off vents to save on heating costs for vacant rooms. The furnace is not as sensitive to an airflow reduction as a cooling coil, it can operate reliably with less airflow, so make sure any closed registers are reopened each spring (probably the first thing you did when you found the no airflow problem).

 

[pdharrin]

Yeah the leak was located-it is in the evaporator coil assembly and the part was something like $500, which I didn't have at the time and still don't, but the technician said the leak was extremely slow and it would probably be at least a couple of years before we needed to top it off again. Hopefully we will have the $ to just replace the part then.

 

[pdharrin]

I always clean the filters twice a year-before heat and before AC. I think only 1 register was closed from the winter-my office because I like it 65 degrees and my woman doesn't really like that (she is cold at 70). I did notice the fan was dirty but I'll check and clean the fins for the coils. Thanks guys.

 

[Tom R.]

I always clean the filters twice a year-before heat and before AC.

Only twice a year?! I replace my filters about a dozen times a year. The commercial units we use to cool a mobile testing shelter need the filters cleaned at least monthly to keep the coils from freezing up. You may want to clean the filters more often.