How to run your pellet stove wide open!? Harman stove but probably applies to others

[davidfieldsnwa]

Ok team - my Harman P43 is great and I‘ve read all the stickies in the forum about how to use the controls. I’ve also amused myself by reading way too many posts on this forum and I’ve got a new question for you. I’ve also watched a bunch of YouTube videos. Its cool how pellet stoves can be in modes that flex the heat up and down and I believe I’m understanding the basic mechanics of my stove. I’m also keeping my stove fairly clean thanks to all the input on this forum.

Here’s my question:

Lets say my house is cold or the outside temp has decreased dramatically. The stove is either off or at a low settIng. I’m cold! I want to manipulate my stove controls to enter “turbo mode” where I’m accessing the full heating potential of my stove for a period of time. In this scenario, for a little while, I’m not interested in saving pellets or being efficient - I want the max heat output per unit time! After my house is feeling more comfy, of course I’ll reset the controls to my nice room temp/stove cycling modes. (yes I understand that if I’ll keep it on and in those modes all the time then I won’t have to use turbo mode because the area will be at a more constant heat).

Now because I have read this forum way too much, I’ve seen a lot of posts where people make comments about “melting your stove” - ie - maxing things out and using multiple pounds per hour of fuel. That’s what I want! The max of everything!

So the question is - what combination of settings is “turbo mode”????! Obviously increasing the left dial (either temp or 1-7) to max is a given. Would I have more rate of change in heat output if I briefly raised my feed rate dial ( from normal 3.5ish to much higher?). I assume increasing the distro fan to max only helps. Would I have a higher theoretical output in Room Temp or Stove Temp? I believe that if I’ll turn off the auto ignite to manual that might help too - that setting is a bit confusing since if the stove runs hard it won’t be entering maintnance burn.

I look forward to your answers!

 

[Washed-Up]

When I want big heat quick out of my P61, I switch it to stove temp and feed rate at 4-5, doesn’t take long

Currently -21c with a possible -40c/f on the way

 

[guatamican eye fake]

P61 as well. Same approach as washed up.
Doing a complete clean right now, getting ready for some Minnesota cold

 

[tiger]

Currently -21c with a possible -40c/f on the way

Wow, close to the point where the electrons are going around the nucleus slowly enough to count the revolutions?

 

[SciGuy]

Ok team - my Harman P43 is great and I‘ve read all the stickies in the forum about how to use the controls. I’ve also amused myself by reading way too many posts on this forum and I’ve got a new question for you. I’ve also watched a bunch of YouTube videos. Its cool how pellet stoves can be in modes that flex the heat up and down and I believe I’m understanding the basic mechanics of my stove. I’m also keeping my stove fairly clean thanks to all the input on this forum.

Here’s my question:

Lets say my house is cold or the outside temp has decreased dramatically. The stove is either off or at a low settIng. I’m cold! I want to manipulate my stove controls to enter “turbo mode” where I’m accessing the full heating potential of my stove for a period of time. In this scenario, for a little while, I’m not interested in saving pellets or being efficient - I want the max heat output per unit time! After my house is feeling more comfy, of course I’ll reset the controls to my nice room temp/stove cycling modes. (yes I understand that if I’ll keep it on and in those modes all the time then I won’t have to use turbo mode because the area will be at a more constant heat).

Now because I have read this forum way too much, I’ve seen a lot of posts where people make comments about “melting your stove” - ie - maxing things out and using multiple pounds per hour of fuel. That’s what I want! The max of everything!

So the question is - what combination of settings is “turbo mode”????! Obviously increasing the left dial (either temp or 1-7) to max is a given. Would I have more rate of change in heat output if I briefly raised my feed rate dial ( from normal 3.5ish to much higher?). I assume increasing the distro fan to max only helps. Would I have a higher theoretical output in Room Temp or Stove Temp? I believe that if I’ll turn off the auto ignite to manual that might help too - that setting is a bit confusing since if the stove runs hard it won’t be entering maintnance burn.

I look forward to your answers!

David,
Having the stove set on auto ignite will not lessen your maximum eat output. Distribution fan on max will increase it as will turning stove temp to max. The stove will probably hit the max ESP will allow at a feed rate of 4.5 or less so turning it up higher will likely not have any affect. You ought to find that the stove throws a good deal of heat set up that way. If not, there's a problem.

Hugh

 

[SidecarFlip]

One thing to keep in mind is that you won't 'melt your stove by running at maximum feed for hours on end, but you will warp things inside the firebox because your convection fan cannot strip the heat from the firebox fast enough and the end result will be warping of internal components that can adversely impact operation.

A short duration is ok, continuously over a period of hours or days in not ok. No matter who much fuel you put to it, it will only give you X numbers of BTU output, limited by the CFM of the convection blower.

How it plays. You don't drive your car with your foot to the floor constantly, don't drive your stove with your fuel rate maxed out either.

Warping internal components from too much heating can be a bugger to fix and if you compromise the firebox, the unit might be junk. Been there and did that but was able to correct the issue because I'm an accomplished welder-fabricator and I have the tools to do it. Was it easy. No, it wasn't and I learned a valuable lesson and that is, don't run any stove balls out for extended periods of time because bad things can and do happen.

Remember. all these biomass stoves are space heaters and not designed to heat an entire house comfortably. The only exception to that would be a pellet furnace running in conjunction with an existing central heat plant.

it's false economy to rely on a biomass stove as a sole source of heat because it's not. If you do, at some point you will be surely disappointed.

Once feature of the unit I own is I can custom program all the algorithms that control fueling rate, combustion air rate and convection fan speed in any of the pre selected parameters, the primary reason I purchased it in the first place because I want the ability to combust any pelletized biomass.

I've combusted pellets, field corn, untreated seed corn, cherry pits, switchgrass pellets, straw pellets and dry hay pellets and they all require specific fueling parameters.

I even have my own extruder which allows me to play with various fuels. I think next year I'll make some pelletized ground coal and see how that burns.

Burn on but do it with discretion or you'll compromise your unit, maybe fatally.

 

[guatamican eye fake]

You can run a bixby wide open hour after hour with no problems. It helps there distribution blower is 230 cfm or there about on max.

 

[SidecarFlip]

You can run a bixby wide open hour after hour with no problems. It helps there distribution blower is 230 cfm or there about on max.

Think I'd be a bit more discretionary about a no longer built antique.

 

[railfanron]

Sidecar you technically can't over heat a Harman because it's output is limited by the exhaust sensing probe (ESP). It has no snap discs in it to control distribution fan cycling or hi temp shutdown. This is all controlled by the ESP.
I don't know exactly what the original poster is after but from my experience a P series can run at maximum output in any mode. It depends on where you set the controls. If your running room temp auto and have the temp set to 85 and the feed rate set to 4 and the room temp is only 70 the stove will run at close to maximum output till the room reaches its intended temperature. If the ESP senses the exhaust temperature getting to hot it will throttle the feed rate back to compensate. As the room temperature gets close to the thermostat setting it will also throttle back for a "Soft" shutdown. In this cold weather my stove is running at a feed rate of 3 1/2 or 4 and when it starts up it will run very close to maximum for a few minutes until the ESP temp reaches maximum and then it will throttle back a little and run until the thermostat puts it in shutdown mode.
Ron

 

[guatamican eye fake]

I've heard of over firing a wood stove but doesn't seem likely in the pellet stoves I've owned.

 

[SidecarFlip]

Sidecar you technically can't over heat a Harman because it's output is limited by the exhaust sensing probe (ESP). It has no snap discs in it to control distribution fan cycling or hi temp shutdown. This is all controlled by the ESP.
I don't know exactly what the original poster is after but from my experience a P series can run at maximum output in any mode. It depends on where you set the controls. If your running room temp auto and have the temp set to 85 and the feed rate set to 4 and the room temp is only 70 the stove will run at close to maximum output till the room reaches its intended temperature. If the ESP senses the exhaust temperature getting to hot it will throttle the feed rate back to compensate. As the room temperature gets close to the thermostat setting it will also throttle back for a "Soft" shutdown. In this cold weather my stove is running at a feed rate of 3 1/2 or 4 and when it starts up it will run very close to maximum for a few minutes until the ESP temp reaches maximum and then it will throttle back a little and run until the thermostat puts it in shutdown mode.
Ron

Mine don't have that and far as I'm aware none do but the Harman. I do know that running the custom algorithms I do, I can kick the stove into an overheat shutdown without even running it at maximum PPH feed. About the maximum I can run is notch 6 on corn. After that it gets touchy and I did warp the front panel on the firebox some years back when fiddling with the settings and that was on pellets, not corn. Corn has a higher btu output compared to pellets at the same weight ratio.

 

[SidecarFlip]

You can run a bixby wide open hour after hour with no problems. It helps there distribution blower is 230 cfm or there about on max.

I'd kind of like Rona to chime in on this. He's an old time Bixby owner from the old IBC forum and he's on here.

 

[Ssyko]

The big difference is if the stoves firebox is made of sheet steel they can be damaged by overfireing. But a stove firebox that is cast they do not tend to warp. I will get some pics of the frankenstove big-e, its been overfired a few times and the back wall is pretty bad. I neever had a harman so i can only speculate it is constructed like a cast wood stove. They will handle more high temps in the firebox than any pelletstove.

 

[SciGuy]

Corn has a higher btu output compared to pellets at the same weight ratio.

Flip,
That's not my understanding. https://extension.psu.edu/burning-shelled-corn
Bone dry corn only has an energy content of 8000 to 8500 at the most BTUs per pound so your 12% moisture corn has an energy content of 88% of that i.e. a maximum of 8500 X .88 = 7480 BTU/lb not counting the energy needed to drive off the .12 lb of H2O per pound. Most pellets I burn range between 8000 and 9000 BTU's per pound. There's bushels of misinformation out there regarding corn's BTU content

Hugh

 

[rickwai]

Flip,
That's not my understanding. https://extension.psu.edu/burning-shelled-corn
Bone dry corn only has an energy content of 8000 to 8500 at the most BTUs per pound so your 12% moisture corn has an energy content of 88% of that i.e. a maximum of 8500 X .88 = 7480 BTU/lb not counting the energy needed to drive off the .12 lb of H2O per pound. Most pellets I burn range between 8000 and 9000 BTU's per pound. There's bushels of misinformation out there regarding corn's BTU content

Hugh

With that being said, I burn straight corn to heat my 1600 SF home with a St Croix. I have it on a tstat so it goes from 1.7 lb/hr on idle to 3.1 lb/hr when calling for heat. 12,750 btu and 23,250 btu. I keep the house at 72 or above, and the stove has no problem. If it gets down to single digits or below and the wind is ripping that is a different story. But that dont happen here much. I typically burn about #50 lb per day give or take.

 

[SciGuy]

With that being said, I burn straight corn to heat my 1600 SF home with a St Croix. I have it on a tstat so it goes from 1.7 lb/hr on idle to 3.1 lb/hr when calling for heat. 12,750 btu and 23,250 btu. I keep the house at 72 or above, and the stove has no problem. If it gets down to single digits or below and the wind is ripping that is a different story. But that dont happen here much. I typically burn about #50 lb per day give or take.

Burning corn will certainly put out a good deal of heat......just not quite as much as an equal amount of quality wood pellets. One doesn't need to worry that they'll "melt their stove down" if they move to burning an equal number of pounds per hour of corn as they have with pellets. The difference in heat content is fairly small but in favor of wood pellets. One other thing to remember is that Harman and everyone else is talking about "input" BTUs as opposed to output BTUs. Most of the manufacture's claims of efficiency run on the order of 75% to low 80 something percent. They all have to be taken with a grain of salt. I suspect few stoves actually deliver more than 75% thermal efficiency unless perfectly clean and run with the distribution blower maxed out and draft ideally set. So the house is probably only receiving about 3/4 of the input BTUs on a good day. The other 25% is being blown out the vent pipe.

YMMV,

Hugh

 

[mtnbiker727]

Lets say my house is cold or the outside temp has decreased dramatically. The stove is either off or at a low settIng. I’m cold! I want to manipulate my stove controls to enter “turbo mode” where I’m accessing the full heating potential of my stove for a period of time. In this scenario, for a little while, I’m not interested in saving pellets or being efficient - I want the max heat output per unit time! After my house is feeling more comfy, of course I’ll reset the controls to my nice room temp/stove cycling modes. (yes I understand that if I’ll keep it on and in those modes all the time then I won’t have to use turbo mode because the area will be at a more constant heat).

There's a VERY common misconception that turning your heat source all the way up (no matter what type of heat source it is) will warm the house up quicker. The stove/furnace/heat pump, etc. can only burn as hot as it can burn. They're all configured to burn at a high rate when the demand for heat is there and then throttle down when the target temperature is reached. Turning the thermostat up higher than the temperature you want doesn't mean it will get warm faster, it just means it will burn at full tilt longer if you forget to turn it back down.

Having said that, obviously there are several settings on the pellet stove aside from just temperature....

Set the temperature you want the room to be in Room Temp mode, set your pellet feed to 4 (the default) or maybe more, turn the fan on as high as it will go, and let it get there by itself. It'll burn hot and heavy, and then once it reaches the temperature you've set, the stove will slow down and then try to maintain the temperature you've set.

Remember: the pellet feed rate is the MAXIMUM the stove will use... if it doesn't need that many, it won't use them.
Also remember: If you set your feed rate too high, it could throw unburned pellets into the ash pan, wasting money and heat value.

When I first turn it on, my P68 really roars set at 75 degrees, feed rate 4, and fan turned all the way up. The flames touch the top of the stove and the room quickly turns into an oven at over 80 degrees (of course that depends on the size of your room and where your temp probe is, mine is coiled up behind the stove next to the cold outside wall). I don't even want to stand near the stove when it's cranking like that. I wouldn't want to turn it to 90 degrees feed rate 6... that would be unbearably hot, and I would start questioning whether the items in the room closest to the stove could handle that kind of heat.

 

[SidecarFlip]

Hugh you could very well be right. The 'felt' heat output seems greater to me with corn than with pellets and from a cost per unit standpoint my corn wins hands down. Almost free beats 210 a ton for pellets anyday. I got that information from the old IBC forum many years ago and never delved into the actuall hard facts. My corn is way below 12%. it's actually around 9.5% according to my Delmhorst moisture meter and the drier it is, the hotter it combusts.

 

[SciGuy]

Hugh you could very well be right. The 'felt' heat output seems greater to me with corn than with pellets and from a cost per unit standpoint my corn wins hands down. Almost free beats 210 a ton for pellets anyday. I got that information from the old IBC forum many years ago and never delved into the actuall hard facts. My corn is way below 12%. it's actually around 9.5% according to my Delmhorst moisture meter and the drier it is, the hotter it combusts.

I agree that you get more heat from drier corn. It takes ~ 1000BTUs t evaporate a 1lb of water. That energy that is wasted in a non condensing biomass stove. At 9.5% moisture the equation goes 8500 X .905 = 7692.5 BTU lb - ~ 100BTU to evaporate H20 = ~7600BTU/lb for 9.5%MC corn vs 8500BTU/lb for my plain jane pellets. As you say, at your cost per pound, there's absolutely no comparison. You've made yourself some excellent luck

 

[SidecarFlip]

Keep in mind again, that any biomass stove will only output as much 'felt heat' as the convection blower is capable of producing as it flows room air across the HX or firebox. Don't matter how high the PPH feed rate is and it don't matter what fuel medium you are combusting, the maximum BTU output is limited by the convection blower's CFM output.

Now that I understand the mechanics of a Harman a bit better I can understand how it won't overfire but that applies (I presume again) to only a Harman. Don't apply to my unit. The only 'safety' on mine ids the high limit snap disc shutdown and because it's physically attached to the firebox in the side corner, the firebox can overheat and warp in an adjacent area without ever tripping it, exactly what happened with my front firebox sheet where the feed door meets it. I was able to repair it (was not easy) but it taught me a lesson in firing the unit I won't forget.

Another reason to keep the fans (convection and draft) clean and lubricated to insure free rotation. A dirty fan or dry bearings reduces airflow and combustion draft flow and compromises the stove's ability to produce heat and efficiently burn the fuel. The feed rate (auger and fuel) cannot 'see' what the combustion air fan and convection fan are doing as far as the airflow. All the brain box does id=s set the PPH and in my case it's a custom rate so if the convection air and combustion airflow is compromised, the fuel keeps right on getting delivered, no matter what.

I guess my big concern with a fabricated steel firebox (which mine has and I presume most are), is thermal expansion and contraction and how it impacts the welds. No firebox is one solid sheet of formed steel, they are all comprised of welded sections and those welds are constantly subjected to expansion and contraction and over firing a firebox can and will reduce the useful lifespan of those welds and being a somewhat professional welder, fabricator, I can say with confidence that the welds in any biomass stove will be MIG and none are certified or magnafluxed. What you have is some employee on a fabrication line using an ordinary MIG with 75-25 shielding gas to weld them up with basically no QC other than the 'it looks good so go with it' philosophy.

From a cost standpoint as well as a production standpoint, it's the most economical way to build but it's also the most prone to failure from compromised welds so to mitigate that, you don't want to overfire the stove.

 

[SidecarFlip]

I agree that you get more heat from drier corn. It takes ~ 1000BTUs t evaporate a 1lb of water. That energy that is wasted in a non condensing biomass stove. At 9.5% moisture the equation goes 8500 X .905 = 7692.5 BTU lb - ~ 100BTU to evaporate H20 = ~7600BTU/lb for 9.5%MC corn vs 8500BTU/lb for my plain jane pellets. As you say, at your cost per pound, there's absolutely no comparison. You've made yourself some excellent luck

Most of that was being in the right place at the right time and being a farmer and knowing other farmers one of whom is a seed corn producer. Not adverse to buying him a fifth or two of Crown, he likes his 'toddy's' after a cold day outside. Likes Captain Morgan spiced rum as well.

Just a mile down the road so transportation is easy but I do need to have the proper equipment to haul 2500 pound supersacks and skids of the corn as well as indoor storage, all of which I have.

My only downside is the huge amount of ash produced. Corn don't make fine ash like pellets do. It produces a coarse ash, looks almost like tiny lumps of fluffy coal but that also necessitates me cleaning the stove every couple days inside. I don't get anymore or less fly ash in the cleanout Tee, it all stays inside the firebox and has to be manually shoveled (brushed) into the ashpan and emptied in the driveway (found out years ago that the garden don't like corn ash), so my gravel drive grows black spots over the winter.

If I ran a clinker pot like Firepot Pete does, that would all but eliminate the ash issue but I don't. With a clinker pot, you pull the clinker daily, I guess it takes all of 30 seconds and no need to shut the unit off either. Just pull the clinkner (with a clinker hanger which is a bent metal coathanger), swipe off some of the burning corn on top back into the firepot, close the door and keep on trucking.

Pete sent me the dimensions for a clinker pot and I may fabricate one or more this summer and give that a shot as well. That would all but eliminate my need for the pellet mix other than needing pellets to start the combustion process. Nice thing about the unit I have is, I can fabricate the pot as deep in capacity as the draft shutter is which would give me a huge firepot and lots of capacity for a clinker.

I may do that but for now, they way I do it works 95% well. Always room for improvement.

 

[tbear853]

My stove has on, off, t-stat or room mode, and a temp knob that rotates 270 degrees from 7:30 (lo) to about 4:30 (hi). All other adjustments require removal of back to access the screw controls.

Once years ago it got down to about 0 outside for a few days, I cranked the stove up to past 12:00 o'clock, we were both sweating. We usually keep it going around 9:00-10:00 o'clock if outside is just under freezing, but if it gets up to in the 40s, the stove is at idle.

Just thinking of wide open can raise a sweat.

Maybe it's the house layout, stove in living room open to loft and upstairs master bed room, we do run a ceiling fan to try and keep some heat down there.

 

[Ssyko]

My Maxx scares me at 4 the fire is 14” high and 10” wide and it is unbearable 3 ft in front of the stove. Nobody’s gotta worry about me overfireing this one

 

[SidecarFlip]

Only sweating I do right now is when I set the electric blanket too high....... It is 68 in here at 48%RH. I'm all good with that. Mot short temperature but no down coat either.

 

[davidfieldsnwa]

Ok, thanks for all the posts. From what I understand, if I want the fastest "get my stove to its max output" I'm hearing it doesn't matter a lot whether its in room or stove temp. Just high temp, high distribution fan, feed rate 4. That's max my Harman can likely do to quickly get to maximum heating. (doubt I'm really coming close to beating up my stove and I won't keep it there)

As a matter of fact, it sounds like both the room temp and stove temp do the same thing - both seek a target temperature.

• Room temp seeks a temperature measured in degrees that corresponds to the temp of my room which I can use independent thermometers to see and readily understand.
• Stove temp seeks a temperature measured in degrees that corresponds to the temp of my esp probe - which doesn't have much to do with the temp of my room and is much harder to understand . Sounds like less varying of things in this mode - keep 'er where you set 'er.

No poster has said that either stove or room temp is quicker to get the stove hot - really sounds like I can go either way - crank it to high on the left dial (temp/stove temp num) and crank the fan up. That's quickest way - true story?