Harman, high btu pellets needed?

[yrock87]

Hi all! So a recent thread about "cold weather pellets" got me thinking...

Harman stove heat output is governed by a user set temp(be that a degree temp on room temp, or a esp temp corisponding to anumber(1-7) on the dial when in room temp mode) , not by a user set feed rate. That allows the stove to automatically adjust the feed up or down as necessary to keep the set temp. All of this is explained on the Harman sticky and it means that if using low grade, low btu pellets, the user need not be concerned about adjusting set temps in order to compensate as the stove will do it for you.

My question :
Can you reach max btu rating (43k in my case) with a quality pellet? Will the stove ramp up feed rate to reach that output, or will the stove eventually hot a point where you may need higher quality pellets to reach 43k?

And related, is the stove maxed out by feed rate, or esp temp? Ie will 9500 btu DF pellets, if turned up to 7 on stove temp, produce 43k btu because the stove will limit total output (due to esp hitting whatever temp harman set for feed rate 7? Or can it go above 43k if your pellets have the high btus?

This is mostly my curiosity asking. I do have a stove that is running at about 75% right now, (0 to-10) and we have a LOT colder to go still, so this may become a practical exercise for me as well as an academic one.

Thanks for your input!

 

[Jackfire]

Seems to me it would take less premium grade than lower grade pellets to achieve yur goal and also you must take into consideration ash Premium wil produce less or does that matter.

 

[Bioburner]

I talked to someone who has a DDM and he observed stove would push if demanded above the set feed rate to try and meet a demand. Read it as you will. Wish Santa could get me one of those devices. Around $300
75% of stove capacity I would think is at the stoves or passing its best efficiency.

 

[Jackfire]

I agree my next stove will b a Harman

 

[yrock87]

I talked to someone who has a DDM and he observed stove would push if demanded above the set feed rate to try and meet a demand. Read it as you will. Wish Santa could get me one of those devices. Around $300
75% of stove capacity I would think is at the stoves or passing its best efficiency.

But what about the max end? If I have it set to feed date 6 and stove temp 7,will it still meet 43k with low grade pellets? And if so, will it exceed 43k with high end ones? Is physical feed rate or esp temp what limits your output? Or something else?

I understand I may not be running at top efficiency at - 30 outside temps. I'm okay with that.

 

[Bioburner]

ESP monitors the exhaust temp and if the stove needs-calls for more heat it will as I was told, will screw in fuel to meet the need but not enough to toast the exhaust. I was told when he had the stove feed at 4 it would, if called for, boost the feed to all out.

 

[railfanron]

I have been watching mine at feed rate 2.5 room temp set at 80 degrees. It's set that way all the time and controlled by an external stat set at 69 or 65. When the stat calls for heat moving from low temp to high temp it will run all out for a few minutes until the room temp gets close to the high temp. I expect when the parameters for heat output are right the stove will run all out no matter what the feed rate is set at. When it's calling for heat and the temperature differential is wide I expect the stove will feed fuel until the esp reaches the maximum stack temp and then hold it there until the differential narrows and the it will back off. This way pellet btus and length mean nothing.
Ron

 

[GeHmTS]

But what about the max end? If I have it set to feed date 6 and stove temp 7,will it still meet 43k with low grade pellets? And if so, will it exceed 43k with high end ones? Is physical feed rate or esp temp what limits your output? Or something else?

On the low grade side, you may run into incomplete combustion as the feed rate will increase to try and produce the required heat. If the pellets are bad enough that they don't burn all the way, then fuel will be thrown away in the ash pan. Therefore, for low grade pellets, e.g. ones with high moisture will be limited by feed rate and incomplete combustion because it will be difficult to max out the stove. The stove will then drop to a low burn mode for safety concern.

On the high end pellets, I believe you'll use less pellet because the feed rate will throttle down to meet user's requirement. Therefore, the ESP is limiting the output since the feed rate is unlikely to max out.

I partly think that's why there's a PFI certification so that pellets with this standard will not run into unexpected situation on the low side. So the issue is on the minimum grade side with recommendations to use higher grade pellets for ease of operation.

 

[yrock87]

Thanks for the responses everyone. I have low grade non pfi pellets that I am using right now. But i am also sitting on 4 tons of DF. Efficiency of burn (using fewer DF to get same results) isn't my concern right now. Just raw power capabilities. I am very much looking forward to getting rid of my low grad stuff so I can switch over to df.

GeHmTS, do you know what would happen if I my user requirement was in excess of the stoves capabilities. Ie, I required 50k btu. Would high btu pellets, at max feed rate, produce more than rated amounts of heat, or will it be limited by max stack temp as registered at the esp?

Thanks for what input you all have. I know this is kinda an odd question with limited real world value. I don't know that anyone without a diagnostic tool would be able to tell me for sure.

Merry Christmas everyone!

 

[GeHmTS]

Practically speaking, you can't exceed the capability of the stove without violating some aspect of the operation. These violations would create a safety concern and thus not recommended. Over firing comes to mind.

As a user with high btu pellets that meets PFI standards, you can only max out on the feed rate; stove or room temp of which the stove can handle. You will be limited by the max sensor output of the ESP probe. Once it's met, the feed rate will throttle down to maintain the maximum ESP probe output. To my understanding, it can't be exceeded under normal operations.

If you need more heat and want to use up your low grade pellets, then mix them with the df and that should produce more heat and allow you to consume the low grade pellets.

I'm failing to understand how you plan on exceeding the stove capabilities of 50 btu's.

 

[Harman Lover 007]

I have been watching mine at feed rate 2.5 room temp set at 80 degrees. It's set that way all the time and controlled by an external stat set at 69 or 65. When the stat calls for heat moving from low temp to high temp it will run all out for a few minutes until the room temp gets close to the high temp. I expect when the parameters for heat output are right the stove will run all out no matter what the feed rate is set at. When it's calling for heat and the temperature differential is wide I expect the stove will feed fuel until the esp reaches the maximum stack temp and then hold it there until the differential narrows and the it will back off. This way pellet btus and length mean nothing.
Ron

That is incorrect Ron. Your stove set on 2.5 will take longer to achieve the desired set temp than if it was set a feed rate 4. I know that you have been around here for a while now but I would like to suggest you read the section on feed rate in the Harman sticky above or in my sig.

 

[Bioburner]

I see by reading this thread several posts basically saying the stove wont exceed the stoves rated output but will feed the amount of pellets needed to get it to the rated btu.
Its a smart stove that won't allow one to hopefully exceed the ventings ability to handle heat and burn your home down.

 

[Harman Lover 007]

As it relates to all of the above, the ESP will max out stove production at 500 degrees. The stack temp will not be allowed to go any higher.

 

[alternativeheat]

This is what I know from practical experience only, nothing scientific.. With hot pellets in a P61 you can feel the heat difference radiating off the stove and out the heat exchanger air tubes into the room when compared with low grade pellets.. Looked at this way: X amount of heat from your pellets goes to satisfy the ESP, what is left is usable to heat your house. Maybe that sheds some sort of light on the subject.

 

[Harman Lover 007]

This is what I know from practical experience only, nothing scientific.. With hot pellets in a P61 you can feel the heat difference radiating off the stove and out the heat exchanger air tubes into the room when compared with low grade pellets.. Looked at this way: X amount of heat from your pellets goes to satisfy the ESP, what is left is usable to heat your house. Maybe that sheds some sort of light on the subject.

I know I've said this before but the Harman system is unlike any other stove on the market. It is very difficult to determine when one pellet is "hotter" than another given the Harman ESP operating system. If you set your stove for 70 degrees a Harman automatically gets you there by increasing the amount of fuel required to achieve the set temp. If you are using lower quality pellets it will likely take longer and use more pellets to get to there. Use a high quality, low ash pellet and you get there quicker using less pellets. With a Harman the only real tangible evidence is "pellets consumed" not "this pellet is hotter than that pellet".

 

[TonyVideo]

The only way to tell if you are using hotter pellets is if you use less pellets on the same setting. The ESP will will regulate the temp regardless of the type of pellet used. If all settings are the same the stove temp will remain the same regardless. It is a temp probe that regulates the feed rate. Hotter the pellet the less fuel used. The bottom feed system design and ESP is what allows a Harman to burn any type of pellet.

 

[alternativeheat]

We, my wife and I both must be feeling the get hot faster aspect of the hotter pellets several times then..

 

[TonyVideo]

It will get up to temp faster with hotter pellets.

 

[woodmakesheat]

I wish my stove had ESP

Then I could sit here at my parent's house and think about the hopper filling itself and the stove restarting and viola! Done.

 

[GeHmTS]

The only way to tell if you are using hotter pellets is if you use less pellets on the same setting. The ESP will will regulate the temp regardless of the type of pellet used. If all settings are the same the stove temp will remain the same regardless. It is a temp probe that regulates the feed rate. Hotter the pellet the less fuel used. The bottom feed system design and ESP is what allows a Harman to burn any type of pellet.

If the weather changes outside and draft conditions changes, i.e. ΔT moves then all bets are off. So any comparison would have to be close in time and temp, or you will have to employ statistical methods to do an effective analysis. It's possible to do the statistical analysis, but you have to know what you're doing.

 

[Harman Lover 007]

We, my wife and I both must be feeling the get hot faster aspect of the hotter pellets several times then..

Exactly

 

[alternativeheat]

If the weather changes outside and draft conditions changes, i.e. ΔT moves then all bets are off. So any comparison would have to be close in time and temp, or you will have to employ statistical methods to do an effective analysis. It's possible to do the statistical analysis, but you have to know what you're doing.

My wife was stuck next to the stove last winter with a busted rib. She sat there knitting for weeks. During much of that time was mid winter with pretty steady NW winds and day temps in the upper single numbers and low teens . The DF's ran out so I picked up some crappiest of the crap pellets and dumped them in the hopper ( remember last winters shortage on pellets). Came home from work the next day. She says, did you do something different with the stove ? I said changed pellets. She said , well we don't need buy any more of those. Nuff said, don't need any gauges or graphs. Look, She Who Must Be Obeyed tootsies were not as warm ok ! There is more to the story but that much is sufficient for Christmas Day.

 

[alternativeheat]

Exactly

There is 0 question the stove gets hotter faster with hotter burning pellets. Even just the time it takes for the distribution fan to kick on is sooner. Softwood pellets, hot softwood are great for a quick distribution. I never questioned that actually.

 

[Harman Lover 007]

My wife was stuck next to the stove last winter with a busted rib. She sat there knitting for weeks. During much of that time was mid winter with pretty steady NW winds and day temps in the upper single numbers and low teens . The DF's ran out so I picked up some crappiest of the crap pellets and dumped them in the hopper ( remember last winters shortage on pellets). Came home from work the next day. She says, did you do something different with the stove ? I said changed pellets. She said , well we don't need buy any more of those. Nuff said, don't need any gauges or graphs. Look, She Who Must Be Obeyed tootsies were not as warm ok ! There is more to the story but that much is sufficient for Christmas Day.

You're right....it's Christmas Day. Enjoy!

 

[GeHmTS]

My wife was stuck next to the stove last winter with a busted rib. She sat there knitting for weeks. During much of that time was mid winter with pretty steady NW winds and day temps in the upper single numbers and low teens . The DF's ran out so I picked up some crappiest of the crap pellets and dumped them in the hopper ( remember last winters shortage on pellets). Came home from work the next day. She says, did you do something different with the stove ? I said changed pellets. She said , well we don't need buy any more of those. Nuff said, don't need any gauges or graphs. Look, She Who Must Be Obeyed tootsies were not as warm ok ! There is more to the story but that much is sufficient for Christmas Day.

Nice Christmas story and thanks for sharing. You illustrate my comparison nicely.