Troubleshooting St. Croix Prescott

[GBFloyd]

Greetings to you all! I have been reading the threads here for some time, and finally have a problem that encouraged me to "sign up". I would like to start out by saying that I am impressed with the quality of posts and responses I've read here. There are obviously some pretty serious "pellet stove people". I had no idea!

I have a 10 year old St. Croix Prescott EXP that has run fairly well for the past 10 years. The stove is located in the basement and is run more or less every evening on manual only. (I don't leave it running at night or when I'm away from the house.) Weekends and when I'm home I run it full-time while I'm awake. Every fall I give the stove a thorough cleaning, including hooking a leaf blower up then follow up with several times during the winter when the weather permits. This season the stove started out running perfectly until about a month ago. I burn only hardwood pellets, and always run the stove on max setting as I've had issues in the past with running it too low (gumming it up). I clean the stove daily, including removing the covers for the ports on either side of the unit, scraping the grate, and removing and cleaning the heat exchange baffle.

Recently it has developed an issue (in max setting) where the stove starts and runs great, the main blower kicks on and it runs as it should for about 45 minutes. At about the 45 minute mark (it seems like when it really gets up to full operating temperature) the auger begins slowing down the feeding of pellets and the unit gradually slows down until the fire goes out. When I let it go, the unit will go out (although it continues to feed pellets) and the #3 led is lit solidly. (Proof of fire, I know). I have attempted to rectify the situation by performing the following steps, though not in any particular order:
- Pulled the interior panels out and cleaned inside the stove, behind the ports (banged on the housing with the vacuum cleaner nozzle and got quite a bit out; and run a flexible snake up through both sides of the ports).
- Again ran the leaf blower to clean it out.
- Adjusted the butterly damper on the back of the unit.
- Removed and cleaned the room fan.

Today I attempted to adjust the voltages on the combustion fan by following the instructions in the Operations Manual (Page 21), but I don't think it was effective and I believe the manual I have is for the newer version control boards and am not certain that it applies to the older control boards. On my list of "things to do" is go through my files and see if I can find the original owners manual.................

I have to say that a great many of the things I've tried to "remedy" this current situation I read by going through the threads on this site, and I have been amazed at how much I cleaned out of the stove I would have said was "clean", so I know there much more knowledgeable people out there that may have some suggestions for what I can try. Any suggestions you all could offer would be greatly appreciated.

Thanks!

 

[stovelark]

Did this stove do this from day one? Or is it older and you have had it ten years? on older stcroix mother boards, there was no slide switch on them, you put a jumper on the back to run them in manual mode or hooked up a thermostat- is yours this way, or do you have a selector switch on the MB? I'm wondering why you have always ran in on heat level 5? Most folks use 2 or 3 and its pretty adequate. Is the combustion blower operating normally and is good and clean? Also, if it feeds normally at first, this sounds like this is during startup mode. Once the stove is warmed up and through startup, is this when the auger slows down and eventually stops?? You may have a tired auger motor or its not getting proper power from the MB, you could put power directly to the auger and let it run, see if maybe the MB is not working correctly. On heat level 5, the auger should pretty much run constantly, a short break between feedings. The manual would give you timings for the feed cycle, but I think medium (3) is 3 secs on, 6-7 secs off. That's where I'd start, with the combustion blower and making sure voltages to the auger from the MB is correct. I'd check for that jumper on the back too, unless you have the MB with a selector switch on it. Good luck with it. Stcroixs are a pain to clean, but are good reliable heaters normally...

 

[heat seeker]

Try oiling the auger motor bearings/bushings. Mine acted similarly, and that was the cure. It doesn’t take much to slow the motor down at the armature bearings.

 

[rickwai]

I would suspect stiff auger motor of bearings. You can verify by holding auger button in and time the motor. They use a 2 RPM motor should turn approx. 1 revolution in 30 seconds.
I would take auger out and clean auger shaft at bearings and oil to make sure all is turning free. You should be able to pull it all in 1 piece by removing the 4 nuts on the plate behind the motor.

 

[GBFloyd]

Did this stove do this from day one? Or is it older and you have had it ten years? on older stcroix mother boards, there was no slide switch on them, you put a jumper on the back to run them in manual mode or hooked up a thermostat- is yours this way, or do you have a selector switch on the MB? I'm wondering why you have always ran in on heat level 5? Most folks use 2 or 3 and its pretty adequate. Is the combustion blower operating normally and is good and clean? Also, if it feeds normally at first, this sounds like this is during startup mode. Once the stove is warmed up and through startup, is this when the auger slows down and eventually stops?? You may have a tired auger motor or its not getting proper power from the MB, you could put power directly to the auger and let it run, see if maybe the MB is not working correctly. On heat level 5, the auger should pretty much run constantly, a short break between feedings. The manual would give you timings for the feed cycle, but I think medium (3) is 3 secs on, 6-7 secs off. That's where I'd start, with the combustion blower and making sure voltages to the auger from the MB is correct. I'd check for that jumper on the back too, unless you have the MB with a selector switch on it. Good luck with it. Stcroixs are a pain to clean, but are good reliable heaters normally...

Stovelark,
Thanks for your response!

- I bought the stove new, so no it hasn't done this since day one. Yes, I've had it ten years.
- It has the slide switch for Thermostat, Smart Stat, and manual mode. I don't have any stats hooked up to the unit, so it runs in manual mode only.
- The stove is technically "in the basement", but that is also where my family room is located. It's open to the main floor. I leave the fan on my furnace running continuously to circulate the air, then I run the stove on high to supplement the main furnace, most of the time not having to run it so frequently. I turn it down to 2 or 3 when I'm physically in the family room.
- Yes, it seems like it runs exactly the way it should until it gets hot. At that point the auger doesn't kick out as many pellets and it gradually dwindles off. I was thinking it was getting hot and pulling in the high limit switch, but I haven't had to reset that- so I'm fairly certain that is not the case. It also seems like it does this until the stove cools down, then begins feeding pellets again to bring the fire back up.
- The combustion motor seems to be running normally, but I'm wondering if that has something to do with the unit getting too much combustion air. As I said, I tried lowering the voltages to the combustion motor using the instructions in the operating manual- but I'm wondering if the instructions are for a newer control board. I've tried setting it when the stove is on the lowest setting '1', but I don't get the blinking led's when I hold down the auger motor button and press either the trim or feed buttons.
- I was hoping to avoid having to pull the auger, but if that is the recommendation ( I see a few other responders have mentioned this ), I guess that is my next step to investigate.

 

[GBFloyd]

Try oiling the auger motor bearings/bushings. Mine acted similarly, and that was the cure. It doesn’t take much to slow the motor down at the armature bearings.

Heat Seeker,

Thanks for the reply! I'll give that a try...

 

[GBFloyd]

I would suspect stiff auger motor of bearings. You can verify by holding auger button in and time the motor. They use a 2 RPM motor should turn approx. 1 revolution in 30 seconds.
I would take auger out and clean auger shaft at bearings and oil to make sure all is turning free. You should be able to pull it all in 1 piece by removing the 4 nuts on the plate behind the motor.

Hi Rick,

As I posted to Stovelark, I was hoping to avoid pulling the auger but that looks like the best option at this point. I've watched a YouTube video on that very process. I guess I'll give it a try.

 

[heat seeker]

You may not have to pull the auger. The motor has a set screw(s) you loosen, and in theory, the motor comes right off. I had to judiciously use a pry bar to get my motor off the auger shaft, but it did come off. The oil holes on the motor were inaccessible, and on the bottom, to boot, so the motor had to come out anyway, to oil properly. I used 3-in-1 in the blue can; it's not supposed to gum up in motors.

I check my auger periodically for freedom of movement. When the hopper gets really low, I grab the flutes of the auger from inside the hopper, and move the auger axially and rotationally. It's still nice and free, so I don't take it out to lube it. I used high temp grease on the upper bearing a few years ago. I had to sand the auger bearing surface to clean it up, added a dab of the grease, and it's been good for years now.

I confirmed that it was the armature bushings by shooting some WD-40 on them. It's a poor lubricant, but it worked for an hour or so, and proved to me I had found the problem.

 

[stovelark]

Thanks for all the info- I think maybe the auger motor is getting tired, or maybe overheating and going into an internal thermal shutdown.. I too would put direct power to it and time the auger movement, but bear in mind, try to do this under load, with the auger in the stove moving pellets....its difficult, but if you could monitor voltage coming to the auger motor from the MB, that might tell a story too. Good luck with her,if its the original motor, it doesn't owe you anything, ha...

 

[jzm2cc]

Ditto on dry / galled auger bushings. Pull auger, clean and lube them. Probably good for another year assuming motor is still ok. Either way pulling auger is a good idea on a 10 year old St Croix.

 

[GBFloyd]

Update: Thanks for the great advice. This is what happened...

A week ago Saturday (January 20th) I pulled the auger motor, cleaned it, oiled it and reassembled the unit. The stove fired up and worked absolutely perfectly. It burned great all day Saturday, then I turned it off for the night. Clearly it was the auger motor bearings. However, when I went down to light it Sunday it reverted to it's previous pattern. I decided it needed to be replaced.

This weekend I again pulled the motor, auger, and whole assembly apart. Gave the entire stove a solid cleaning, replaced the auger motor (thank you Earth Sense) and reassembled the unit. It has been running exactly as it should since. All day Saturday, shut it down for the night. Fired up Sunday and ran the entire day before shutting it down for the night. Fired up perfectly this morning.

Thanks everyone for the great advice! I'm suggesting this site to everyone I know that owns a pellet stove...

 

[heat seeker]

I’m glad you got it fixed. And, thanks for the feedback!

 

[rickwai]

Sounds good! The auger bushings/bearings get dry and dirty over time and auger needs pulled and shaft ends cleaned up. Usually You can hear the motor laboring when this happens. Once everything is cleaned up and lubed the motor has a noticeably smoother sound to it. As you saw, Auger is not a big job to remove. You can pull the motor and auger together and get motor off shaft on the bench where you can get to it easier.