Please help, newbie with F400 - Awful Efficiency Issues!

[franzic]

Hey everyone, I've been lurking a while trying to get some insight into my problem here, but I just can't figure it out.

We moved into this home with a Jotul F400 and I've been enjoying having it, but the more experience I get with the stove, the more I understand how horribly it is operating, and I can't figure out why.

The setup - vertical pipe with one elbow into the wall, joining with a block chimney. I also added a 3" inlet flex hose that draws from the crawlspace beneath the stove.

I'll use a ton of kindling, top down style, I'll leave the cracked open for like 10 minutes letting a big hot fire get going (I have no chance of getting a big fire without the door open) and if I can eventually hit 400 or so, I'll close the door, but more often than not, the fire slowly dies once the smaller stuff burns up, and I'm left with hot coals and the big log on the bottom, but it just wont burn nice.

I see videos of other stoves and it seems like most people get MASSIVE airflow with their damper all the way open. Its a RARE thing that the right magic circumstances allows me to achieve a nice reburning fire where I have ANY latitude to close the damper a little to regulate. I have to crack the ash pan door to get the kind of flow I usually see from people who have all the doors closed but the damper open.

I have tried many fire building methods, I have a moisture meter, wood is fine. Is there a chance my air inlet is blocked somewhere and I need to get in there and inspect/clean? Is that a thing?



EDIT - I say "closed the damper...." I meant I had latched the ASH PAN door.

Thanks so much. I've attached a video example. This was after a morning fire, started about 2 hours prior, so the chimney is drafting, and the flue should be plenty hot.

 

[EbS-P]

You checked your moisture on a room temp piece that was just split? How tall is the chimney? Don’t open the ash door when burning.

Wet wood is my guess. I got to the bottom of my stack this week. It’s wet. Wet wood sucks.

 

[stoveliker]

Can you describe your chimney? How long is the total horizontal run? How tall from stove top to chimney cap?

Can you see if the chimney cap is clogged?

(And indeed, how's your wood, and don't open the ash door - you risk ruining your stove, cracking parts.)

edit: I see the chimney question was already asked...

 

[franzic]

Can you describe your chimney? How long is the total horizontal run? How tall from stove top to chimney cap?

Can you see if the chimney cap is clogged?

(And indeed, how's your wood, and don't open the ash door - you risk ruining your stove, cracking parts.)

edit: I see the chimney question was already asked...

Chimney top is about 11' from the stove top, horizontal pipe run is 2'.
I recently had sweeps come and inspect, and they said the chimney looks great and clear, good to go.

I just wacked open a split and measured it at 15%. Really confusing.

 

[Todd]

Looks like an outdoor block chimney? Is there a clean out door outside on the bottom block? If so it may not be sealed properly and is killing your draft.

 

[Prometeo]

try disconnecting that combustion air hose and open the window slightly, if solve there is a problem with that tube (OAK)

 

[gthomas785]

Couple issues here, first of all, you need to use more wood than that. You want to burn at least 3-4 decent sized splits at a time.

The fact that your wood did not immediately blaze up when you opened the door tells me it is wet.

I didn't see smoke rolling out when you opened the door so draft is probably not a huge issue, although the soot stains above the thimble tell me your draft is not great. There should never be smoke leaking out of there as the chimney should always be under negative pressure relative to the indoor air. Exterior chimneys do not usually draft well and it looks like yours is on the short side so that doesn't help either.

 

[kborndale]

The 90 degree turn is making you chimney more like 9 foot, too short to get a good draft going. If you can replace the 90 with two 45s should help a bit. Still a rather short chimney. If a freshly split piece is 15% your wood is good, maybe check a few more to make sure the wood is all dry and not a mixture of wet and dry. You may need to extend your chimney as well.

 

[franzic]

Looks like an outdoor block chimney? Is there a clean out door outside on the bottom block? If so it may not be sealed properly and is killing your draft.

You're right about both of those things. There is an old clean out and it is definitely not sealed well. Any advice on a simple solution? Guess it ultimately needs to be replaced of course.

 

[EbS-P]

Does unhooking the air intake make any difference??

You're right about both of those things. There is an old clean out and it is definitely not sealed well. Any advice on a simple solution? Guess it ultimately needs to be replaced of course.

Seal with silicone bead around outside (don’t glue it together closed) and then if when to clean it out cut the bead in a way it will make a reusable seal.

 

[franzic]

Does unhooking the air intake make any difference??

Seal with silicone bead around outside (don’t glue it together closed) and then if when to clean it out cut the bead in a way it will make a reusable seal.

Good idea about the silicone 'gasket.'

When I first got in here there was no air intake and I was having these issues, so i added that in an attempt to solve the problem, so no removing it wouldn't help.

 

[begreen]

The chimney is too short. This stove needs decent draft into a 6" flue. It needs 16' straight up to perform well. If the total vertical flue height is 14' (3' +11') then the losses due to the two 90º turns and the horizontal run, plus oversized, cold, clay tile in the block chimney, draft is dilluted too much. Each 90º turn is like losing 2 ft of chimney height and horizontal runs really slow down draft. In the least, change the stove pipe 90s to two 45º elbows with an offset and add a 6" stainless liner that extends 2 ft above the block.

 

[franzic]

The chimney is too short. This stove needs decent draft into a 6" flue. It needs 16' straight up to perform well. If the total vertical flue height is 14' (3' +11') then the losses due to the two 90º turns and the horizontal run, plus oversized, cold, clay tile in the block chimney, draft is dilluted too much. Each 90º turn is like losing 2 ft of chimney height and horizontal runs really slow down draft. In the least, change the stove pipe 90s to two 45º elbows with an offset and add a 6" stainless liner that extends 2 ft above the block.

I was considering installing a liner, but this is great info. Didn't consider I could use the liner to increase the chimney height.

I'll get a 15' liner and run it on up (or down, rather), and some 45's for the pipe.
I assume I also need a T for this chimney so debris can fall to the cleanout?

 

[gthomas785]

I was considering installing a liner, but this is great info. Didn't consider I could use the liner to increase the chimney height.

I'll get a 15' liner and run it on up (or down, rather), and some 45's for the pipe.
I assume I also need a T for this chimney so debris can fall to the cleanout?

You need a tee to make the angle through the wall from the chimney, but don't leave the bottom of the tee open. You can either cap it and use the thimble as your clean out (sweep from top down, then remove stove pipe and vacuum the debris from there), OR extend the liner down to the clean out door and cap it there. You'd remove the cap for cleaning and then put it back.

 

[stoveliker]

Well, I'm back late. All had been said. The chimney is the engine of the stove, and it's not creating enough draft because of height, size, and possibly a leaking clean out.

 

[gthomas785]

Oh and did we mention? Make sure the liner is
I N S U L A T E D.

 

[begreen]

I was considering installing a liner, but this is great info. Didn't consider I could use the liner to increase the chimney height.

I'll get a 15' liner and run it on up (or down, rather), and some 45's for the pipe.
I assume I also need a T for this chimney so debris can fall to the cleanout?

Yes, a tee gets installed with an attachable snout. You have the choice of capping the tee at its bottom or extending it with more liner to connect to a second capped tee that aligns with the cleanout door.

A liner extender can be added. It's not ideal, but will help.

Chimney Flue Extender for Flexible Chimney Liner Kits - Rockford Chimney

Use the chimney flue extender to offset two chimney liner caps or extend your flue. Made in the USA with quick connect clamp system for easy install.

www.rockfordchimneysupply.com

What is the current liner diameter in the block? That's going to determine what insulated liner options are possible.

 

[D. Hermit]

Ill just add one thing to check that I dont think has been mentioned yet.

Pop the inspection cover and make sure the holes are clear, and that ash is not built up around the air control, and verify the air control is working properly.

Its the little cover inside the stove, on the bottom center, directly behind the bottom of the door. Its 2 10mm bolts.