Harman Accentra 52i - burn technology question

[OK_Bill]

I took the plunge and ordered a new 52i insert for my home. I'm amazed at the claimed efficiency of this stove, at 85%. That's right up there with the very best catalytic wood burners and they get astounding efficiency numbers only by using secondary burn technology that often requires a catalytic element in the stove.

So, my question is: how in the world does Harman get such high efficiency? Does this pellet stove achieve secondary burn? I don't see anywhere in Harman's literature or here on the forum where secondary combustion is built into the design of the Accentra, but I can't imagine getting 85% efficiency w/o it.

Anyone know?

 

[Peterfield]

A lot has to do with pellets versus cordwood. The water content of wood is about 37% when seasoned versus significantly less moisture content in a pellet. I would say the air circulation within the pellet stove is another factor.

 

[Big papa]

Welcome to the harman gang not sure how they get the efficiency numbers but I can say that the stove operates very precisely when burning, keeping a set temp within one degree,it adjusts the fans and feed rate automatically I'm sure it's technologies and design help it achieve its ratings.

 

[OK_Bill]

Thanks Big Papa... glad to be coming aboard the pellet ship!

What do you see coming out the chimney? Do high efficiency pellet stoves produce any smoke out the stack?

If the stack exhaust is clear, then that's evidence they're re-burning the smoke as I understand it.

 

[Big papa]

When I look out at the chimney there is no smoke at all coming out some say that they can see a little smoke at start up but I've never seen any.i can hear the air flowing thru the vent when outside but no smoke.

 

[spirilis]

Seasoned wood is typically 15-20% I think, while pellets are <6% if I'm not mistaken. I have been a bit curious about this myself- while pellet stoves don't seem to produce visible smoke once warmed up, do they truly burn as much of the available fuel value in the smoke gasses (CO, etc) as a catalytic or even burntube based woodstove?

The one thing that is certain is they extract more heat from the flue gasses, using an electric fan to guarantee the draft unlike a conventional woodstove.