Why flames are hugging the back of the pellet stove?

[Kight]

Hi folks,

I have Whitfield WP 2 pellet stove from the early 1990s. Do you have any idea as to why the flames are hugging the back of the firebox? The picture is attached. I am suspecting some airflow issues. I have taken the firebricks, and air baffles out and cleaned them thoroughly. FYI, I have applied some Rutland refractory cement on the firebrick; that's why you see the bubbles on the firebricks; I will have to re-do that in the summertime. Thank you.

 

[Stovensen]

My Whitfield Quest Plus from 1998 does that too. And it has always had this flame pattern. I remember the subject was adressed here in this forum some years ago by other pellet stove owners wanting to find an explanation.
I can't find the thread, but one suggestion was that the airwash in a negative pressure fire box, will create a gentle, but constant airstream of cold air hitting the flames, thus forcing them towards the back of stove. Doesn't this sound plausible?

 

[Kight]

Hi Stovensen, thank you for your input.
I suppose that hot exhaust air should rise and go through the heat exchanger. See attached image; the highlighted vents are behind the central firebrick. The hole on the left side is for inspecting the exhaust fan. I don't know the function of the hole on the right side. I hypothesize that air is getting sucked through these holes bypassing the heat exchanger; this issue would lead to flames hugging the central firebrick and reduced stove efficiency. Would it be recommended to stop exhaust air from being sucked by these holes directly from the fire-pot? What could be the best way? Thank you.

 

[Ssyko]

The two plate are access panels for cleaning ash from behind the wall. If they are flat against the wall they should be fine.

 

[cpetku]

Forgive my ignorance, but the flames look like they are heading towards the pellet shoot. Since I have a Harmon the feed is from below and I don't know the significance in your pictures. Maybe a senior member can comment if that is normal for top feeders...

 

[Ssyko]

Forgive my ignorance, but the flames look like they are heading towards the pellet shoot. Since I have a Harmon the feed is from below and I don't know the significance in your pictures. Maybe a senior member can comment if that is normal for top feeders...

yeah its common with top feeders. But if the combustion blower creates a good vacuum and stove is clean it will actually pull a little air through the drop chute and the flame will dance all over

 

[Kight]

The two plate are access panels for cleaning ash from behind the wall. If they are flat against the wall they should be fine.

Should I seal the plates flat against the back of the stove frame with refractory cement or a high-temperature sealant? That would allow me to remove the plates for cleaning and inspecting in the future. Thank you for your help.

 

[cpetku]

yeah its common with top feeders. But if the combustion blower creates a good vacuum and stove is clean it will actually pull a little air through the drop chute and the flame will dance all over

So if I were the OP I would read that as there is potentially an air leak somewhere reducing the amount of air pulled through the feeder but not so much that the vacuum switch detects a problem. Maybe check the door seal with a dollar bill?

 

[Ssyko]

So if I were the OP I would read that as there is potentially an air leak somewhere reducing the amount of air pulled through the feeder but not so much that the vacuum switch detects a problem. Maybe check the door seal with a dollar bill?

No. no potential leak, a dirty stove will cause the same issue. Air wash under the bottom of the door will let air in. Its all calculated when the stove designed. All in all “ its normal for the flames to lick the back wall“. Most do

 

[Ssyko]

Should I seal the plates flat against the back of the stove frame with refractory cement or a high-temperature sealant? That would allow me to remove the plates for cleaning and inspecting in the future. Thank you for your help.

no don’t seal them permanently you have to remove them for cleaning. If they are not warped And sit tight to the wall just put them back and install your insulation.