Backdrafting secondary system, chimney drafting normally

[Highbeam]

In another thread a member believed he had smoke spillage out of the back of his stove and I disclosed that I often had smoke backdraft through the secondary system of my noncat nc30 even though the primary inlets and the chimney were working properly. This is repeatable and I took some photos today.

It only happens when starting a fire in a cold stove with the door open. The secondary system flows properly once I close the door.

35 degrees outside, 55 degree stove.

 

[Highbeam]

No spillage out the loading door, drafts like a champ. All vertical 19 foot chimney. Just a part of the smoke gets sucked into the secondary system.

Oh and this isn’t a cry for help, just that we all should know that it can happen. I doubt any of us will know why it happens but I’m sure the guessing will be fun.

 

[Highbeam]

20 minutes later. 725 stove temp and 350 pipe skin temperature. This stove is a hoss!

 

[bholler]

Like i said in the other thread the only thing that makes any sense is that the large ammount of air being sucked in the door is causing negative pressure behind the stove. I have no clue if i am right but its the only thing i can come up with.

 

[begreen]

Cold stove, cold interior temps. First time I've seen this. Could be good information for someone that has a stove in a remote cabin with no supplemental heat. Also first time I've seen stove temp measured on the side of the firebox.

 

[lsucet]

Are the buffles sitting all the way back?

 

[Highbeam]

Cold stove, cold interior temps. First time I've seen this. Could be good information for someone that has a stove in a remote cabin with no supplemental heat. Also first time I've seen stove temp measured on the side of the firebox.

If you think about it, it’s not that cold. My house and house stove was 64 today. Further, the difference in temperature between inside and out is what powers draft and a 20 degree differential is quite normal.

With the super convection deck and super blower I had to seek another hot spot on the stove. The high volume of air flow would overcool the meter if it was on top.

 

[Highbeam]

Are the buffles sitting all the way back?

Yep. I reset them with every fire. That is shove them tight together and back. A bit of a habit.

One hour later and we’re well past the peak of the burn. Flue temps down to 250 and coals, 650 stove temp and falling. Time to give it more air.

 

[bholler]

If you think about it, it’s not that cold. My house and house stove was 64 today. Further, the difference in temperature between inside and out is what powers draft and a 20 degree differential is quite normal.

With the super convection deck and super blower I had to seek another hot spot on the stove. The high volume of air flow would overcool the meter if it was on top.

Your blower doesnt happen to be on when this happens is it?

 

[lsucet]

Are you sure is thru the secondary? What about the ash plug? That is a good one.

 

[Highbeam]

Your blower doesnt happen to be on when this happens is it?

No sir, the blower is thermostatically controlled and doesn’t kick in until way later. 105 on top of the convection deck.

 

[Highbeam]

Are you sure is thru the secondary? What about the ash plug? That is a good one.

Absolutely. The square hole puking smoke feeds only the secondary air manifold. The ash plug is under an inch of ash and the ash drawer opens to the front.

225 flue temp and really slowing down after 1 hour 20 minutes.

 

[begreen]

If you think about it, it’s not that cold. My house and house stove was 64 today.

That's a little chilly. Our house didn't drop below 70F. But still, a 20º differential in the shop vs 29º in the house and a different stove design. Maybe more important is that the inside of the flue was cold enough to start reversing draft? Or maybe it was just internal in the stove?

 

[Ludlow]

I dont think its anything unnatural or to worry over. Its just a cold chimney and a stove stuffed with wood. The smoke builds and just goes where it goes. Maybe if you have a cold stove you could try to start a smaller tinder fire until the flue is warm before stuffing it so full. The smoke rises and hits the cold logs and simply lingers there instead of getting sucked up the flue. The secondaries are right above it and get filled with the smoke. Small kindling fire until the flue is warm. Then the big logs. JMO.

 

[bholler]

No sir, the blower is thermostatically controlled and doesn’t kick in until way later. 105 on top of the convection deck.

I didnt think so but i had to ask

 

[Highbeam]

I know it’s not lack of chimney draft because as soon as I get the door even within 4” of being closed, the chimney sucks every bit of smoke up. The open door allows tons of room air to satisfy the chimney draft and so there’s a lower than normal vacuum strength in the firebox.

Close the door!

190 flue skin temp. 1 hour 40 minutes. Fuel mostly gone, good marshmallow fire now.

 

[Ludlow]

Oh and another thought: I have never seen it recommended to leave the door swung wide when starting a fire. Slightly cracked maybe. Why would the secondaries draw correctly with a gaping wide door and a cold flue? I think its just extreme startup practices causing it.

 

[Highbeam]

I dont think its anything unnatural or to worry over. Its just a cold chimney and a stove stuffed with wood. The smoke builds and just goes where it goes. Maybe if you have a cold stove you could try to start a smaller tinder fire until the flue is warm before stuffing it so full. The smoke rises and hits the cold logs and simply lingers there instead of getting sucked up the flue. The secondaries are right above it and get filled with the smoke. Small kindling fire until the flue is warm. Then the big logs. JMO.

It’s weird, the young fire is lively with no visible smoke accumulation. It’s growing, getting hotter, and then this white cloud sneaks out from behind the stove.

If the stove used a smarter design where all intake air came from one tube this might not happen but there are 4 separate intake holes on this stove. Only one is somewhat controllable with the draft control lever.

 

[bholler]

It’s weird, the young fire is lively with no visible smoke accumulation. It’s growing, getting hotter, and then this white cloud sneaks out from behind the stove.

If the stove used a smarter design where all intake air came from one tube this might not happen but there are 4 separate intake holes on this stove. Only one is somewhat controllable with the draft control lever.

I thought you said this stove was very controllable. Even that you could snuff it out by shutting the air off. Yet another contradiction

 

[Ludlow]

That is part of the EPA regulations. They have a preset minimum burn rate. They know some hacker will get the bright idea to block the intake so they make it draw from multiple small leaks in the system.

 

[Highbeam]

I thought you said this stove was very controllable. Even that you could snuff it out by shutting the air off. Yet another contradiction

Not sure what you’re talking about. Maybe you’re confused again? I can easily snuff the fire by closing the air control when it’s ripping along. At this point, it’s just coals.

Grasshopper, just because something is uncontrollable doesn’t mean it needs to be controlled.

 

[Highbeam]

So now 2 hours into the burn and the fans have kicked off. 3.5 cubic feet of fuel reduced to just cooking coals. If it was daytime I would reload now. Flue temps under 200, stove temp near 400, room temp has climbed to 72.

 

[begreen]

So now 2 hours into the burn and the fans have kicked off. 3.5 cubic feet of fuel reduced to just cooking coals. If it was daytime I would reload now. Flue temps under 200, stove temp near 400, room temp has climbed to 72.

Methinks you were a locomotive fireman in a previous incarnation.

 

[lsucet]

Does regency has a controlled secondary and dog house? Please I am just asking cause I don't know.

 

[bholler]

That is part of the EPA regulations. They have a preset minimum burn rate. They know some hacker will get the bright idea to block the intake so they make it draw from multiple small leaks in the system.

All tube stoves and cat stoves for that matter have a minimum burn rate. But most of them offer more control than this stove. That is how they get it to burn so cleanly while keeping the price down. They just give it more air. It is a very good stove for the money. But there are many other tube stoves available that put perform the 30. But they should most cost atleast double.