Smoke from underneath a Mansfield-Hearthstone

[robbingham]

Hopefully I am posting this question properly- apologies if not.

I have a large Hearthstone ~Mansfield~ wood burning stove which really is like a mini-furnace and I am quite happy with it.... EXCEPT, that it has, in the rear, of the underneath, two little holes [about the size of fifty-cent pieces] which allow smoke to billow out into the room when the fire is first igniting and the door is still open. This was never a problem before and I do not know what has changed but it is now not safe to start a fire and leave the room, until one is quite sure it is underway and the door is again closed. For two years I did not even notice these holes [vents, whatever they are] and no smoke came into the house. Now, HUGE amounts of pure smoke simply wafts out into the room until the door is shut...

Can anyone tell me what these holes ARE and if I was supposed to have closed them or something??? [I had someone install this a couple years ago and only use it when visiting this cabin]...

Any ideas? Many thanks in advance,
Rob

 

[LLigetfa]

The holes are essential to the operation of the stove and except in the worst cases of overdrafting, should be left alone. Your problem is not the stove but rather the flue and/or the house. Fix the reverse drafting of the flue or the negative pressure situation of the house. Try a top down fire that produces less smoke. Try starting the fire with Super Cedars. Try opening a window to relieve the negative pressure.

 

[rwhite]

I have found on my stove that if the door is wide open and the fire is just starting I will get wafts of smoke out my primary air. Doesn't do it when adding wood later, only at start up and only if I leave the door open for several minutes. I was just experimenting with the stove and discovered this, it's not how I burn. I assume that new stoves are not designed to run with the door wide open especially when you have not yet started a draft.

 

[robbingham]

Thank you guys. I think what you [Idaho] said is exactly my situation and i will just make sure that the fire is going good and the door is shut... [I'd started a fire with a lot of kindling and went upstairs. No BIG deal but could have been dangerous to a baby or something left in the room- and I'd never seen it before]... My conclusion is that it was a ~draft~ situation [windy day, not used in a while etc]...
Thanks again,
Rob

 

[LLigetfa]

Rule #1, never EVER leave the room with the stove door open. Rule #2, ascertain the draft condition before striking the match.

 

[begreen]

Walking away from a stove with the door wide open is really asking for trouble. Please, never do this. I have had embers pop out of freshly heated wood as far as 6 ft away from the stove. Murphy's law says that just when you least anticipate it, something very unexpected will happen. This is really playing with fire. If the door needs to be open for starting the stove, then just leave it slightly ajar. Usually being open just a 1/4-1/2" is more than enough air to get the fire started.

PS: Welcome to the forum!

 

[robbingham]

I feel duly rebuked- and have learned from it. Thanks.

OTOH, it is funny, I also have a European wood-burner which is made to use with the door open [more show than heat]... So I did not think of it as verboten. As I said, I realize now that the Mansfield is a serious stove and IS made to work with the door CLOSED.... So, this forum has been good for me. Glad I joined.

 

[Chettt]

It seems odd that a stove would be built with two 1.5 inch holes in it.

 

[LLigetfa]

The holes on the exterior are probably not sized to regulate the air. There is most likely some form of internal restriction to regulate the volume of air.

I'm not familiar with that particular stove but many stoves have a separate intake for zipper (doghouse) air that in some cases are not adjustable.

 

[LLigetfa]

There have been anecdotes of folk leaving the room with the door ajar and then getting distracted, only to realize much later that the door was still open and the now raging fire turning their stove top or pipe cherry red. It is too easy to get distracted, no matter how well intentioned you may be. I never leave my door ajar for more than a minute or two but have been guilty of leaving the air wide open and forgetting about it or dozing off. Fortunately, my stove has a thermostatic bi-metal control that helps to limit a runaway situation.

Others have suggested setting a timer to alarm as a reminder.

 

[firecracker_77]

I don't leave mine open more for fear of runaway fire, but more just the idea that the stove won't properly burn with secondaries without the door closed and the air shut down.

 

[begreen]

Some stoves are design so that they can be run with the door open, but only with a screen in place. Otherwise it can be very risky business.

 

[snowleopard]

I've got a Hearthstone stove, and one of the things I appreciate about this stove is that I can walk into the house and not be able to smell that we heat with wood---i.e., smoking has not been an issue. However, I don't leave the door open to start because it's usually not necessary, and if it is, it's only an inch or so for only a few minutes. One of the things the owners' manual and the stove store drills into you upon purchase is the importance of avoiding overfiring this stove. The two ways that you can do that is to first, leave the ashpan door open and walk away, and second (but not as great a risk) is to leave the front or side door open and walk away.

The thing that caught my eye about this is that it hadn't smoked for you previously. That would make me ask, what is different now than before? It could be, as the folks above have mentioned, a reverse-chimney effect (window open above the stove, no air intake available below that, for example), or pressure differential on a warm day.

Another possible cause is a partially-obstructed chimney or other impediment to airflow. The Mansfield has a baffle in the top of the stove (a somewhat fragile ceramic baffle that is easily punctured by an overenthusiastic top-down chimney brush, btw) that can get covered with ash or other obstructions. It's recommended that you check this and clean if needed at least twice a year.

The other thing you may need to attend to is cleaning the chimney.

No rebukes here, just all of us sharing what we've learned and learning as we go. There's a freebie posted at the top of some of the forums, a link to an ebook entitled something along the line of `your stove and house as a system'. It's worth the time to peruse.

You've got a great stove there, and I'm sure it will do a good job for you once you've climbed the learning curve a bit.

 

[Highbeam]

I believe those holes feed the unregulated secondary air system, the top tubes. It is good to know where they are as in the event of an overfire you can plug them. The heritage takes secondary air from the same intake as the primary air so we have no holes underneath.

Something has hurt your flue's draft. If you have a spark arrestor screen in your chimney cap this is about the time of year when they first become clogged. I fought that clogging screen every three months until I got smart and got rid of the stupid screen. It is easy to clean the screen but you need to get up there to inspect it.