Jotul F55 — Where does the heat go?

[otsegony]

Sorry for the lengthy post, but this is a complex issue.

A bit of background: We live in upstate NY in a 2000 sq. ft. house built in 2003 that is very well insulated. When we originally built the house it was designed to have an internal wood boiler to supply hot water to the radiant heat system. However, as the project neared completion we ran out of money and I ended up with a chimney, but no boiler. The chimney runs from the basement through the center of the house and is about 30’ tall and has a very strong draft.

As an interim measure I bought an old Fisher Grandpa stove hooked it up, thinking it would be a good supplement to our oil boiler. To my surprise that stove worked very well and supplied about 80-90% of the house’s heat load and could easily heat the house without the oil boiler kicking in down to about 10 - 15 degrees. Typically the stove easily maintained temperatures of about 70 degrees in the basement, 68 degrees on the first floor and 65 degrees on the second floor.

Five years ago I decided to upgrade the stove for a few reasons. one being my homeowner’s insurance was doubtful about a stove without a UL tag, the others being I wanted a cleaner burning stove and one that would use less wood. After doing a lot of research we purchased a Jotul F55 stove and had it installed in 2014.

Unfortunately, although it does an adequate job, it cannot hit the same heating levels as the Fisher and the house doesn’t feel as warm. It seems like the convective design of the stove heats the air more effectively than the structure of the house, whereas the old stove heated radiantly and the whole structure of the house was warmed by the stove. When the Fisher was going all the time the floors would feel warm and the wall that the chimney chase that went through also seemed to radiate out some heat on the second floor. Now although the air temperature hits 65 to 67 degrees on the first floor, the house just isn’t as warm. Also, the stove itself doesn’t get very hot. If i get it going in the morning and stuff the box full of wood I can get the surface thermometer to about 450 degrees tops. It then settles down and will cruise at 300 degrees, but no warmer and as soon as the fire dies down the stove gets cold.

My questions are:

1. Is there anything that I can do to get the Jotul stove to burn hotter and retain heat? Everything about the stove hook up is within spec except that the chimney is 8” rather than the listed 6”. It has plenty of draw from the chimney and my wood supply is consistently around 17% moisture content.
2. My wife wants me to get the old stove out of the barn and hook it back up. I’d rather not return to the past. Is there a contemporary stove that heats radiantly like the old Fisher models that is also UL listed?

Thank you for your thoughts.

 

[sutphenj]

Seems odd you cant get temps above 450. I can pretty easily get to 750 in my f55 without much trouble. Either the draft is too strong or the wood is not at 17%. Maybe try splitting a piece and taking a read from the center....

 

[Ashful]

30 feet of insulated 8” pipe would be sufficient to suck the heat out of almost any house. Does Jøtul specify a max draft (usually measured in inches or cm of water column) for that stove? You are likely over their test numbers by 4x, with that chimney

Also, how are you supplying fresh air?

 

[kennyp2339]

I had an issue with my old epa air tube stove with excessive draft literally sucking all the heat up the stack, it seemed far fetch but it is what it is.
This stove was first installed upstairs on the main living floor, but it was to much for the house, literally heated me to the basement with the windows open until the temps dipped into the teens, wasn't to fun, and I wasn't smart enough to realize a cat stove was my best option at that point.
The next heating season I moved the stove to the basement, re-routed the chimney and increased my stack height from 14ft, to 26ft. The stove burnt great, but I was loosing control due to increase draft, soon after it started getting colder out and I noticed I couldn't heat the upstairs past 72, I would run the stove a little harder (keeping from over-fire though) and I suffered from excessive coaling and increased wood consumption because the heat was literally being produced and being sucked up the chimney before is could radiate off the stove. I soon started experimenting with a draft damper and immediately had great results. I then upgraded my stove, de-creased my stack height and lived happily ever after.
The point is that draft is the engine that drives the heating system.
A couple questions regarding your setup, what size is your chimney, if I'm not mistaken the old fisher needed a 8" chimney due to the volume of the stove with typical draft conditions, but if you have a 6" chimney or a masonry with similar cubic inches as a 6" round with an over draft it may have cancelled out the required volume output of the fisher, but when switching to the new stove that same 6" is over drafting giving you similar conditions I once experienced. I suggest buying a cheap manometer from amazon and testing your draft, you may need to add a damper or two to bring it down so the stove can heat exchange properly. This is all hypothetical though because there's tons a questions on your setup that need to be answered, including how the stove is hooked up, wood type & dryness, were your located (heavy woods, top of a hill) ect… but this is just some food for thought.

 

[otsegony]

According to the owner's manual:

"Optimum draft force should be in the .05 - .10 in. w.c. range measured by a Magnahelic gauge. Draft at .07 w.c. is ideal.
Excessive chimney height can promote over-strong draft resulting in high stove temperatures and short burn times. Excessive draft can be corrected by installing a butterfly damper. Your Jøtul dealer is an expert resource to consult regarding draft issues or other performance-related questions."​

There is a butterfly damper, which I do use, but my problem is under heating, not high stove temperatures. What is the difference between a magnahelic gauge and a manometer and do I need one or another to get an idea of the draft?
Just to review, the chimney is 8" prefab metal and the wood is mostly ash and locust with some oak and seasoned to about 17% moisture content according to my moisture meter. The house is located on a hillside where it is sometimes quite windy and being upstate NY generally cold, occasionally dropping to -10 degrees in winter.
The stove is located in the middle of an open basement area, so there is no OAK hooked up to it. However, when we first moved into the house we were having trouble with air quality and the oil-fired boiler does have a dedicated fresh air feed.

 

[Ashful]

According to the owner's manual:

"Optimum draft force should be in the .05 - .10 in. w.c. range measured by a Magnahelic gauge. Draft at .07 w.c. is ideal.
Excessive chimney height can promote over-strong draft resulting in high stove temperatures and short burn times. Excessive draft can be corrected by installing a butterfly damper. Your Jøtul dealer is an expert resource to consult regarding draft issues or other performance-related questions."​

There is a butterfly damper, which I do use, but my problem is under heating, not high stove temperatures. What is the difference between a magnahelic gauge and a manometer and do I need one or another to get an idea of the draft?
Just to review, the chimney is 8" prefab metal and the wood is mostly ash and locust with some oak and seasoned to about 17% moisture content according to my moisture meter. The house is located on a hillside where it is sometimes quite windy and being upstate NY generally cold, occasionally dropping to -10 degrees in winter.
The stove is located in the middle of an open basement area, so there is no OAK hooked up to it. However, when we first moved into the house we were having trouble with air quality and the oil-fired boiler does have a dedicated fresh air feed.

My chimney pulled 0.18” WC at full bore, and it’s both smaller and shorter than yours. You might be over 0.25”!

A Magnehelic is just a specific type of nanometer, but it’s a particularly versatile and durable one. I’d recommend it over most other types, for this application.

 

[begreen]

This is not an issue of a radiant/convective stove. The stove should run at about 650º stove top. Put the thermometer on the stack about 18" from the flue collar and let us know what it reads. It may be that too much heat is going up the stack. If so using the key damper in the stove pipe should help quite a bit.

Or it may be a case of the wood. The old Fisher would be much more tolerant of partially seasoned wood. The Jotul is going to want fully seasoned wood to burn well. Has the wood been tested for moisture content?

Or this may be the way the stove is being operated. Describe the procedure for starting and running the stove including wood size and loading direction.

 

[otsegony]

The wood is well seasoned, averaging about 17% moisture content according to my meter. I've been heating with wood for over 30 years and my procedure hasn't changed much. Top-down start with kindling, the loading direction is mixed between E/W and N/S depending upon how it fits, but with good air flow always in mind. Most of my firewood is 16" long and fits best N/S, which is also good for air flow. The firebox on this stove is smaller than it would appear due to the construction of the secondary burn system.
I don't think that this stove has ever run at 650 degrees. If I fill the firebox and keep the air vents open it might that, but just at its peak.

 

[begreen]

If the wood is being tested on the freshly exposed face of a resplit then the 17% reading is fine. A N/S loaded fire will burn hotter, If the thermometer on the stove top is accurate, something is preventing the stove from performing at proper temp. Need more data. Flue temp would help. I'm sure you have a lot of experience, but this stove does not run like the old Fisher. Describe how the air control and pipe damper are used throughout the burn.

 

[Hogwildz]

Burning techniques and need of drier wood has changed a lot over 30 yrs. Wood that burns great in an older stove, won't burn worth shat in newer stoves. At 30' stack height, I would think that stove would be like a blast furnace if any issues due to how tall the stack is. 8" flue instead of required 6" is def going to cause issues.

 

[firefighterjake]

This may be a dumb question . . . but once the stove is up to temp I assume you start closing down the air control to get the secondary burn?

 

[begreen]

In order to help we need to know a lot more details. The stove is being run at the low end of its output capacity, but without a lot more details it's hard to know where the problem lies.

 

[otsegony]

I will get another stove thermometer to show flue temperature vs. stove temperature at different points in the burn cycle. All I can say about my operation of the draft control and damper is that it follows common practice and the owners manual, full open at start of the burn and then close it down about 15-20 minutes later. Generally I close both the damper and the draft control fully down, but if the fire didn't start as strong as I would like I leave the draft control 50% open until the fire hits that mark.
Also, this morning I resplit the three pieces of the firewood used to start the fire and they averaged 17% moisture level.
Aside from the flue temperature can you tell me what consists of "a lot more details"?

 

[SuperJ]

How does it perform if you leave the damper wide open and just control it with the combustion air control?
When it's warm out in the shoulder season, it won't draft as hard maybe you don't need the damper.

Have you tried it like this: Open up all your controls, get a fire going, gradually shut down the primary air (leave the damper open) as it comes up to temp to promote a good secondary burn. If the stove top temps are getting away on you (sounds like this isn't a problem), only then tweak the damper a bit.

Can you post a video of your burn when you've started to shut things down? Maybe some pictures of your setup?

 

[SuperJ]

The stove is located in the middle of an open basement area, so there is no OAK hooked up to it. However, when we first moved into the house we were having trouble with air quality and the oil-fired boiler does have a dedicated fresh air feed.

One more thing to try, can you crack a window open in the basement? Do you run any sort of exhaust? Bathroom fans, kitchen range hood, ERV/HRV? If it runs a lot better with the window open you might need some sort of make up air inlet.

 

[begreen]

I will get another stove thermometer to show flue temperature vs. stove temperature at different points in the burn cycle. All I can say about my operation of the draft control and damper is that it follows common practice and the owners manual, full open at start of the burn and then close it down about 15-20 minutes later. Generally I close both the damper and the draft control fully down, but if the fire didn't start as strong as I would like I leave the draft control 50% open until the fire hits that mark.
Also, this morning I resplit the three pieces of the firewood used to start the fire and they averaged 17% moisture level.
Aside from the flue temperature can you tell me what consists of "a lot more details"?

Thanks. The flue temps are a good next step. I would also verify the stove thermometer is relatively accurate. Some can be off by quite a large degree.

Have you tried it like this: Open up all your controls, get a fire going, gradually shut down the primary air (leave the damper open) as it comes up to temp to promote a good secondary burn. If the stove top temps are getting away on you (sounds like this isn't a problem), only then tweak the damper a bit.

Good suggestion. I would also run that full load with all the splits oriented N/S.

 

[Hogwildz]

You may want to check the moisture level with another meter. I have never seen moisture content of 17%. I can see that on the west coast, but highly doubtful in NY. Given the wet summer alone, 17% seems a bit off. 8" flue is not going to draw as hard as the required 6", which will also pull less on the fuel. These systems are all dependent on all parts of the system performing correctly. Draft is a big part, and 8" is not going draft as 6" would.

 

[Ctwoodtick]

You may want to check the moisture level with another meter. I have never seen moisture content of 17%. I can see that on the west coast, but highly doubtful in NY. Given the wet summer alone, 17% seems a bit off. 8" flue is not going to draw as hard as the required 6", which will also pull less on the fuel. These systems are all dependent on all parts of the system performing correctly. Draft is a big part, and 8" is not going draft as 6" would.

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

 

[Hogwildz]

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. Rediculously wet. I've had several trees just flop over taking the root ball out of the ground.

 

[Ctwoodtick]

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. Rediculously wet. I've had several trees just flop over taking the root ball out of the ground.

Wet for sure. I’m glad this year my wood is all top covered.

 

[Rearscreen]

Yup, been burning wood a long time in New England. Wettest by far.

 

[Hogwildz]

Wet for sure. I’m glad this year my wood is all top covered.

Mine is in my barn, but everything is just damp as shat this year. Even 60 degrees feels damp cold to the bone.

 

[Ctwoodtick]

If all this rain becomes snow in a month or so, we’ll be in for it. Sure hope it dries out.

 

[7acres]

Here's some hope for you. I loaded our F55 up with a partial load yesterday evening. I could have put 2 or 3 more splits in the firebox. 3+ year seasoned wood. Dry & lightweight in the leather log carrier. From a cold firebox I lit it from kindling and then did some chores before going to bed. Wife stays up much later than me. She informed me that the thermometer 10' from the stove in the dining room was 90F. She opened a bunch of windows to let a lot of the heat out before going to bed.

Sounds like a fairy tale. I'm not trying to brag here. This stove can roast you out of your house.

 

[otsegony]

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.