Jotul 602 update...how hot is too hot?

[nola mike]

I'm amazed by this thing. It cranks out some heat. 30' outside temps, 62' inside temp, warmed the stove room to 70' in about an hour. It also managed to heat the rest of my 2 story, 2k sqft house to 66'. And I'm burning pallets. Firebox is small, but without the secondaries seems like I can really pack it. I'm getting about 2 hours before a reload, but I can go 3-4 hours with it still pumping out heat. Overnight temps dropped to 62' without a reload, which isn't bad at all, especially when it heats back up so quickly. Only problem is that it burns EVERYTHING by 4 hours, requiring almost a fresh restart. That, I'm hoping, will be cured by better wood. Anyway, it wants to run HOT. Noticed that my flue got a nice glowing red on a couple of occasions; it was around 600' at the time, stove top temps 750 or so. I shut the air down, and everything cooled right down. I'm guessing this is too hot for the flue temps, but is it dangerous? So I've been LNG free for 3 days now. Looks like we'll be getting in the low 20's this week, we'll see what happens...

 

[DAKSY]

The way you're burning that little guy, you'll be lucky if it lasts the winter.
What you're doing is like driving a Honda Civic at 100 miles an hour everywhere.
It'll work for a while, but you'll KILL it (& maybe yourself) in a relatively short period of time....
In VA, that unit is probably rated to do 600 - 800 SF, MAX, NOT 2K sf.
Your stove top should be in the 400-600 range. NOT 750.
Glowing red pipes are a bad sign. What gauge steel connector do you have?
Without the secondaries you can really "pack it."? Why?
Those secondaries are EPA mandated for clean burn & the baffle protects the stove top.
This could be considered "Stove Abuse,"IMHO

 

[precaud]

Mike,
Glad to hear you're enjoying your 602. Sounds like yours is performing like a 602 should. It's a runner for sure - now you have to control it. But there's no need to get alarmist about it, DAKSY.

And I’m burning pallets.

It is going to be difficult to control the burn rate using pallets for fuel. The piece size is too small. Use fewer but larger pieces to slow the burn rate. I used to burn one pine split the same width as the stove at a time. Worked great. Nice, controlled burn.

Only problem is that it burns EVERYTHING by 4 hours, requiring almost a fresh restart.

Sounds about right for a 602 burning pallet wood. Again, larger pieces will help some. But with these small "airtight" stoves, your best chance to have coals in the morning is to "bank" the fire before you go to bed. After your last load of the night flames down, push all of the coals into a pile against the back wall of the stove, and close the air control fully. In the morning, rake out the pile and you should have hot embers to restart with.

Anyway, it wants to run HOT. Noticed that my flue got a nice glowing red on a couple of occasions; it was around 600’ at the time, stove top temps 750 or so. I shut the air down, and everything cooled right down. I’m guessing this is too hot for the flue temps, but is it dangerous?

The glowing red pipe is not good. Slow down the burn rate. As I wrote before, your air control should be barely open once the load is burning well. And I do mean barely - 1/4" or so. Or just a sliver, if your draft is really strong. There's nothing wrong with 750F at the stove top. Mine did that for many years. Where are you measuring it? The cooking plate will always measure the highest. Right between it and the top exhaust exit is probably the best place.

 

[Backwoods Savage]

Any stove can and will run super hot if burning only pallets. Can you get some other wood to mix in? Also, like precaud states, larger pieces of wood will hold a fire much longer than the dry pallet lumber.

 

[nola mike]

Glowing red pipes are a bad sign. What gauge steel connector do you have?

Dunno. It's actually not the direct black stovepipe connection, but the liner adapter that came with the kit.

Without the secondaries you can really "pack it."? Why?

Umm, to heat my house? Trick question?

Those secondaries are EPA mandated for clean burn & the baffle protects the stove top.
This could be considered "Stove Abuse,"IMHO

Those secondaries weren't mandated until 20 yrs after my stove was built...

@precaud: Yeah, unfortunately I think I'm resigned to burning pallets for this season. Everybody on CL is trying to scam me. I may end up buying something semi-seasoned and throwing it in the mix. My next stop is the roadside vendors, but I need to do some driving to get there. I guess I wasn't clear earlier. I'm not having a hard time controlling the rate--when I damp it down, it cools down and is controlled. The 2 times I've noticed the glowing is when I've had the damper open for too long I guess. I was surprised, because 600' didn't seem dangerously hot, not hot enough to glow. Yes, I think that 1/4" is the sweet spot. Still trying to learn how to control a stove with no window, and balance getting the stove up to temp quickly but not overshoot. This thing likes to smoke a lot when it's cold, unfortunately, so I'm really trying to get the fire blazing before turning down at all. Smoke seems worse with a full box, so I'm playing around with trying to get it hot before packing it. I've been running it wide open until the flue temps hit 500 or so, then back it off halfway, then maybe 1-2 min later shut it to 1/4". When I do that, it coals pretty quick, but the firebox is full with coals/blue flame, and is pretty hot. More that that and it smolders. Temps are measured at the hottest part of the top, typically just aft of the burner plate. Thanks for the help! I'm having a lot of fun with this...2 stove installs in 2 months! Running out of places for them...

 

[begreen]

As I noted when you got the stove, it likes to take off quickly. Pallet wood is like running the stove on nitro. Even with good wood, 700F stove top temps are common.

Are you using the flue pipe damper and closing it all the way once the stove is getting hot (say 400F)? Precaud is right on about the air control, run the air control barely open (if at all with pallet wood). Just the slightest opening will be more than enough air. For our stove that is more like 1/8".

 

[precaud]

Adding to BG's comments, in all the years I had mine, I NEVER had the front air control wide open. Never had it more than 1/2 open, and that even not for more than a minute or two. Not even on startup. With a good chimney like you have, that turns it into a mini blast furnace. With pallet wood, don't try to get it all ablaze quickly. That's asking for an out-of-control burn. Try to keep it under control from the start.

The only way to see what's happening inside the stove is to get on your knees and pray, I meant squint though the air control opening. It's best to wear glasses so you don't do damage to your eyeball.

 

[nola mike]

The only way to see what's happening inside the stove is to get on your knees and pray, I meant squint though the air control opening. It's best to wear glasses so you don't do damage to your eyeball.

Hah! that's what I've been doing. No, I haven't touched the flue damper at all. Guess I'm confused on what my goals should be. I'm trying to follow flue temps more than stove top initially, since I figure that the stove takes a while to catch up. It actually is a bit sluggish starting out--I need to crack the door when it's cold or else it takes forever to catch. Why wouldn't I want to get it up to temp as quick as possible? Otherwise I'm smoking for a while...And again, I haven't had any problem keeping the temps as low as I want them when I shut the primary air. I've been keeping the air as low as possible that will still maintain a flame once everything's hot--and that gives me a stove top temp of 600-650 during the hot part of the burn. That seemed reasonable to me. Also, I still haven't fully insulated the chimney (I was waiting to see if the perlite would find a leak in my install before adding it all), so I guess my draft isn't as good as it will be when it's complete. Oh, and don't forget I'm running 5" pipe, so I'm not sure how that would affect the draft. I can promise you that it will never catch, even with pallet wood, if I don't run the air full open initially. So if this isn't the right way to fire this thing, what is? If I shut the air completely, seems like I lose my flame, and I end up with some partially burnt chunks when it's all said and done.

 

[begreen]

Noticed that my flue got a nice glowing red on a couple of occasions; it was around 600’ at the time, stove top temps 750 or so.

This sounds like what you have been doing sometimes and what got folks anxious. If you can regulate at 650 stove top and keep the flue pipe at or below 500 surface temp, then you are running the stove right. FWIW, without dampering the flue pipe we would see our flue temps get too hot. Dampering down the flue pipe will drop the flue temps and it will extend the burn. It makes the fire much easier to regulate as well.

 

[nola mike]

Noticed that my flue got a nice glowing red on a couple of occasions; it was around 600’ at the time, stove top temps 750 or so.

This sounds like what you have been doing sometimes and what got folks anxious.

I can see that. Didn't mean to imply that's what I was shooting for/regularly happening. It happened twice when I wasn't paying close enough attention and still learning the stove. So what's the max acceptable flue temp? Any advantage playing with the flue damper if I'm able to regulate with the primary?

 

[begreen]

Dampering down the flue pipe will drop the flue temps and it will extend the burn. It makes the fire much easier to regulate as well.

 

[nola mike]

Dampering down the flue pipe will drop the flue temps and it will extend the burn. It makes the fire much easier to regulate as well.

Won't just shutting the primary damper drop the flue temps and extend the burn as well? I understand how it could make the fire easier to regulate.

 

[precaud]

Mike, theoretically there is no difference. But these older cast iron stoves have air leaks in the seams between all of the plates. The air control doesn't regulate those.

 

[nola mike]

Fair enough.
Just got home from work. Before leaving, shut the air down completely. 8 hours later, house temp 68' (69' when I left), outside temp 34'. Box still had embers/charred wood which flamed right away when I turned the air back up--stove top temps 200'. Surprising. Seems that this may not be ideal; I think I probably was smoldering/had an inefficient burn. Got home 1h ago, reloaded (pallet wood again), and shut air to just a sliver. Temps now 580 on top, 380 in the flue. Awesome. This is so much fun! We'll see what it looks like in the AM. Merry Xmas!

 

[Trouthead]

I used a 602 since 1980. It had enamel pipe the same size as the stove outlet (4" ?) with a pipe damper in it. For the first 10 years or so I used paper underneath small kindling with larger spit or whole logs on top. Usually used 2 whole sheets of newspaper crumpled up on top of everything to warm the chimney, and get a good draft going. I would generally keep the air open fully until things were really going well and then close the air down to about 1/2 an inch open and after a few minutes close the damper if I was going for a long burn during hours I would be home awake. For night burns I would close the air to a bare sliver and close the damper. I almost always used either pine, cottonwood, or aspen. Never would it hold a fire more than 8 hours, unless I had hardwood, (1 load of cherry once) then it would have good coals after 8-9 hours.

I ended up using fatwood the last 20 years or so to start it. Usually 3-4 sticks would get things going and get the chimney good and warm for good draft. No more newspaper with the fatwood.

I replaced the top burn plate once and I also replaced the side burn plates. The back does not have any protection and sure enough it finally cracked. I plastered stove cement over the cracks and never had a problem, but I don't think that is really recommended. I believe backs are available, but taking it all apart after 30 years was more than I wanted to mess with.

In your neck of the woods the choice of wood has to be super. With VA temps and good hard wood a 602 would be great. I would only use pallets for starting the fire, and would try to find any type of split hardwoods. Even at high prices I doubt you could cram a cord through this stove this season.

I live in Wyoming and used the Jotul with outside temps of -20 at night for much of the season with usually a drop down to -40 or -50 for a few nights many years.

I might have kept using it had gas not gotten so cheap and the crappy wood in wyoming gotten so expensive, not to mention a wife that is always cold . It is going to do service next in a wood heated mountain cabin. Maybe I will rebuild it.

When I first bought the stove it had a plate on the ash tray saying "caution stove is hot during operation" My dogs never did learn how to read but they never did touch the stove. I have to wonder about someone being able to read and not knowing a stove is hot. Lawyers, and the government.

 

[begreen]

The 602 is an easy rebuild. I did ours in a morning, including snapping off a few bolt heads, drill and retapping. To make the stove bulletproof, I'd also recommend adding a custom rear burn plate to avoid cracking the back.

 

[Battenkiller]

Dampering down the flue pipe will drop the flue temps and it will extend the burn. It makes the fire much easier to regulate as well.

Won't just shutting the primary damper drop the flue temps and extend the burn as well?

Not at all. Without a pipe damper, shutting down the inlet opening on those box stoves actually increases the velocity of the air coming into the stove. Up to a certain point, the smaller the opening the more intense the burn. Increased velocity causes increased turbulence, leading to better mixing of air and gases and more complete and efficient burns. But that baby is gonna get really hot with that dry pallet wood in there. Shutting it down too far at that point is going to cause it to smolder (as you found out) and create much more creosote. By using the pipe damper, you can reduce the strength of the draft itself, allowing you to close the intake air down without creating excessive intake velocity. Makes controlling the fire a lot easier, and keeps more heat in the stove.

I'd go ahead and get some of that semi-seasoned wood. Get the stove hot with the pallet wood and then start slipping in the wetter stuff. Not too wet... those little stoves just don't contain enough heat to get a decent size split going well unless it's had at least some drying already. Get a cheap moisture meter and try for stuff in the 25-30% MC and that should help both control the burn and give you a longer fire. You'll have to experiment with the air to get good reloads without the stove cooling off. Little stoves just have a harder time with unseasoned wood than big stoves, mainly because it's hard to keep internal temps up at reload time.

I never burned that stove, but I have 18 years experience with a copy of its bigger brother, the 118. I found that the ideal intake opening was about 5/16" with my flue. I kept a small piece of 5/16" drill rod under the stove and used it as a spacer to set the opening once it was up to temp. With a bit of luck, I always had some active coals in the back of the box in the AM.

FWIW I don't think air leaks at the seams are contributing to your problem. The last year I burned my stove I lost a 4" section of gasket from the front door and didn't replace it for weeks. I thought for sure the stove would be impossible the control, but after a few emergency fires, I realized that it didn't affect much of anything. In fact, even with that piece of gasket missing, if I closed the stove down all the way it would actually go out. As well, my stove had gobs of stove cement missing from the seams by the time I got rid of it, and I never saw any tendency toward uncontrolled burns. I read about this all the time, but in my experience, it has never happened. Instead, what I found was that if I closed down the intake air too far, the stove went out every single time. Those "S" joints between the plates create the same type of effect on air trying to sneak past them that 90º elbows and such have on the flue gases. Air likes to go in a straight line, bends and curves create a lot of resistance to flow.

 

[precaud]

BK, I agree that mixing in some semi-seasoned wood might be a way to deal with this. But the bit about air leaks I don't. I suggested it because I saw that very thing with my old 602. Stare into the firebox through the small gap in the air control, and you could clearly see licks of flame emerging from the spots where the leaks were. Leaks toward and at the rear of the firebox behave quite differently from a door gasket leak, which goes mostly up and out the chimney. Firebox leaks contribute to an already difficult-to-control fire.

Also, the 118 and 602 burned very differently. The 118 was easy to control. I can't remember ever having a runaway fire in mine. But the 602 was easy to overfire.

 

[begreen]

When I rebuilt our 602 it definitely behaved better in response to the air control and burned longer as well. But it was still an easy overfire. When we were traveling a friend that was watching the house did just that. I came back to a burned stove back. That's when I added the rear burn plate.

 

[nola mike]

BG--looking at adding a rear burn plate when I redo the side baffles after the season. But doesn't this take away more of my limited firebox? As it is, I'm having a bear of a time finding good wood, never mind in 16" length. BTW, I stopped last night in the snow at some roadside wood that I found--15% on the MM. Don't know the length of it; waiting for the guy to call me back. VA totally shuts down at the hint of snow...

 

[begreen]

Our rear burn plate takes up about 1/4" of space. It's 3/16" steel and has a #10 nut as a spacer from the back.

 

[nola mike]

Our rear burn plate takes up about 1/4" of space. It's 1/8" steel and has a #10 nut as a spacer from the back.

Then that sounds like a no brainer--how is it attached to the rear (or is it?)