Jotul F600 Firebox dynamics

[OldHickory]

I've had my Jotul F600 for one year now & I've got a couple of issues. I'm new to the air-tight EPA stove setup, having previously burned since the early 80's with a plate steel VolcanoII from Defiant (was a great stove)! With the Jotul, I notice I can only get an active burn with material above the grates. Around the border of the firebox (off the grates), wood just smolders (if even that). Also, even when I have a healthy fire going I notice wood at the back of the firebox will not burn (dead spot)... again this just smolders or does nothing. Does anyone else experience these characteristics with their Jotul?

I'm not getting surface temps much above 400-450F (Top corners with magnetic thermometer) and to get a fire going or after adding new wood, I have to burn with the ash drawer ajar for a while or else it can smolder profusely. Draft may be the issue... My stove pipe travels up 2' and sideways 2' via an elbow through a thimble to the bottom of an exterior masonry chimney with a 6.5"x10.5" flue (~25' to chimney top). When I had my Jotul delivered & installed, the crew was supposed to install a flue liner to assure a good draft but said it couldn't be done with his stock liner which wouldn't make the tight 90 degree needed at the bottom of the flue. Even thought the fire doesn't roar without the ash door ajar, I don't have negative pressure problems or down draft problems. I'd look at putting in a more expensive flexible flue liner for better draw but this may be my last season in this house.
So is the draft part of the issues outlined above?

Thanks. I look forward to your comments.

 

[begreen]

Agreed, it sounds like a draft issue. Exterior chimneys are a bear. You should not need to use the ash pan door. Side door cracked open should be enough to start a good fire. What is the pitch of the 2 ft horizontal section? Is it generously uphill? Is the flue sealed well to the stove? or is it just a push fit of the crimped connector?

 

[Bill]

Can we assume the wood is good and dry?

 

[woodconvert]

"I have to burn with the ash drawer ajar for a while or else it can smolder profusely."

Ats a no-no. You'll warp/crack the grate. Slightly open the front doors while getting it going. I have an older firelight with about a 3 foot rise before a 90 el, horizontal for about 2-3ft and into an unlined masonry chimney that is a bit taller than yours.

First, are you sure your wood is good and dry??. I'd guess it is as you said you are at least running at the 400-450f range. If I get a couple of non-seasoned pieces in the mix I have a hell of a time holding 300f.
Second, how long do you let it get going before you shut the doors and damper???. With an unlined masonry chimney you need to get that thing hot and it takes a while to do that. It's a pain in the arse during the spring and fall as I start a fire daily. Once the 24/7 burn season starts it's not an issue. For example, right now, temps in the 40-50f range I may let it run with the front doors open/ajar for 20 minutes to a half hour. If I were starting it in the middle of a cold snap I can see that time doubling.
Third, my stove doesn't seem to run "properly" until a good 2"-3" ash bed is established. By that time the chimney is hot and drawing like crazy and the stove barely cools with a fresh load of cold wood from the porch.

When you say that it runs only to 400-450f range...how long into the burn do you get to that temp??. Are you saying that's the max temp you get no matter how long you've been burning it??. If you've established a good ash bed and your fuel is good and seasoned you definitely should be able to achieve higher temps than that.

 

[begreen]

Also, what size splits are you trying to add to the kindling? Even though this is a big stove, you still need to add 2-3" dry splits to the dry kindling when starting off. If the splits are too big, they will sit and smolder and perhaps go out.

As others have noted, don't use the ash pan door as an air valve. It turns the coal bed into a foundry and stresses the cast iron ash grate. If this is damaged, it will not be covered under warranty. Instead, for additional air, try leaving the side door open a crack for the first 20 minutes.

 

[carpniels]

Those are all excellent tips guys. I have had issues similar and mostly the reasons were:
1) wood not dry and seasoned.
2) splits too large to get the fire started
3) forgot to open the air supply.

All can be tested and corrected relatively easy.

Carpniels

 

[elkimmeg]

first of all you installation is a direct code violation you cross sectional area of that clay flue can only be 2x your flue size Most liner companies will sightly ovalize a liner for minimum cost .
this would allow for installation a tee 90 hole can be cut prior to inserting the liner and a connector pipe can be attached to that cut out from the inside of the connection hole its a pain in th asr but can be done, A cap can be applied to the bottom of the flue lined then pulled down the connector hole lining up with your pre cut hole. then there is the possibility of using a 5.5" liner.

I don't buy it can't be done it can be but a little preparation is needed. I have installed plenty 6 ' liners in an 8/12 clay liner. If your wood is dry then you have a a draft issue


Finally what installer would go ahead and install a stove that was a direct code violation? If they did not know the code ,then what business do they have,

preforming non compliant installations?

 

[OldHickory]

Thanks for all the input. I may need to emphasize that my deficient burn results were not confined to firestarting but all phases of operation. First more details on my setup...
My pipe is vertical for 22-24" then 90-elbow and horizontal (without a pitch) for 18". No cement was used on any connection by the installer except the thimble to stove pipe. However, when I reassembled after cleaning the stovepipe I sealed all joints and connections with furnace cement. (a syringe is the perfect tool for this BTW (don't jump to any conclusions--I work in a hospital).

My fires are intermittent (start at 5pm- night load 11:30pm), of relatively short duration, and the stove/chimney completely cools off between fires. When I start a fire, I'm using a bed of crumped or shredded paper, then small kindling like slivers split from 2x4s or chips/fragments from maul splitting my firewood, then topped by 2-4 splits that are 2-4" thick. After lighting up, I have employed propping the front doors slightly cracked, or using the ash-drawer (I'll stop doing that--thanks), or the side door ajar. I like using the front doors best because it prevents soot deposition onto the glass at the low temp. I ALWAYS use the side door for adding wood due to some smoke roll-out with the front doors open (even with a warm stove or good bed of coals).

I avoid heating the stove too quickly so it takes about an hour to 90 min to get to 250-300F. I usually have to keep a door ajar when starting a fire or anytime I add new wood to avoid excessive smoking/soot to glass deposition and I will close the door if I get a good bed of coals, the temp is about 300F, and fire is self sustaining after I close the door for a few minutes. It can take me about 3-4 hrs to get to 400F and the stove doesn't generally run any warmer than that on its own. In general, I don't achieve temps beyond 450F even on extended burns or a huge bed of coals (and the draft setting is full-open) unless I've got some door open.

Also, if I close the damper to get secondary combustion then the stove cools to 250-300F most of the time (not sure how quickly-maybe between 1-2 hr?) and I'm having to build up the fire again. I think I have only seen secondary combustion when I've used the damper at 50% or lower.

As far as wood goes, I don't buy wood but find it cut by the roadside and I split it myself. I generally burn wood that is aged 9mo-2 yrs under a carport elevated off the ground (oak, maple, hickory mostly). Last year I did have some variable wood supply but within my supply I burned some 1-2 yr seasoned/dry oak. Maybe I'm more accustomed to burning bigger pieces than suits this stove. Some logs/splits I'm using during a full burn are 4-6" diameter. I did notice better burn behavior with smaller splits.

However, the back or sides of the firebox doesn't burn well. If a split was burning well and rolled back from the grate it usually self-extinguishes and becomes charcoal. It seems like active burning takes place right in front of the door and that the rest of the firebox lacks air supply. I suspect this because if the stove door is ajar and wood is burning well, it will cease burning when I close the door..all except the wood in front of the air supply below the glass doors or above the grate. I also get a moderate to heavy accumulation of soot on the glass and specifically it is on the sides of the hinges around the retention clips. I spend 20-30 min cleaning this off before starting a new fire.

As for code and the installation comments, I don't know why the sweep didn't feel he couldn't make it work. My house was built in the 40's and constructed with some weird dimensions. Somehow I recall something mentioned by the sweep about a T piece wouldn't work in the bottom of the flue unless distorted and connecting to it after distorting it compromises the connection & he had never installed a T-elbow in such a way before. You'd have to ask him, as I'm not a sweep. When I bought my stove from the Jotul dealer with installation fees this is the sweep who delivered and installed it. I didn't hire any outside vendor. I had already prepaid for the liner and the store refunded that part of the installation to me.

After consideration of the groups comments I will not utilize the ash-door for any venting purposes but will use the side or front doors during firestarting. I'll also try to use smaller splits (I've been splitting smaller for this years supply). My wood supply is probably better this year than last so that may boost my results. Otherwise poor draft could explain the rest.

Thanks!

 

[jtp10181]

The liner could also be done with DuraLiner 6" OVAL rigid pipe, which is double wall and pre insulated. 4-3/4" wide on the skinny side. At the bottom you use an oval to round branch Tee which has a snout you remove and then slide on and clamp once the hole in the Tee lines up where you need it.

 

[woodconvert]

"My fires are intermittent (start at 5pm- night load 11:30pm), of relatively short duration, and the stove/chimney completely cools off between fires. When I start a fire, I’m using a bed of crumped or shredded paper, then small kindling like slivers split from 2x4s or chips/fragments from maul splitting my firewood, then topped by 2-4 splits that are 2-4” thick. "

How much kindling do you use??. Don't skimp on kindling and criss cross it. Use more 2"-4" splits. Lay three or so on the kindling and put two or three more on top of that but criss crossed. You want the fire to get up through the kindling and the splits. When you say you "slightly crack" one of the doors...how much?. When you are trying to establish a draft in a unlined masonry chimney you want to be somewhat aggressive. IF YOUR CHIMNEY IS CLEAN, open the front doors a half inch or so. Let it get going so the splits are on fire and as a piece or two of bigger stuff. You won't hurt the stove and it should get hotter quicker for you.

"I avoid heating the stove too quickly so it takes about an hour to 90 min to get to 250-300F.

Like I said above, if your chimney is clean, fire it like ya stole it. It's not a china doll. The kindling/splits need to burn down to start a coal bed. "Usually" by the time your first load is burned down into coals the stove/chimney should be nice and hot and drawing really strong. And don't worry about soot on the glass. Once you get a proper fire going it will burn off.

"Also, if I close the damper to get secondary combustion then the stove cools to 250-300F most of the time (not sure how quickly-maybe between 1-2 hr?) and I’m having to build up the fire again. I think I have only seen secondary combustion when I’ve used the damper at 50% or lower."

You are not getting the stove and chimney hot enough before you shut the damper. Be more aggressive getting the fire going with the door open. You need to heat that chimney up for it to draw. It takes a lot to get it hot.

"As far as wood goes, I don’t buy wood but find it cut by the roadside and I split it myself. I generally burn wood that is aged 9mo-2 yrs under a carport elevated off the ground (oak, maple, hickory mostly). Last year I did have some variable wood supply but within my supply I burned some 1-2 yr seasoned/dry oak. Maybe I’m more accustomed to burning bigger pieces than suits this stove. Some logs/splits I’m using during a full burn are 4-6” diameter. I did notice better burn behavior with smaller splits."

Fresh cut oak or hickory (wood that was pulling up water, ie alive when cut down) will probably not be dry in 9 months. The harder/denser the wood the longer it takes to dry. Also, the bigger the split the longer the dry time. I burn plenty of 4"-7" unsplit rounds in mine with no problem but you have to have a well established fire/coal bed to do it. If you put wood that size on your 2"-4" splits that is probably your problem. When you start a fire, think of it like a reverse pyramid. Small (kindling) on the bottom, bigger splits on the kindling, bigger splits yet on top of that.

However, the back or sides of the firebox doesn’t burn well. If a split was burning well and rolled back from the grate it usually self-extinguishes and becomes charcoal. It seems like active burning takes place right in front of the door and that the rest of the firebox lacks air supply. I suspect this because if the stove door is ajar and wood is burning well, it will cease burning when I close the door..all except the wood in front of the air supply below the glass doors or above the grate. I also get a moderate to heavy accumulation of soot on the glass and specifically it is on the sides of the hinges around the retention clips. I spend 20-30 min cleaning this off before starting a new fire.

DO NOT TAKE THE BIG CHARCOAL PIECES OUT when you empty the ash pan. These will help you get the next fire going. Move them over the grate and build your fire on top of them. That's less of a coal bed that you need to make. Also, once you learn to get the stove going properly, those "dead spots" will be glowing embers.

"After consideration of the groups comments I will not utilize the ash-door for any venting purposes but will use the side or front doors during firestarting. I’ll also try to use smaller splits (I’ve been splitting smaller for this years supply). My wood supply is probably better this year than last so that may boost my results. Otherwise poor draft could explain the rest."

Don't split all of it smaller. Once you get used to getting the fire going and getting the chimney hot, those big ones will be excellent for overnight/longer burns.

 

[ncmallard78]

one thought. you have a big fire box. on my oslo, which also has a pretty big box, i dont really get my stove going unless i have a full charge of wood. if i put in 3 pieces of oak, it takes a long time to get going. if i add 2 more to it, i get a very nice secondary burn and can then shut the air down for long burns. try more wood, and i bet you get a better, longer burn. I recomend that you sit and watch if you intend to do this. i did it one time and came back and my stove was at 700 degrees.

 

[WOODBUTCHER]

Elk has it right, if your wood is dry, then its a draft issue.

I am not bragging here, just listing how our 2 stoves operate compared to yours

My Oslo 500 runs off a Class"A" type chimney and my Brother-in-law's Firelight 600 runs off a 6 inch chimney liner.

His firelight 600 is in the basement and I go over there often and I can easly get that puppy up to 500- 700 no problem.
When we first installed the stove and had it hooked up and ready to go. I tested his cold draft buy holding my hand over the intake (bottom rear)
I put his draft control 1/2 way and could feel it pulling a draft up. When your stove is cold I bet your draft is totally dead or pretty near non existent.

1. Both of our stoves burn in the sweet spot with our draft controls open anywhere between 10-25%.
2. The 2 stoves can be easily over fired if the draft control is left wide open.
3. Both stoves require a door to be left open during start up.
4. Even with dry wood, we both have to poke the coals and logs now and then to stimulate the fire (especially if we are just burning a couple of casual logs)

Hope this helps you out

The WoodButcher

 

[OldHickory]

Thanks guys. I think you've answered my big questions which were... what temps are you running on your Jotuls in full burn and do you have dead spots that don't necessarily burn well in the firebox.

1. I think I'm hearing that most people are burning at 500-700F stove temps WHILE their dampers are engaged or else the stoves can run hot (and that must mean you're easily getting secondary combustion and greater efficacy & heat from your loads).
I have been burning 100% wide open on a long burn in most cases to achieve 400F-600F (600F probably max).
If I close the damper to get secondary combustion, my stove temp drops to ~250-350F. When I cram it FULL of wood for an
overnight burn I might get to 600F while getting everything burning & with the damper wide open but engaging a secondary
combustion by cutting air supply will drop the temp down to 300s. This is at least what I can recall from last years experience.
2. Probably some of you with less than ideal drafts may be using additional venting to get a draft going during startup with a cold
stove and a cold masonry chimney.
3. Dead spots probably aren't troublesome for most of you. It isn't necessary for you to micromanage the firebox.
Seems my dead spot is most noticeable when I've got more wood in the box. It is almost as if the log in front of the glass
and directly in front of the air supply/damper is 'stealing' all the air and the fire on a log in the back of the box burns minimally
(this is with the air wide open on a hot bed of coals well into a long burn & after the logs in the box have been surface charred).
If I add more wood anywhere in the back of the box, the surface will flame-char but not completely burn & logs continue to pile
up until the stuff up front burns completely & then the fire will proceed to work its way toward the back of the box.

Thanks everyone for your comments. I appreciate your experience with the Jotul stoves.

 

[elkimmeg]

Might I note something? at times fully open air fills the fire box and forces more heat to leave up the chimney. A that point ,I find reducing the air slows the exit of heat in the exhaust ant the stove temps rise. sometimes wide open waste heat. I mean posters have all but instructed you to place a turbo charger in your stove to over come week draft.
You still have an exterior exposed chimney with a too large cross-sectional area that needs to be addressed you need a liner. Maybe if the stove drafted correctly you would not have that dead spot

 

[OldHickory]

I agree Elk. To get a fire going sometimes you may want to fan the flames, but then to heat your stove and home you will close the doors to contain that heat. That is what I did last year and what I'm doing now. After 15+ years of woodburning the firestarting process isn't a mystery to me but instead my lack of robust burning, max temp, and heat extraction seems less than anticipated with this new stove. I agree that a liner is what is needed for better performance. Whether or not this gets done this season is questionable because it looks likely that I won't be residing in this house next burning season & the woodstove is supplementary heat with free firewood to burn. I'll have to weigh my options with the knowledge that my performance is probably lacking as a result of my flue setup and go from there.

 

[elkimmeg]

life. money situations, forces all of us to make compromises good luck maybe when it gets colder your draft will be better and you will get some heat out of it