Our home central A/C has developed a problem recently - water sometimes
drips out of the ducting surrounding the evaporator coil at a high rate.
Cooling in the home seems to be diminished as well.

This condition is sporadic, and we never had the problem in years past.
I've also heard sporadic banging sounds coming from inside the duct from
this area.

Today I formed the hypothesis that condensate is freezing on the
evaporator, blocking airflow. The banging could be ice falling off the
evaporator, and the fairly significant water could be the ice melting.

Does this sound like a plausible/likely explanation? What other things
might cause this problem? What ultimately is the cause. And what should
I do about it?

Part of my hypothesis is that after several years of drought and dry
weather (here in sodden Maryland), this year's rainfall has meant high
humidity and hence more condensate than in the past.

Could it also be that grime/dust has built up on the heat fins in the
evaporator? Is opening up the ducts and cleaning these something
reasonable to think about doing, or does build up usually signal the
need for a new evaporator/heat exchanger? Is cleaning practical without
specialized tools?

What about insufficient airflow through the ducts - would this increase
condensation and lead to ice formation (which would further restrict
airflow)? If I increase the airflow (by opening all vents wide open), is
the problem likely to go away?

Thanks.

Bill Christens-Barry

--
Wm A Christens-Barry, PhD
Equipoise Imaging, LLC

http://www.eqpi.net/eqpi/