This customer in Sachse Texas had a 15 year old evaporator coil with multiple problems:
The main drain line had been clogged for several years and the condensation had been dripping into the auxiliary drain pan for this entire time. The customer thought that the water they saw dripping outside from the eve of their house was normal, (which is a pretty common thought among customers) when actually, condensation that drips outside is your alarm that the main drain line is clogged. If not addressed, this standing water will eventually rust-out the evaporator coil and housing and the auxiliary drain pan, which was the case here.
During an especially humid day your air conditioning system can condensate up to 8 gallons of water per hour. This condensation, when properly plumbed and not restricted, will flow through the main drain line and drain somewhere within your sewer system, normally to a sink or bathtub. The auxiliary drain pan is simply a galvanized steel pan that is for “emergency” use only. It is not made to catch water full time and will rust out fairly quickly, which is what happened here. The customer had ceiling damage from the rusted out auxiliary drain pan which had rusted through and dripped water onto his ceiling.
The evaporator, due to it’s age, had developed a large freon leak.
An evaporator, during Spring-Summer months will condensate water almost constantly. As this water drips across the evaporator coil, the coil began to rust. The rust builds over the years and starts to flake off the coil. When the rust particles flake away you begin to develop pin-hole leaks within the coil. The leaks start small, and then get larger over time. This, of course, is not the only way a refrigerant leak can develop, but in this case, it was.
The customer’s initial call was that the AC unit was not cooling. We noted that we had added refrigerant the year before. At our arrival, we found that the system was extremely low on refrigerant and with the cost of R-22 rising as it is phased out we gave the option to add the refrigerant, knowing that it may or may not last the remainder of the summer or find the leak and repair or replace the leaking piece of equipment. The customer opted to locate the freon leak and go from there. We performed a leak check on the outdoor unit and on the indoor evaporator coil. We found no leaks outside and a large leak in the evaporator coil. The leaks were the rusted pin hole leaks throughout the coil which cannot be repaired so we gave the customer prices of replacing the evaporator performed the installation.
The pictures show the poor condition of the existing coil and the severe rusted out condition of the auxiliary drain pan. We also have a picture of the new drain pan and the new evaporator coil, installed.