Harmon P68 Blowback?

[drc1912]

Hi All,

Longtime reader first time poster! I would like to thank everyone here for helping inform us on how to best heat our house over the past five years. When we bought in Seattle 5 years ago we opted for a craftsman built in 1920 with little to no insulation, and terrible windows. We bought a Harmon p68 based on research done in this forum and love it! We just lit it up for the first time this year and it leads me to this:

After doing a full cleaning of our p68 and firing it up with new pellets, it lit up like a charm. Then, the next morning when it was lighting, there was a small amount of sparks, some embers, and then a pressurized "boom" (very minor) where i saw some ash blow out from around the glass and the ash chamber below. It seemed like there was a pressure buildup, and I have never seen that before! After the blowback, it worked just fine, we have had it running for over 24h, multiple restarts, and haven't been able to recreate this phenomenon. Anyone have any ideas what that could have been?

Really appreciate all the help over the years, and on this head-scratcher in particular.

Thanks!

 

[jackman]

Mine's done that occasionally. The pellets get hot, lots of smoke, and then the flames start up with gusto. It happens if the burn pot gets overfilled and the vent holes are covered up. I consider it normal.

 

[drc1912]

Mine's done that occasionally. The pellets get hot, lots of smoke, and then the flames start up with gusto. It happens if the burn pot gets overfilled and the vent holes are covered up. I consider it normal.

Thanks for the quick response - which vent holes are you referring to?

 

[jackman]

Thanks for the quick response - which vent holes are you referring to?

The vent holes in the bottom of the burn pot.

 

[jzm2cc]

Open up the burnpot cover, remove the ash with your fingers or a vacuum, and give the pot a few taps from the end of the cleaning tool to knock ash off igniter. Assume the burnpot holes are all open, if not then clean these out with a small Allen wrench or drill bit while being aware the igniter is beneath it so you don't damage it.

 

[MellieNH]

Hi there!

I have had this happen a couple times too and it sure will get you out of your chair quick! It happened just the other day where the pressure build up went off with a BANG! Felt like someone was shooting a shotgun in my chimney!!

On myy stove which is also a Harmon it's because too many pellets are in the burnpot. As mentioned above this happens when the ignition wires have Ash on them. On the Harmon just twist off those wing nuts on your burnpot front face then vacuum in there gently. I got a vacuum attachment that is for cleaning computers so the tip is real small. Be gentle you don't want to pull an ignition wire out!

I clean in there whenever the stove is cool. Try to make that a habit, it is an easily forgotten area. But you get that blow back bang and you won't forget it! Lol I think mine happened the other day because I half assed cleaned it the last time. Won't happen again... I like having my house