Most efficient flame for heat transfer

[NYBurner]

Hi Everyone,
Ive got a question regarding flame, and heat transfer efficiency. I haven't seen a thread directly addressing this..but in regards to "burn" in other posts I see a lot of conflicting advice.

So here is my question, to extract the maximum amount of heat from my burning pellet do I want a flame that is burning as slow and close to rich afr as possible, or do I want a lean as possible (just shy of popping pellets) fire??

I understand a lean burn is "cleaner", however this means the damper is bypassing as much air as the fire can withstand....burning fuel faster and I'm not sure if this translates to better heat transfer out into the room?? Ive tried running "lean" the past few days and I find we are running through pellets fast and I'm running on a higher heat setting. Im wondering if this correlates to a fireplace ripping through wood relative to a wood stove that restricts combustion air and slows the burn down.

For reference I am running an eviro m55c insert, sorry for the long winded post...just hoping I am convey my question clearly. Appreciate the shared information!

 

[reallyte]

I would follow your manual for setting the burn. They usually have you balance efficiency and what is safe.

 

[acammer]

I think you've got the basic idea down NYBurner - a rich flame is a bit more efficient, but a lean flame runs clean. I spent some time experimenting with this in my stoves and I found that I could get a little more output at a given feed rate by running the stove rich. It wasn't a big change in output, and it would take a few hours of running that way to get there. However, I ultimately learned and decided I prefer a lean burn, so that the stove stays cleaner longer. I run my PAH flat out 24/7 now that it's cold, so I stretch as long as I reasonably can between cleanings, which is typically every other day as long as I keep it leaned back. Eventually, it'll swing rich as the burn pot begins to crude up and the cradle is loading with ash, restricting airflow. Once it starts down that path, you just gotta shut it down and clean it. Running it rich off the bat means I end up doing that far more frequently, for a very small increase in output.

 

[Deromax]

On my stove, i can alter the pellet feed and air feed + - 5% on top of the overall burn rate (Level 1 to 5). Even at idle (Level 1), it was outputing too much heat for my taste. I decided to lower the pellet feed to minus 5% and up the air feed + 2%. This decreased the heat to a near perfect level, lowered the pellet useage and lowered the ash residue, so it's a win win win situation, all the while knowing that I can increase the pellet feed back up if higher heating needs should arise.

 

[NYBurner]

Im running my unit at 5 (full power) and its not particularly hot. Im burning barefoots, have feed trim cranked all the way up. Wondering if I need to open up the restrictor in the hopper some.

Everyone with the m55 comments they rarely run over setting 3....but mine just does not seem that hot?

 

[bcarton]

Enviro usually recommends setting your stove with a magnehelic gauge. Exact numbers vary with stove model, so you'll have to refer to your manual. I bought a gauge and I can run my stove right at manufacturer spec when it's 25d + outside, but when it gets this cold outside my vent starts to draft like a beast and the stove runs a little lean even with the damper closed all the way. I'd rather run lean than rich, because I'd rather spend a few extra dollars a year on pellets than deal with a messy and possibly dangerous creosote issue.

 

[NYBurner]

Thanks for the information so far everyone!

We did use the mag gauge to set it initially but Ive been tinkering with it. At the recommended vacuum the burn was a bit dirty as it sooted the glass fairly quickly. It did make heat though and burned a nice flame. As Ive opened the damper to give it more air the flame fluctuates in size between pellet dumps noticeably and decreased in size overall....which prompted this post. Im speculating that with the air, the flame is burning through the pellet faster than it is reloaded?

 

[bcarton]

At lower burn rates, my flame varies a lot. At higher burn rates it still varies but not as much.

Well every house is different, every vent is different, and every batch of pellets is different - which I guess is why in my manual it says that after I adjust the stove to spec with the gauge, I may still need to adjust my damper for different pellets, or different feed rates (my stove only has a spec for running at full blast, which I never have done other than when adjusting pellets. My glass soots up fairly quickly at low feed rates unless I open the damper a bit. Once I'm past the 50% mark on the Dial-A-Fire, it stays a lot cleaner even with the damper fully closed.

I found this post very helpful: https://www.hearth.com/talk/threads...lazy-and-or-getting-smoke-in-the-house.11413/

Especially this part right here, which IMO is worth reading over and over until it becomes your burning habit:

Without a Magnahilic this is the best way to dial In air adjustment.

With the stove on High and running for 15 minutes after start up.
Push the air rod in. you will see a tall ugly lazy flame
then [b}slowly[/b] pull the rod out
as the flame comes down, more intense and be more yellow
when the flame looks like it is not changing anymore stop pulling out.
If you have sparks popping this is normal
but you don’t want to see PELLETS popping out.
If you get Brown or Grey soot on the glass and firebrick this is normal
if you have BLACK soot on the firebrick and glass pull the air out a little more.

That's it, that's my burning bible right there.

 

[NYBurner]

Ah ok, that also corresponds to what i was thinking.....run more towards "rich stoich". K great info, thank you for sharing!