Jotul F55 — Where does the heat go?

[begreen]

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.

After careful inspection of the stove door and stove door glass gaskets and verification that they are sealing properly there may be only a couple practical choices, restrict the flue more with another key damper or restrict the air intake more.
http://www.gulland.ca/florida_bungalow_syndrome.htm

 

[Highbeam]

Fascinating discussion. I run a big noncat in my shop for big heat which is not unlike the OP's situation of trying to get maximum output. I run it hard and hot and can blow through 3.5 cubic feet of fuel in three hours. Flue temps on my single wall pipe surface are about 400 when stove top temperature is about 750. My flue is only about 20 feet long. I don't see any problems, in the OP's pursuit of maximum output, of letting the surface temperature of his flue cruise at 450 as the stove temperatures come up. What I picked up on pretty early is that the OP is shutting the air control down fully as SOP. I run at about 50% open for maximum heat. I leave it as open as possible while staying under my desired maximum flue temperature.

The big difference with the OP's setup is the likely super high draft strength. The draft strength of a 30' 8" flue is very strong and will create high flows through the stove due to the unregulated secondary air system. The heat could be sucked right up the stack before it has a chance to warm the stove. Can't wait to see what the draft strength is and how reducing that strength with dampers will slow the flows and allow heat transfer to increase the stove top temperatures.

 

[otsegony]

An update on this thread. I installed a second flu damper on the stove pipe yesterday and it is definitely making a difference. The stove is cruising at a higher temperature and the burns are lasting much longer. I'll keep an eye on this and see if I can put some numbers to these changes. Also, have ordered a manometer so when that comes in I will have a good idea of what the actual draft is.

 

[begreen]

It's good to hear there's progress.

 

[jzinckgra]

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.

I was reading the newer V2 manual and it says the optimal draft is 0.05 - 1.0. I assume the 1.0 is a typo and should be 0.1?

 

[Ashful]

I was reading the newer V2 manual and it says the optimal draft is 0.05 - 1.0. I assume the 1.0 is a typo and should be 0.1?

Yes. At 1.0"WC, you'd be shooting flames out the top of the pipe!