roll-out tripping!

[Chuck]

CO rots steel! Any CO. If you have pulled a water heater burner covered with flakes of rust, you have seen CO at work. I concur with the flakes in the secondary. ALSO; you mentioned the Delta T being high. Perhaps a restricted duct? What is the External static on the system?

Rust is from the acidic flue gases condensing on metal surfaces, it has nothing to do with CO.

Rust is always a sign of a venting problem. It is a sign that the flue gases are not venting out of the appliance properly at the end of each cycle.

[mason]

the "saga" continues, received the secondary yesterday, so we proceeded to change it today when I pulled it out I found 2 rings from the clam shell of the primary and proceeded to pull that out and visually inspected found a total of 6 rings busted out, so the primary will have to be replaced. Then I needed to make sure the secondary is in fact cracked or leaking and the only thing I could think of doing was to stand it with the bends towards the bottom and fill the tubes with water and let it sit for a while and had no water leakeage at all now the dillema is where was the water coming from? and obviusly why wasn't my combustion analizer registering CO in the conditioned air dam thing is brand new and for $2K you'd think it be calibrated..........

Please don't rely on CO in the supply air as your determining factor for a breached heat exchanger, you will miss the ones that are. The blower is forcing are across the chambers(read: positive pressure), that's why it's protected by roll-out limits.

[frustraded tech]

upon replacement of both exchangers there was no signs of rust or sludge build up on the socondary, also no restrictions or considerable lint or debris found on the AC coil the rings from the clam shells had busted suspect the draft inducer was pulling air from the conditioned space rather than from the intake causing the flame to run slower down the exchanger therefore heating the burner box.