Harman Pellet Stove Effeciency

It has only been a recent sales ploy to market the efficiencies of pellet stoves. The Harman burn pot actually burns the pellets better overall than most other brands. The bottom feed pushes the pellets up and the air flow is slower than the top feed designs. The Harman does not have to blow the ash out of the fire pot so there is less heat blowing through the stove and out of the exhaust. The stove body acts as part of the heat exchanger so there is more surface area to transfer heat into your home. Ratings are deceiving due to the different types of pellets and how clean the end user keeps the stove.

The fact is that few pellet stove companies publish any really reliable ratings - with the exception of Thelin and perhaps some others. That makes it tough to compare.

From the little that I know, I will say this...or these:

1. When pellet stoves were first tested in-home many years ago - by a test lab, the efficiencies came out MUCH lower than was being claimed. The bottom of the line - at the time - was the Earth Stove (bottom fed) with a mechanism by Traeger. Not sure if that reflects on bottom fed or on the stove design or both.

2. Like most combustion equipment, pellets stoves are more efficient when burning hot. This probably makes a lot more difference than the stove itself - how the stove is used. Early in the game (90's), the Quad pellet stove burned at one setting - hot - and it was one of the most efficient out there! It used a thermostat to turn on and off. It is very difficult to get a very high efficiency over a very broad range of outputs.

3. A bottom fed stove may end up working better with high-ash, higher moisture or otherwise imperfect pellets.

4. Figuring "best case" scenarios when considering efficiency is, IMHO, fooling ourselves! At least until someone actually develops and pays for a ratings system that figures everything in. It would probably be generous to make the following assumption with pellet stoves - and maybe even less with pellet inserts.

Wood BTU content after first adjustment for moisture: 8,000 BTU lb
actual efficiency when on-off cycles and various assumptions are taken into play: 70%

Output per lb: Approx 5600 BTU