CB1200 - Very Hot Exhaust Pipe & Strong Exhaust Blower with Moderate Heat Output/Weak Convection Blower

[misfitinme]

Hello from Maine - I have a Quadrafire CB1200 that came with the house I purchased last December. The heat seems moderate at best with both the Heat and Fan on High. The convection blower seems to blow weakly compared to the exhaust which is so powerful it has a deep throbbing/pulsing bass hum that can easily be felt on the exhaust vent pipe and the exhaust pipe is hot hot hot both immediately exiting the stove and even hot outside. You can't hold a hand to it on the inside and it's pretty hot on the outside. No smoke coming from the top of the vent, just see the heat shimmer in the air.

Details:

• I had the original dealer/installer service/clean December of 2020 and December 2021. When cleaned a few weeks ago, I mentioned that the back vent pipe did not seem attached to the stove. He looked at it, agreed it was not completely sealed, he re-gooped it (with the red stuff) and said he put a screw in it to hold it in place. He also replaced the thermocouple and the wire.
• I clean the burn pot and pull the heat exchanger rods every time before starting.
• I vacuum out the entire stove, including removing the baffles at least once a week.
• I have started taking off the side panels, the plate in front of the burn put flapper/igniter, and the access panel on the right and vacuum everything I can reach in those places as well. I make sure the burn put flapper closes completely.
• I took off the pellet stove's vacuum hose where it attaches on the left side of the unit and blew canned air through it as shown in Quadrafire's troubleshooting videos.
• Flame is okay (I removed the logs and no longer use them), fairly consistent with an occasional intermittent high flame or low flame but it tends to sort itself out.

Last year I had minimal issues with it other than lots of ash from the pellets recommended by the previous owner (had to dump the pan frequently). This year I am using Vermont Wood Pellets on the recommendation of the dealer. There is very rarely any ash in the pan, though it does collect in the nooks and crannies but even this is a very small amount. I don't think I've had enough ash altogether this season to completely fill the ash pan. At this point it feels like I am going through pellets faster than I should compared to how much heat I am getting from them (and how much is going out that exhaust pipe!).

I don't want to start randomly throwing parts at it, but am wondering what to try next. Vacuum issue? Blower issue? Wondering if the resealing/screw on the exhaust pipe has upset the balance of air so it is pulling more to the exhaust than pushing out into the room. Can't find anything on how to adjust the airflows on the CB1200. I did find a video on cleaning the blowers, but not sure I can completely remove the assembly (stove is in a corner and with that screw in the vent pipe, I'd have to undo everything the tech just did.) Any guidance on what to try next would be appreciated. Thanks!

 

[jzm2cc]

If it's the free standing model it should have a high and low room fan setting for each heat setting, set on high if not there already. Inserts just have low, med, high fan settings. It could also be a fan issue causing low air flow (bad bearings, or clogged fan blades that need cleaning.(

With the exhaust blowing so much heat out the pipe makes me wonder if it has the correct fan/motor? Does the fire die out on low settings? You could try restricting the inlet air little by little to see if you can keep more heat in the stove verses blowing it out the exhaust.

 

[misfitinme]

If it's the free standing model it should have a high and low room fan setting for each heat setting, set on high if not there already. Inserts just have low, med, high fan settings. It could also be a fan issue causing low air flow (bad bearings, or clogged fan blades that need cleaning.(

With the exhaust blowing so much heat out the pipe makes me wonder if it has the correct fan/motor? Does the fire die out on low settings? You could try restricting the inlet air little by little to see if you can keep more heat in the stove verses blowing it out the exhaust.

Thanks so much for the reply. It’s the freestanding model and I keep the fan setting always on high. The fire does tend to disappear on the low setting, barely any flame above pot. The stove was just professionally cleaned inside and out including venting and I’m going in regularly to clean the fan blades. Whatever pushes the air out the exhaust is very powerful. The exhaust vent is much hotter than any part of the stove itself (and even hot outside, yesterday I noted I can smell a pleasant woodsy smell outside but there is no smoke, and no such smell on the inside. I have cedar siding but it’s not black or sooty near the vent so it looks like whatever is coming out is clean.

How would I restrict the air inlet? The manual says not to install a damper. There is no outside air exchange that I can see. The tech mentioned that the stove has a power vent when I told him I’m worried about the exhaust vent being so hot. My concern is that is too powerful and I’m blowing most heat outside.

I did notice that the screws over the auger box are somewhat loose (maybe stripped) they sit in the holes and spin but don’t really tighten or create a tight seal when using a screwdriver. Not sure if that impacts anything but thought I’d mention. I’ll Research the air intake idea, and replacement fan(s). Any recommendations would be appreciated. Thanks again for taking the time to reply!

 

[jzm2cc]

Usually in cases with too much air blowing out the exhaust the flame dies on low setting. Where do you have the auger feed gate placed? Fully up, down or somewhere in the middle?

I assume the two flame baffles are in place below the heat exchanger tubes?

Do the exchanger rods pull out fully or do they stick part way?

Can you determine whether the exhaust motor runs at different speeds for low medium and high? Probably easiest to determine this before the room blower turns on after start up.

 

[misfitinme]

Yes, flame tends to die at low settings.

Auger feed gate is medium, leaning toward the low side (otherwise I get lots of white flame with blue in the bowl). The flame seems to get plenty of air seems very lively at all times. However without changing anything, there is a lot of variability in the flame. I’ll look at it one minute and it’s dancing above the bowl, then a little while later it’s barely above the bowl.

Baffles are in place correctly. Rods to exchanger tubes pull easily, bit of clunkiness at the end before I slide back down. The tubes themselves tend to get covered in black soot. When cleaning I remove the baffles, I use an old 2 inch paintbrush to clean them and the heat exchanger tubes and get the fine ash that rests in the books and crannies.

Exhaust blower seems consistent no matter whether heat or fan switches are high low/high low medium. The heat blower seems to go silent if I flip the fan switch down which I assume is the off position.

the space in which the unit is installed rarely gets beyond 70 degrees even if I bump up the feed rate. The wall mounted thermostat (about 14 feet away) gets to about 70 but no warmer than that. It’s a post and beam house with center staircase and is pretty open, but last year running supposedly crappy pellets I was getting a lot more warmth and the exhaust rarely got so warm that I couldn’t touch it.

Right now I prefer to get the space heated then turn the unit off and let it cool to about 62 before turning back on. I had issues with the remote (it will turn off but not restart once it goes 3 degrees below the set temp) so I now only use it in either on or off mode. I’m going through pellets at a faster rate than last year. considering these Vermont pellets are supposed to throw more BTUs it feels like the majority of the heat is being exhausted.

It does have trouble getting lit at times. It drops pellets and might ignite but I’ll come back in the room half an hour later and the stove has shut down. If I have the hopper door open for any amount of time the flame dies way down, and if the hopper is full, the pellets create a very steep angle of repose as they feed and the stove shuts off so I have to keep an eye on it and constantly check to make sure the pellets are pushed back over the auger opening, tamp them or move them around to keep the feed going.

 

[misfitinme]

One other thing I should mention, when I checked the exhaust pipe today on the exterior of the house, the clear silicone applied to the joint between exhaust pipe and the exterior of the wall thimble is no longer in place. It looks like maybe the tech who cleaned it this year pulled the exhaust pipe away from the thimble, breaking that seal. I’ll try to grab a picture.

 

[misfitinme]

Another thing I should mention. The air blowing out of the right side (the right side as your looking at the unit which would be the left side if your back was in front of the unit ) feels cool. When I put my hands about 2 inches in front of the vents in front of the heat exchanger tubes, the air blowing out is warm on the left and warm in the center, but on the right it feels cool. And yes I’m cleaning heating exchanger tubes with both the rods about 2-3 times a day) and by hand with baffles removed after each bag of fuel. Im determined to figure this out, but geez it’s turning into a full time job!

Hope everyone is off to a warm and happy new year!

 

[jzm2cc]

Make sure your firepot floor is fitting to firepot without a gap larger than a dime so proper air flow is maintained.

Black soot on heat exchanger tubes is concerning as ash should be brown not sooty black assuming unit is burning properly. Usually soot means too much fuel or lack of combustion air/plugged exhaust.

The room fan should not turn off on the lowest setting (assuming it will run on medium or high settings). Try spinning fan blades by hand to see if there is high drag. Suspect fan is turning slowly thus heat is not being removed from stove and sent throughout room properly.

 

[misfitinme]

Thanks for the feedback, I agree the black soot on the heat exchanger tubes has me troubled. Last year they would get covered in greyish brown ash when I was burning the hardwood pellets. The black soot does not scrape off with the cleaning rods, hence I have to remove the baffles everyday to clean them by hand. I always check the firepot floor and it is sealing tightly - no gap. The only other thing I have a question about is the glass windows and where they seat on the door - the gasket around the door itself (where it meets the threshold/frame of the stove itself) seems fine, but I do feel air around the inner sill where each piece of glass is "seated" in the door frame. Should those be sealed tightly to the door frame? I really appreciate the advice. I'll play with the fan again tomorrow and let you know how I make out. Thanks again!

 

[jzm2cc]

The top pieces of the three panes of glass are not sealed, that's the air wash that helps to keep the glass clean.

Does the rest of the stove insides get covered in black soot like the heat exchanger tubes? You shouldn't have to remove the baffles daily, that's an indication of a burn issue. Make sure all holes in burn pot are open and not carboned close. Does stove have an outside air intake? If so, check it's not plugged.

 

[misfitinme]

The left and right side of the fire box get covered in the black soot. And the burn pot gets black spots that I scrape off. Last year I used hardwood pellets, lots of ash but none of these issues. This year I’m using the recommended high quality softwood pellets and I’m worried I’ve ruined the stove with them. The unit does not have an outside air intake. How does one determine if one is needed?

 

[jzm2cc]

I'd try a couple bags of other brands to see if you have the same black soot problem. If so, then you probably have blockages in the exhaust path. Have you verified the outlet nozzle is not plugged with soot causing a restriction?

 

[misfitinme]

Forgive my ignorance…what is the outlet nozzle?

 

[misfitinme]

Quick update… I’m slogging through diagnosing and checking things as suggested. Despite being serviced 3 weeks ago and specifically asking them to check the door and ash pan gaskets (and being told they were fine), I tested them both and the door showed some signs of gasket fail - dollar tight in some spots, slid through in others. The ash pan, total fail. No snugness anywhere. I also found the latch bolts on both the door and pan to be too loose.

After a lot of thought and checking things here and there, I finally called the dealer and expressed my dismay on how the stove was running. No anger, didn’t ask for anything, just explained the issue with soot everywhere, poor burn, poor heat, etc. and said how disappointed I was, explained that I’m not rich - even though I live in an area of multi million dollar second homes, I live in a modest home and have to budget for everything, do almost all things myself rather than hire out, and it was bothering me to pay all that money for servicing and cleaning (I had no problem paying for parts and labor if needed, but between the several hours a day every day cleaning soot and looking at spending my weekend tearing apart the stove to truly clean it and replace the gaskets,etc. I let them know I wasn’t happy with the work and basically having to redo the entire thing myself. I asked them to order the gaskets I would need and told them I will pick them up before Friday. Thirty minutes later they called back, apologized, and are sending out a veteran tech to replace the gaskets, redo a thorough cleaning, run through a burn cycle to make sure the soot issue is resolved (right now it starts soothing up within 30 minutes of starting). All at no charge. If anything like a motor needs to be replaced obviously that’s on my dime but I’m pretty confident it’s an air issue thanks to the advice I’ve received here.

I am removing baffles and cleaning exchangers and everything else every 12-24 hours to keep it going, but even with the few small things I’ve been able to do in addition to the cleaning, I was able to get it to run over night at a steady 70 degrees on the low setting using about half a bag of pellets last night. Never been able to do that before…

So stay tuned, I’ll let you know how Saturday goes. I think the gaskets and deep cleaning the rear where the motors are will yield good results. And thank you all for the help so far. So much appreciated.

 

[misfitinme]

Mystery solved! Short answer - two big things going on: a leak (door gasket was giving poor seal in a couple of places) and - the bigger culprit - a massive obstruction (to the air intake). After I called the stove shop, they called their senior tech - he knew what it was immediately and when he showed up yesterday he told me he had reached out to the guy would did the initial servicing and confirmed his hunch.

Here's what happened. The nut holding the flapper door to the burn pot had become loose and caused the flapper door to hang down more than 1/4". This happened after the annual servicing in 2020 but before the annual servicing I just had in 2021. Being unfamiliar with pellet stoves before buying this house, I didn't know about the access panel to the area under the burn pot until I noticed the drooping flapper door whilst cleaning the burn pot (I take a quick video with my phone after cleaning to make sure all the parts I can't see are clean). After researching the issue here (yay Hearth.com!), I was able to fix the drooping flapper door but it still sagged more than I liked (it didn't seem to seat properly when I closed it) so I made a note to have them check it when it was serviced. This was about 2.5 months ago.

However, what I did not know was that, before I noticed it/fixed it, every time I was pulling the rod to empty the burn pot, I was flinging all the ash and pellets into the intake port at the rear of that area and it was all going onto the floor (between the bottom of the store and the actual floor). When I had called to schedule the 2021 servicing, I mentioned it as I wanted them to check that I had fixed the flapper door correctly. I also reminded the person who came out to the do the servicing. However, that person never cleaned the air intake area, never checked under the stove.

The senior tech had confirmed that the other guy hadn't done what was needed before he arrived. He got to work cleaning the stove again. As I had disassembled the stove prior to his arrival to speed things up (which he really appreciated), he took the time to walk me through the process and the tools to use to thoroughly clean and service the stove, including the heat exchanger tubes and the whole air intake system, and gave me a SUPER comprehensive timetable of what should be cleaned/checked and when (lots of things that aren't mentioned in the owner's manual) and what tools to use. When we titled the stove back , lo and behold there was a mountain of ash and pellets under the bottom of the stove. He also fixed a few other things the other guy forgot (like replacing the seal on the exterior of the exhaust pipe where it exits the thimble) and applying sealant to the connection between the interior exhaust pipe and the exhaust port on the stove.

The person who serviced the stove three weeks ago was the owner of the shop so I guess he'll be keeping his job - he was pitching in because the senior tech had gotten COVID when my original appt was scheduled. But I can't be mad...they put things right by having the senior tech come out yesterday at no charge and I got profuse and hearty apologies. I learned a lot, and the stove has been running nice and hot - so it looks like a happy ending!

Thank you @jzm2cc and @leaver441 for your help and suggestions, really helped me learn about the stove and gave me the confidence to call the stove shop to address the issue. And the knowledge I gained will help me avoid/fix issues going forward. You guys rock!

 

[jzm2cc]

Thanks for the detailed follow up Misfitinme! Every time repairs like this get posted someone else can learn from them. You're now a super tech with regard to your stove cleaning routines, congratulations!

 

[misfitinme]

Thank you, I really appreciate the help. You and @leaver441 (in a separate convo) were giving me good advice of things to check and clean and the only thing I hadn't done yet was check under the stove (was waiting for my son to have a day off from snowmaking at the local mountain). I never would have imagined how much ash and pellet accumulated in the air intake area (like a full pan worth!). I'm going to buy a leaf blower and plan to try that trick when I finish the current ton of fuel and do the next round of deep cleaning.

I actually like the stove because it is relatively simple, which makes it easier to fix. I'm going to tear the thing completely apart this summer and give it a real good scrubbing and repaint some places. It's an older stove but the tech said it was in great condition and should stay serviceable for many years if I take good care of it.

Now I'm off to research wood stoves to put in the addition - spent much of the summer and fall cutting, bucking, splitting and should have some nice ash ready to burn for next season. The maple and oak can sit another year. I'm hoping to find a nice older stove (either rebuilt or rebuildable). Thank goodness for this site - y'all are the best!