Smoke coming from underneath woodstove.

[chriscarson]

Hey all, so far this season I’ve lit the wood stove maybe a half dozen times. Each time there has been smoke coming from underneath the stove. This only happens on start up and not while I’m reloading. Any ideas what the reason for this is?

 

[kennyp2339]

Sounds like a cold flue, try using a blow torch or a hair dryer in the stove first to warm up the chimney.

 

[begreen]

Might be mild outside temps. Might also be stove is in a negative pressure zone. We need more info about the installation, temps, flue system, exhaust fans that might have been on at the time?

 

[chriscarson]

Ya I was leaning on the idea that the chimney is cold. Outside temps are around +4°C. I do have an air exchanger vent in the room but that’s bringing in outside air. Coming off the stove is 5ft of double wall stove pipe then 90° outside attached to 18ft of prefab that’s about 3ft over the peak. I don’t think it’s a back draft, like both you guys said between mild temps and a cold clue could be the culprit.

 

[begreen]

At 4ºC draft should be good. Is this stove located in the basement or ground floor of the house?

 

[Highbeam]

Was the loading door wide open? I can get just the secondary system to flow smoke backwards on my nc30 noncat during startup if the door is wide open.

 

[chriscarson]

It is a basement install yes, and yes my door is wide open at first sometimes, just as the paper starts to light the smoke lately has been coming through the bottom, the stove does suck the smoke back in for the most part while the door is open but some gets away.

 

[billb3]

Could this be smoke exiting via your secondary tubes rather than going (exclusively) up the chimney ?
Mine will do that on a cold start if I try to cheat and use the old leave the door open a crack trick.

 

[Woody5506]

I get the same issue when lighting my stove on mild days or most shoulder season days. It's next to a sliding glass door so I just prop a box fan nearby to try and blow the smoke out the door. I assume in a basement install it'd be harder to get rid of the smoke though.

 

[begreen]

It is a basement install yes, and yes my door is wide open at first sometimes, just as the paper starts to light the smoke lately has been coming through the bottom, the stove does suck the smoke back in for the most part while the door is open but some gets away.

Most likely this is negative pressure. You can help reduce the issue by reducing any leakage upstairs. Make sure all windows closed, attic vents and doorways sealed for the winter. If opening a nearby window or door an inch helps the situation then providing an air supply to the stove will help. This gets trickier in the basement, but there are some workarounds like a valved fresh air supply with an outlet close to the stove intake or an HRV that is balanced to put a slight positive pressure in the room.

Be sure to have a good, readable CO alarm in this room in addition to the smoke detector.

 

[Highbeam]

It is a basement install yes, and yes my door is wide open at first sometimes, just as the paper starts to light the smoke lately has been coming through the bottom, the stove does suck the smoke back in for the most part while the door is open but some gets away.

Yep, mine does this too. I documented it with photos so others could see. It’s just the secondary system flowing backwards and all you have to do is close the loading door most of the way so the flue suction pulls hard enough on the firebox to get your secondaries going the right way.

Give it a try. It’s free.

 

[chriscarson]

Thanks everyone for the help