Increase Distribution Fan Speed in Harman XXV

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carnini

New Member
Jan 17, 2023
3
Vermont
This is a bit of an odd question, is there a way to increase the speed of my Distribution Fan in a XXV, I have it set to high and it does seem to be pushing enough air into the room but...

When on test mode, or start up sometimes the distribution fan seems to go into extra high speed then settle back to the normal high speed.

I am wish there was a way for it to always run at that high high speed.

My thinking is if more air is going over the heat exchange, then more of the heat will be extracted and not sent up the Chimney

My XXV is the one with the double barrel blower under the stove, I think newer XXV that has a back distrubution fan?
 

Golfeur

Member
Nov 15, 2014
222
Val-d'Or Québec
I don't think there is more heat extracted.
The higher the speed, the less hot the air will come out in the room.
If the speed is low the air will be hotter so I don't think more hot air comes out in the chimney.
 

SciGuy

Feeling the Heat
Aug 17, 2007
391
Constableville, NY
I don't think there is more heat extracted.
The higher the speed, the less hot the air will come out in the room.
If the speed is low the air will be hotter so I don't think more hot air comes out in the chimney.
The higher the blower speed, the more heat will be extracted from the pellet stove so the OP is correct.
 
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Mt Bob

Minister of Fire
Oct 31, 2013
4,322
park county montana
This is a bit of an odd question, is there a way to increase the speed of my Distribution Fan in a XXV, I have it set to high and it does seem to be pushing enough air into the room but...

When on test mode, or start up sometimes the distribution fan seems to go into extra high speed then settle back to the normal high speed.

I am wish there was a way for it to always run at that high high speed.

My thinking is if more air is going over the heat exchange, then more of the heat will be extracted and not sent up the Chimney

My XXV is the one with the double barrel blower under the stove, I think newer XXV that has a back distrubution fan?

This is a bit of an odd question, is there a way to increase the speed of my Distribution Fan in a XXV, I have it set to high and it does seem to be pushing enough air into the room but...

When on test mode, or start up sometimes the distribution fan seems to go into extra high speed then settle back to the normal high speed.

I am wish there was a way for it to always run at that high high speed.

My thinking is if more air is going over the heat exchange, then more of the heat will be extracted and not sent up the Chimney

My XXV is the one with the double barrel blower under the stove, I think newer XXV that has a back distrubution fan?
XXV and Accentra FS use the same blower,as does the p35i. Biggest thing is, keep it clean, lube it if you can.
Now if you do suspect a problem, as you have described, I can only think of a few things, if yours is older, and has the hi-lo switch for the blower, make sure it is on high. Clean your potentiometers.
If you are still sure this is happening,I can only think the exhaust probe does not think the stove is burning hot enough, or the control board is flaky.
 

Cincinnati Kid

Feeling the Heat
Jan 6, 2009
336
Cincinnati
The higher the blower speed, the more heat will be extracted from the pellet stove so the OP is correct.
To a certain extent, that is correct but you can over do it. As an example, I would not run my stoves on the maximum distribution fan speed while the temperature dial is on a low setting.
 
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Mt Bob

Minister of Fire
Oct 31, 2013
4,322
park county montana
The higher the blower speed, the more heat will be extracted from the pellet stove so the OP is correct.
Are you sure? The burning/heat made by the stove is fixed(on high), just like a furnace. Now consider this question, from a HVAC test--
To a certain extent, that is correct but you can over do it. As an example, I would not run my stoves on the maximum distribution fan speed while the temperature dial is on a low setting.
To a certain extent, that is correct but you can over do it. As an example, I would not run my stoves on the maximum distribution fan speed while the temperature dial is on a low setting.
Yep, and you cannot,on a Harman. It is regulated by the exhaust probe, and programming.
 

carnini

New Member
Jan 17, 2023
3
Vermont
Going to pull the fan this weekend, its a pain as most people know as its underneath the stove.
Since its winter, its on continual heat setting of around 4 or 5 and a feed rate or 4/5 too.
Going to check to see if there is any crude in it.
 

rickwai

Minister of Fire
Nov 1, 2011
1,457
ohio
If you typically run in room temp hi fan try running in Stove temp hi fan and see if it changes. There could be a bad spot in the knob not powering the fan up to 100%
 

Golfeur

Member
Nov 15, 2014
222
Val-d'Or Québec
My P68 is in the basement at the beginning when I had my stove I ran my room air fan to the maximum. My house has the first floor and the second floor and the stove in the basement.
Now I put my ambient air fan on the minimum because the heat coming out of the stove is hotter and we know that the heat rises so the heat rises more towards the first and second floor, in my case it's better that way.
If the stove gets hotter the fan speed automatically increases to remove the heat.
In my case the performance is better like this
 

SciGuy

Feeling the Heat
Aug 17, 2007
391
Constableville, NY
Are you sure? The burning/heat made by the stove is fixed(on high), just like a furnace. Now consider this question, from a HVAC test--


Yep, and you cannot,on a Harman. It is regulated by the exhaust probe, and programming.
Yes I am sure:) A higher distribution blower speed puts more cooler air in contact with the heat exchange area which cools the combustion gases on the other side of the exchanger. This leads to cooler exhaust being sent out of the stove, i.e. less heat sent up the chimney. That said, if you're running the stove in stove temperature mode this cooler exhaust contacting the esp will then cause the computer to ramp the pellet addition up until the esp reaches it's assigned temperature and the stove will begin to output even more heat while burning additional pellets. If running the stove in room temperature mode increasing the distribution blower speed will extract more heat out of the exhaust stream and call for less pellets to be added for a given need for heat.

That's my story and I'm sticking to it.

Hugh
 
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SciGuy

Feeling the Heat
Aug 17, 2007
391
Constableville, NY
My P68 is in the basement at the beginning when I had my stove I ran my room air fan to the maximum. My house has the first floor and the second floor and the stove in the basement.
Now I put my ambient air fan on the minimum because the heat coming out of the stove is hotter and we know that the heat rises so the heat rises more towards the first and second floor, in my case it's better that way.
If the stove gets hotter the fan speed automatically increases to remove the heat.
In my case the performance is better like this
The air coming out will certainly be hotter but in vastly less amount so the BTUs extracted will be less and the heat flying out the vent pipe will be more.
 

Golfeur

Member
Nov 15, 2014
222
Val-d'Or Québec
I have a thermometer on my stove outlet pipe and I don't notice any change.
 

SciGuy

Feeling the Heat
Aug 17, 2007
391
Constableville, NY
Are you running the stove in room temperature mode or stove temperature mode? How granular is the thermometer on the exhaust pipe?
Is it single wall or double wall pipe?

Thanks for playing:)

Hugh
 

Golfeur

Member
Nov 15, 2014
222
Val-d'Or Québec
stove temperature double wall pipe
 

SciGuy

Feeling the Heat
Aug 17, 2007
391
Constableville, NY
stove temperature double wall pipe
Well that explains why your stove pipe temperature hasn't changed. Stove temp is driven maintaining a constant ESP temperature i.e. exhaust gas temperature. You ought to be able to get more actual BTUs with a higher distribution blower speed and a lower stove temperature setting. You'll burn less pellets per day for you needed BTUs in doing so. If you're happy you're doing this so be it.
 

Golfeur

Member
Nov 15, 2014
222
Val-d'Or Québec
If I follow your logic you say increase the fan speed to have less heat coming out through the chimney so the temperature at the ESP sensor will drop so to keep its temperature the ESP sensor will say burn more pellets to be able to keep its temperature so I will take more pellets for the same temperature setting in stove temperature
 

SciGuy

Feeling the Heat
Aug 17, 2007
391
Constableville, NY
If I follow your logic you say increase the fan speed to have less heat coming out through the chimney so the temperature at the ESP sensor will drop so to keep its temperature the ESP sensor will say burn more pellets to be able to keep its temperature so I will take more pellets for the same temperature setting in stove temperature
You're correct but to keep the house at the same temperature you'd need to turn down the stove setting to a lower number otherwise you'd way overheat the house on the old setting.
 

Golfeur

Member
Nov 15, 2014
222
Val-d'Or Québec
I'm already on the minimum
 

SciGuy

Feeling the Heat
Aug 17, 2007
391
Constableville, NY
I'm already on the minimum
Aha, well you're SOL if you want to stay in stove mode, want to be as efficient as possible wringing as many BTUs out of your pellets as possible and not overheat the house. You could switch to room temperature mode if you did want to squeeze more BTUs out of your pellets but I suspect you're enjoying a constant output enough to make it worth soldiering on.
 
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rickwai

Minister of Fire
Nov 1, 2011
1,457
ohio
You need to run in room temp with fan on medium to high. Stove will shut down when room temp is met then relight when needed. I extended my room temp sensor so it is about 15 ft from the stove and have it about 3.5 ft off the floor. That makes my stove heat more evenly and run longer cycles instead of short on and off cycles.
 
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Mt Bob

Minister of Fire
Oct 31, 2013
4,322
park county montana
You need to run in room temp with fan on medium to high. Stove will shut down when room temp is met then relight when needed. I extended my room temp sensor so it is about 15 ft from the stove and have it about 3.5 ft off the floor. That makes my stove heat more evenly and run longer cycles instead of short on and off cycles.
Yep, I have had personal experience with 2,now, P-68's, not too big for the house, but too big for the rooms they are in. Stoves ramp up and down, on/off. Thermostats relocated to another room fixed both, heat is way more even in houses.
 

Golfeur

Member
Nov 15, 2014
222
Val-d'Or Québec
When it's colder I run at room temperature because the stove modulates non-stop to maintain the temperature.
If it is not cold enough I run in stove temperature to prevent the stove from stopping and restarting it gives a more constant temperature in the house
It is 25 celcius in the basement and 22 celcius upstairs
 

Mt Bob

Minister of Fire
Oct 31, 2013
4,322
park county montana
Well to each
When it's colder I run at room temperature because the stove modulates non-stop to maintain the temperature.
If it is not cold enough I run in stove temperature to prevent the stove from stopping and restarting it gives a more constant temperature in the house
It is 25 celcius in the basement and 22 celcius upstairs
To each his/her own, but in real cold, I prefer room temp. , on my wall thermostat, igniter switch "up". Then it functions mostly as "hi-low". Sometimes, for a week straight. Stove does not shut down in this mode, and room temp is more consistent.
 

rickwai

Minister of Fire
Nov 1, 2011
1,457
ohio
I experimented on room sensing probe placement with the DDM hooked to the stove to see what the probe was seeing compared to my thermometer about 20 ft away. My conclusion was that with the standard length cable I could not get it far enough away from the P43 to not pick up the radiant heat from the side of the stove when it was at a medium/high fire. SO if the stove had been off and the room was 62f and I had it set at 72 the stove would come on and up top a hi fire for a bit then start cutting back even though the room was maybe 66f. Then as the stove cooled and the radiant heat was not as much it would ramp back up. With probe 15 ft away and about 3' off the floor it will come up to a hi fire and stay there until the whole room is getting close to set point.
 
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Mt Bob

Minister of Fire
Oct 31, 2013
4,322
park county montana
I experimented on room sensing probe placement with the DDM hooked to the stove to see what the probe was seeing compared to my thermometer about 20 ft away. My conclusion was that with the standard length cable I could not get it far enough away from the P43 to not pick up the radiant heat from the side of the stove when it was at a medium/high fire. SO if the stove had been off and the room was 62f and I had it set at 72 the stove would come on and up top a hi fire for a bit then start cutting back even though the room was maybe 66f. Then as the stove cooled and the radiant heat was not as much it would ramp back up. With probe 15 ft away and about 3' off the floor it will come up to a hi fire and stay there until the whole room is getting close to set point.
Yep