New Mt.Vernon AE pellet stove owner - not as toasty as I thought!

[becasunshine]

Let the record show that at 11pm, I turned the feed rate from 4.5 lbs./hour to 4 lbs./hour. I hope that the stove will cool down and that the override switch on the convection fan will drop off before we go to sleep.

Mr. Sunshine is still head's down with work, but we will go to bed eventually. I don't want to attempt to drift off to sleep thinking about the convection fan override switch being switched ON for hours.

 

[Madcodger]

So, just a quick note to the OP (Gregt823) - What's the status on your stove? Did you get things resolved? Questions remaining?

 

[Harvey Schneider]

For those who aren't toasty warm with their Mt Vernon AE, I thought that I would post some measurements that I just took.
Outside this morning was 5 deg F, at 7:30 the thermostat did it's program change from 65 deg to 70 deg. The stove was running in manual mode at heat output 3. With room temperature at about 70 near the stove and still 68 at the thermostat the convection output was at 210 deg. I was cold from being outside getting the snow blower ready so I put the heat output to 5. convection output temperature rose to 315 degrees over about a 15 minute period. I am burning Greene Team Platinum.

 

[john193]

For those who aren't toasty warm with their Mt Vernon AE, I thought that I would post some measurements that I just took.
Outside this morning was 5 deg F, at 7:30 the thermostat did it's program change from 65 deg to 70 deg. The stove was running in manual mode at heat output 3. With room temperature at about 70 near the stove and still 68 at the thermostat the convection output was at 210 deg. I was cold from being outside getting the snow blower ready so I put the heat output to 5. convection output temperature rose to 315 degrees over about a 15 minute period. I am burning Greene Team Platinum.

I'd be curious to add my results, but, how are you measuring the temp. Can you provide specifics on thermometer placement?

 

[Harvey Schneider]

I'd be curious to add my results, but, how are you measuring the temp. Can you provide specifics on thermometer placement?

I am using a type K thermocouple suspended in the air stream near the middle of the output port. The thermocouple is about 1.5 inches in from the front casting and suspended midway between the upper and lower surfaces of the port. My cheap meter is good to about 1/2 degree F and the thin thermocouple is very fast to respond.
It takes a while for the stove output temperature to stabilize after a change in settings. Both measurements were taken with the inlet air temperature within a few degrees of 70 F.
I am interested in seeing your temperature results.

 

[gregt23]

P.S. My apologies to gregt23 for hijacking your thread.

BecaSunshine <---- Thread Thief

I'm sorry!

No apologies necessary. My thread is your thread. LOL.

 

[gregt23]

I just wanted to give an update on our new Mt. Vernon insert. After several days of using the stove, it continues to get better and better. After about two weeks of use, it seems to be heating much better. The company we purchased the unit from received some new ultra premium pellets (sorry, I can't remember the brand) and using this new pellet, I was amazed at how much better the stove performed. I was able to turn down the flame level to 0 or +1 and the stove performed amazingly. My entire home is about 2500 square feet and the stove is heating the entire house very nicely. When it gets really cold (around 15 to minus 15 degrees) it works much better when running it on Manual High mode - it heats much better and blows much hotter. Any other time, the Auto setting works fine.
I wanted to thank everyone for their help and the information that you so freely offered to help someone you don't know. This forum is a great help for those of us with little knowledge of these wonderful stoves. Thanks again and I would like to wish everyone a Very Merry Christmas (or whatever you and your family celebrate this time of year, because that is what makes our Country such a beautiful place to call home) and a Happy New Year.
Sincerely,

Greg

 

[becasunshine]

Hello!

I am back to give an update as well, on this thread that I stole from gregt23. ^^ Waves at Greg!

Napoleon customer service did respond to my email! They thanked me for the feedback and for the information, saying that they don't often get feedback from stove shops nor from customers, and they appreciate it. The customer service rep forwarded all of our tracked data and observations to the design and maintenance engineers.

Based on our data, the engineers say that the feed rate potentiometer/rheostat is functioning correctly, with the correct resistance readings. Given that the potentiometer/rheostat is functioning correctly, this would leave the auger control relay as the culprit, and replacing it should address the feed rate issue.

I looked this part up on the Mountain View Hearth Product site. (LOVE that site- so awesome!) Visual inspection of the photograph of the part on Mountain View Hearth Product's site reveals schematics that say "3 secs" and ".5-15 secs." Given that my timing of the auger duty cycle was done via the "One Mississippi, Two Mississippi" method, one can apply the upper and lower limits of intervals described on the schematics for this part to the auger duty intervals I timed with an allowable variation for my less than digital method of counting.

In other words, the schematics drawn on the part, with the corresponding time intervals, seem to match the auger duty/auger off intervals that I counted while observing the stove- 3 seconds of auger "duty" or actual turning time, with non-duty/non-turning intervals in between each turn that last from 0.5 seconds to 15 seconds. This almost exactly matches the intervals that I counted.

So if the auger duty cycle, as well as the upper and lower limits of the non-duty intervals, matches what I've observed and counted off with our auger, why would I replace this part? That would be $120 to replace a part that appears to be functioning as expected for at least the auger turning portion of the cycle, and the upper and lower limits of the rest intervals in between.

Of course, there is the sag or dip in the curve plotted for us by Harvey Schneider, so that could explain some lack of feed... but that dip could also be the result of my less than accurate/scientific method of timing the intervals.

I asked the Napoleon customer service rep to take this observation re: my counted intervals and the schematics on this part back to the engineers and to ask them to reconsider this potential solution. That was right before Christmas, and I haven't heard anything back yet. I figured that if I didn't hear anything back by the first or second week in January (allowing for the holidays to pass) that I'd send another email to request more information.

I dunno, what do y'all think? Is it worth replacing a $120 part that appears to be working correctly, at least according to the intervals as listed on the part?

Here's the part itself:

http://www.stove-parts-unlimited.com/NPI40-and-NPS40-Auger-Control-Relay-p/w190-0019.htm

P.S. Greg, we are happy that your stove is working well for you!

 

[Harvey Schneider]

Hello!

I am back to give an update as well, on this thread that I stole from gregt23. ^^ Waves at Greg!

Napoleon customer service did respond to my email! They thanked me for the feedback and for the information, saying that they don't often get feedback from stove shops nor from customers, and they appreciate it. The customer service rep forwarded all of our tracked data and observations to the design and maintenance engineers.

Based on our data, the engineers say that the feed rate potentiometer/rheostat is functioning correctly, with the correct resistance readings. Given that the potentiometer/rheostat is functioning correctly, this would leave the auger control relay as the culprit, and replacing it should address the feed rate issue.

I looked this part up on the Mountain View Hearth Product site. (LOVE that site- so awesome!) Visual inspection of the photograph of the part on Mountain View Hearth Product's site reveals schematics that say "3 secs" and ".5-15 secs." Given that my timing of the auger duty cycle was done via the "One Mississippi, Two Mississippi" method, one can apply the upper and lower limits of intervals described on the schematics for this part to the auger duty intervals I timed with an allowable variation for my less than digital method of counting.

In other words, the schematics drawn on the part, with the corresponding time intervals, seem to match the auger duty/auger off intervals that I counted while observing the stove- 3 seconds of auger "duty" or actual turning time, with non-duty/non-turning intervals in between each turn that last from 0.5 seconds to 15 seconds. This almost exactly matches the intervals that I counted.

So if the auger duty cycle, as well as the upper and lower limits of the non-duty intervals, matches what I've observed and counted off with our auger, why would I replace this part? That would be $120 to replace a part that appears to be functioning as expected for at least the auger turning portion of the cycle, and the upper and lower limits of the rest intervals in between.

Of course, there is the sag or dip in the curve plotted for us by Harvey Schneider, so that could explain some lack of feed... but that dip could also be the result of my less than accurate/scientific method of timing the intervals.

I asked the Napoleon customer service rep to take this observation re: my counted intervals and the schematics on this part back to the engineers and to ask them to reconsider this potential solution. That was right before Christmas, and I haven't heard anything back yet. I figured that if I didn't hear anything back by the first or second week in January (allowing for the holidays to pass) that I'd send another email to request more information.

I dunno, what do y'all think? Is it worth replacing a $120 part that appears to be working correctly, at least according to the intervals as listed on the part?

Here's the part itself:

http://www.stove-parts-unlimited.com/NPI40-and-NPS40-Auger-Control-Relay-p/w190-0019.htm

P.S. Greg, we are happy that your stove is working well for you!

It is possibly either the pot or the relay that is giving you the non-linear response. The pot is a much less expensive part to experiment with, and more likely to fail, although I have never seen a pot go from linear to logarithmic as a failure mode. If you do decide to replace the relay you should take a close look at this one:

Infitec TRS51A13S2A

http://controlsourceintl.com/scripts/prodView.asp?idproduct=645

At less than half the price of, what appears to be, the same part.
The part number was copied off of the photo on the Napoleon web site. The search for the part took me less than one minute. Unfortunately the the data sheet does not say whether the response to the external pot is linear or inverse logarithmic like your data. Of course, the pot could be a log curve pot, so we would have to know more about that part in order to know what to expect
By the way, your data showed a small irregularity (bump in an otherwise smooth curve), but that curve looked too regular to be a counting rate error. It doesn't take a digital stopwatch to time seconds, any watch or clock with a second hand will do.

 

[chken]

Also, this is interesting:

When we start up the stove, we typically start it with the feed rate set on 4. This feed rate puts enough pellets in the pot for the igniter to light them, and we can walk away from the stove during the start up cycle and not worry about the burn pot overflowing and/or backing up into the drop tube, or worry about the stove over firing if we get called away. We leave the convection blower OFF until we feel that the air coming out of the heat exchange tubes is very warm. Once the stove warms up, we turn the convection fan to its mid-range setting of about 2.5. Typically the stove runs along at feed rate 4, convection/room blower fan rate 2.5 with no change in cycle, and no issues, unless we inadvertantly let it run out of pellets or we shut it down. If we aren't standing right beside the stove when it gets hot, we will hear the convection blower override switch trip and the convection blower fan come on at its highest setting. This is a factory installed/engineer designed safety feature that helps keep the stove from over firing. If we aren't standing right there during the start up cycle, and we hear the convection fan kick on, we go back to the stove and set the convection fan dial to 2.5. The convection fan will run on high until the stove is cooled enough to allow the over ride safety feature to drop off. When that happens, the convection fan will drop down to the speed that we've manually set. It typically stays right there, with no intervention from a safety feature or over ride, unless we change something.

We've been running the stove on feed rate 4.5, the top of the recommended range, since 6pm, or almost 4.5 hours. The pellet level in the hopper has dropped by 2". At a feed rate of 4.5, which is supposed to correspond to 4.5 lbs./hour, for 4.5 hours, we should have burned 20.25 pounds, or 37% of the 55 lbs. of pellets in this hopper. I would expect more pellets to be gone, i.e. for this hopper to be at least one third empty by now, really, over one third empty, not merely lowered by 2 inches.

BUT- here's the interesting thing- the override switch on the convection/room blower fan has been activated, and the convection fan has been blowing on HIGH even though it is manually set for 2.5, for a couple of hours now.

The stove is putting out heat. The IR thermometer centered on a center heat exchange tube is registering 300'F.

The flame in the burn pot is bright white, sharp and active. Dropping pellets cause lots of popcorn sparks (no pellets jumping out of the burn pot, but lots of sparks fly.) Damper is set on 2 out of five. The flame has a normal, bright burn and a typical life cycle; it will diminish to bright cinders in the pot, and a few smaller flames, until the auger delivers enough pellets to revive the flame and continue the cycle. There is absolutely no build up in the pot. The ash on the door glass is grayish-white. The stove is burning immaculately right now. The only thing that's causing me some concern is that the override switch has had the convection fan on high for quite a while now to keep the stove from overheating.

The over fired override switch has NOT been triggered. The stove has NOT gotten hot enough to shut itself down.

Tonight we are burning a mixture of Turman's and Presto Logs.

Pictures of pellet level at 10:30pm, plus pictures of flame and flame cycle are attached.View attachment 120761 View attachment 120761 View attachment 120762

I'm no expert, but if the stove is reacting like it has an over temp situation, then that implies heat is going up the flue? Your comments and pictures indicate a good burn. I've already forgotten, but wasn't the original problem you weren't getting enough heat?

So, on a high feed rate on the dial, but low actual pellet usage, you get a good burn, and an over temp. Does the augur feed rate change when you get the over temp? I'd guess it would go to a very low feed rate if you're getting an over temp situation. If that's the case, then maybe your low feed rate with a high dial setting is due to the stove going into a low feed mode due to high flue temps. Perhaps, the flue needs a thorough cleaning?

[edit]

Relooking at your post, I was wondering, have you tried setting your convection blower on high rather than 2.5? Also, have you considered that maybe you're getting too much air in the burn pot? I know the pellets aren't popping out, but should the flame cycle down and up like that? Sounds like they're burning too fast for the feed rate selected, thus the flame goes down, before the next cycle of pellets. This might explain if the heat is being pushed out the vent, thus triggering your over temp alarm, leading to a slowing of the feed rate.

 

[Harvey Schneider]

Hello!

I am back to give an update as well, on this thread that I stole from gregt23. ^^ Waves at Greg!

Napoleon customer service did respond to my email! They thanked me for the feedback and for the information, saying that they don't often get feedback from stove shops nor from customers, and they appreciate it. The customer service rep forwarded all of our tracked data and observations to the design and maintenance engineers.

Based on our data, the engineers say that the feed rate potentiometer/rheostat is functioning correctly, with the correct resistance readings. Given that the potentiometer/rheostat is functioning correctly, this would leave the auger control relay as the culprit, and replacing it should address the feed rate issue.

I looked this part up on the Mountain View Hearth Product site. (LOVE that site- so awesome!) Visual inspection of the photograph of the part on Mountain View Hearth Product's site reveals schematics that say "3 secs" and ".5-15 secs." Given that my timing of the auger duty cycle was done via the "One Mississippi, Two Mississippi" method, one can apply the upper and lower limits of intervals described on the schematics for this part to the auger duty intervals I timed with an allowable variation for my less than digital method of counting.

In other words, the schematics drawn on the part, with the corresponding time intervals, seem to match the auger duty/auger off intervals that I counted while observing the stove- 3 seconds of auger "duty" or actual turning time, with non-duty/non-turning intervals in between each turn that last from 0.5 seconds to 15 seconds. This almost exactly matches the intervals that I counted.

So if the auger duty cycle, as well as the upper and lower limits of the non-duty intervals, matches what I've observed and counted off with our auger, why would I replace this part? That would be $120 to replace a part that appears to be functioning as expected for at least the auger turning portion of the cycle, and the upper and lower limits of the rest intervals in between.

Of course, there is the sag or dip in the curve plotted for us by Harvey Schneider, so that could explain some lack of feed... but that dip could also be the result of my less than accurate/scientific method of timing the intervals.

I asked the Napoleon customer service rep to take this observation re: my counted intervals and the schematics on this part back to the engineers and to ask them to reconsider this potential solution. That was right before Christmas, and I haven't heard anything back yet. I figured that if I didn't hear anything back by the first or second week in January (allowing for the holidays to pass) that I'd send another email to request more information.

I dunno, what do y'all think? Is it worth replacing a $120 part that appears to be working correctly, at least according to the intervals as listed on the part?

Here's the part itself:

http://www.stove-parts-unlimited.com/NPI40-and-NPS40-Auger-Control-Relay-p/w190-0019.htm

P.S. Greg, we are happy that your stove is working well for you!

Pardon my confusion. With these interlacing threads, I've lost track of exactly what problem you are trying to resolve. Please take the time to clearly and simply state what it is that you need.

 

[becasunshine]

Hi All!

The original problem: The stove is rated to put out 8500-43,500 BTUs. (I am at a different location than the stove and its manual right this minute. Please excuse me if I don't get these numbers exactly right- I'm pulling them from memory. I know that these numbers, if not absolutely correct for our year of NPS40 stove, are very close.)

The feed rate should be one to five pounds of pellets per hour, corresponding to the numbers painted above the feed rate dial. The recommended feed rate setting is 4, in which case, the stove should be feeding 4 lbs./hour into the burn pot. This feed rate would use up a 40 lbs. bag of pellets in 10 hours, or a little over 2 40 lbs. bags in 24 hours.

Per our observations above, at the recommended feed rate setting of 4, our stove takes approximately 22 hours to burn through one 40 lbs. bag of pellets. It seems unlikely that the stove can produce the BTUs as advertised. There are approximately 8300 BTUs in a pound of pellets. If the stove is burning through one 40 lbs. bag of pellets in 22 hours, then it is burning approximately 1.8 lbs./hour of pellets. That's 14,940 BTUs/hour at the next to highest feed setting- the dial runs from OFF through 5. (I think it might turn a little past 5, but I'm not with the stove right now, so I can't swear to that.) It is recommended in the manual that the stove NOT be run continuously on low or high feed rates, but that it should be run continuously at a feed rate setting of 4. OK. And at a feed rate setting of 4, it should be (according to the manual) burning 4 lbs. of pellets per hour, and producing 33,200 BTUs per hour- or over twice as many BTUs as it is apparently producing now, if one uses pellet consumption to calculate BTU production.

I do think that it's interesting to note that even though we are not burning 4 lbs./hour at the feed rate setting of 4, if we bump the stove up to the top of the recommended feed range at 4.5 with good quality pellets, the convection override switch is triggered and the convection fan comes on to help keep the stove from over-heating. ????

So yes, we are eyeing the disconnect between the stated feed rates/BTU production in the owner's manual, and our actual experience with the stove's feed rate, burn rate, and the convection blower override switch kicking in at a feed rate of 4.5 with good quality pellets, when the stove is apparently not feeding/burning as many pounds per hour as the stove is supposed to burn. ???

That being said, we are also eyeing the curved, non-linear graph of the auger on/auger off intervals as plotted by Harvey Schneider. Perhaps the feed rate is closer to the numbers posted in the owner's manual at feed rate 4.5. I've not had a chance to time an extended burn at that feed setting. I'll do that when we get back to town.

 

[Harvey Schneider]

Hi All!

The original problem: The stove is rated to put out 8500-43,500 BTUs. (I am at a different location than the stove and its manual right this minute. Please excuse me if I don't get these numbers exactly right- I'm pulling them from memory. I know that these numbers, if not absolutely correct for our year of NPS40 stove, are very close.)

The feed rate should be one to five pounds of pellets per hour, corresponding to the numbers painted above the feed rate dial. The recommended feed rate setting is 4, in which case, the stove should be feeding 4 lbs./hour into the burn pot. This feed rate would use up a 40 lbs. bag of pellets in 10 hours, or a little over 2 40 lbs. bags in 24 hours.

Per our observations above, at the recommended feed rate setting of 4, our stove takes approximately 22 hours to burn through one 40 lbs. bag of pellets. It seems unlikely that the stove can produce the BTUs as advertised. There are approximately 8300 BTUs in a pound of pellets. If the stove is burning through one 40 lbs. bag of pellets in 22 hours, then it is burning approximately 1.8 lbs./hour of pellets. That's 14,940 BTUs/hour at the next to highest feed setting- the dial runs from OFF through 5. (I think it might turn a little past 5, but I'm not with the stove right now, so I can't swear to that.) It is recommended in the manual that the stove NOT be run continuously on low or high feed rates, but that it should be run continuously at a feed rate setting of 4. OK. And at a feed rate setting of 4, it should be (according to the manual) burning 4 lbs. of pellets per hour, and producing 33,200 BTUs per hour- or over twice as many BTUs as it is apparently producing now, if one uses pellet consumption to calculate BTU production.

I do think that it's interesting to note that even though we are not burning 4 lbs./hour at the feed rate setting of 4, if we bump the stove up to the top of the recommended feed range at 4.5 with good quality pellets, the convection override switch is triggered and the convection fan comes on to help keep the stove from over-heating. ????

So yes, we are eyeing the disconnect between the stated feed rates/BTU production in the owner's manual, and our actual experience with the stove's feed rate, burn rate, and the convection blower override switch kicking in at a feed rate of 4.5 with good quality pellets, when the stove is apparently not feeding/burning as many pounds per hour as the stove is supposed to burn. ???

That being said, we are also eyeing the curved, non-linear graph of the auger on/auger off intervals as plotted by Harvey Schneider. Perhaps the feed rate is closer to the numbers posted in the owner's manual at feed rate 4.5. I've not had a chance to time an extended burn at that feed setting. I'll do that when we get back to town.

Okay, I'm up to speed now.
This is my take on what I now know:

1. The manual says that the feed rate runs from 1 to 5. I did not see anywhere in the manual that those numbers correspond to pounds per hour. That may be a reasonable assumption but it may not be correct.
2. The stove is specified to consume a range of BTU input, but it doesn't say that it can do that continuously.
3. If you are running a high feed rate you probably need to have the convection fan running at a high rate in order to avoid overheat, That may be why the max fan mode is kicking on automatically. It is desirable, from an efficiency point of view, to run the convection blower at the highest speed that your ears will tolerate.

So the long and short of what I am saying is that Napoleon has played a specsmanship game that led you to expect more from the stove than it is capable of. That happens all the time in specifying the capabilities of electrical and mechanical equipment. The specs aren't lies (even though it may seem that way), but they may not all apply at the same time and they may not apply all the time.
An example of this last statement is that the stove cannot produce it's maximum heat output if it is running at the minimum convection fan speed. That is true of most stoves, they will overheat if you try to run them that way. Similarly, they may be capable of putting out max BTUs only for limited times or only if the input air is cold otherwise they may overheat.
So although your stove doesn't do what you want it to, I don't necessarily think that it needs fixing.

 

[Madcodger]

And... 8,000+ BTUs assume max efficiency. You'll never achieve that, as heat going up the chimney is heat produced but not used. I'd say we're lucky to achieve 70% in real world conditions, so that has to be considered. If you're in the 1 - 1.3 / day bag range in VA right now, I'd say you're OK. I love data, but there's a limit to its practical use sometimes.

 

[becasunshine]

I am still not in the same location as the stove and the manual, but IIRC, my manual does state that the feed rate settings 1-5 correspond to feed rates of 1-5 lbs./hour. I'll see if I can find a link online.

Generally we run the convection fan at about mid-range. I can run it higher if we need to do so; the stove is in one corner of the house and is not in the room in which we tend to watch t.v., listen to music, etc.

Harvey Schnieder and Madcodger, you have hit upon the essence of the matter: is the stove operating consistent with and true to design? If it is- then it is not putting out the BTUs as advertised, period. I know that we have been given a range of heat outputs and that rarely is any piece of machinery designed to operate flat out, with no reserve, all the time. My point is, the manual says that the stove is capable of ~ 42k - 43k BTU output, and at the recommended feed setting it should, according to the manual, be feeding 4 lbs./hour and thus putting out 8300 BTUs X 4 lbs./hour, 33200 BTUs. Instead, at feed rate setting 4, our stove is burning 1.8 lbs./hour and, based on pellet consumption, it is putting out 14,940 BTUs per hour. That's less than half of what one would expect, based on the pounds/hour corresponding to the feed rate settings listed in the owner's manual. Houston, we have a problem. Even if I lop 25% heat production off of both of those BTU output estimates, the fact remains: pellets burned = BTU output, and it the stove cannot feed and burn the advertised pounds of pellets per hour, then it virtually cannot produce the amount of heat that it is advertised as producing.

Now, two factors we have inadvertently discovered:

Harvey demonstrated that our auger duty vs. auger rest cycles do not produce a linear graph. In fact, the duty vs. rest time cycles produce a curved graph. Is our auger control relay not operating consistently or as expected in the mid-range feed settings? This could explain why the stove needs to cut on the convection fan to prevent over-heating at the higher feed settings: auger control relay operating as expected in the higher ranges, at the terminal end of that graphed curve, auger time intervals as designed at that point on the feed dial and on that graphed curve, more pellets making it into the burn pot, stove burning hotter. I'm parsing out whether it's worth replacing that part to find out. I don't really have an answer to that question, because short of hauling a stove tech with some sort of computer diagnostic capability out to our stove, I don't really know what the auger control relay is doing in the middle of the cycles. I'm betting that I can buy the Napoleon branded auger control relay from Mountain View Hearth Products for about the same amount of money that I'd pay for a diagnostic visit. I say with certainty, however, that at feed setting 4, this stove is putting about 1.8 lbs./hour in the pot. That's not 4 lbs./hour on the best day.

Harvey, thank you for finding that alternate part. We are not electrical engineers and I'm a little confused by the spec sheet on that part. Do we have to set the time intervals with that part? Given that I've engaged the engineers at Napoleon, I think I prefer sticking with Napoleon branded parts. In this way, if we replace that auger control relay and the stove performs exactly as it performs now, there will be no question around whether we used the right replacement part.

When I get back to town, I can do a timed burn at feed setting 4.5 to see how many hours it takes to empty the hopper. We have about 40 lbs. in there now. The hopper was empty (as in, see the auger empty) when The Hubs dumped the last bag into the hopper- and IIRC, he did not top the hopper off with additional pellets. At any rate, I can do a timed burn with 40 lbs. pellets at feed setting 4.5 to see how many pounds/hour that setting burns. Perhaps we will find that, indeed, the correlation is not linear. This could confirm the curve on the graph that Henry Schneider created- and it could be a confirming fact that points us toward replacing that auger control relay.

At feed rate setting 4.5 with the convection fan set at 2.5 (mid-way through the dial) the convection fan override switch will, at times, come on and stay on, to prevent a stove over fire. So either the stove is feeding many more pellets at feed rate setting 4.5 thus again confirming a curved graph with a steep terminal rise, or, alternately, the stove is simply not designed to handle the higher feed rate pounds/hour as listed in the manual. The fan comes on at the higher settings as designed, to keep the stove from over firing. The stove was never designed to handle the pounds per hour that correspond to the numbers on the dial. ??? That could explain why we are cautioned not to run the stove for extended amounts of time on a feed rate higher than 4 - even though there is a bracket painted above the feed rate dial, and that bracket spans the area between feed rate 3.5 and feed rate 4.5. The bracket is never explained, nor mentioned in text, in the manual, although it is visible on the photograph of the feed rate dial.

So, is my stove operating as designed, but not consistently with the performance as stated in the owner's manual, or is my stove NOT operating as designed? And if not, why not? And how do we fix that?

 

[Harvey Schneider]

at the recommended feed setting it should, according to the manual, be feeding 4 lbs./hour

In the manual I found on line, it states that the stove can burn 1 to 5 pounds per hour. It also shows settings of 1 to 5 on the feed rate. There is no statement that the two are directly and linearly connected. One would expect that they have to align at the two ends of the scales, but there is no claim that the numbers on the dial are, in fact, pounds per hour. You can get more pounds per hour by turning the dial up, but you will probably need to increase the convection fan setting to keep the stove temperature reasonable.
Is it so important that the numbers align with the pounds per hour consumed? If you can get stable operation with some combination of feed rate and convection speed you are getting the performance the stove is capable of. I really don't think that changing the pot or relay is going to make a difference other than changing the dial position slightly.
The circuit that is used there is simply a two state time delay relay that is programmed by the pot for off time (fixed on time of three seconds). There isn't any computer diagnostic that is going to interface with that. By the way, the original manufacturer's label and part number for the relay are visible in the photo on the Napoleon web site.

 

[chken]

At feed rate setting 4.5 with the convection fan set at 2.5 (mid-way through the dial) the convection fan override switch will, at times, come on and stay on, to prevent a stove over fire. So either the stove is feeding many more pellets at feed rate setting 4.5 thus again confirming a curved graph with a steep terminal rise, or, alternately, the stove is simply not designed to handle the higher feed rate pounds/hour as listed in the manual. The fan comes on at the higher settings as designed, to keep the stove from over firing. The stove was never designed to handle the pounds per hour that correspond to the numbers on the dial. ??? That could explain why we are cautioned not to run the stove for extended amounts of time on a feed rate higher than 4 - even though there is a bracket painted above the feed rate dial, and that bracket spans the area between feed rate 3.5 and feed rate 4.5. The bracket is never explained, nor mentioned, in the manual.

1) When the convection fan override comes on, does the augur still pour pellets into the pot, at the same rate? Does the augur stop or does it run at its lowest setting?

2) You say that the convection fan override comes on at feed rate setting 4.5, is it at all possible that it is also coming on at feed rate setting 4.0, but that you haven't witnessed it, as it takes more time to occur?

If that's the case, then perhaps, your 2lbs/hr feed rate is due to the stove slowing or stopping its feed rate, intermittently, due to high flue temps. You could be getting 4lbs/hr initially, but when the override occurs, the feed rate drops or stops, resulting in an average rate of 2lbs/hr.

You could address this by raising your convection fan rate from 2.5 to something higher. Also, you mentioned your flame is white, and leaves no ash in the pot, and that the flame drops in height as the pellets burn up. It seems to me that the pellets are burning too fast for the feed rate, indicating perhaps that you have too much combustion air, leading to heat going up the vent, which triggers the convection fan override. I would try lowering the combustion air.

Regardless, there is something occurring as your convection fan override indicates. Resolving that, may fix whatever feed rate issues you have.

 

[becasunshine]

In the manual I found on line, it states that the stove can burn 1 to 5 pounds per hour. It also shows settings of 1 to 5 on the feed rate. There is no statement that the two are directly and linearly connected. One would expect that they have to align at the two ends of the scales, but there is no claim that the numbers on the dial are, in fact, pounds per hour. You can get more pounds per hour by turning the dial up, but you will probably need to increase the convection fan setting to keep the stove temperature reasonable.
Is it so important that the numbers align with the pounds per hour consumed? If you can get stable operation with some combination of feed rate and convection speed you are getting the performance the stove is capable of. I really don't think that changing the pot or relay is going to make a difference other than changing the dial position slightly.
The circuit that is used there is simply a two state time delay relay that is programmed by the pot for off time (fixed on time of three seconds). There isn't any computer diagnostic that is going to interface with that. By the way, the original manufacturer's label and part number for the relay are visible in the photo on the Napoleon web site.

Harvey, you are *EXACTLY* right. In no place in the manual does it state that the feed rate in pounds/hour will correspond, linearly or number to number, with the feed rate settings as seen on the feed rate dial. Well that's what I get for "assuming."

I guess that I have been wed to the idea that at the recommended feed rate setting of 4, the stove is burning 4 lbs./hour and we are getting 32,800 BTU's/hour out of it. BTW, I have amended that optimistic output number because the manual states 8200 BTUs/pound minimum output per pound of pellets.

Another interesting hint that the numbers on the feed rate dial may not directly correspond to pounds of pellets burned per hour: the stove is rated to produce 8500 BTUs to 42,500 BTUs. These lower and upper range figures do not directly correspond to 1 lb./hour = 8200 BTUs/hour and 5 lbs./hour = 41,000 BTUs/hour, which would be the correlation if the numbers on the dial indicated a direct pound/hour feed rate.

SO THERE. The stove is apparently doing what it is designed to do, and it does correlate with the manual. I need to stop inserting my assumptions between the lines in that manual. Thank you, Harvey Schneider, for walking me through the logic... you saved us from replacing a $120 part that is, most likely, doing exactly what it is supposed to do.

 

[becasunshine]

1) When the convection fan override comes on, does the augur still pour pellets into the pot, at the same rate? Does the augur stop or does it run at its lowest setting?

2) You say that the convection fan override comes on at feed rate setting 4.5, is it at all possible that it is also coming on at feed rate setting 4.0, but that you haven't witnessed it, as it takes more time to occur?

If that's the case, then perhaps, your 2lbs/hr feed rate is due to the stove slowing or stopping its feed rate, intermittently, due to high flue temps. You could be getting 4lbs/hr initially, but when the override occurs, the feed rate drops or stops, resulting in an average rate of 2lbs/hr.

You could address this by raising your convection fan rate from 2.5 to something higher. Also, you mentioned your flame is white, and leaves no ash in the pot, and that the flame drops in height as the pellets burn up. It seems to me that the pellets are burning too fast for the feed rate, indicating perhaps that you have too much combustion air, leading to heat going up the vent, which triggers the convection fan override. I would try lowering the combustion air.

Regardless, there is something occurring as your convection fan override indicates. Resolving that, may fix whatever feed rate issues you have.

The convection fan override switch trigger does not appear to affect the feed rate, nor the auger turning. Huh. Do the stoves have a convection fan override associated with the flue temps? The manual for the NPS40 (I found our owner's manual online, thus I can refer to it from where I am now) says that the convection fan over ride switch responds to the temperature at the back of the fire box:


"BLOWER OVER-RIDE SWITCH:

Your heater is equipped with a convection blower that circulates

hot air into your room. This switch will automatically turn the blower

on, when the temperature at the back of the fi re box reaches a certain

temperature. The blower can cycle from your desired setting

to maximum speed depending on the feed rate. When the heater

cools back down, the blower will return to the initial setting.

Also here, and this is where the note about operating the stove at the optimal feed setting of 4 is recommended:

Blower Speed Dial

By adjusting the Blower Speed dial you will vary the rate of airfl ow

into the room by varying the speed of the convection blower. When

you fi rst start the heater, it should be placed in the "OFF" position

in order to heat up the unit as quickly as possible. Once the room

has come up to temperature, the control may be set to a comfortable

level.

NOTE: The convection blower may cycle to high automatically

depending on the setting of the pellet feed rate and the Blower

Speed. This is a normal safety feature of the unit. Once the heater

has cooled down the blower will return to the set speed.

WARNING: IT IS NOT RECOMMENDED TO BURN THE UNIT


ON LOW OR HIGH. THE MOST EFFICIENT SETTING IS 4


(OPTIMUM)."


The safety feature to which you are referring, I believe, is the high limit switch, described here:

"HIGH LIMIT SWITCH:

Your heater is equipped with a high limit switch. In the event that

the temperature of the heater approaches an unsafe operating

temperature, this switch will shut down the pellet feed, which will

eventually shut down the unit. If this happens, it is important to fi nd

out why the unit overheated. Contact your local dealer."

This feature will stop the pellet feed.

 

[Harvey Schneider]

output number because the manual states 8200 BTUs/pound minimum output per pound of pellets.

Most fuel burning appliances including my two stoves only spec the input BTU rating. Most pellet stoves have an efficiency of 76% (that is what the EPA assumes) some like my MVAE are rated higher (83.6%). Those efficiency ratings are best case scenario and you will hardly ever see them.
All that aside, I think if you increase your convection setting some and nudge the feed rate up until the stove produces a comfortable amount of heat you will be okay. From my reading of the manual, I think it is okay to let the fan high speed kick on and off as needed. I would not run the stove in a condition where the fan high speed is always on, because that is close to over fired. There is still an over fire limit switch (I didn't check your model, but I haven't seen a stove design without one) that will shut the stove down if there is an over fire condition.