I've always wondered just who or how pellet-multifuel efficiency is obtained...

  • Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.

    We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.

    We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.

SidecarFlip

Minister of Fire
Feb 7, 2010
5,273
S.E. Michigan
I realize that Warnock-Hershey 'tests' biomass stoves for reliability but who determines the efficiency of any model and what testing criteria is used.

It's unlike AGA certified gas appliances (I worked at AGA years ago btw. AGA does very comprehensive testing on appliances that are fueled with NG and propane but the realized BTU output of NG and Propane is an established value whereas with pellet and biomass stoves there is no set standards of BTU output per unit of fuel so it would all depend on the brand of pellets or the RM of the corn (whichever the units are base lined with).

Reading manufacturers ads about their stoves, they always list the 'efficiency' in high percentage numbers but, how are those numbers arrived at and by whom and with kind of fuel?

With so many different extruders, extruding a vast mount of different wood stock, I keep thinking that advertised efficiency rating are just 'pie in the sky' advertising phooey. You have outfits like Somerset Hardwood Flooring that uses their forestry slash and excess trim from their flooring mill to make (extrude pellets to the extruder in White Pigeon, Indiana that uses scrap pallets for their feedstock as an examples.

Unlike NG and propane, there appears to be no baseline measurement for efficiency other than just tossing a figure out and sticking with that figure.

Just wonder who determines that percentage and what method is employed to arrive at that percentage and more importantly who or what does the first article testing?

Anyone know?

Kind of reminds me of the 'air wash' bs that manufacturers like to entice potential buyers with that in reality is just hot air (no pun intended).
 

monteville

Member
Nov 23, 2019
152
Dallas
It's not that hard to measure efficiency of a stove. You need standard pellets that you already know the BTU/lb.

Assume the stove always burns fuel lean (so there will be some O2 in the flue), which is probably true because EPA limits CO emission.

Burning a certain amount of pellets, measure intake air mass by an automotive MAF sensor, measure exhaust temperature and O2 concentration by wide band O2 sensor after a catalyst converter, you get the overall fuel-air ratio of the target stove.

From the temperature and the fuel-air ratio, you know how much BTUs goes out by exhaust, the rest of BTUs goes to the room.
 
  • Like
Reactions: tlc1976

stoveliker

Minister of Fire
Nov 17, 2019
1,959
Long Island NY
It's not that hard to measure efficiency of a stove. You need standard pellets that you already know the BTU/lb.

Assume the stove always burns fuel lean (so there will be some O2 in the flue), which is probably true because EPA limits CO emission.

Burning a certain amount of pellets, measure intake air mass by an automotive MAF sensor, measure exhaust temperature and O2 concentration by wide band O2 sensor after a catalyst converter, you get the overall fuel-air ratio of the target stove.

From the temperature and the fuel-air ratio, you know how much BTUs goes out by exhaust, the rest of BTUs goes to the room.
The point made was that your second sentence is not possible:
"there is no set standards of BTU output per unit of fuel so it would all depend on the brand of pellets or the RM of the corn (whichever the units are base lined with)."
 
  • Like
Reactions: SidecarFlip

SidecarFlip

Minister of Fire
Feb 7, 2010
5,273
S.E. Michigan
exactly. With so many different fuels out there I'd say it's impossible or highly unlikely obtain a set standard (BTU output), unlike NG or propane where it's common knowledge that a certain amount produces x amount of btu output.
 

DAKSY

Full Time RVer
Staff member
Dec 2, 2008
9,099
Wherever we're parked
Until ALL USA pellet manufacturers willingly adhere to the guidelines as dictated by the PFI,
their fuels are tested to those guidelines & the results are verified & documented,
there won't be any way to confirm what they say about their fuel rating is accurate...
 
  • Like
Reactions: SidecarFlip

monteville

Member
Nov 23, 2019
152
Dallas
Until ALL USA pellet manufacturers willingly adhere to the guidelines as dictated by the PFI,
their fuels are tested to those guidelines & the results are verified & documented,
there won't be any way to confirm what they say about their fuel rating is accurate...
We don't need all pellet manufactuers to adhere to the same standard, we only need to know the BTU/lb of the pellets we are testing with, it is enough to get an efficiency number,
We can assume similar efficiency with other pellets -- such as leaf pellets, stalk pellets, corn etc.
 
  • Like
Reactions: John Ackerly

stoveliker

Minister of Fire
Nov 17, 2019
1,959
Long Island NY
Nope
 

SidecarFlip

Minister of Fire
Feb 7, 2010
5,273
S.E. Michigan
Until ALL USA pellet manufacturers willingly adhere to the guidelines as dictated by the PFI,
their fuels are tested to those guidelines & the results are verified & documented,
there won't be any way to confirm what they say about their fuel rating is accurate...
Exactly correct and I said long ago that pellet extruders join the PFI (membership entails a monetary fee) so they can put the PFI certification stamp on their pellet fuel.

If they were all equal in BTU output as well as ash generation, we wouldn't have threads about what fuel is best and what isn't. Pellets are all over the place concerning quality and BTU output.

That might not be a concern for bulk users like biomass boilers in a commercial setting but it is a concern for residential users.

Good example is corn as a fuel source. Corn has to be at a specific RM to combust and when the RM varies, so does the BTU output per given quantity.
 

Ocelot

Member
Dec 27, 2010
87
Hudson Valley, NY
We don't need all pellet manufactuers to adhere to the same standard, we only need to know the BTU/lb of the pellets we are testing with, it is enough to get an efficiency number,
We can assume similar efficiency with other pellets -- such as leaf pellets, stalk pellets, corn etc.
That makes some sense, but in order for each stove tested to claim a certain BTU or efficiency, there would first have to be a standard or control pellet that they all used. I've gotten different pellet quality and heat output from the same brand in different production batches or year to year.
 

SidecarFlip

Minister of Fire
Feb 7, 2010
5,273
S.E. Michigan
Heat output is entirely dependent on the feedstock the extruder uses and that can vary from season to season and even month to month.
 
  • Like
Reactions: Ocelot

SidecarFlip

Minister of Fire
Feb 7, 2010
5,273
S.E. Michigan
Not something I'm overly interested in doing. Beside, I run a 66% corn 33% pellet mix.