How do they measure burn times?

DeWoodBurner said:

I'm a newbie to the pellet world and I recently installed a lennox montage. The manufacturer says 15-37 hours with a full 50lb hopper. Last week when the temps dropped around here in the 20's I had to run the stove full bore to keep up which I expected but I'm lucky if I get 10 hours on a full hopper. Does this seem right? I'm burn American fiber premium pellets which seems to be a decent pellet.So do they rate the burn times on the low or medium setting?

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Lets see I suspect the 15 is on the highest usable firing setting (which may or may not be the high firing rate) and the 37 on the lowest possible firing rate and these figures only hold for the mythical test pellets.

Take a look at the density information in Jay's testing here: https://www.hearth.com/econtent/index.php/forums/viewthread/50101/ , https://www.hearth.com/econtent/index.php/forums/viewthread/42511/ , and here https://www.hearth.com/econtent/index.php/forums/viewthread/60581/ , then ask yourself the all important question. Is there a weighing station in the feed system and exactly how does the volume of that hopper translate into weight?

they (Lennox) may calculate this with the auger trim turned all the way down....or the test pellets may have been on the longish side. I'd be less concerned with how long the stove runs, and more concerned with whether or not its doing what you ask it to do...heat wise. Usually these numbers aren't actually based on a test run, but a culculation of the volume of the hopper in relationship to the average mass of pellets being fed during auger cycles...its a "loose" type of science....like vehicle milage.

So what your saying is that your burning aprrox. 2.5 - 3 bags in a 24 hour period to heat your house, where the manufacturer says you should get approx. 30 hrs out of 2.5 bags, thats a 10 hr difference and could be related to pellet length and density, or feed and air settings, but is most likely due to underestimated pellet usage... Lennox bought out Whitfield, so that fact that they underestimate usage is no big news to me. They must have had some magical pellets or been on some serious drugs when they printed their specs. for my whitfield. Big bold print in their brochure said 80 lb hopper for up to an 80 hr burn time, which if you do the math equates to 1 lb / hr. or 40 hrs. / bag. I tried every single trim position for air and feed, and probably tried 8-10 different pelelt brands and I averaged right around 24 hrs. / bag on the lowest heat setting, and the best I ever did was 28-30 hrs / bag, longer hardwood pellets lasted the longest, shorter softies burned and fell through the grate faster. As much as I loved my old whitfield stove that fact to this day still bothers me, no where close to being accurate and honest in their specs.

There is always a large difference in burn times between fireing a stove on setting one versus setting five.

The difference is similar to having a pile of logs and loading them one log at a time or five logs at a time and properly adjusting your burn air.

You'll get more heat into the room on five than one for any given firing time.

On high my stove is rated to burn 5 lb per hour, in 10 hours 50 lbs. I would think on high yours would be about right.
It's on a thermostat so it never runs steady, even with zero temp the other day.

You need to find the lowest density pellet you can, that might mean your 40 lb bag of pellets might fill your 50 pound hopper to overflowing.

Keep in mind the laws of thermodynamics are at work also.. The larger the temperature differential between outside and inside
will result in heat moving faster towards the colder outside air and more energy (pellets) to replace those heat losses.

So depending on the difference in temperatures, their claims could be justified or even bested if it's only 50 degrees out.

Hailfire

TOTAL CRAP, I love my pellet stove dearly, but like I said before most manufacturers claims are BOGUS and 14 years later it still bugs me. I did a lot of shopping to replace my stove and I saw a claim on Harmans site that in maintenance mode, meaning the lowest possible flame to keep the stove running without cycling on and off " the accentra burns .7 lbs / hr. and I think they said the XXV was 1 lb / hr., which i haven't been able to test yet, and even so with the whitfield I had the air trimmed down, the feed trimmed down the damper closed off and there wasn't any chance in a million years it could burn 1 lb. / hr. i had it so low it was like a candle burning in the pot...

hailfire said:

Keep in mind the laws of thermodynamics are at work also.. The larger the temperature differential between outside and inside
will result in heat moving faster towards the colder outside air and more energy (pellets) to replace those heat losses.

So depending on the difference in temperatures, their claims could be justified or even bested if it's only 50 degrees out.

Hailfire

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Not applicable, those burn times are based upon manual firing not on a thermostat.

AWF pellets don't have a very good rep here...try another pellet