Originally Posted By: jonofrey This post was automatically imported from our archived forum.
this looks normal due to condensation, etc…
This is an evap coil in a condo and the differential was 18 degrees (sorry snowbirds, we can still sometimes measure that down here this time of year).
I don't see enough of the guts of evap coils to know if this is normal or something to be concerned about.
Originally Posted By: jmyers This post was automatically imported from our archived forum.
John,
I would say that is rust and yes it is something to be concerned about. Get enough of it and you can kiss the coils bye, bye! 
Originally Posted By: Blaine Wiley This post was automatically imported from our archived forum.
I’ll take the other side.
Looks like the rust is on the sheet metal portion of the coil sides, which is very common. We test temperature splits just about all year down here, too, and those copper tubes on the outside of the coil package sweat profusely. I have been seeing rust on the sides like that after about a year of operation. The fins are aluminum on those coils, and the tubing copper, so just note the condition, and recommend routine maintenance.
BTW, I did one the other day that was 31 years old, and the sheet metal was rusted through in places. It had a nineteen degree split on a 77 degree day. Not bad for an old guy.
Originally Posted By: Guest This post was automatically imported from our archived forum.
I agree with Blaine,
Probably the rust you’re seeing is the result of galvanic corrosion where the copper passes through the end support. I don’t recall having seen the combination of copper and steel ever in evaporators or condensers where the steel was integral to the unit. It’s an end support, I’d note it , but it doesn’t get me too excited.
Originally Posted By: rsummers This post was automatically imported from our archived forum.
If the sides looked like that how did the bottom look? Hope there is a secondary pan under the coil. What do you guys use to determine if the temp split is correct on an A/C unit with out putting gauges on it?
Originally Posted By: rwills This post was automatically imported from our archived forum.
Rolland,
I use a Raytek infrared thermometer. It’s a great tool that can be used for many applications besides feed and return temps such as oven door seal leaks, elec panel hot spots, poorly insulated walls etc. just to name a few.
Originally Posted By: jpeck This post was automatically imported from our archived forum.
That rust is bad enough to call for a coil replacement.
Rusting is typical, those copper tube ends sweat. Rusting that bad (you can see the bubbling and flaking) leads to rust through, which is a failure of the coil.
You want all the air to blow through the coil and then into the duct. You don't want air to blow out of the coil through rusted through holes.
Time for a coil replacement, or even a replacement of the air handler (depends on the condition of the air handler cabinet).
this looks normal due to condensation, etc…