First year pellet consumption seems high

tjnamtiw · Jan 1, 2015

F4jock said:
Yeah but won't need ducting if he moves it upstairs.

Yea, but won't be able to EVENLY heat his entire home with it upstairs. He said he should have gotten a furnace. He realizes an upstairs installation would not suit his house or his expectations. That's a plus that someone actually accepts the fact that these space heaters won't evenly heat a house like his.

acammer · Jan 1, 2015

Trickyrick said:
Just to clarify when a stove is rated at 61000 btu per hour that is the btus of pellets it chews through. So 61,000 actually amounts to 7.5 pounds of good pellets an hour. Due to many factors heating appliances tend to be rated in the amount of fuels it eats not what you get our in your living space...

In some cases, you're correct. As you stated a lot of stove manufacturers advertise a BTU rating based on input BTU - how much fuel you put in. However, not all manufacturers do this, and that's why you need to check the manual for specifics. In the case of the Harman P61a the manual clearly states a BTU output of 61,000 (hr). No efficiency or feed ratings are stated there, so you have to make an intelligent guess at one to get to the other. It's confusing because on a few places on their website the list the same stove with an input rating of 61,000 BTU. I had to make a choice, but in my opinion it's much more likely that the manual is correct and the website is wrong - they even have a disclaimer on the specs page of the website to refer to the owners manual for complete specifications. My PAH is the same way, it's advertised by its output rating, 25,000 BTUs. Fortunately, my manual also has listed the feed rates, and efficiency - and shockingly enough all the numbers match up like they should.

At any rate, like I said before, if you're getting 61,000BTUs out you need to put in 82,000BTUs at 75% efficient - 10lbs/hr. Really, if the owner chimes in an lets us know how many bags a day he goes through a full day of wide open running, we could confirm/deny some of this. I really have to question the 85% efficiency number too - I'm sure if Harman was able to get that kind of performance out of their stove they would be praising that number all over the place. In my stove research I did when shopping I found a lot of manufacturers don't post their efficiency. The one's that do are usually the strong performers with regards to efficiency and usually around the 75-80% range. I gave Harman the benefit of the doubt in my calculation and gave a pretty good number - I don't recall seeing many stoves at all above the 80% mark when I was actively shopping - and those that were rated about 80% were highly touted as being such.

SidecarFlip said:
Snowy... Thermal induced stress comes from expansion/contraction cycles, not maintained heat. Get 'er hot and keep 'er hot is just as good as getting her warm and keeping her warm. Really no difference so long as you don't exceed the design parameters (like I inadventerntly did because my stove allows very flexible inputs that most stoves don't.

Besides, my glass is always clean or a light white haze....

You got my 100% agreement there - heat cycles are what kills stuff in general, not operating temp (as long as the device in question does not exceed a maximum operational temperature.) We'll see in a few years if the door still shuts tight on my stove!

White haze indicates a clean hot burn, and a nicely tuned stove!

chken · Jan 1, 2015

acammer said:
In some cases, you're correct. As you stated a lot of stove manufacturers advertise a BTU rating based on input BTU - how much fuel you put in. However, not all manufacturers do this, and that's why you need to check the manual for specifics. In the case of the Harman P61a the manual clearly states a BTU output of 61,000 (hr). No efficiency or feed ratings are stated there, so you have to make an intelligent guess at one to get to the other. It's confusing because on a few places on their website the list the same stove with an input rating of 61,000 BTU. I had to make a choice, but in my opinion it's much more likely that the manual is correct and the website is wrong - they even have a disclaimer on the specs page of the website to refer to the owners manual for complete specifications. My PAH is the same way, it's advertised by its output rating, 25,000 BTUs. Fortunately, my manual also has listed the feed rates, and efficiency - and shockingly enough all the numbers match up like they should.

At any rate, like I said before, if you're getting 61,000BTUs out you need to put in 82,000BTUs at 75% efficient - 10lbs/hr. Really, if the owner chimes in an lets us know how many bags a day he goes through a full day of wide open running, we could confirm/deny some of this. I really have to question the 85% efficiency number too - I'm sure if Harman was able to get that kind of performance out of their stove they would be praising that number all over the place. In my stove research I did when shopping I found a lot of manufacturers don't post their efficiency. The one's that do are usually the strong performers with regards to efficiency and usually around the 75-80% range. I gave Harman the benefit of the doubt in my calculation and gave a pretty good number - I don't recall seeing many stoves at all above the 80% mark when I was actively shopping - and those that were rated about 80% were highly touted as being such.

You got my 100% agreement there - heat cycles are what kills stuff in general, not operating temp (as long as the device in question does not exceed a maximum operational temperature.) We'll see in a few years if the door still shuts tight on my stove! White haze indicates a clean hot burn, and a nicely tuned stove!

Wow, I assumed all the mfrs used input BTUs. Learn something new every day.

SidecarFlip · Jan 1, 2015

Unlike gas appliances where the AGA sets the standards that a manufacturer can advertise under (incidentially I worked at AGA Labs for a couple years testing and certifying gas appliances), solid fuel / biomass stoves and boilers are pretty wide open (other than being certified as safe by Warnock Hershey (the equivalent of AGA for non-gas appliances), so it pays to read the fine print and not use the owners manual as fire starter.....

jayman81 · Jan 1, 2015

Im at around 120 bags used so far heating from my finished basement. Mind you I'm 3000 sq and the stove runs constantly maintaining a basement temp of 76F. Stays a nice 72 on the main level with some assistance from the LP furnace at times.

I wasted a bit at first getting the new stove running like I wanted and tried a bit too hard getting it to heat my big house at all times. Its a space heater and that's how I treat it now but it does provide supplemental heat which is a big bonus. In the end I save money.

Nothing ducted like OP. Harman P68.

woodmakesheat · Jan 1, 2015

chken said:
Wow, I assumed all the mfrs used input BTUs. Learn something new every day.

I think they do. I believe that the P61A is 61k input BTUs and that the only reason they don't show output is because they don't have to due to stove is not EPA certified.

Witness from web site:

And from P43, P61A, P68 manual:

So if the P43 puts out 32163 BTU/hr with 43K input, then the efficiency is 32163/43000 = 75%

Assuming similar efficiency of similar big brother stove, P61A, it's output is 61000*.75 = 45.8k BTU/hr.

Even 45.8k seems like a lot for a stove that weighs just 249 lbs. My 350lb CPM-10 puts out 25k BTU/hr and it gets pretty hot, no wonder the P61A needs 3x the wall clearance - wouldn't even fit in my house.

acammer · Jan 1, 2015

woodmakesheat said:
I think they do. I believe that the P61A is 61k input BTUs and that the only reason they don't show output is because they don't have to due to stove is not EPA certified.

Witness from web site:

And from P43, P61A, P68 manual:

So if the P43 puts out 32163 BTU/hr with 43K input, then the efficiency is 32163/43000 = 75%

Assuming similar efficiency of similar big brother stove, P61A, it's output is 61000*.75 = 45.8k BTU/hr.

Even 45.8k seems like a lot for a stove that weighs just 249 lbs. My 350lb CPM-10 puts out 25k BTU/hr and it gets pretty hot, no wonder the P61A needs 3x the wall clearance - wouldn't even fit in my house.

So, there are some problems here - you're calling the specification in the manual (32,163/hr for the P43 and 61,000/hr for the P61a) an output specification in the case of the P43 and an input specification on the P61a. I think that's faulty - either that specification is output, or input. It's listed as output, that's what it should be. I agree that the website lists 61,000BTUs as the input specification for the P61a, but the website also says to refer to the owners manual for more details on the specifications.

Now, to further twist this, if we look at what Harman says each stove is capable of in square footage it looks like you're 46k output BTU is about right on. The P43 has an output of 32,163, if we divide that by 2,400sqft that's 13.4 BTU per sqft. Multiple that by the 3,500sqft that the P61a is rated for and that's 46,904 BTU, right around 61000 input BTU at 77% efficient.

So, in short, there may be something to the input vs output argument here. I think we can certainly say that Harman's manual isn't very clean, it lists an output BTU that seems to actually be the input BTU, at least by the square footage figures provided. If we say the P61a's input is 61,000BTU, then that's a feed rate of 7.4lbs/hr. That would burn 177lbs a day, 5,310lbs a month. So getting back to the original post, and a thoughtfully researched and discussed result - 3 tons in 6 weeks is completely in range for normal consumption based on the stove type and understood usage of near full power continuously.

SmokeEater · Jan 1, 2015

SidecarFlip said:
Is your fluid storage all contained within the unit/plumbing or is there a bulk storage d/a tank?

I have a 100 gallon Smart buffer so there's over 150 gallons of water in the system.

reeltime · Jan 1, 2015

SmokeEater said:
I have a 100 gallon Smart buffer so there's over 150 gallons of water in the system.

reeltime · Jan 1, 2015

Hearthstone heritage center of house 2100 cape wide open so far 65 bags 25 bags of okie golds and 40 Okies firs house 73 the 2 additions either end of house one end sunroom 68 the other end den 68 2 fans upstairs 2 bedrooms 1 bath doors open 2 inches 68

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First year pellet consumption seems high

tjnamtiw

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acammer

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chken

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SidecarFlip

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jayman81

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woodmakesheat

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acammer

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SmokeEater

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reeltime

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reeltime

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