Harman Accentra keeps shutting down with the same error code: "Incomplete Combustion"

[vferdman]

Hi, all.

I've been using the new to me Accentra for over a month now and it's been great. The stove is not new, but was cleaned by myself before it was installed. It's been throwing a 6 blink code every now and again, but would usually restart and run great for days after a reset. I make sure the burn pot is clean, the exhaust is clean, etc. Today the stove refused to stay running. I tried several times and it will ignite and start, but then shut down with 6 blink code. According to the manual it means "incomplete combustion". There are no unburned pellets in the pot when that happens and during the time it does run the fire is lively. I am guessing the exhaust temperature probe (called ESP probe by Harman) may be bad tricking the controller into shutting down. Any ideas before I go replacing the sensor?

Thanks in advance!

 

[summit]

most probably an esp probe

 

[rickwa]

we saw this alot when pennington was sending was having a problem with long pellets. 1 1/2-2 inches long. they hang up like pixy sticks over the slide plate. turn knob to test and see if auger is feeding correctly the next time you get this code

 

[Lousyweather]

most probably an esp probe

concur....most likely, but also, when you clean, do you remove the two grooved heat exchanger covers on either side of the stove and clean there too?

 

[vferdman]

most probably an esp probe

concur....most likely, but also, when you clean, do you remove the two grooved heat exchanger covers on either side of the stove and clean there too?

Yes, absolutely! I took the heat exchanger covers and the combustion fan cover out. Cleaned it all BEFORE the stove went in last month and also repeated the procedure a few days ago. It was filthy the first time, but second time it was very clean.

So, now my question is: can the ESP probe be tested? I am sure it's some sort of thermo-resistive affair and should have some parameters at room temperature. I would hate to spend money to replace a good probe. The only other cause I can think of is insufficient pellets. The controller is activating the feed motor, but somehow not enough pellets get to the burn pot. Is this a possibility? An intermittent motor? I do see plenty of pellets come down at the beginning of a cycle, so the motor is not dead, but I do not sit there and monitor it for hours, so it could start cutting out some time into the burn (because of temperature changes inside the stove or something). I am not real familiar with these beasties, so not sure what the more common malfunctions are. Any and all wisdom highly appreciated.

 

[Souzafone]

If you removed the cover of the combustion motor, you should have been able to see the probe, it's in the outlet path, where it exits the stove. Make sure it's not covered in ash.

 

[vferdman]

If you removed the cover of the combustion motor, you should have been able to see the probe, it's in the outlet path, where it exits the stove. Make sure it's not covered in ash.

As I said, everything was clean in there. Probe was not covered in ash. I vacuumed in there anyway, but there was nothing to vacuum.

Got a new probe a few hours ago. It is now in and the stove is going through its first cycle. I took apart the feed mechanism by taking the feed motor off and the plate that cuts the pellet flow out. Everything looked good. I re-assembled and decided to get another probe. Local farmer supply store is a Harman dealer and had a dozen of these things in stock. $54 including the governor's share. Hope it works. I quickly compared resistance readings on both probes at room (cold room due to stove being out) temperature and the two probes read the same at room temp. I then heated up the suspect probe with a lighter and its resistance quickly dropped as I applied the flame and went back up as I let the probe cool off. I did not do the same to the freshly bought probe in fear of ruining it by testing with a lighter flame. As far as I could see the old probe appeared to be working. But the failure was also fairly intermittent. The stove could run for days with no issues and then shut down and be stubborn to start up. I am really becoming an even bigger fan of a wood burning stoves as I go through this experience. Yes, it's nice to have a convenience of the fully automatic pellet stove, but I sure do hate all the trouble with all the various complex systems of it. Wood burning stove only requires a chimney with a good draft, the rest is just simple combustion.

 

[vferdman]

Well, after a few days with a brand new exhaust temperature probe I have this to report. The stove still shuts down with 6 blink code (incomplete combustion). I have it on "Room Temp" and set the temp at about 70. This way it will burn all day without trouble. Then at night I turn the temperature setting down to about 65 and go to sleep. When I wake up I have a cold room and a shut down stove with 6 blink error code. My installation is brand new last month before Thanksgiving. A professional installer put the stove in and it looks like the install is very good. I have outside air connected to the outside with a corrugated aluminum tube and the exhaust vent is Harman-approved piping consisting of: 10" horizontal out of the stove, 90 degree elbow, 3' vertical, 90 degree elbow, 3' horizontal through the wall to outside. At the end of the vent pipe is a 45 degree elbow pointing down. That's it. I tried disconnecting the outside air intake and using inside air without the corrugated pipe. No difference. Still get the 6 blinks in the morning.

I am more and more inclined to think that the stove is just incapable of keeping going at low room temp setting. Whatever the combination of things that comprise my particular installation seem to be conspiring against the stove. I will try different ways of running it at night. I want the room to be at around 60-65 during the night and then go to 68-70 during the day. The daytime regime seems to be working fine, but the low temp regime is a problem.

Anyone else running into similar problem under similar circumstances? Am I just not getting something?

 

[SmokeyTheBear]

Well, after a few days with a brand new exhaust temperature probe I have this to report. The stove still shuts down with 6 blink code (incomplete combustion). I have it on "Room Temp" and set the temp at about 70. This way it will burn all day without trouble. Then at night I turn the temperature setting down to about 65 and go to sleep. When I wake up I have a cold room and a shut down stove with 6 blink error code. My installation is brand new last month before Thanksgiving. A professional installer put the stove in and it looks like the install is very good. I have outside air connected to the outside with a corrugated aluminum tube and the exhaust vent is Harman-approved piping consisting of: 10" horizontal out of the stove, 90 degree elbow, 3' vertical, 90 degree elbow, 3' horizontal through the wall to outside. At the end of the vent pipe is a 45 degree elbow pointing down. That's it. I tried disconnecting the outside air intake and using inside air without the corrugated pipe. No difference. Still get the 6 blinks in the morning.

I am more and more inclined to think that the stove is just incapable of keeping going at low room temp setting. Whatever the combination of things that comprise my particular installation seem to be conspiring against the stove. I will try different ways of running it at night. I want the room to be at around 60-65 during the night and then go to 68-70 during the day. The daytime regime seems to be working fine, but the low temp regime is a problem.

Anyone else running into similar problem under similar circumstances? Am I just not getting something?

How about checking the vacuum switch's tubing a bit of dust or cracked tubing could cause a shut down, stove would think its exhaust path was blocked. This is just a guess. Perhaps the combustion motor running on low just can't keep the vacuum conditions needed.

 

[kinsmanstoves]

Bad ESP.

I stock the red p/n 03-20-00844 $44 and black p/n 03-20-00744 $47 wired probes.

Eric
330-448-0300

 

[vferdman]

How about checking the vacuum switch's tubing a bit of dust or cracked tubing could cause a shut down, stove would think its exhaust path was blocked. This is just a guess. Perhaps the combustion motor running on low just can't keep the vacuum conditions needed.

Well, the vacuum switch tubing looks pretty clean right at the switch, but I have not followed it the entire way. Where does it go from the switch?

I think if the combustion motor can't keep the vacuum conditions on low, it should switch to high. Am I wrong? Maybe it's a software problem? Being a software and electrical engineer I am aware of these issues all too well... Is there a firmware upgrade for this stove just like my iPod, LOL? It's funny, but I will check. And, oh, BTW, the low draft is set to the highest speed possible.

 

[rickwa]

try a couple of bags of pellets that are shorter. you said pellets are 1 1/2 to 2 inches it will hang that stove up every time. on a low burn it is not feeding enough pellets because some are hanging up over the slide plate. clean all pellets out of the hopper and get acouple of bags of another brand and i will bet this will solve the problem. we had the same problem with my parents accentra and pulled our hair out until we figured it out.

 

[kinsmanstoves]

If the vacuum switch is bad the stove will not work at all. It is not a wait and it will stop, it just stops the stove.

Eric

 

[vferdman]

Bad ESP.

I stock the red p/n 03-20-00844 $44 and black p/n 03-20-00744 $47 wired probes.

Eric
330-448-0300

Eric, if you read one of my latest posts you'll realize that I have replaced the ESP with a brand new one (it's a P/N ending with 744, but Harman now sells a probe you splice in yourself to the existing wire rather than replacing the wire in the circuit board. The P/N for that is something like 03-00-00744). Anyway, symptoms did not change after the new probe was installed. Now I am out $50 and no better off. So much for replacing parts at semi-random. I wish there was a known way of testing the ESP before choosing to buy a new one. I measured the resistance at room temp and at various temperatures using a lighter. Old probe seemed to be functioning properly, but could be intermittent. I did not subject the new probe to testing. It came from a Harman dealer sealed in a bag, so I assumed it's good. Are you suggesting I got a bad one?

 

[kinsmanstoves]

No not a bad probe but it all depends on what board you have. If you can call me and I will get the tech bulletin out and check your numbers.

Eric
330-448-0300

 

[SmokeyTheBear]

How about checking the vacuum switch's tubing a bit of dust or cracked tubing could cause a shut down, stove would think its exhaust path was blocked. This is just a guess. Perhaps the combustion motor running on low just can't keep the vacuum conditions needed.

Well, the vacuum switch tubing looks pretty clean right at the switch, but I have not followed it the entire way. Where does it go from the switch?

I think if the combustion motor can't keep the vacuum conditions on low, it should switch to high. Am I wrong? Maybe it's a software problem? Being a software and electrical engineer I am aware of these issues all too well... Is there a firmware upgrade for this stove just like my iPod, LOL? It's funny, but I will check. And, oh, BTW, the low draft is set to the highest speed possible.

I don't know the routing inside a Harmon.

Eric,

There is a trip point at which that switch changes state. Anything that can affect the pressure differential can cause that switch to shut the stove down it, that condition need not be present at start up. So the stove could start and later get shut down, simple movement of ash for example. Like I said it is something to check and the checking doesn't involve part swapping.

 

[cac4]

don't know the answer, but I just wanted to chime in and say that my Accentra FS keeps my house @65 overnight, without issue. So its not that it "can't" maintain a low temp.

 

[vferdman]

try a couple of bags of pellets that are shorter. you said pellets are 1 1/2 to 2 inches it will hang that stove up every time. on a low burn it is not feeding enough pellets because some are hanging up over the slide plate. clean all pellets out of the hopper and get acouple of bags of another brand and i will bet this will solve the problem. we had the same problem with my parents accentra and pulled our hair out until we figured it out.

Well, I did not measure my pellets, but they are New England Pellets brand and are premium hardwood pellets. I have two tons of them and they are pretty much what most people burn around here (they are made in New Hampshire, which is local enough for most New Englanders). I may try some other pellets just to see if the problem is caused by the actual pellets, though. If it is, that would be a bad thing as I think the stove should be able to burn whatever you put in it. I normally buy pellets at the best price possible and if I have to consider what length they are before buying them it may effect the cost effectiveness of this stove.

At the risk of repeating myself I will state that the wood burning stoves are way easier to operate. Pellet stoves are way too complicated for their own good it seems. They sure are nice when they work right, but if this forum is any indication this does not happen very often. I've been using a wood burning insert for three seasons now with absolutely no surprises or issues constantly popping up. Also, the maintenance is pretty simple on that stove. Not much to it, really. No moving parts save for the distribution fan, which is really not even part of the actual stove. The stove will burn and burn predictably no matter what I put into it (within reason, of course). The pellet stoves have a long way to go and many parts to shed before reaching the genius of the simple draft powered wood stove.

Having said all that I still love the pellet stove and I think I will get to the bottom of this problem or just learn how to live with it.

 

[vferdman]

don't know the answer, but I just wanted to chime in and say that my Accentra FS keeps my house @65 overnight, without issue. So its not that it "can't" maintain a low temp.

Chuck, could you describe your setup? The venting and the intake as well as the space the stove is working with. Mine is in a large open space in the basement, maybe 1000 sq ft or a little more. It would be helpful to know what your setup is before concluding what the stove is capable of. Every setup is different and presents a different set of challenges for the stove. Also, do you use room temp or stove temp? If former, where is your room temp probe located?

Thanks!

 

[rickwa]

vferdman, typically wood pellets are about 1 inch some shorter ones in the bag some 1 1/4 inches. that is the goal of the pellet mill. if the moisture or material is not correct when the pellets are extruded they can be fragile and turn to dust or be to hard and not break when leaving the die and end up like pencils. take a tape measure and measure some of the longer pellets if you are not sureof length

 

[Lousyweather]

try a couple of bags of pellets that are shorter. you said pellets are 1 1/2 to 2 inches it will hang that stove up every time. on a low burn it is not feeding enough pellets because some are hanging up over the slide plate. clean all pellets out of the hopper and get acouple of bags of another brand and i will bet this will solve the problem. we had the same problem with my parents accentra and pulled our hair out until we figured it out.

Well, I did not measure my pellets, but they are New England Pellets brand and are premium hardwood pellets. I have two tons of them and they are pretty much what most people burn around here (they are made in New Hampshire, which is local enough for most New Englanders). I may try some other pellets just to see if the problem is caused by the actual pellets, though. If it is, that would be a bad thing as I think the stove should be able to burn whatever you put in it. I normally buy pellets at the best price possible and if I have to consider what length they are before buying them it may effect the cost effectiveness of this stove.

At the risk of repeating myself I will state that the wood burning stoves are way easier to operate. Pellet stoves are way too complicated for their own good it seems. They sure are nice when they work right, but if this forum is any indication this does not happen very often. I've been using a wood burning insert for three seasons now with absolutely no surprises or issues constantly popping up. Also, the maintenance is pretty simple on that stove. Not much to it, really. No moving parts save for the distribution fan, which is really not even part of the actual stove. The stove will burn and burn predictably no matter what I put into it (within reason, of course). The pellet stoves have a long way to go and many parts to shed before reaching the genius of the simple draft powered wood stove.

Having said all that I still love the pellet stove and I think I will get to the bottom of this problem or just learn how to live with it.

Vlad- cool name, by the way-

New England pellets are made in Jaffrey, NH AND Schuyler, New York. If there are any 2"ers or more, you WILL get hang issues in the hopper.

I dont beleive this forum is a good indication as to how they work....people post here mostly when they have issues they cant solve themselves....its like a "problem" forum.......check out the wood forum. There are definitely alot of moving parts that can fail though! As for wood stoves, yep, pretty simple.......but, i wonder how much more work they are? Oh, yea, sorry, you enjoy that! How about cleanliness?

 

[vferdman]

Vlad- cool name, by the way-

New England pellets are made in Jaffrey, NH AND Schuyler, New York. If there are any 2"ers or more, you WILL get hang issues in the hopper.

I dont beleive this forum is a good indication as to how they work....people post here mostly when they have issues they cant solve themselves....its like a "problem" forum.......check out the wood forum. There are definitely alot of moving parts that can fail though! As for wood stoves, yep, pretty simple.......but, i wonder how much more work they are? Oh, yea, sorry, you enjoy that! How about cleanliness?

Well, I realize people come here with problems, but the point is that in 3 seasons with a wood stove I never had to figure anything out, but with about a month of pellet stove I have had nothing but issues. All having to do with so called "conveniences" that pellet stove is supposed to afford over the wood stove. The automatic stop/start, hands-off operation, cleanliness, etc. I've been doing nothing but troubleshooting this stove since the day I got it (though if I leave it at 70 it seems to work fine) and am up to my elbows in soot (every time I clean the burn pot). With wood stove I just take the ashes out with a scoop and I'm done. Yes, I have to babysit the wood stove at start time and then get it up to temp, then choke it down (all manually), but my experience is: it is cleaner, more reliable and in the end is less hassle than the constant troubleshooting, burn pot scraping, and monitoring of the pellet stove. And from what I understand Harman is one of the better ones out there. Geesh! If I had a proper flue where I put the pellet stove I would definitely get a wood stove in there. The biggest advantage of the pellet stove is ability to direct-vent. Can't do that with a wood stove. Anyway, once I figure this out I'll be happy, but so far I am frustrated and either cold in the morning or spending way more fuel than I need to.

 

[cac4]

Chuck, could you describe your setup? The venting and the intake as well as the space the stove is working with. Mine is in a large open space in the basement, maybe 1000 sq ft or a little more. It would be helpful to know what your setup is before concluding what the stove is capable of. Every setup is different and presents a different set of challenges for the stove. Also, do you use room temp or stove temp? If former, where is your room temp probe located?

Thanks!

My stove is in the corner of a 24'x36' garrison colonial, first floor, with an open floor plan. the second floor has 3 bedrooms off a small hallway at the top of a center stairwell.

The stove is vented out, then up with 3" pipe, through the fancy harman thimble, with its built-in outside air intake.

I normally use room temp, with the probe extended about 10' along an adjacent wall, and sticking up behind the couch.

I think LW is right when he says that you'll see a high percentage of reported problems here. I, myself, don't recall ever starting a thread to remind everyone here that my stove is still working a-ok. (but it is). ;-P

In my experience, nothing could possibly be any easier. pour in pellets; turn it on. enjoy heat. thats it. but...my stove ain't broke.

Anyway, the notion that this model stove is not capable, by design, of maintaining 65F, even when its working correctly, is bunk. mine does it every night.
I don't know what the problem might be, but I'm not sure I'm buying "long pellets", either. If there was a jam-up, and pellets ceased feeding...the stove would just think that it ran out of pellets. I don't believe I see an error code when I run out of pellets. (maybe I do; can't remember. I'm sure I'll be corrected promptly if I am mistaken).

 

[SmokeyTheBear]

Chuck, see last line ....

A 6 blink status may be caused by several things:
1. Blocked or partially blocked flue.
2. Blocked or partially blocked inlet air.
a. backdraft damper on the inlet pipe may bestuck closed.
b. if outside air is installed the inlet cover may be blocked.
3. The air chamber under the burnpot may be filled with fines and small bits of ash.
4. The holes in the burnpot may be getting filled with ash or carbon buildup.
5. Combustion blower fan blades may need cleaned.
6. Combustion intake assembly not properly latched.
7. No fuel in the hopper. <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< Out of pellets gets you a 6 blink status

 

[cac4]

but with about a month of pellet stove I have had nothing but issues. All having to do with so called "conveniences" that pellet stove is supposed to afford over the wood stove.

yes...it is "supposed" to be that way. (more convenient than a wood stove). if it isn't...its BROKEN.

...The automatic stop/start, hands-off operation, cleanliness, etc. I've been doing nothing but troubleshooting this stove since the day I got it

cuz its been broke since the day you bought it.

Imagine if I only had a crappy, run down, unreliable car to drive. and its the only one I ever had, and it was "50/50" whether I ever reached my intended destination. I might conclude that I'm better off to just walk. And I might be right. But to conclude that "cars are more trouble than they're worth"...well, thats not correct. Busted ones are indeed, a pain in the arse. But working ones are great!