Jotul F55 — Where does the heat go?

[Ashful]

So I went out and bought a new thermometer for the stove pipe. It is a Ventis brand that measures the actual stack gas temperature, rather than that of the metal pipe. I started a fire about two hours ago and the basement was at about 65 degrees. Ran it as hot as I could and put in fresh splits N/S as needed. Although I only have one wood moisture meter that I bought from Lowe's and therefore cannot vouch for its accuracy, I don't think that the problem is wet wood. All of my wood is in a wood shed and has been since at least June. The wood itself, according to my firewood dealer, was cut and split in the summer of 2017. All I can say is that I know what wood that hasn't been properly seasoned burns like, smells like and feels like, and this isn't it.

The fire has now been burning for 2.5 hours. I've tried running it with a cellar window cracked open for more air and with different combinations of the air control and the flue damper. The only observable effect is that the air control has speeds or slows combustion the quickest (obviously) and the damper seems to slow the combustion while keeping the temperature up.

After 2.5 hours the stovetop is cruising at 450 degrees after peaking at between 550 - 600 for awhile and the flue gases briefly hit 1000 degrees before settling at 750 degrees where they are now. The basement temperature rose during that period from 65 to 76 degrees and the first floor went from 65 to 68 degrees. All this while the outside temp is 50 degrees and rainy.

If this was my old stove, it would be very warm throughout the basement and into the second floor. I guess the only thing left from the above suggestions is to find a manometer and check the numbers on the flue draft.

I’ve never run an F55, but those numbers look good to me, it’s possible the stove is just too small for your needs.

On firewood, one fall and winter outside, followed by one summer in the shed, is pretty marginal for hardwoods. Most here will target at least two full summers for medium hardwoods, and three summers for oak, locust, or Osage. But I don’t think this is your problem with getting heat, your stovetop numbers look good.

 

[begreen]

The flue gases are too hot. Too much heat is being wasted up the chimney. Ideally the flue gas temp would be equal to or around 100º less than the stove top if everything is working right. Our stove cruises with a ~ 500-550º flue temp and 650º stove top after the air has been closed down.

PS: I am assuming this is double-wall stove pipe. Where is the stove pipe damper located, above or below the new thermometer? Was the stove pipe damper open or closed when reading the temp?

 

[begreen]

Also, with a fully packed stove there should be little to no room or need for adding more wood within the first several hours of the burn.

 

[otsegony]

The thermometer is in the black single wall pipe that leads to the Metalbestos chimney, about 20" above the stove. It is positioned per instructions over the damper which was open at the time. It sounds like the conclusion here is that there is too much draft for the stove and it is sucking the heat up the chimney.

 

[begreen]

Still uncertain. That's the wrong thermometer for single-wall stove pipe. A probe thermometer will give erroneous readings on single-wall. It is calibrated and designed for double-wall stove pipe and will read too high. Put the stove top thermometer on the stove pipe about 24" above the stovetop. Let it settle down and take that reading.

 

[SuperJ]

I'm not familiar with your stove's baffle, but is it possible there is an issue with the baffle? If it is out of place, warped, missing or mis-assembled it will affect the secondary burn and throw too much heat up the chimney. Some stoves have a baffle made of fragile materials, or easily movable design.

Visually does it look like you have a strong secondary burn happening?

You might be able to rig up a heat shield for your flue thermometer out of a piece of can to simulate double wall pipe.

 

[sutphenj]

My f55 will cruise at 400-500 with marginal wood but in the 600's with well seasoned wood from what I can tell.

 

[Trey1979]

So I went out and bought a new thermometer for the stove pipe. It is a Ventis brand that measures the actual stack gas temperature, rather than that of the metal pipe. I started a fire about two hours ago and the basement was at about 65 degrees. Ran it as hot as I could and put in fresh splits N/S as needed. Although I only have one wood moisture meter that I bought from Lowe's and therefore cannot vouch for its accuracy, I don't think that the problem is wet wood. All of my wood is in a wood shed and has been since at least June. The wood itself, according to my firewood dealer, was cut and split in the summer of 2017. All I can say is that I know what wood that hasn't been properly seasoned burns like, smells like and feels like, and this isn't it.

The fire has now been burning for 2.5 hours. I've tried running it with a cellar window cracked open for more air and with different combinations of the air control and the flue damper. The only observable effect is that the air control has speeds or slows combustion the quickest (obviously) and the damper seems to slow the combustion while keeping the temperature up.

After 2.5 hours the stovetop is cruising at 450 degrees after peaking at between 550 - 600 for awhile and the flue gases briefly hit 1000 degrees before settling at 750 degrees where they are now. The basement temperature rose during that period from 65 to 76 degrees and the first floor went from 65 to 68 degrees. All this while the outside temp is 50 degrees and rainy.

If this was my old stove, it would be very warm throughout the basement and into the second floor. I guess the only thing left from the above suggestions is to find a manometer and check the numbers on the flue draft.

This is the pipe temp?

2018 drolet ht2000

 

[Knots]

I can't figure this one out.

I have an F55 with about 26' of straight up steel pipe, most of it insulated. My draft is almost too good. I have a damper and I had to tape over 85% of the opening in the bottom for the secondaries.

I usually fill the box with very dry, very seasoned oak. Run everything wide open for 20-30 minutes until it's up around 450-500. Then I start closing things down gradually.

Ultimately I end up with the damper almost closed, the primary at around 25-30% open, and (as mentioned above), the secondaries mostly taped off.

I get rolling secondary flames and it starts to burn top-to-bottom and front-to-back. Temp will go to around 550-600 and heat will pour out.

I hope this helps...

 

[Woody Stover]

The wood is well seasoned, averaging about 17% moisture content according to my meter.

All of my wood is in a wood shed and has been since at least June. The wood itself, according to my firewood dealer, was cut and split in the summer of 2017.

On firewood, one fall and winter outside, followed by one summer in the shed, is pretty marginal for hardwoods. Most here will target at least two full summers for medium hardwoods, and three summers for oak, locust, or Osage.

Yeah, the "17%" and the "split a little over one year" that you report wouldn't hold here for Red Oak, our most common wood. It's possible that the wood you re-split and tested was some soft Maple or other faster-drying wood that was mixed in with Oak, and the wetter Oak is affecting your actual burns. Maybe not but I think it's a possibility, anyway..

What is the lowest moisture content that you see in your area? Agreed that this drying season has been poor.

Merely guessing on this year alone, 20 to 23% Maybe slightly more. This area has been the wettest summer and fall I can remember since moving here in 2006...I have never seen moisture content of 17%.

Your lowest moisture content should be lower according to this chart. I've seen 16-17% here, which is pretty similar to where you live. Granted, this has been a soggy summer..
http://www.woodweb.com/knowledge_base_images/zp/equilibrium_moisture_content.pdf

 

[begreen]

As a test, pack in some 2x4 cut offs in with the splits so that there is some known dry wood in the mix.

 

[otsegony]

I added another Rutland thermometer to the vent pipe to check that temp against the stove top. This morning I started a fire with mixed Ash cordwood (17% moisture) and some dimensional lumber out of my scrap pile. I got a good fire, with the secondary burn system working as designed and achieved temperatures of 550 degrees stove top (it peaked a bit after this photo) and 450 on the flue. This lasted for about an hour or so and then died down to 250 degrees and below. The basement temp hit 73 and that was it...
Not sure of where to go after this.

 

[begreen]

450F surface temp = about 8-900º internal. Surprisingly the Ventis probe is not that far off from this. Too much heat is being lost up the flue. With a full load like that you should be seeing ~650º stove top temps for an hour or two and 250-300º surface temps on the stove pipe.

Can we assume that about 20 minutes after the fire was started that the air was closed all the way down? If yes and the draft is too strong it may take two key dampers to tame it down.

 

[otsegony]

Yes, the air control was turned down after about 30 minutes... I'll try another key damper and report back when that is installed.
Thanks for your time.

 

[begreen]

If the air control is turned all the way down and you are still going through wood like candy, the draft is likely too strong or there is leakage in a gasket at the door or ashpan.

 

[stovelark]

I've read this and it does seem to me that the stove is hitting pretty normal stove top temps. I do find it hard to believe 17% MC is accurate after hearing how long its been cut split and stored, seems suspect. It sounds like temps are able to be controlled with the air control so doesn't sound like a leak anywhere (the f55 does not have an ashpan). At 3 cuft, it is a large stove with large heat output, as was the papa bear fisher too. The 8 in chimney while not ideal, sounds like it is drafting fine, again perhaps a bit too much. All in all, it does sound like the stove is within normalcy as far as heat output. You do say the stove cruises at 400-450 degrees with the air control about 1/4-1/3 open after the fire is up and burning. How about opening it more and seeing if STT can be made to cruise at 500-600? How is the glass looking in all of this? Does it stay clear? Is there a bit of visible smoke when the fire is burning, that is indicative of wetter wood... Someone mentioned the baffle, the f55 has a cast iron/stainless top baffle system that is bolted in place, so its not moved. It still seems most likely that the wood is not quite ideal, or simply the stove is not enough, but she is doing what she can. Normally, we hear the Carrabassett is a heat hammer, moreso than inadequate.....

 

[begreen]

2+ hrs burntime and 8-900F stove pipe temps are not normal for this stove. There are however some fundamental differences between this stove and the papa bear. Capacity and secondary combustion are big ones, but also the Papa Bear was unshielded and very radiant. The F55 with its cast iron jacket is not radiant except through the front of the stove. That can make a different impression of 'blasting out the heat'.

 

[sutphenj]

I think I mentioned it already but check that glass gasket....I ran min like this (see pic) for quite awhile and struggled through the same problems you are having. (Came from jotul like this) Also the door gasket is vulnerable by the latch.

 

[RandyBoBandy]

This is a basement install right? Looks like exposed concrete floors and walls? Not that this has an effect on burn times but with the f55 being a jacketed stove is it possible the concrete is soaking it up faster than the stove can convect the heat to the rest of the house?

 

[otsegony]

It is a basement install, however the walls are insulated per NYS code.

The gasket issue, I'm not sure what I am looking at with the picture of the latch. Am I checking the snugness of the fit of the door against the frame?

As to the moisture content of the wood, I found another moisture meter in the house and checked one against the other. They agree with each other and that the wood averages 17% mc.

The burn time issue is also one that concerns me. One of the reasons that I moved to replacing the old stove was to cut down on my wood consumption. With the current situation I am at least at the same level of consumption, perhaps a bit more.

 

[maple1]

Have you actually measured your draft with a manometer?

 

[otsegony]

No I haven't. I would have to buy one on-line. I am a bit confused about which would work in this situation. Any suggestions?

 

[maple1]

I have a Dwyer Mark II Model 25 hooked to my boiler pipe. Mail ordered it from somewhere, simple & works well & reasonably priced. Isn't what I'd call pretty though if you want to leave it hooked up and looks are an issue. Would be good to have to take a big uncertainty out of the equation. I am thinking that chimney would make all kinds of draft.

 

[SuperJ]

At a risk of suggesting a band aid, perhaps a blower kit would help to strip more heat before the gases make it up the flue? Doesn't solve the short burn time issue, but might help with the heat output.

(broken link removed to https://jotul.com/us/products/accessories/blower-fan-kit)

Do you have a convective air flow path to upstairs? And back down?​

I hesitate even going here... but others have said they've get good results and a smoke free burn when covering some of the air inlets. You could temporarily restrict them with a metal magnet, as an experiment. If successful, the damper would be more of a recommendation than plugging the air inlets. It seems like dampers are a grey area that manufacturers don't really want to get involved with, but plugging air inlets is definitely an EPA no-no.

Unfortunately, stoves are certified on shorter chimneys, and the methods to deal with tall chimneys/high draft are left up to the installer with little guidance from manufacturers.

 

[sutphenj]

It is a basement install, however the walls are insulated per NYS code.

The gasket issue, I'm not sure what I am looking at with the picture of the latch. Am I checking the snugness of the fit of the door against the frame?

As to the moisture content of the wood, I found another moisture meter in the house and checked one against the other. They agree with each other and that the wood averages 17% mc.

The burn time issue is also one that concerns me. One of the reasons that I moved to replacing the old stove was to cut down on my wood consumption. With the current situation I am at least at the same level of consumption, perhaps a bit more.

Check two things. Open the door and see if the glass is square to the door frame so it is snug against the glass gasket. Mine was way out of whack with loose brackets and all. Also throw a dollar bill near the latch and shut the door and try to remove the dollar bill. If you can remove it easily the door gasket needs work.