Brand new Harman P61A installed at 8,500' MSL in below-grade, walk-out basement, with outdoor air kit. exhaust starts with 3.5' vertical rise, 4" flue, 45 degree bend, rises 8" on diagonal over 1.5' to 90 degree bend & wall penetration. Vents outside to a sheltered area under a deck (32" clearance above vent termination, 18" to house wall), but 36" below "grade" (house sits on the side of a VERY steep hill). Here's the issue - it burned fine for about 10 bags of premium pellets, then started sooting up & shutting down with error code 6 "blinks". Not sure why first 10 bags burned fine (multiple "auto" re-starts using room temp & settings feed:4; temp 70), now it does auto shut-down. I cleaned thoroughly (incl. ESP), verified damper operable, verified outside air not blocked, verified chimney clear. After cleaning, I blocked the intake air damper "full open" to see if I could increase the combustion air - didn't help - same 6-blink "shut-down within 1 hr. Thoroughly cleaned again (incl. ESP). I consulted with an installer, then did the install myself to save $450. Dealer wants $100 just to show up for warranty 'look-see" (Harman SUCKS this way - while their product is good, their dealer & service network is quite "hit-or-miss" - they'll soon be out of business unless they address this part of their business model!) The issue seems to be that the install location just sucks - I think I need to somehow increase the stove's negative pressure inside the box. Can I use the "low draft voltage adjustment" to increase the combustion blower speed to get greater negative pressure? if so, which direction would I turn the plastic screw - far clockwise or far counter-clockwise? BTW- my house usually runs at 115 - 116 volts, not 120... Ideas? Thoughts? Advice?