P68 burning a bag of pellets in 7 hours

Well, it could be a few things. How big an area are you trying to heat? What was the starting temperature in the area you were trying to heat? A P68 is definitely capable of burning through over 3 bags of pellets a day if it needs to. You should have got a lot of heat out of it in those seven hours. If you did not get a lot of heat, then there might be a problem.

Can't speak to exact settings...but, you are using about 5.7 lbs per hour, which represents probably a little over 30,000 BTU per hour.

Since that stove claims it can run up to double that (which is probably a bit overstated), then 30K is a good middle range. Your house probably needs the heat due to heat loss factors, size, etc.

A pellet stove is still subject to the same "laws" as any other heat in terms of the number of BTU's needed to fill a certain space. I dislike all the generalizations about "I burn one bag every 14 hours", etc. because that really means nothing without a detailed heat loss study of the space being heated.

You did raise the temperature. How well your house is insulated, and how drafty (air leaks) it is will have a big effect on heating requirements. It does seem like a lot of BTU input to your pellet stove for that period of time.

One thing that seems to be unknown, as far as I can tell, if the heat exchanger efficiency of pellet stoves. I hear 80% all the time, but is it really? Do pellet stove manufacturers actually test there stoves for efficiency, or just make up some number that sounds good? How often do you have to clean a pellet stove's heat exchangers to maintain reasonable heat transfer? It would seem like if a pellet stove manufacturer claims a certain efficiency, they should have to provide proof.

Walls, windows, and air infiltration are going to be major factors.

Can you tell us the length and width of the house, how many floors, ceiling height, where in the house the stove is located, thickness of the walls and weather or not there is any insulation, the age and type of the windows and if there are any storm windows?

Or the firing rate of your central heating system?

Is this house a cape or is the second floor the same size as the first only with just 462 square feet finished?

Is any of the basement wall above ground, if so how much, and is the stove in the finished part of the basement?

I'm looking for the basement wall area here since the stove is in the basement.

snodays,

if you dont have any insulation on the concrete in the basement then the crete will be a heat sink...you will burn more pellets to get the house up to 70* because the crete is sucking it up.


mike

snodays700 said:

The stove is in the unfinished part of the basement.

Click to expand...

thats why

try standing some poly (styrofoam) insulation aginst the bare walls and see if that helps...the concrete is sucking up the heat

Put the stove upstairs and you will get more heat with less pellets. I bet a bag will last three times as long if the stove was upstairs on the first level and not in the basement.

Steveo said:

Put the stove upstairs and you will get more heat with less pellets. I bet a bag will last three times as long if the stove was upstairs on the first level and not in the basement.

Click to expand...

I have to agree. You are wasting a lot of heat down in the basement. It's going to be tough to get the heat up through the basement door and then circulated around to the rest of the house. Obviously you must not have had much of an option. But, if you can move it upstairs to the first floor, that would work best for you.

Webmaster said:

Can't speak to exact settings...but, you are using about 5.7 lbs per hour, which represents probably a little over 30,000 BTU per hour.

Click to expand...

Since wood pellets average about 8,500btu/lb then 5.7lbs/ hr translates into 48,450 btus.

Parrot Head said:

Webmaster said:

Can't speak to exact settings...but, you are using about 5.7 lbs per hour, which represents probably a little over 30,000 BTU per hour.

Click to expand...

Since wood pellets average about 8,500btu/lb then 5.7lbs/ hr translates into 48,450 btus.

Click to expand...

I think he was talking about BTU output of the stove. 30,000 would put it at 62-63% efficient, if we use your 8500 BTU per pound value. Harman would probably claim almost 40,000 BTU output with this BTU input. Their several factors that effect the BTU output. If a pellet stove ever does 80% efficiency, I think it would be under ideal conditions. My opinion is that the manufacturers just pull these numbers out of their A**. If their is proof, I take back what I said, otherwise, it is akin to lying.

Don't get me wrong, I like pellet stoves. Whatever their efficiency, they are the best cost option for some people, depending on what fuel they used for heating. They look nice too, as nice as a wood stove, and less work.

You have an interesting situation, if it were me I'd basically finish the unfinished portion of your basement with a foil faced foam board (as thick as you can fit and afford), foil towards the inside.

I also suspect that your central heating system might be in the unfinished portion of your basement. If that is the case then I'd look very closely at the chimney and its race along with the damper system on the central heating system as being a means by which heat can be escaping. You didn't mention the use of an outside air kit on the pellet stove. That will also help provided the Harmon has a closed combustion air path by not causing air infiltration for combustion air.

I'd also suspect that your walls could use additional insulation as you likely have more heat loss through those walls then you might think. I'll play with a heat loss calculator sometime in the next 24 hours and have some results for you (they will not be exact but will give a feel for what is going on).

As for the heat moving out of the basement and to the upper floors, there must first be enough heat left to move. You also need to understand that it will take time to basicly pull all of the air in your house (many thousand cubic feet) through the heat exchangers using the convection fan.

Parrot Head said:

Webmaster said:

Can't speak to exact settings...but, you are using about 5.7 lbs per hour, which represents probably a little over 30,000 BTU per hour.

Click to expand...

Since wood pellets average about 8,500btu/lb then 5.7lbs/ hr translates into 48,450 btus.

Click to expand...

I think that MIGHT be true in stove mode but not in room temp mode..in room temp mode that it is only gonna burn that amount at the start time or when it comes back from idle..I leave mine on manual so the fire NEVER DIES OUT..but it DOES eat a few more pellets...other than that I think the stove will autoadjust the temp output(btu) once it hits the desired temp..

sidenote:
the feedrate that I've seen makes NO difference in ROOM TEMP MODE ONLY...Harman designed this stove to feed itself what IT thinks is the best feedrate regardless of where YOU set it ...I haven't seen any dramatic difference in pellet usage with feedrates 6 or 1 in ROOM TEMP MODE ONLY..HUGE DIFFERENCE IN STOVE TEMP MODE though..
still keeps the house 70 and uses pellets in approx the same amount of time with ROOM TEMP MODE

so definetly if you plan on keeping it in basement COVER them walls and ceiling with something of a high R value..styrofoam will work but with an Rvalue below 4 not too efficient...unless you get the much denser and thicker style foam wall insulation with that shiny coating...it reflects the heat back

all these are my opinions which may prove to be false but if they are thats ok..I learn from my mistakes

snodays700 said:

I think I'm going try to bring the stove up stairs. I have a fire place in my living room I want to duct it up the chimney. Has any one tried to run the exhaust in through their fire place up the chimney ?

Click to expand...

My former neighbor did exactly that. Unfortunately, I can't just go over and ask him how it turned out or how he had it installed, it was also a Harman.

NOTE NOTE NOTE this poster disavows any relationship of these figures to the real world example under discussion.

Making a few assumptions I find that at 20 degrees you'll need 37,324 net btus to maintain 65 degrees a 5.7 lb/hr firing rate should be able to do that. Which would lead me to think your stove was about 80% efficient.

There are several areas that I improvised when plugging numbers into the calculator ... the first was the seasonal heating degree days figure since I didn't have your exact location. I used 7500 heating degree days, I also used the existing construction air infiltration exchange rate of 1/hr. I also had to figure out how your cape was configured. I used a 20% window coverage area for the walls. Based upon a design nominal average yearly low temperature of -20 degrees you need to replace 67,183 BTUs/hr to maintain 65 degrees on the coldest day of the year.

The areas of heat loss from high to low:

Air infiltration, window loss, wall loss, and lastly cap loss (attic). I suspect that the window and wall loss ranking will flip and the total heat loss would drop with additional information.

I didn't know much about your windows nor did I have a % of wall area covered by windows figure, so I used default values which may be incorrect in your case.

NOTE NOTE NOTE this poster disavows any relationship of these figures to the real world example under discussion.

Much more detailed information is needed to do a truly accurate heat loss calculation. This should be somewhat in the ball park but none the less it is based upon several estimates.

If the OP wishes something closer a PM with location data, window square footage and type, and information as to the layout of the top portion of the house would result in a recalculation.