Rust stain below burner

Damon

This is a pic of 12 yr old Thermopride OL5-85 with a Beckett AF in a rental I own. It has been "serviced" regularly by two different companies but it appears that they have only been servicing the oil side while neglecting the HX since I found about 1-1/2" of soot in the bottom of the entire length of the 8" flue. It runs fine, no smoke out of the chimney and after I cleaned out the soot and wire brushed the flue the net stack was 450 after running about 15 min. I don't have the tools to test anything else so I'll clean out the HX later and stand over the tech while he's tuning. The last service was in May and the furnace has been idle since. Now to my question...what is the staining under the burner. There is AC so I'm not sure if it's condensate from the AC or flue gas condensate. Your thoughts are appreciated. 

Damon

Here's another pic.

from another angle

Alan R. Mercurio_3

condensate tray?

From the picture it looks like the condensate tray for the A/C coil is over flowing? I can’t guarantee that, but that’s what it looks like.

Damon

Thanks for the input

I'll open her up later in the month when I get to the house again and see what's up.

Alan R. Mercurio_3

Damon

You're very welcome.

Damon

Hmm...I didn't see any evidence

of an overflowing drain pan. When I opened her up to clean inside the HX I looked around with a borescope and mirror at the outside of the HX. the base pan and inside of the cabinet. It looked like new and was as clean as a whistle. Not a stain or bit of rust anywhere. That rust stain just starts where you see it in the pic. I guess I'll check it out again when I start the AC next summer.

Coany

Rain down the chimney over the summer?

is the smoke pipe a short run?

 does the chimney have a cap?



 any evidence of rain(yellow stuff) in the flue pipe  you cleaned?

Damon

There is a rain cap

Flue run is probably 4-5 ft from chimney to breech with another 2 ft to the back of the HX. This is a rear flue version and man is it a beast. I did see some small "yellow popcorn" in the flue. Not much. Soot was like 98% black and maybe 2% yellow. Did see a similar yellow crust on top of the insulation above the burner (no black). Not much again but I was thinking this was probably sulfuric due to condensation. Chamber is perfect though.