Merrimack Smoke back into room

[tedott]

Greetings All.
I am entering my fifth season with the VC Merrimack insert. I am having lots (lots and lots) of smoke coming back into room during initial start. I realize it is due to lack of updraft, but how to overcome? I have opened the window next to the insert. I have tried lighting a bunch of paper to try and prime the flue...no go, once I close the door it just stifles the flames and then pooffffff a ton of uncontrollable smoke into the room. Had a few issues last year, but this year it is unbearable. Once the fire is started, the updraft takes over and all is fine...but I now have to live with a smoky house for next 4 hours (and very unhappy wife...need I say more?). Chimney has been cleaned. Firebox and air ports all cleaned. Automatic setback is open and air control lever all the way to left (open). If I do not solve smoke back issue the insert is going into the trash. Are there mechanical elements elsewhere that could be broken/plugged? Hence not allowing air into the firebox? Looking through a plethora of forums I could not find advise or detailed explanation on how air gets into and out of firebox. Could the primary air vents be blocked "inside" the stove? I removed the bricks and steel plate and cleaned the air ports. The flue has a steel liner in a tile lined chimney; two story house high. I am a pretty advance DIY'r. I am prepared to pull the unit out and dissect it. But would like to know if there is anything in particular to look for...or is the air flow as simple as it seems and the install is doomed....

 

[Grisu]

Do you get the smoke only when you close the door? Does the fire burn well with the door open? Does opening the window help? Once the fire is fine, does the air control change the appearance of it?

How dry is the wood? Do you have a moisture meter to measure whether it is below 20%?

When was the chimney last cleaned? Did you take a look at the cap whether the screen is clogged?

 

[mellow]

How many feet in liner do you have from the top of the insert to the cap? Is the liner insulated? Sounds like a draft issue to me.

Some have taken a hairdryer or a torch and pointed it up the liner to try and reverse the draft.

 

[tedott]

Grisu, thanks for the post. To answer your questions:
Do you get the smoke only when you close the door?
Upon starting the fire...lighting the paper for priming the draft, the smoke will roil out the open door(s) since it is the path of least resistance...so I close the doors which ultimatly smothers the fire due to accumulation of smoke in the firebox (lack of oxygen). then within a few seconds, smoke starts coming out from top and bottom of unit and fills the room.
Does the fire burn well with the door open?
I cannot open the door during the initial startup or all the smoke comes out. Once the fire is going, yes the fire burns well with door open. Some smoke does escape such as when adding firewood. But this is minimal.
Does opening the window help?
No. I opened the window right next to the fire. No benefit.
Once the fire is fine, does the air control change the appearance of it?
hmm. not sure. I never really evaluated the difference between full open and closed air control. Come to think of it, I usually leave the air control wide open. Fire burns good but does not get ripping as a see in other posts.
How dry is the wood? Do you have a moisture meter to measure whether it is below 20%?
Wood is proabably not at optimal MC. But my current issue is with startup using paper, kindling, and wood scraps from the shop that ignite easily.
When was the chimney last cleaned? Did you take a look at the cap whether the screen is clogged?
Chimney was cleaned this past summer. I did not look at cap recently, but being that the system exhusts effectively once going, I am somewhat confient the exhust side is not my issue (except for draft).

The more I ponder, I cannot help but think the internal air supply is being compromised. Is it possible that the air ducts are somehow clogged between the air control (intake) on the top of the unit to the air supply port under the bricks?

 

[tedott]

mellow, also thanks for your post. To address your questions:
How many feet in liner do you have from the top of the insert to the cap? Is the liner insulated?
It is a stadard two story home with wood stove on first floor, so approximately 25 to 30 ft from top of stove to cap. I do not think the liner is insulated. I pondered that myself but I do not know how that makes a difference. Even if insulated, the metal liner gets chilled from above, and after a day or two would be thouroughly chilled regardless of insulation.

Sounds like a draft issue to me.
I tend to agree but want to thoroughly rule out the air supply possibility.
Does the air supply go through the tubes on top of the unit (inside fire box)?

Some have taken a hairdryer or a torch and pointed it up the liner to try and reverse the draft.
I hate to sound dificult, but having to hold a hairdryer (or similiar device) seems like a pain if I want to get a nice warm fire going.
Along those lines I have wondered about placing a candle or two in the firebox to reverse draft, but would that be enough? And now I have candles all dirty from the ashes and being in the firebox.
I'm heading down a road that seems odd. I may have to just give up and paint a picture of a fire on the glass.

I have seen in other posts where people mention installing a tube/pipe from the outside directly into the firebox. I can't fathom that task. I imagine the unit would have had to have been manufactured for such an addon. Also while investigating draft issues I saw a post on having an exhust fan insatlled on the top of the flue, also $$$$.

 

[Fod01]

Just thinking out loud: perhaps a kink in the liner, something new in the house like upgraded windows etc., though you did mention opening a window does not help. Make sure the baffle plate above the tubes is pushed to the rear of the stove. Top down starts with plenty of kindling should fire that stove with minimal smoke.

 

[Fod01]

Ever take the surround off? Check the connection of the liner to the stove

 

[Grisu]

I second the suggestion to check if the baffle plate and the ceramic blanket (if the insert has one) are positioned correctly which usually means pushed all the way to the back. If opening a window does not help then an outside air connection will not do you much good either. Your problem is likely that your chimney gets so cold that you get a serious downdraft. You would use a hairdryer or blow torch before you light the fire to warm up the flue by blowing hot air up the liner. An insulated liner may also make a difference as the warm air from your house will have an easier time to keep the flue warm and overcome the downdraft. The same will be true when you light the kindling. Is that fireplace at an exterior wall? Insulating around it with Roxul insulation may also make a difference plus make the insert a much better heater. See this thread: https://www.hearth.com/talk/threads/finally-got-around-to-insulating-my-fireplace.75755/

 

[surfing woodsman]

I have had a similar problem when I started using my stove when it was really cold out. I have a 25 ft. chimney and used some kindling from splitting pallets. the wood catches fire quickly and starts the draft in a few seconds. Defiantly check behind your surround to make sure there are no other leaks with your insert and also your door gasket.

 

[seabert]

I have a Montpelier and sometimes have the same issue. My issue is mostly a cold chimney pushing back down outside air. I tried the heat gun-did not help. Forget newspaper. If you have a bad down draft newspaper will not reverse the draft. The best method I have found is to use a firestarter and a bunch of kindling that i make by busting pallets and splitting into pieces about an inch or less wide. I separate oak and pine pallet wood. For the start I find that a few strips of pine pallet wood help me get things going and also put in a few oak pieces as well. I use a propane torch to light the firestarters and also light the kindling. With this method you will find that you will be able to leave the door open just bit until you get a good solid flow into the stove and up the chimney. I also sometimes put a small fan on the floor pointed at the bottom of the insert. Most of the time this works just fine. Once you get a strong flame of kindling drop in a nice super dry split or two. I cannot stress enough how important dry wood is especially at startup. I also use Envi blocks when I think my cordwood is marginal. With the Envi's I put in two (north-south) with the firestarter in the middle and a bunch of kindling. Yes opening a window is also a good idea... however it is important to only open the bottom of the window... the idea is to get cold air to be fed into the base of the insert. Opening the top will make your draft issue worse.

Most of my starts are now fairly smoke free but if I have any marginal wood at all at startup I get lots of smoke. Considering our inserts are both made by VC my guess is what works for me should help you. My wife hates smoke and wears contacts so I try to start a fire when she is not in the room.