Jotul F602CB - Is this "normal"?

[MoreCowbell]

Hello,

First off, thanks to the many contributors here. I've been reading on the Hearth forums over the last few months before buying my first stove and have learned lots.

A bit of background...
My house is a 140 year old victorian 2 storey home, with a narrow open pit fireplace and a masonry chimney that goes from the main floor, in the middle of the home, up through the second floor and roof. The chimney stack is probably about 30 feet long. We've burned wood in this 16" wide by 27" high pit for about 4 years since moving in. The last batch of wood I purchased (mostly maple) spent about a year outside seasoning before bringing it into our wood shed last November.

Following the recommendations from an energy efficiency audit last fall, we were going to get a chimney top damper to stop the major source of airleak: the open pit fireplace with a cast iron damper. After further thought, we decided to instead install a wood stove in this opening to reduce the air infiltration and actually provide some heat when we burn wood, rather that cool the house.

Given the narrow width of the firepit, an insert was out of the question. The only local options I was able to find for woodstoves were the Vermont Castings Aspen or the Jotul F602CB. The Aspen would have been a very tight fit so we decided to go with the F602CB.

The installer recommended a 6" stainless steel liner for the install. They also mentioned that I may have an overly strong draft but that I'd have to see how the stove performed. The stove is installed about an inch from the back of the fire pit so that the stove door pretty much flush with the front of the fire pit.

Jotul F602CB Hearthmount into a masonry fireplace

• MoreCowbell
• Jan 22, 2018

I performed the 3 break in fires as recommended in the manual, using an IR thermometer (using emissivity=0.95) to measure the surface temp at the front top of the stove. It threw in an extra break in fire to 400F for good measure. On the next firing, I used the top down method: two quarter splits on either side, with some smaller kindling across those, with some tinder, topped with four news paper knots.

Jotul F602CB Cold Start

• MoreCowbell
• Jan 22, 2018

Once the quarter splits on the bottom had caught fire for a few minutes, I added 3 more small half splits to the fire, leaving the draft open for a few minutes and then closed the draft as the fire was running strong (in retrospect, I probably should have checked the surface temp before reloading as I'm guessing the pre-load temp were about 500F) . Even with the draft fully closed, the temperature soared to over 1000F on the front of the stove (measured above the door). I quickly turned on the range hood exhaust and dryer to try to slow down the chimney draft further. Also added a fan to blow air toward the stove. The cooking plate glowed slightly red for about 5 minutes and then the temperature came back down. I've since learned that I have to wait for the surface temperature of the stove to drop to around 300F so that when I reload, I only peak to about 750-800F. Keep in mind, I only ever open the stove draft on the initial cold start. When it comes time to add wood, I just rake the coals towards the front of the stove, add 2 unsplit or large half splits and keep the draft fully closed.

It occurred to me that maybe my wood was very dry. So to verify my wood moisture, I checked a few logs with my moisture meter (inserted pair of nails to the center of log lengthwise, then used those as contacts for my Electrophysics CMT-908 probes) and I'm typically in the 18-25% moisture range so nothing overly dry as far as I can tell.


At this point, I figure I can control against overfiring by very carefully adding large pieces (as large as you can expect to fit in this tiny stove) when the stove temperature drops to 200-300F (measured on front, above door) and making sure to keep the draft to the fully closed position. That being said, what options do I have to make it a bit more resistant to overfiring?
- Reduce the diameter of the liner at the top of the chimney to 5" (suggested by the installer)
- Install a chimney pipe damper, but this wouldn't be straightforward as only the first 2 inches of the pipe is visible. So I'd have to drill a hole through the masonry to be able to toggle the damper on-off. Installation would be tricky as well, I suspect. Plus a pain when it comes time for a chimney sweep.
- ??? or are these behaviors "normal" for the Jotul and I just need to be careful to keep the temps 300F or less between refills and expect 750F-850F front surface peaks with the damper closed?

Also, for those that have the Jotul F602, I often read that the surface temp is taken between the pipe and the cook plate. Since I don't have access to that due to minimal clearance between the top of the stove and the top of the fireplace, what is the typical delta between the temperature there and the temperature taken in front of the cook plate (near the front of the stove)?

Any suggestions welcome!

 

[begreen]

Welcome. As you are finding out, 30 ft of liner is going to create a very strong draft. Normally I wouldn't run this stove without a draft damper with this tall a flue, but as you've pointed out, this is not an option for numerous reasons. As a test I would have the sweep put on a reducer up top with a smaller cap. It may take a 6" to 4" reducer to be effective. This is going to take some experimental testing to see what works best.

The other option that would be preferable to me would be to rear vent the stove and extend the hearth. Unfortunately with the long box body of the F602 this may not be practical. Did you consider any other stoves like the F3CB with a rear vent option for this location? Rear venting would allow a draft damper to be installed on the horizontal pipe going to a cleanout tee. The extra 90º turn plus the damper should provide a lot more control as it will slow down the draft. Plus you would get much more heat from the stove and you would gain a nicer fireview.

Is this an interior or exterior wall fireplace? Is there a blockoff plate installed at the damper area?

 

[webby3650]

I would have with with a rear exit and a Tee. The stove would heat much more effectively and a damper could be added.

 

[djkeev]

Your installation is beautiful!
It does not mess up the period fireplace or hearth.
Much praise for that!

I did a similar install (though custom built) for my Jotul F3CB.

Not knowing the details of your old flue or how they put in the liner......

Is there space still alongside the new liner in the old flue?
If so, can you fit a chain operated top damper?

One wonders with technology, is there yet a powered blue tooth controlled damper?

Dave

 

[MoreCowbell]

begreen - Yeah, when I open the draft, sounds like a blast furnace Weak draft is definitely not going to be a problem here. This is an interior wall fireplace. No blockoff plate installed. They filled the void around the liner with fibreglass insulation. When they come for my chimney sweep, I will look into getting a blockoff plate installed with a ceramic blanket on top.

begreen/webby3650 - I forgot to mention that the driver to have the stove fit within the fireplace came from my wife for aesthetic reasons. She did not want the stove coming out beyond the fire pit. If it was up to me, I would have gone with a slightly larger stove and had it in front of the fireplace. That would have opened up way more options and more efficient heating. This stove is really just meant to heat this room, which has 3 exterior walls. The 3 minisplit heads that I have in other parts of the home don't really heat this area much.

I'll be contacting the installer to figure out cost to have a reducer. With what they charge around here for installs/hourly, I'm going to want to pick one option and will probably have to live with it, at least for this year.


Will peak stove surface temperatures of 850F shorten the life of the stove or am I within acceptable temp ranges?


Here's a few graphs that show the temperature increases when I load the stove (with damper closed):

Jotul F602CB - Stove Surface Temp vs. Time - 2 unsplit logs vs. 2 half split logs

• MoreCowbell
• Jan 23, 2018

Jotul F602CB - Stove Surface Temp vs. Time - 3 med split logs

• MoreCowbell
• Jan 23, 2018

 

[MoreCowbell]

Thanks djkeev.

There's probably about an inch or so of space between the liner and the masonry flue. Is a chain operated damper an option with a stainless steel liner?

I've never heard of a Bluetooth controlled damper but I'd be concerned about the longevity with the wild temperature swings as well as the huge pain when it would come time to change the batteries! Also, the transmitter range could be a problem.

 

[begreen]

begreen - Yeah, when I open the draft, sounds like a blast furnace Weak draft is definitely not going to be a problem here. This is an interior wall fireplace. No blockoff plate installed. They filled the void around the liner with fibreglass insulation. When they come for my chimney sweep, I will look into getting a blockoff plate installed with a ceramic blanket on top.

begreen/webby3650 - I forgot to mention that the driver to have the stove fit within the fireplace came from my wife for aesthetic reasons. She did not want the stove coming out beyond the fire pit. If it was up to me, I would have gone with a slightly larger stove and had it in front of the fireplace. That would have opened up way more options and more efficient heating. This stove is really just meant to heat this room, which has 3 exterior walls. The 3 minisplit heads that I have in other parts of the home don't really heat this area much.

I'll be contacting the installer to figure out cost to have a reducer. With what they charge around here for installs/hourly, I'm going to want to pick one option and will probably have to live with it, at least for this year.

Will peak stove surface temperatures of 850F shorten the life of the stove or am I within acceptable temp ranges?

Here's a few graphs that show the temperature increases when I load the stove (with damper closed):

Jotul F602CB - Stove Surface Temp vs. Time - 2 unsplit logs vs. 2 half split logs

• MoreCowbell
• Jan 23, 2018

Jotul F602CB - Stove Surface Temp vs. Time - 3 med split logs

• MoreCowbell
• Jan 23, 2018

Yes, the stove life will be shortened. The peaks indicate overfiring the stove. If you turn out the lights at a peak reading. Do parts of the stove glow dull red?

 

[webby3650]

850 is way too hot, especially for extended period of time.
We were just discussing in another thread how the wives somehow get to make these decisions that are a huge compromise in performance. Even though the man gets to do all the work....

There’s no way to install a lock-top damper on a flue servicing a stove with a liner. A damper in the stovepipe is the only option here that will make any difference, or even possible really.

 

[MoreCowbell]

begreen - yes when I reached 1000F that one time, there was a dull red glow on the cooking plate with the lights off. I don't see that when I reach 850F.

webby3650 - without moving the stove (which will be a problem ), not sure how I'd get a stovepipe damper in. Thinking a reducer at the top of the chimney, as others have suggested, may be my best option.

For now, what max temperature is considered to be ok for this stove, without long term negative effects? 700F? I'm sure I can probably stay under that, although it means I'll have to wait longer before adding wood to ensure the temperature goes below a certain threshold. Will have to follow this until I can get a more permanent solution.

 

[begreen]

For now, what max temperature is considered to be ok for this stove, without long term negative effects? 700F?

Yes, that's a good max temp target.

Is there a block off plate at the damper area of the fireplace?

 

[MoreCowbell]

No, there's no block off plate. Just the fibreglass insulation that the installer put to fill the void around the liner.

 

[begreen]

With the stove buried in the fireplace a lot of heat is going up the chimney. Insulation is not a great barrier, especially fiberglass. Is this an interior or exterior wall chimney?

 

[MoreCowbell]

Is this an interior or exterior wall chimney?

Interior wall chimney

 

[begreen]

Interior wall chimney

That helps. At least some of the heat will be stored and released in the home envelope.

 

[bholler]

Interior wall chimney

Did they insulate the liner?

 

[MoreCowbell]

Did they insulate the liner?

No, not insulated. What is the function of insulating the liner in a masonry chimney? Does it extend the clearance to combustibles?

 

[bholler]

No, not insulated. What is the function of insulating the liner in a masonry chimney? Does it extend the clearance to combustibles?

It makes it so combustibles can touch the outside of the masonry. Without insulation you need 2" of clearance

 

[Zack R]

I'd consider a rear vent hearth mount stove that is a bit larger. Beautiful installation but it looks like it will be tough to regulate and you will be reloading frequently. Also a hearth mount will disperse heat into the room more effectively.

 

[MoreCowbell]

Out of curiosity, are there ANY stoves that could handle the strong draft of my configuration or is it just that the F602CB is particularly sensitive to strong draft?

 

[nola mike]

Fwiw, I'm thinking there's something "special" about this stove (search my posts for some of my 602 adventures). Even with a pipe damper and a 5" liner i peak at 800-850 as well. Doesn't last too long. Anything less than that and it's smoldering.

 

[MoreCowbell]

Thanks nola mike, makes me feel a little better I read through some of your posts and it sounds very much like my experience. I just haven't taken all the remediation steps you've tried so far.

Basically, in my week of experience, I find I have to follow these guidelines to avoid a 850F+ overfire:

• Never reload the stove before the surface temp is lower than 300F, 200F is even better.
• Only put large pieces after the initial start and never more than 2 (not that you can fit more than that most of the time)
• When adding wood, I might open the draft control just until I get ignition, typically under 60 seconds, after that keep the draft fully closed.
• Point a fan at the stove if it starts rising over 750F to try to slow it down

I would still like the ability to run this at a 500-700F without walking on eggshells. Right now, I'm thinking I may look to get the flue reduced to 4 or 5" at the top of the chimney. Any other F602 users take this approach with any success?

 

[begreen]

We have neighbor down the street with this stove. They've had it for 7+ yrs now I think. I've asked how it runs for them and they say fine. IIRC he says they run it with about a 650F stove top, but I'll ask the next time I see them. Their stove is on about a 13-14' flue I would guess, straight up.

 

[nola mike]

After everything I've tried with this stove, I'd really be surprised if it can cruise at 650 with a full load of dry wood. At 650 at the peak of the burn it really is smoldering. It seems happy with just behind the cook plate at a bit over 800. This is a temp of about 750 or so just above the door. I don't know that the reducer will do much for you. Things that WILL help are reducing/eliminating air intake through the air wash on the glass and the secondary air intake. 2 ways to cut down your primary air through the glass:
1. The air enters behind the top of the glass. There's a metal piece held off the glass by a gasket. If you remove that part of the gasket, the metal piece will rest right up against the glass, eliminating all of that air.
2. Alternatively, you can stuff part of that gap with more gasket material. That way you can reduce the air a variable amount.

The secondary intake really lets in a lot of air. You can close it part way by blocking it somehow. I have a piece of sheet metal on a rod running to the front of the stove. I can snug the metal up to the air intake on the back by pulling the rod, thereby cutting the secondary air. This works very well to cool the stove down.

 

[begreen]

As noted, I'll ask to verify. Their stove is a 602CB, bought new and on a short chimney.

 

[Dustin]

After everything I've tried with this stove, I'd really be surprised if it can cruise at 650 with a full load of dry wood. At 650 at the peak of the burn it really is smoldering. It seems happy with just behind the cook plate at a bit over 800. This is a temp of about 750 or so just above the door. I don't know that the reducer will do much for you. Things that WILL help are reducing/eliminating air intake through the air wash on the glass and the secondary air intake. 2 ways to cut down your primary air through the glass:
1. The air enters behind the top of the glass. There's a metal piece held off the glass by a gasket. If you remove that part of the gasket, the metal piece will rest right up against the glass, eliminating all of that air.
2. Alternatively, you can stuff part of that gap with more gasket material. That way you can reduce the air a variable amount.

The secondary intake really lets in a lot of air. You can close it part way by blocking it somehow. I have a piece of sheet metal on a rod running to the front of the stove. I can snug the metal up to the air intake on the back by pulling the rod, thereby cutting the secondary air. This works very well to cool the stove down.

I had one too,

25 feet and I HAD to install a damper and make all of the other listed modifications. Once I did that, I was able to control it.

Blocking the gap above the glass with gasket material was huge.