I think you might have answered your own question. " The all aluminum coil

is clean but about 50% of it has a coating of white aluminum " corrosion "

on the surface." Sounds like your coil is dissolving. Electrolysis can do that.

Any slight bleed of power to ground through the coil ? Any corrosive

air going through the A.H. ?

I'm sure there is no corrosive air in this office, just people and paper. In checking for electrolysis would it be best to check for voltage between the coil and cabinet, the coil and ground wire, or shotgun everything with the coil and get back?

The cabinet and coil will be all one " connection ". You'll have to check from

coil, cabinet to a known ground. Hopefully one that is not connected to the

system. Try to use a different circuit if possible. A compressor leaking to ground could flow through the piping and cause the same effect as it exits

through the coil.

Just returned from the office, here's what I checked and got 0.000 volts between all.

"problem" A/H and an older A/H in the same closet, different circuits.

Problem A/H and extension cord ground lug I had plugged into a wall outlet.

Corroding coil and extension cord ground.

Corroding coil and older A/H case.

I verified the ground connection in the problem unit was clean and tight, but was not brave enough to disconnect it for a voltage measurement. Measurements taken with a digital multimeter.

You have an aluminum coil ( as you say ) steel A.H. copper piping and condensation that may be contaminated with who knows what. you now have a small battery. was the coil foam cleaned at any time ? Your coil could just be bad from day one. I know there was a recall and warranty extension on many aluminum coils at one time. Don't remember which ones but I think one was carrier. Some aluminum coils work fine some are junk. Hope you get it sorted. Good luck. When I say aluminum I mean the piping is also aluminum and not copper pipe with aluminum fins.

Yes, the coil is aluminum tubing and fins. I don't think the coil has been foamed as it is less than a year old. At this point I'm going to ask for the installation contractor to come in on it.

Trying to get a handle on the cause of this so they don't get duped into a "duct cleaning is all it needs". Thanks for the help.

Tom

not a problem. Let me know what happens if you get the chance.

Your discription of flakes sound like plastic sheet that deteriorated to the point of turning to dust. I lean toward the plastic because it disappears between fingers and i don't think coil corosion will do that.

The best description I can give of these flakes is that they look like white ash then smear out to a powder between the fingers. The duct system is plastic lined flex duct maybe 10-12 years old. The inner lining of the ductwork I can see is black and appears to be in good shape.

I doubt the duct liner degraded that bad,I suspest somthing accidently left inside unit at installation ( owner's manual,part list,warranty info plastic pocket or similar). I'd compare material from evap coil for appearance and feel. If it seem's to be same material that leave's you with figuring out what caused evap to corroad. I think you have two unrelated issues because I've dealt with several badly corroaded coils and none shed particals as you described.

I recently found the insulation from inside the air handler cabinet lying inside of the squirrel cage. 5 hvac companies had cleaned the system, but never

questioned where all the yellow fiberglass particles came from.

I'd take a look inside the equipment, plenum & supply boxes.

and wasn't there a lady recently with a similar issue & it turned out

to be something from the puppy pee pads?

best of luck