lsayre wrote:-0.03" sounds quite adequate to me. I'm baffled by your problems. Could there be a blockage somewhere? Where are you seeing the -0.03" mano reading? Where is your manometer take-off located? Mine is only a few inches above the boiler.
Is your sight port cover plate springing open nicely when the fan shuts off? Is it slamming shut tightly when the fan comes on?
The port cover plate does spring open nicely when the blower stops and set up tightly when it is running. My interpretation of -.03 reading is that a draft is coming down the chimney versus sucking up the chimney and out. My manometer is connected by way of a small piece of break line tubing located 8 and 3/4 inches above the unit on the only section of vertical pipe. The manometer is reading -.01 right now. (Unit is not running) I thought most efficient running was around .04. I thought my vent pipes might be blocked with fly ash as I have everything taped off to try and increase my draft. Therefore I have not cleaned them in 3 months. When the smoke started pouring out of the pipes, I ripped off all the high heat tape from my barometric damper and started checking the pipe. There was some fly ash build up but less then 1/2 an inch. That's when I checked the manometer. Basements file up with smoke quick ya know!!
If there is blockage I don't know how it could have happened so quickly as I have been running the unit consistently, albeit with frequent re lights, since January.