A couple days ago, someone here asked a good question; what can happen to make an EPA-compliant stove burn less clean with time? It so happens I stumbled into one cause last weekend. While staring mindlessly into the Morso 2110's fire one evening, I noticed something I'd never seen before; occasional licks of flame shooting downward torward the left-rear corner of the firebox. Given that there is no air inlet down there and this must be caused by a leak of some sort, I watched it hoping to spot the source. Well, it wasn't so simple... I could isolate it to a region but not to one spot. So I let the stove cool for a few hours, and then prepared to stuff some kaowool into the various gaps and crevices down there. (In the attached photo, the area behind and below the lowest green arrow is what I'm referring to.)
While reaching into the firebox, my hand bumped the front of the secondary manifold. (It's that stainless steel thingy with step-folds and four rows of holes at the top of the firebox.) It made a 'clink', the sound of metal to metal contact. Odd, I thought... that shouldn't be. So I pushed again. Sure enough, the front edge of the manifold (see the three green arrows along the edge) was NOT tightly against the cast iron piece above it that it was secured to. With a lamp, I looked all along the front edge and could then clearly see a gap along the entire width. That's one big leak.
Some of the ramifications of this immeditely flashed through my mind. In terms of upsetting the balance of air sources in the stove, this is the absolute worst place in the firebox to have a leak. Why? Because draft in a stove is like water flowing - it will always pull from the closest source possible. So... leaks closest to the flue connector will upset things inside the stove the most. In this case, it will (theoretically) happily pull from this gap and pull alot less air from the secondary holes at the back of the firebox.
My curiosity piqued, I checked for other possible leak sources around this secondary plate, probing along the stair-step edges on both sides (see the four green arrows in the photo.) Oddly, there was no cement there - yes, there are plenty of screws holding it in place and it fits pretty well. But I could easily press a fingernail into several of the joints on both sides. Air is leaking out there too.
So I let the stove cool down all the way, cleaned and moistened those surfaces, and sealed them good with stove cement. (Great stuff, by the way... every stove owner should have a tub of it around for maintenance.) I gave it an hour to set (should have given it longer but it was getting cold!) and then fired the stove up.
What a difference. With the same air control settings, there was more flame burning inside the firebox, especially the blue secondary flame toward the back of the stove. And MUCH LESS long, yellow flames curling around the front edge of the manifold and exiting up the chimney. There's more turbulence in the secondary flames, always a good thing. The net effect is as if someone rolled the flame 6 to 8 inches back into the stove. Stack temps are lower too. Before sealing, the thermometer on the stack was normally in the 440-500F range. After sealing, it's down to 380-430. And an unexpected added bonus; the stove is less prone to the runaway burn that I had complained about previously. It's a more controlled fire.
Oh, and I haven't again seen the licks of flame that started all this. The air feeding them was probably leaking out of the side of the manifold at the very back.
I think it's pretty obvious that the stove is now operating more like it's supposed to.
I'm not sure that stoves with the "tube"-style secondaries will benefit as much from this. If you decide to try it on yours, please post the results. Sealing those tubes where they enter the air channel may make them too difficult to remove. However, if your stove has a secondary manifold of similar design to the Morso, it will very likely benefit from this treatment.
While reaching into the firebox, my hand bumped the front of the secondary manifold. (It's that stainless steel thingy with step-folds and four rows of holes at the top of the firebox.) It made a 'clink', the sound of metal to metal contact. Odd, I thought... that shouldn't be. So I pushed again. Sure enough, the front edge of the manifold (see the three green arrows along the edge) was NOT tightly against the cast iron piece above it that it was secured to. With a lamp, I looked all along the front edge and could then clearly see a gap along the entire width. That's one big leak.
Some of the ramifications of this immeditely flashed through my mind. In terms of upsetting the balance of air sources in the stove, this is the absolute worst place in the firebox to have a leak. Why? Because draft in a stove is like water flowing - it will always pull from the closest source possible. So... leaks closest to the flue connector will upset things inside the stove the most. In this case, it will (theoretically) happily pull from this gap and pull alot less air from the secondary holes at the back of the firebox.
My curiosity piqued, I checked for other possible leak sources around this secondary plate, probing along the stair-step edges on both sides (see the four green arrows in the photo.) Oddly, there was no cement there - yes, there are plenty of screws holding it in place and it fits pretty well. But I could easily press a fingernail into several of the joints on both sides. Air is leaking out there too.
So I let the stove cool down all the way, cleaned and moistened those surfaces, and sealed them good with stove cement. (Great stuff, by the way... every stove owner should have a tub of it around for maintenance.) I gave it an hour to set (should have given it longer but it was getting cold!) and then fired the stove up.
What a difference. With the same air control settings, there was more flame burning inside the firebox, especially the blue secondary flame toward the back of the stove. And MUCH LESS long, yellow flames curling around the front edge of the manifold and exiting up the chimney. There's more turbulence in the secondary flames, always a good thing. The net effect is as if someone rolled the flame 6 to 8 inches back into the stove. Stack temps are lower too. Before sealing, the thermometer on the stack was normally in the 440-500F range. After sealing, it's down to 380-430. And an unexpected added bonus; the stove is less prone to the runaway burn that I had complained about previously. It's a more controlled fire.
Oh, and I haven't again seen the licks of flame that started all this. The air feeding them was probably leaking out of the side of the manifold at the very back.
I think it's pretty obvious that the stove is now operating more like it's supposed to.
I'm not sure that stoves with the "tube"-style secondaries will benefit as much from this. If you decide to try it on yours, please post the results. Sealing those tubes where they enter the air channel may make them too difficult to remove. However, if your stove has a secondary manifold of similar design to the Morso, it will very likely benefit from this treatment.
![[Hearth.com] Seal those secondary manifolds!](/talk/data/attachments/2/2788-a8be42bc8308013fce74adf50568084c.jpg?hash=1eA5vhanHB)
