Harman accentra with smoke in hopper??

[glockshooter2]

wondering if anyone has any input on what would cause my FS Harman Accentra to pressurize the hopper with smoke? saw it happen this weekend. it was burning fine, i went to check the pellet level before leaving and saw the hopper filled with gray smoke. pressurized, rolling smoke. i yanked the plug, and let it set a second while i gathered my thoughts. opened the hopper and filled the living room with smoke. The pellets were gone except for a handful, but they don't look like they were burned.
stove and stack were just cleaned a week or so ago. hopper lid was definitely latched as well.
trying to get a service on it, but the store doesn't like to return calls. i haven't touched it since last weekend, but may tear into it today looking for anything obvious. I did take the rear covers off, but everything there looks intact and not out of the ordinary.

 

[Washed-Up]

I’d check the vacuum switch first

 

[tbear853]

Any chance the stove run out of fuel (pellets) so that none were being fed into the auger to go into the burn pot, then once the pellets in the auger tube were emptied to burn, the burn pot burnt it's last pellets and smoldered and this smoldering smoke found it's way back to the hopper through the tunnel of the auger?

I forget exactly how the Accentra hopper / feed gate/ auger / burn pot are arranged, but it is a Harmon burn pot that lives in my Vermont Castings Reliance. VC doesn't have a pressure switch as far as I know.

 

[johneh]

Did your stove run out of pellets when this happened?
If it did and some smouldering pellets were left in the burn pot
and the stove cooled to the point that the combustion fan turned
off the smouldering pellet smoke made its way into the hopper.
There may not have been enough natural draft to draw the smoke up the chimney
Smoke like water will find the path of least resistance.