Seeing/Smelling Smoke from Chimney

[Nelson]

Hey All-

I know this question seems to get asked a lot and I've been around here long enough to have read a lot of the posts about it. However, I'm not satisfied with any of the prior discussion.

Background:

1. On my 4th season with my Princess - original cat
2. Burns have been going as anticipated/expected all season. Regularly getting 23-25 hours on a load and I'm on a once a day load cycle (in the evenings)
3. Cat probe thermo (a Condor) has been working as expected - my burns generally run about 11-12 o clock on my thermometer when cruising
4. Wood is a mix of 2 year old CSS red oak and some kiln dried wood I purchased this year (yeah, got behind on my wood processing)


Over the past week or so, I'm noticing a good amount of smoke coming out of the chimney about 3 hours into the burn. It happened tonight ( I load in the evenings). Was outside a bit ago and could smell smoke so I got my headlamp out and flashed the chimney. It was smoking like it does when I'm doing a reload (before closing bypass). At that moment, cat probe thermo was at 3p so plenty hot enough. Stack temps were 400F. I suspect if I go out and look in an hour, I will be back to a clear stack/no smoke.

I can't say I've ever noticed this much smoke coming out at this point in a burn before. Certainly had times, over the 4 years, where I've seen wisps of smoke coming off the stack but nothing like this.

Bypass seems to be operating normally. Doesn't feel like it isn't camming over all the way or completely shutting but I'm wondering if I've got a leak at the bypass?? Or maybe it's time to replace my cat? I do burn roughly 24x7 from November to March so it's possible I'm reaching end of life for the cat.

Any way, looking for thoughts and opinions from the brain trust.

Thanks!!

 

[moresnow]

4th season. Hmmm.
Grab some cat gasket and pull your cat. Give your cat a 50/50, vinegar/distilled water bath, soak. Rinse with distilled. Let completely dry and reinstall. Easy, peasy.
Bet you will see a nice performance boost.
It's the end of the first week in Feb. Squeeze your existing cat for the remainder of the season.
Worth a shot for the minor cost of the gasket.
If you do it, let us know how it worked out.

 

[stoveliker]

5 months times 30 days times 24 hours times 4 years equates to 14000 hrs.
Your cat may be done for.
Get a new one (with gasket).Even if the washing makes you not need it, you'll need it soon anyway.

 

[Highbeam]

Your cat is past its expected lifespan. It failed the test of making smoke when it shouldn’t. They’re cheap, pop a new one in, takes like 30 seconds.

 

[Nelson]

Thanks for the feedback everyone. Sounds like I need a new cat.

 

[reaperman1]

Your cat is past its expected lifespan. It failed the test of making smoke when it shouldn’t. They’re cheap, pop a new one in, takes like 30 seconds.

It sounds like everything is working properly with long burn times. He didnt claim he's using more wood than normal. The only symptom is smoke coming out of the chimney. Is there really a issue here? I'm curious because mine smokes too. But it still glow and stays in the active range when there are very few coals. My wood is at least ten years seasoned.

 

[Highbeam]

It sounds like everything is working properly with long burn times. He didnt claim he's using more wood than normal. The only symptom is smoke coming out of the chimney. Is there really an issue here? I'm curious because mine smokes too. But it still glow and stays in the active range when there are very few coals. My wood is at least ten years seasoned.

Yes, smoking chimney when it shouldn’t means dead cat.

 

[Dieselhead]

High draft past spec can cause smoke to not have enough “residence time” and bypass the cat. Using many small splits in a load can produce more smoke than the cat can handle also. Imho, his oak is suspect at 2 years, also depending on split size. After a few hours once the oak burns towards the center where it’s wetter than the outside, can cause some cat issues as well. Just some additional food for thought that I hadn’t seen mentioned.

 

[stoveliker]

Good points.

I thought he started seeing smoke when he didn't do so before.
(That does leave the wood quality question tho.)

 

[Nelson]

Wood is mostly from the same stack, though I do have some kiln dried that I bought this year - however, I haven't gotten into that wood yet. Wood is red oak, which in my experience tends to dry relatively quickly but I certainly wouldn't rule out some moisture issues in some of it. I tend to cut my pieces fairly large. To my knowledge, I wasn't seeing this issue earlier in the season which is what raised some of the concern.

I went ahead and bought a new cat (which I was planning on doing for next year anyway).

Are people getting more than 12-14,000 hours out of their OEM cats? I think that tends to be about the warranty limit so I always assumed that was the theoretical life. Maybe a bad assumption though.

 

[Nelson]

High draft past spec can cause smoke to not have enough “residence time” and bypass the cat. Using many small splits in a load can produce more smoke than the cat can handle also. Imho, his oak is suspect at 2 years, also depending on split size. After a few hours once the oak burns towards the center where it’s wetter than the outside, can cause some cat issues as well. Just some additional food for thought that I hadn’t seen mentioned.

Though I haven't officially tested my draft, I don't believe draft to be an issue. The times when I was noticing the smoke was during my lowest burn setting and relatively warm conditions (40Fs). My stack is approximately 20 ft and I have a 2-45s and a 90 in that run. Based on the calcs in the manual, I think I'm in a decent spot re: draft. However, I have not officially tested it so I can't rule out the issue you speak of.

 

[stoveliker]

Oak is notorious for drying slow.
Big splits exacerbate that.

20 ft can be okay if the horizontal run is short.
At higher ambient temps you may run into insufficient draft when running low, and it may be fine if you run higher (but then you would have to open windows...)

Yes, cat lifetimes are around this number of hours.

 

[Nelson]

Oak is notorious for drying slow.
Big splits exacerbate that.

20 ft can be okay if the horizontal run is short.
At higher ambient temps you may run into insufficient draft when running low, and it may be fine if you run higher (but then you would have to open windows...)

Yes, cat lifetimes are around this number of hours.

Yep, the horizontal run is short - roughly 4 ft or so.

My burn times are pretty consistent (~24 hours of active cat) regardless of temps so I feel like I'm in a good spot re: draft. That said, once or twice over the past few years, I've had to nudge up the dial as I had it too low. My Princess is in a corner so getting my head back there, and at an angle, is a challenge to be looking at the dial head on. It's my only complaint with this stove - I wish that therm dial was facing the front.

 

[reaperman1]

Yes, smoking chimney when it shouldn’t means dead cat.

Im reading from the manual.

"Light the fire as per lighting instructions. Then set the thermostat knob on a MED setting. When the fire is well established, turn the thermostat knob between LOW and MED. A properly operating combustor will remain active, and the combuster thermometer will remain in the active zone until the wood is mostly consumed. A tired or dead combustor will, with the thermostat on MED or lower , go out completely, and the thermometer needle will fall into the inactive zone”.

I’d think the criteria above is a better indication of the combustor’s ability rather than a little smoke coming from the chimney. I may be incorrect, the way I see it is, if it burns, its going to have some kind of by product. Some fuels burn very clean, like propane and natural gas, but as they exit a high efficiency furnace a visible exhaust is present. Especially when hot exhaust gasses are immediately mixed with cold outside air. Water vapor is immediately formed and appears as “smoke”.

Are people getting more than 12-14,000 hours out of their OEM cats? I think that tends to be about the warranty limit so I always assumed that was the theoretical life. Maybe a bad assumption though.

The original warranty is in years, not hours.

 

[stoveliker]

4 ft is not short (it's all relative though).
Each 45 deg adds 1 ft to the recommended height of 15 ft for this stove. And each horizontal ft adds 1 (or 2?) ft as well.

So the minimum recommended height for your set up is at least 15+2+4=21 ft (and possibly 25 ft...) At sea level.

 

[stoveliker]

Im reading from the manual.

"Light the fire as per lighting instructions. Then set the thermostat knob on a MED setting. When the fire is well established, turn the thermostat knob between LOW and MED. A properly operating combustor will remain active, and the combuster thermometer will remain in the active zone until the wood is mostly consumed. A tired or dead combustor will, with the thermostat on MED or lower , go out completely, and the thermometer needle will fall into the inactive zone”.

I’d think the criteria above is a better indication of the combustor’s ability rather than a little smoke coming from the chimney. I may be incorrect, the way I see it is, if it burns, its going to have some kind of by product. Some fuels burn very clean, like propane and natural gas, but as they exit a high efficiency furnace a visible exhaust is present. Especially when hot exhaust gasses are immediately mixed with cold outside air. Water vapor is immediately formed and appears as “smoke”.


The original warranty is in years, not hours.

Years have no meaning; burning 5 weekends vs burning continuous in a season...

The cat is supposed to allow burning without smoke (yes, when it's cold you can see water vapor).

If the exhaust shows smoke when it previously didn't, something changed. Given the age of the cat that is the first suspect.
Wood may be marginal making things worse (cooler fire, more smoke for an elderly cat to eat...).

(Draft is possibly marginal too here, affecting the lowest setting one can burn at when it's warmer outside.)

 

[Highbeam]

A puff here and there is normal as the thermostat opens and closes but it’s usually blue. Steady white smoke when the cat meter reads active is a sure sign of a dead cat.

The manual is not helpful here. The 10 year warranty is easier to administer than a 12000 hour warranty.