Harman Invincible- doesn't work right, all obvious cures failed- help please!

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paulgeiger

New Member
Nov 11, 2008
7
Maryland
I have a 1995 Harman Invincible pellet insert which I bought used a year ago. I thoroughly cleaned it as per owners manual and at first it seemed to work properly when I burned only a partial bag of pellets. Since it was summer, I didn't touch it until this heating season. Now, the fire burns out before the automatic feed kicks in. All the motors seem to work fine. When I first start it, the combustion blower works and a good fire gets started. When I turn it to "TEST", the dist. blower and auger work fine too, and I can keep a fire going only by repeatedly turning to the TEST setting to keep the pellets feeding in. If I don't, it just dies out in 5 min. or so. Sometimes, if I keep feeding pellets manually like that (maybe 20 min. or so- seems like way to long to reach 140 degrees or whatever the set point is), it will presumedly get hot enough to start the auto. operation. Then it usually will keep going but then it seems like the fire is too big and doesn't respond much to changing the temp. setting as well as smoking up the glass.
In addition to cleaning, I've replaced the circuit bd., ESP probe, and thoroughly cleaned everything I can find to clean including taking the burn pot off, all covers, shields, etc. I think the dooe seals are good. I have heard about a low and high limit switch but I don't think the Harman has this on the Invincible.
I'm at a loss as to what the problem is. Any help would be greatly appreciated. Thanks in advance.
Paul
 
I am thinking room temp probe??? But I don't know about a stove that old....

:coolhmm:
 
I did put a new room temp probe in (stove didn't have one when I bought it), but also you use a different setting to govern by room temp rather than by stove temp. I usually choose stove temp. but it seems to act the same on either setting. Thanks for your input.
Do you know if there is any way to bypass on the circuit board the limiter for temp. so the automatic operation is always on without having to wait until the stove gets hot for the feeder to work? That might work for me?
 
Hi, I just found this forum from a search. Don't know if you have found the answer yet, but here's my experience.

I've got an invincible from the same era. The problem you are describing isn't the room temperature probe, it's the exhaust temperature probe, just downstream of the combustion blower. (back of the stove, center at the bottom). The leads on these elements are extremely thin and they will break internally but still sort of stay together.

The stove will not feed pellets until it senses that the firebox is hot enough to sustain the flame. Then once you have the fire burning, if the probe doesn't sense the increases in temperature from feeding pellets, it just keeps feeding them and they overfill the pot. It's pretty easy to replace.
 
I actually had already replaced the exhaust probe as well as the circuit bd. No difference in performance. The probe does seem to be regulating the fire pretty well once it gets hot enough. That's the main problem I think. In order to get it to the right temp., I have to not only burn a full pot of pellets, which seem to be burning nicely, with comb. blower stoking it nicely, etc., but it will just go out unless I manually feed more pellets in. I have been doing this by turning the auger feed knob to the "TEST" position which feeds for about 1 minute (along with turning the dist. blower on) and this keeps the fire going. But I have to do this probably about 10-15 times back to back to get it hot enough for the distribution blower to come on and about that time, the auger will kick in automatically. All this takes about half an hour or more. It seems like that's way too long for the exhaust temp. to get hot enough. Not to mention the agrevation of nursing it along. Shouldn't one pot of pellets heat it up enough? I've tried several brands of pellets, so I don't think it's that. I'm wondering if maybe it's some kind of air flow problem, especially since it also seems to smoke up the glass as it burns. I have cleaned and vacuumed every place the manual says to clean, but maybe I've missed something important??? Anyway, once it's hot, it burns on it's own, presumably the way it's supposed to except for the smoking on the glass. I think it's supposed to have an "air wash" feature to prevent this??
Thanks for the reply, and any other thoughts you have will be greatly appreciated.
Paul
 
Doesn't sound like the way an Invincible should be acting. When it's clean, there shouldn't be any smoke to speak of and about a half pot of pellets should be enough to satisfy the exhaust sensor and get the feed going. I'll describe what I've found in the stove assuming that you already know your vent piping is clear.

The air flow passages aren't really all that complex. Normally the inlet wants to be the one at the back of the auger assembly that feeds the air through the bottom of the pot and up through the holes. This passage does want to plug with cinders and pellet dust sometimes. If you haven't cleaned here it's accessible by loosening the thumbscrews for the plate on the front of the burn pot. The same air inlet allows some air to come through the auger itself. That should be obvious as the fire will actually burn down to and sometimes into the auger, but the flame will follow the air flow out and up into the firebox.

Once the air has made its way into the firebox, it's going to want to go up and over the baffles on both sides to make its way through the heat exchanger tubes. If both sides are clear, you should see a pretty symmetrical flame in the pot. If it is burning on one side or the other or the flame seems to be burning toward one side only, it's a fair bet the other side is plugging. If you haven't taken the baffles off, they are again pretty easy to remove with thumbscrews. There's a little bit of a secret combination to rotating them out of the firebox, but with repeated attempts and light drinking you will prevail. If it's been a while, there could be a pretty thick coating of ash and soot on the back of the baffle and the wall of the firebox.

From the top of the baffle, the air flows down to the bottom again and makes it's way into the bottom of the heat exchanger. This is essentially a U-tube that causes the exhaust air to flow up one side and back down the other to make it's way into the final passages going to the exhaust blower. The inside of these tubes can plug pretty easily and is the most likely place the air would be impeded since they are so hard to access and fully clean. There is a formed metal plate that is removable at the bottom of the wall that will give you access to the bottom of both tubes.

I have a small mirror on a telescoping handle that I can hold in there to reflect a flashlight up into the tubes. I would suggest you get one of these (auto parts places, hardware stores, etc.) as two years ago one of my tubes had the dried remains of a bat stuck in it and I would never have figured it out without seeing it. They are actually square tubes and if they are clean, you should be able to make out the straight walls all the way up on each. Normally when they are dirty, they will have formed a kind of round hole up the center.

I haven't found any drop dead - sure fire - only one to use tool to clean these out. You have to have something pretty flexible to get in the bottom hole and still straighten out enought to rod out the tubes. You can bend a piece of wire or stiff cable and just keep shoving up and down until you manage to break all of it loose. Keep the shop vac handy to get the piles out the way.

With the metal plates out of the way you should also be able to shine a light a little ways back toward the exhaust blower to see what these horizontal passages look like. Here again if there is ash and soot built up, you may simply be able to scrape it loose and vacuum it back from the firebox.

If the inlet, the heat exchanger and the passages to the blower are clear, then the only remaining spot is the blower itself. Get a gasket kit before you take this out as the blower gasket is a little sensitive to begin with and gets pretty brittle with age and heat. Bunch of small sheet metal screws holding a flange down. Once these are out, the blower motor and impeller come straight up. The impeller is metal, but fairly thin so be careful not to bend the vanes. Cleaning this should be pretty obvious, although tedious. With the blower out, you can also get another angle on the passages going back toward the firebox. While you are in the back looking at the blower area, you should be able to check the little gravity door on the air inlet to make sure it swings open ok.

With the blower out, you'll see that there is precious little opportunity for plugging after the blower before it gets to the vent. You can push something through it anyway just to ensure it's clear, but go gently remembering where you put that new exhaust temperature probe.

So on my stove that's it. If you have an outside air kit, you may have some more inlet piping to check, I don't.

Hope something in all that rambling helps.

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Wow, I just realized you have an insert and I'm talking about a freestanding. Sorry for any confusion and I hope some of this still helps.
 
Thanks so much for the detailed troubleshooting/cleaning report. Although I do have an insert, I remember most of the areas you mentioned from when I last cleaned it. I believe the guts of this stove must be identical to the free standing model. I intend to go through this procedure within the next few days and I'll let you know what I find- hopefully a problem that gets corrected! Thanks again.
 
Not a problem. I hope it works out for you. I think the Invincible is a heck of a stove and it would be a shame if you can't fully enjoy it. It's not necessarily one of the easiest to clean although I understand it doesn't need to be cleaned quite as often as some others. Doesn't sound like that's the case with yours right now if it's smoking from the start.

One other thing I run into pretty frequently is that the stove will be hard to light and will overfeed pellets when the exhaust probe is dirty. It gets a pretty heavy coat of black nasty sooty on it and that tends to insulate it so that it doesn't respond to temperature changes. If you haven't been checking this, it's another place to look. I just make it a habit to slide it out and wipe it with damp rag.

Good luck.
 
Well, I pulled out the stove and did a thorough cleaning as per your instructions as well as the steps outlined in the owners manual. Didn't find anything surprising. Since I had only burned maybe 6 bags of pellets since I cleaned it before, I didn't expect and didn't find that much ashes built up. I resealed the fan and burn pot. Probe had a light coating on it which I wiped off. The only place I wondered about that I couldn't get to was the top of the 2 connecting U-tubes in the heat exchangers. I couldn't get any brush or wire to bend completely around that crossover link, only the 2 vertical tubes themselves. The verticals were pretty clean (not at all rounded like you said they could be.) Vent pipe clear, etc. All looked good. So, the test- made a fire. Now I'm even more puzzled. It seems to burn a little better- but still doesn't get the probe to kick in without some extra pellets being added. But now, when it gets going, the fire's too hot! Even on lowest auger feed and lowest temp. setting, it spills burning pellets off the edge and flames basically fill almost the whole box. So it may be burning a little more efficiently, but that probe never seems to get hot enough to register and cut it back. It's as though the whole temp range is set too high- needs to be too hot to start and keeps it too hot when burning. Even before, it was working pretty nicely after it got hot enough, but I was still keeping it on the low settings. Now even low is too high. The flame seems to be even on both sides.

Just for comparison can anyone tell me about how long the auger stays on at the different feed settings? Mine seems to turn on every minute like clockwork, but just stay on longer at the different settings. At the lowest, it stays on about 8 seconds every minute, then at higher settings, maybe 16, 24, ~30 at high. Is that about normal? Thanks for any input there.

Unless there's still something keeping the hot exhaust air from getting to the probe before it cools or something like that, the only thing I can think of is that maybe the original circuit bd. was programmed differently. It was made in 1995, but the board I just replaced said 2004 on it. I think it was serviced then with a new board. Wonder what made the original bd. go bad or if the replacement, which is exactly like my new one, was somehow different? So, in any case I'm still not out of the woods with this thing yet.
Appreciate any thoughts or observations. Thanks
 
Sounds like you got the cleaning done quite well. If you are getting a good burn in the pot, I'd quite worrying about the top of the U. I'm not sure what your controller looks like, mine is the original and I don't really think there is any programming to it. It's an analog circuit so all of the adjustment is done using the pots on the front. I'm afraid I'm stuck running off a generator in the middle of an ice storm right now with the stove as my only heat source, so no playing around trying to time the auger for me!!! Here's a link to a previous post I found from 2005. The guy with the reply is evidently still on the forum, so you might try him with a private message or e-mail and see if he can walk you through getting the board set. My feed rate adjustment is set at about 3.5 which is right around what Harman suggests as a starting point. This works pretty well for me with the ash ending up being around 1 to 1.5 inches at the top of the pot.

Try this post and see if that helps. Let me know how you come out. I've been thinking about replacing the controller in mine (the pots are getting a bit loose and are obviously dirty). I'll be interested to see if you find that to be your problem. If you end up with the board out, see if you can get a picture of it and I'll let you know how well it compares to the original.

https://www.hearth.com/econtent/index.php/forums/viewthread/622/

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I just found another post that is discussing feed adjustment. The main point is stove vs. room temp, but the feed adjustment (or limiter) is also discussed. See if any of that helps.

https://www.hearth.com/econtent/index.php/forums/viewthread/33212/
 
Well, Hallelujah! I finally got my problem solved! Or at least I think so, so far. After all the effort cleaning, replacing parts, etc. the problem turns out to be that my combustion blower motor was turning the wrong direction!! When I had it out to clean it, I hot wired it to test it out and the direction didn't seem to be the right way to cause air to flow up and out the chute to the exhaust port. If you view that section from the left side of the stove it seems the air should be pulled in from the rear, and go toward the right side of the stove and then up and out. The fan was turning counterclockwise looking from the rear. That direction seemed to be pushing air away from the chute. Obviously air was going out because the stove was burning but I think the turbulence was keeping the stove from drawing correctly, causing bad flame, soot on glass, and low heat to the probe, causing my general all around poor operation. So, I disassembled the motor and flipped the stator? over the opposite way (switching the leads didn't change direction for this type of motor). That made it go the other way. Stuck it back in and fired it up- Lo and behold the first thing I noticed was a beautiful dancing flame which I hadn't ever seen before. Next, only a couple of minutes later, the blower came on, auger started feeding, and all with no smokey glass. Needless to say, I was very happy. A couple of days later now, I've been burning it almost around the clock and so far, perfect operation. I sincerely doubt that 1 in a million have this same problem, but if you have tried everything else and still no luck getting good operation, check to make sure the blower is going the right way. If you look at the back of the stove, it should turn clockwise (toward you on the top if you look from the left side of the stove). If anyone can verify this or if you think something is wrong with this , please let me know. All I know is it has brought my stove to life. Don't even want to guess why it was wrong to start with.
 
Wow!! That was a strange one! I can see how the air flow from the opposite side tube would be screwed up royally with the blower running the wrong way. Good snag on finding that one.

I'm glad you got it straightened out. I was feeling bad that you were having so much trouble with an Invincible. I've found it to be a pretty nice stove. I'm sure you're enjoying it a lot more now.

Kevin
 
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