Rust on 2 year old evaporator coil

I did a 2 year builders warranty inspection on this home and was able to see the coil in the vertical air handling unit. Apparently there was some kind of a water leak that caused some water staining at the garage ceiling below which was remedied by the builder according to the homeowner.

What is your opinion of the visible rust present on this 2 year evap coil?

I wrote it up like this:

The evaporator coil in the vertical unit on the second level of the structure displays excessive rust for the age of the unit. Deterioration of this nature may cause holes in the coil and loss of refrigerant and pressure. I recommend that you consult with builder regarding the manufacturers warranty on the evaporator coil. My recommendation is for the coil to be replaced.


Good call! I’ve seen better looking 10 year old coils than that. Just replaced a condensor unit (entire unit of a heat pump system) that was only 8 years old. Same thing happened on it. The rust started on the shock frame where the coil loops were and eventually ate through the loops in four places. Replacing the coil would have cost a couple hundred dollars less than an entire unit. Talk about a disposable society!!

Was this a brand name evaporator coil or one of those knock-offs?

John, I don’t know if it warrants replacement under MY business standards, but it is a mess for a new unit.

The evap coil makes water as part of it’s job (absorption of latent heat results in water vapor condensing). I see this as crappy equipment. It should hold up better than this.

My thoughts of the unknown, is that there is a problem with airflow. The coil is getting too cold making the coil frame and adjacent materials to become too cold, causing them to condense and rust. The more air flow, the warmer the coil tends to become. It think it is just getting too wet in there.

To test for this, I would have the return air static pressure measured at the unit. If excessively hi (actually low in the return), this indicates return restriction from improper size or design.

That is because of labor cost for the replacement (which can be a bear!).

It is a TempStar unit. I figured I would recommend replacement and get the builders attention.

Thanks for the feedback.

I would recommend replacement even if it was never turned on, but that does not comply with my business practice…