Jotul F500 Excessive Draft? (and Thermometer placement question)

[cgeiger]

So I've been monitoring my temps on the center of the little faux griddle on the top of the 500 with a standard Rutland stove therm. I know it's not the best thermometer but I figure it's within 100 degrees or so and I can "feel" the fire well enough to avoid smoke/overfiring...or so I thought.

Well, I looked at the manual and noticed that I'm supposed to put it "...directly on the corner of the stove's top plate." Well, noticing there are 4 corners to a rectangle, I arbitrarily chose the back rear corner. But I noticed the temp is about 200 degrees lower than the center of the "griddle."

Tonight, I put a load of wood in on good coals, charred it for about 2 minutes, then backed the primary down to 50% thinking it would be fine while I walked next door for 10 minutes (literally). When I came back my wife told me the room smelled like curing paint (just as it did when we broke it in) and she backed it down to 25%. But when I came in a few seconds later I could see the fire was boiling inside, the logs were all glowing red and the upper baffle was just beginning to glow on the edge closest to the flame (front of the firebox). Thermometer reading was 500 degrees. Right now, 15 minutes later, the temp is still at 500 but the upper is no longer glowing.

Honestly, I figured I might have an excessive draft problem given that my chimney sucks air hard when it's cold, let alone when there's a fire. But now that I've transitioned from a smoke dragon to a modern stove I'm just not sure what excessive draft and burn tubes look like. My secondaries light off fine but they look like blow torches, no lazy flames here and they're blue, barely any yellow at all. My old VC Resolute would routinely glow on windy nights with the damper closed :bug: until I figured how to choke everything down tight enough (even had to close the secondary intake).

So here's my questions:

1. Am I really putting the thermometer in the right place? How can it be 500 degrees and the upper baffle start to glow? and
2. How do I know if I have excessive draft?

 

[WOODBUTCHER]

Been using my Oslo for 5 winters now, the edge of my baffle sometimes glows a little red. Often times (last 2 weeks of extreme cold) I hit 600/650 the other night in secondary burn.
If your front draft control is more than 50% open it's putting alot of heat up the stack, so your pipe paint took a little beating.
Yours sounds normal .....500 is crusing speed for it.....my Rutland is in the back left corner. Your's prob says overfire at the 575 mark (its made more for stovepipe placement)

WoodButcher

 

[cgeiger]

Thanks for the quick reply WoodButcher. I've been running too light then if I was only showing 500 on stovetop center. So that's good to know. However, I'm still concerned about too much draft - right now with the draft lever closed, the burn tubes are literally blowing fire against the front glass. I've seen other posts with "lazy" flames, blue or otherwise, but my blue flames are just boiling all around in there. Is that normal? (I'd take a pic but all you'll see is hot pink and purple - still trying to figure out how to take pics of fire)...

 

[begreen]

Not all wood, or all flue systems are alike. You may be just fine. At the point of maximum outgassing of the wood, secondary combustion can be strong. Your stove is made to work within the temperature ranges you are seeing. A draft damper won't hurt if you want to add one and will give you a bit more fine tuning control when it's cold outside and draft is strong. But as soon as temps moderate, I'm guessing that you will want the full draft of the flue.

 

[colebrookman]

Been using my Oslo for 5 winters now, the edge of my baffle sometimes glows a little red. Often times (last 2 weeks of extreme cold) I hit 600/650 the other night in secondary burn.
If your front draft control is more than 50% open it's putting alot of heat up the stack, so your pipe paint took a little beating.
Yours sounds normal .....500 is crusing speed for it.....my Rutland is in the back left corner. Your's prob says overfire at the 575 mark (its made more for stovepipe placement)

WoodButcher

I agree with WoodButcher. Two other things: fire is sometimes hotter at the ends or in the middle giving a false reading. Also it takes at least 5 minutes, sometimes longer if you have nice dry wood, for the stove to calm down after moving the vent. Just anticipate a little faster as you get to know your stove and your wood. Be safe.
Ed

 

[WOODBUTCHER]

BlueRidge,
Here is what my Oslo looks like about 45 min after cutting back the air 75% (temp on top is 575)
Different species of wood will give you different results (BTU output ect...) I've laoded it up with Pignut Hickory and hickory gives you nice dancing blue flames almost all the time (esp when the bark is near the burn tubes.)


WoodButcher

 

[ansehnlich1]

This doesn't sound unusual to me. My stove will easily walk right up to 600 degrees, thermometer on back right corner of top.

I won't walk away from my Oslo with the air control set above half, and most times I won't leave it when set at half either unless I KNOW it's on the downward side temperature wise.

I've seen it climb to 600+ pretty quick when it's crankin' with the air set at half or less.

 

[firefighterjake]

I'm not surprised to see a temperature difference between the center of the stove and the corner . . . shoot with my IR thermometer I've discovered 100+ degree differences from corner to corner on the stove at the same time. I attribute this mainly to the placement of wood (how close to the stove top it sits in relation to other pieces of wood) and coals (i.e. typically the hottest point for me is the right rear . . . where all the coals tend to build up due to how I load the stove . . . which in turn means the wood I add to the coals typically sits higher in the right rear.

As you have noted some of the magnetic thermometers are notoriously unreliable in terms of getting an accurate temp reading . . . or it could be spot on . . . my thermometers are all pretty much agreeing with each other (50 degree difference).

As to your question on the secondaries and what they look like . . . it depends . . . I would think it depends on the wood you're using, how seasoned the wood is, amount of air, amount of wood and where in the burning cycle the fuel load is. I have seen the lazy "Northern Lights" flames and flickers and I have seen the Welcome to the Bowels of Hell hellfire blowing out the top of the burn tubes -- again I suspect I have seen these two different types of secondary burns based on what wood I was using, how well seasoned it was, how much air was being cut back, amount of wood I was using and where I was in terms of time in the burning cycle.

And to echo Ansehnlich1 . . . after having experienced how fast the temps can rise with the Oslo . . . I never leave the stove unattended until the fire has been well established and the air control is always left between 1/4 or less -- never more than 1/2.

 

[jtdiesel65]

The manual say put it in one of the 4 corners and run it 400-600. It doesn't say if there is a better corner. Maybe get a different thermometer. My thought is that if you are concerned, put a second thermometer on the stove pipe to see what kind of temps are reaching your chimney.

500 is pretty normal.

Was it windy out?

BTW, to choke your Oslo, cut a 5x8" piece of paper and let it get sucked onto the inlet that is on the bottom underside of the stove in the back. This will kill almost all the air including secondaries.

 

[cgeiger]

"...and I have seen the Welcome to the Bowels of Hell hellfire blowing out the top of the burn tubes"

. That's what mine normally looks like. It sounds from folks that I'm probably doing ok and, believe me, I've learned my lesson about walking away with the air control at 50%. Of course, with my semi-seasoned wood my mileage varies greatly and it has normally taken quite some time to keep the fire from stalling out and not burning it all up quickly.

Since we're on the subject and WoodButcher was kind enough to provide a photo (thanks!) does anyone else see their logs seeming to turn into giant log-shaped coals within 30minutes of closing down primary? I ask because I routinely see this and am not sure if that's normal. My own VC didn't have a window so for all I know it's always been like that, I just couldn't see it!

 

[firefighterjake]

"...and I have seen the Welcome to the Bowels of Hell hellfire blowing out the top of the burn tubes"

. That's what mine normally looks like. It sounds from folks that I'm probably doing ok and, believe me, I've learned my lesson about walking away with the air control at 50%. Of course, with my semi-seasoned wood my mileage varies greatly and it has normally taken quite some time to keep the fire from stalling out and not burning it all up quickly.

Since we're on the subject and WoodButcher was kind enough to provide a photo (thanks!) does anyone else see their logs seeming to turn into giant log-shaped coals within 30minutes of closing down primary? I ask because I routinely see this and am not sure if that's normal. My own VC didn't have a window so for all I know it's always been like that, I just couldn't see it!

Giant log-shaped coals . . . kind of, sort of . . . depends on how much I cut back the primary air and how I've stacked the wood to a degree.

Typically I like to get the fire going really well and then cut back the air and the results will be the BOHH (Bowels of Hell Hellfire) effect with some flames coming off the wood, but most of the flames coming off the secondary burn tubes. As I mentioned earlier if I cut back the air way back after getting the fire going really well I often will get the Northern Lightshow with little to no flames coming off the wood itself, but either a steady or flashing burst of flame from the secondaries.

 

[cgeiger]

Woot! :cheese: I finally saw the "northern lights" today instead of the flaming bowels of hell. I found that I need to damper all the way down to fully closed on primary to get an effective, long secondary. And my wood isn't going "poof" - gone!

 

[firefighterjake]

Woot! :cheese: I finally saw the "northern lights" today instead of the flaming bowels of hell. I found that I need to damper all the way down to fully closed on primary to get an effective, long secondary. And my wood isn't going "poof" - gone!

Congratulations . . . sounds like Hearth.com came through for you.

 

[cgeiger]

Indeed it did. Thanks firefighterjake for the good word-pictures - very helpful.

 

[JeffRey30747]

I have also found that heat from or absence of an established coal bed makes a great difference in secondary burn characteristics.