New Owners of the Harman P68

mkmh said:

I told myself I was stepping away from this...but I guess I just love a good mystery!

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I have a feeling that this one is "some or all of the above" including the customer expectation, the weather, the lighter (and possibly faster heating) of the older stove, etc. etc. .....I think the dealer replaced the entire board (earlier in the thread?). It would seem that computer control and sensors would pretty much be able to "know" if something was vary wrong....i.e, if the exhaust was VERY hot, it would shut down the stove?

Confusing, for certain. GVA, too much heat coming out the stack and too little heat could mean the same thing! What I mean is that if the exhaust pressure (flow) is low, then it might be too hot, if it is way too much air coming through the thing (excess air), then it is low.

BTW, back during those old "in the field" tests, it was "excess air" which caused the low numbers of most stoves! The combustion numbers were fairly good.....but too much air (even at a low temp) ends up sending BTU's up the stack.

As is probably obvious, I am just poking around with these theories.

Webmaster said:

mkmh said:

I told myself I was stepping away from this...but I guess I just love a good mystery!

Click to expand...

I have a feeling that this one is "some or all of the above" including the customer expectation, the weather, the lighter (and possibly faster heating) of the older stove, etc. etc. .....I think the dealer replaced the entire board (earlier in the thread?). It would seem that computer control and sensors would pretty much be able to "know" if something was vary wrong....i.e, if the exhaust was VERY hot, it would shut down the stove?

Confusing, for certain. GVA, too much heat coming out the stack and too little heat could mean the same thing! What I mean is that if the exhaust pressure (flow) is low, then it might be too hot, if it is way too much air coming through the thing (excess air), then it is low.

BTW, back during those old "in the field" tests, it was "excess air" which caused the low numbers of most stoves! The combustion numbers were fairly good.....but too much air (even at a low temp) ends up sending BTU's up the stack.

As is probably obvious, I am just poking around with these theories.

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Well when running in stove temp (like they posted they have tried) The stove runs off 2 things..1st the ESP and this tells the board (2nd) what to do...
It does not care what the room temp is only what the exhaust temp is.(not to efficient)
Anyway if you have heat being blown out the flue then you are not burning efficiently..IE that heat is not going into the room..... Is it going out the flue and not into the room.......I dunno but that is why I am asking...
The dealer can plug into the stove and see what all the probes and board are seeing.
So if the Exhaust was very hot and the stove was still running through pellets could be the ESP is bad or the board (even though it has been replaced)
That is the ESP doesn't know that it is running hot therefore the board doesn't either....
He could also try disconnecting the outside air and see if the flames and performance changes. But I don't like to list 75 things to check when I (or others) can narrow it down to 10 things.......

I hear what you are saying Craig (BTW - thanks for the history lesson). But if the draft was set properly, would that not preclude the "heat up the chimmney" theory?

MySpecial, did the dealer set up the stove and do a draft test? Mine wrote the draft number down in the manual for future reference. Or have you decided to go to a different stove?


Cheers


Kenny

Whats a draft test and what does it measure?

I'm not sure I agree that the problem with the stove is that it is too big. At the lowest feed rate that should be about how much it burns....period. And at this low rate it should be fine. If it won't burn at this low rate than something is wrong with the stove.

BIH

BIGISLANDHIKERS said:

Whats a draft test and what does it measure?

I'm not sure I agree that the problem with the stove is that it is too big. At the lowest feed rate that should be about how much it burns....period. And at this low rate it should be fine. If it won't burn at this low rate than something is wrong with the stove.

BIH

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GVA and other can confirm, but I assume it measures "overfire" draft, meaning the excess draft when the unit is on? Too much might mean air going out the stack before it has been properly "squeezed" of it's heat by the heat exchange unit.

As to my guess about size, I'm looking at it from the point of combustion engineering.......maybe our resident expert (T_monter) who deals with this stuff can shed light, but it is my understanding that if we have a large power plant which works most efficiently at a higher firings, then we would lose efficiency if we turned it down. Any system is "tuned" to a certain "harmonic". I think you can get around it by properly slowing down combustion air and convection air, but only to SOME degree. Again, just a shot in the dark. A guess. I have been VERY wrong before, and I will be many times again (biggest example was my idea that chimney caps somehow hurt the draft, when they actually help it).

Since Craig asked me to weigh in on this one I'll give a few comments on stove size and efficiency as I see it from a combustion/thermodynamic perspective:

Everything that matters here is stack flow and stack temperature. Most stove "losses" are from heat leaving up the chimney. A smaller stove won't necessarily be more efficient if the flow + temperature leaving the chimney is higher.

I'm not wholly familiar with most pellet stoves, but unless the blower on them for the pellet pot has a variable speed drive on it to control the air entering the pot, the stove will use more air than needed on low fire and hence lose more heat up the chimney. A good pellet stove will use just enough air for complete combustion and to prevent clinkers, but not too much as to lose more heat up the chimney.

A larger stove may actually be more efficient if the pellet pot blower can be turned down. This is more a question about stove features and general design operation which I can't answer without more details.

Thanks, T.....

I think by nature (price, static pressure, noise, etc.) a low cost (manufacturers are very sensitive to parts cost) Pellet Stove blower can turn down - but not to virtually every level. In other words, it has some kind of range on it (Hearthtools and some other pellet heads probably know more about this)....

So would it be fair to say that you consider excess air to be more of a variable (or perhaps the only variable) - and NOT the fact that the same heat exchanger, firepot, auger, vent, etc. is used for 8,000 BTU or 50,000 BTU and is expected to be as efficient across that entire range?

Then the question is not "can" it possibly be done, but more of whether it is done in commercial products using stock components and having to deal with noise, hums, stalling (at very low speeds), etc.

The Harman board has a voltage adjustment which will vary the speed of the combustion blower. This is usually done at the install because line voltage varies from my home and yours, as does the venting configuration # of elbows length ETC.. Every home is different....
The board will also control what is called low and high draft. These correlate to the draft test #s that are checked at install...

GVA said:

The Harman board has a voltage adjustment which will vary the speed of the combustion blower. This is usually done at the install because line voltage varies from my home and yours, as does the venting configuration # of elbows length ETC.. Every home is different....
The board will also control what is called low and high draft. These correlate to the draft test #s that are checked at install...

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I have a XXV and I am interested in the microprocessor the dealer can plug into my main controller board.
Is this just a diagnostic tool or can adjustments be made to the high and low draft level? (ie combustion blower)

It's just a diagnostic tool. It gives a visual representation of what the Probes are reading, and what he board is doing.
For the Comb blower adjustment you need a magnehelic gauge.
The DDM is a dealer only item, The mag can be purchased by the avg Joe.

Any sugestions about the magnehelic gauge?

Not on settings, but I bought one on eBay......cheap. You have to make certain to get one in the range that you need (usually the lower ranges)

1,500 sq. ft, house and I usually burn 1 3/4 bags for 24 hours to keep the place 78 degrees dowstairs, and that is 20's during the day and low teens at night. I took me a long time to get the temp probe set to the correct location and doodle with the controls, but now I just set it and forget it. Two bags seems like a lot, until you check the price of oil.

Well, I may be spending less than that (on NG), but my house certainly is not 78. Not even 68. More like 64. Hey, it feels warm when there is no draft. I don't wear short sleeves during the winter either.....and about 6 blankets - not because of the cost, by the wifey does not like to hear the noise of the furnace fan, so she turns it down so far at night that is does not go on (house holds heat pretty well)...

Ah, that's what marriage is about - the ability to change for someone else!

BTW, just seeing how far we can beat this topic to death. Our original poster will be long into he new stove (the harman replacement), and we will still be trying to figure it out (for the next person).

Hello everyone NewB here
I am running a P86 for its 3rd season right now. 3000 sq ft colonial with vaulted 2cd foor to 3rd floor master bedroom. I use 6 tons per season, and easily burn 2-2.5 bags a day in the cold of winter. Much less fall and spring. The monitors everything on its own,it certainly does not run me, it runs itself. Maybe yours is possesed?
I know my stove has saved me alot of money in oil, and would get another in a second.
Try keeping your probe sensor higer on the wall in the warm air. Feed rate 1, room setting on dial and room temp at lowest setting 50-55 degrees. I can not imagine the stove would burn hadly anything at those settings.
Regards
Dino

You said the dealer installed a new circuit board. Did the dealer check the draft setting after he had done this. The draft is set to conditions at the factory and should be checked and adjusted according to your house. I'd have the dealer check the draft.

btw.......I burn a Harman Advance for 4 yrs now and can get a day and half from a bag of pellets.

My last stove was a Harmon and it use to inhale pellets too and I was always cold. My new house has a Quadra-fire cb 1200 and it uses less pellets and I'm warmer. My cousin just bought a Harmon XXV and there going through 2 bags a day.

The last three posts here clearly show the folly of listening to other people when it comes to exactly what your stove (pellet or wood) should do!

One of them says 2.5 bags a day, and the other says 3/4 of a bag a day (more than a 300% difference). Another compares the results in one house to the results in another.....

I really do caution folks to have realistic expectations and not to "compare" (and I use that with quotes because the word is not accurate in these cases) one thing to another!

Remember that even in tests with mind-altering drugs......30% or more of people become "changed" by sugar pills! The placebo effect, or in this case the "it was a warm day, I spent $4K, and my neighbor said so" effect, is NOT an accurate way to measure something! I know I keep repeating this, but perhaps it will help some customer avoid disappointment!

Not to say that all posts are not accurate for THAT particular person, room, house and stove, but only urethanes strikes me as somewhat realistic in terms of whole house heating. You need to burn pellets to produce heat, and at a bag each day you are producing the equiv of less than two plug-in electric heaters....not much in this weather in the northeast!

Hey web,

I hear what your your saying. Everyone is going to have different results. I also think people used to a wood stove assume a pellet will do the same. I use about a bag and a half on very cold days. I like being warm and I can't heat my house this cheap with electric. When i had my Harmon it took a long time to get it just right.

I also must state that I have never burned a pellet stove before. Grew up buring wood, but opted for pellets due to ease of use , and cleanliness. Today it was around 15 degrees for a high, and I burned 1 bag in 12 hrs. House stays at 72 degrees on the main floor, high 60's on the second, excpet for our mater bedroom, since that is vaulted to 3rd floor. Our bedroom is a bit cold, mid 60's. 3rd floor is alot warmer since thats where all the heat goes, we have fans to move the air, but it stays cold. Wife helps make up the difference grrrrrrrr.
What I dont understand is if the purpose of the stove was to heat 1 or 2 rooms, why did let youself be talked into such a big stove? That being said I am sorry that it hasnt worked out for you, and I wish you the best with whatever direction you choose.
Dino

urethane dino said:

What I dont understand is if the purpose of the stove was to heat 1 or 2 rooms, why did let youself be talked into such a big stove?
Dino

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I was thinking the same thing reading through this post. Buying a P68 to heat one room is like buying a 4 bedroom, 3500 SF house for 1 person.

I'm all for being a little excessive. Better to buy a slightly bigger stove than get a smaller one and find out it can't heat your whole house. I probably could have survived with a P61, but spent a little extra money on the P68.

HELLO - im new here and a new owner of the P68 Harmon- if anyone hears a high pitched sqeeeeeeeeeek that resonates - thru the whole house, i just found out today what was doing it- it was the auger, from the factory they tightend one side of it down but not the other , and it must have loosend up and started the squealing . Ive only had it for six days! so i hope that is IT for the problems- we are using three bags of pellets per day too- but its at least seventy two in here , not a large house but a drafty one. Anyone got any better suggestions on settings since i dont know what im doing ? im a set and forget it kind of person also-so far its working except for the noise -but thats corrected now too . Its running MUCH quieter now then when they installed it- i have a great dealer - he came out the same day -today- and fixed it- he tried replaceing the motor but it was the auger itself making the noise.

I have a couple penny's to add here. Harman P68, in MN., heating 1728 sq ft upper floor of split level, 15 ft vaulted ceiling over half of that, unfinished lower level, uninsulated crawl space under unheated entry way. House is 6 yrs old and sits north south, stove is in south east corner of the living room. Direct exhaust vent out south wall, air intake on east wall. Stove settings are stove temp., feed @ 2 & 1/2, temp @ 72, blower @ low/med setting, 3rd heating season with stove. I can maintain temp of 72-74 degrees (on wall thermostat for furnace bout 20 ft from stove down main floor hallway) burning 40#s a day. My P68 will do this for a 2 week period 24 hours a day before I shut down for a good cleaning! I spend about 30 minutes cleaning and my routine is very thorough! I do make small adjustments to settings from different pellet brands as I am still learning this stove. I also run a 4 & 1/2 gallon table top humidifier and fill it every 48 hours maintaining a 30% humidity level. The only dislike I have is that I have a thick layer of frost on the intake pipe from the sheetrock to the back of the stove. Air intake pipe looks to be aluminum flex pipe. Sorry to hi jack this thread but could I use a pvc pipe for air intake? I am real happy with my Harman and will not hesitate to consider their products when I finish my lower level!

KJF470,
I did what one member suggested and bought some flexible alluminum looking insulation from Lowes and wrapped it, then duct taped it si itd stay on . You dont really see it seeing its behind the stove, and its kept the condensation from dripping on the drywal, and floor.

I believe Ya'all have figured it out. Big stove consumes more pellets period. Small stove, smaller amount consumed. She needs a smaller stove. I watched my stove which is rated at 45,000 BTU an hour and found that the auger motor is not variable speed. Its a timed movement. So on low, my stove auger runs 3 seconds on and 12 seconds off. On medium, the auger runs 3 seconds on and 8 seconds off. On high, the auger is on 3 seconds and 4 seconds off. I have found that my stove on high, producing 45000 BTU consumes one bag every 8 hours with about 8 ounces of pellets left in the hopper. All most out. So the difference from high and low is three times the amount. Period. Its all about auger speed. On low, it will consume one bag in 24 hours. Not rocket science. The setting for draft are for making the stove more efficient in producing BTU. NOT using less pellets. The only way the stove will use less pellets is to find the optimum location for the thermostat. Once it is satisfied the stove should stop, resulting in less pellets consumed. If the room is poorly insulated, then it won't be long before the stove cycles. She needs a smaller stove. In my opinion, there is nothing wrong with that Harman. My logic, take a car with a V8 engine in it, verses a car with a 4 cylinder in it, Lets not drive them up and down hills, just setting there idling. Which one is going to use more fuel?