VC Montpelier II - Single Burn Rate vs Chimney Height

[Tweedle]

Hi guys, I'm new here. I signed up to get advice on my new wood stove.

I recently installed a Vermont Castings Montpelier II wood insert into my masonry chimney. I chose the Montpelier II because the unit and surround fit my chimney firebox well, it looks decent, and appeared fairly simple to operate. I figured the "single button air control" was marketing speak for a fancy damper. Well, as some of you know, I was wrong. Thanks to these forums, I've learned the phrase "single burn rate" and the implications of that.

For me, that means I start a fire up, the fire rages heating up everything nicely, then hits the coaling stage and rapidly loses temperature. Within an hour I'm loading wood again and fire rages, temp spikes, coals, rinse, repeat. If I load too much or too small of splits, the fire really takes off and I have ZERO CONTROL. I've learned to be conservative when loading wood because I've become paranoid about overfiring the stove.
Video of a startup fire: https://photos.app.goo.gl/HKjgcrraJncatmpB6

I asked about this on another forum and someone suggested the unit is over-drafting because it was intended and tested with a chimney height of around 11-14 ft. My chimney is about 23ft from the top of the stove to the cap. He suggested installing a flu damper which would be great... but this is an insert with a surround. I saw another thread here where some rigged a damper in the stove pipe collar. This is an expensive (yes, overpriced) stove. I'd hate to screw something up by over-firing or a bad hack damper job.

Do I have any options? I'm stuck with this thing either way. I just hate that I can't trust it.

Single burn rate seems like a misnomer. It's more like "whatever burn rate your chimney draft choses".

 

[begreen]

The stove was tested with an equivalent of a 16' flue. 23' ft is not extremely tall. The best control will be to pack the firebox tightly with thick splits. The firewood showing is on the thin side. 5-7" splits will burn slower.

 

[Tweedle]

The stove was tested with an equivalent of a 16' flue. 23' ft is not extremely tall. The best control will be to pack the firebox tightly with thick splits. The firewood showing is on the thin side. 5-7" splits will burn slower.

The attached picture is from a startup fire, so it's fairly thin splits cross stacked for lots of air. The wood is also very dry which doesn't help slow things.
I do need to get some thicker splits. I bought 1/3 cord and most of it is on the 2-3 in splits. A lot of the oak is split into boards rather than wedges.

 

[agonyzhou]

I have the same stove with an even taller chimney. Your fire seems fine to me. Yes, you have zero control except how did you load it. However, it is pretty consistent so after a season or so you will know what to expect after loading.

 

[Tweedle]

I have the same stove with an even taller chimney. Your fire seems fine to me. Yes, you have zero control except how did you load it. However, it is pretty consistent so after a season or so you will know what to expect after loading.

Yeah, I'm definitely still trying to get my bearings with this stove.
Do you have any idea how hot is "too hot" for this stove? I'm not sure if there is a good spot to measure temperature. I'm using an IR thermometer gun. I've seen as much as 750 degrees on the glass, but never more than about 350 on the metal just above the door. I'm guessing it's much hotter in the firebox.
The user manual warns against overfiring every other page, but never gives specific temps for operation or max temps.

 

[Woodsplitter67]

The attached picture is from a startup fire, so it's fairly thin splits cross stacked for lots of air. The wood is also very dry which doesn't help slow things.
I do need to get some thicker splits. I bought 1/3 cord and most of it is on the 2-3 in splits. A lot of the oak is split into boards rather than wedges.

So.. as stated above your splits are thin.. its fine to get it started but once its going bigger splits are better.. and cross stacking is a big no,no.. Your creating way to much surface are.. the more surface area.. the hotter and faster it burns. When you stack the wood like this your literally doubling the burning area of the wood

 

[Woodsplitter67]

Yeah, I'm definitely still trying to get my bearings with this stove.
Do you have any idea how hot is "too hot" for this stove? I'm not sure if there is a good spot to measure temperature. I'm using an IR thermometer gun. I've seen as much as 750 degrees on the glass, but never more than about 350 on the metal just above the door. I'm guessing it's much hotter in the firebox.
The user manual warns against overfiring every other page, but never gives specific temps for operation or max temps.

So you dont measure thetemperature.. on the glass or inside the box.. you measure the actual stove or insert itself. You should have a manual.. in the manual . it will state operating temperatures of the stove and where to measure stove temperature.

 

[agonyzhou]

I've seen as much as 750 degrees on the glass,

That's fine. The hottest I ever got is 1000 on the glass; it was a bit scary but I checked afterward and nothing broke.

I have a pretty powerful floor fan, and anytime it got scarily hot, I aim it at the glass and blow it cool. It is not as direct as the air control (which you don't have), but one hour of blowing does rein it back into normal range. I only need to do that once or twice so far.

 

[vbu]

I have the same stove. Like you said, there's no control. Load 'er up and let 'er rip. Do not crosstack as that is a sure way to overfire it. I've had mine very hot and nothing has happened yet. You'll learn as you go how to load it to keep it under control. It's not ideal and I will never buy a single burn rate insert again, but just like you I didn't know any better. I am trying to heat 3300sq ft with this insert, so I need all the heat I can get off of it.

 

[Tweedle]

You should have a manual.. in the manual . it will state operating temperatures of the stove and where to measure stove temperature.

I do have a user manual. It's also available online: https://downloads.hearthnhome.com/installManuals/MONTPELIER_II_WOOD_INSERT_OWNERS_7101_803.pdf

I'll admit my vision isn't great, but no where in this manual does it mention operating temperatures or where to measure temperature.

 

[Tweedle]

I have the same stove. Like you said, there's no control. Load 'er up and let 'er rip. Do not crosstack as that is a sure way to overfire it. I've had mine very hot and nothing has happened yet. You'll learn as you go how to load it to keep it under control. It's not ideal and I will never buy a single burn rate insert again, but just like you I didn't know any better. I am trying to heat 3300sq ft with this insert, so I need all the heat I can get off of it.

3300 sq ft, wow. I have 2500, but I'm just trying to help out our heat pump when it's below freezing. Most of the heat goes straight from the den to upstairs, so it works out for the night.
Tonight I tried adding some large splits after getting the initial fire going and it seems to struggle to stay hot. I can't find that middle ground yet.

Thanks for your comment. It gives me some hope. 😅

 

[vbu]

3300 sq ft, wow. I have 2500, but I'm just trying to help out our heat pump when it's below freezing. Most of the heat goes straight from the den to upstairs, so it works out for the night.
Tonight I tried adding some large splits after getting the initial fire going and it seems to struggle to stay hot. I can't find that middle ground yet.

Thanks for your comment. It gives me some hope. 😅

Yeah it doesn't manage to heat it all when it gets around freezing, which is fine, I never expected it to. I wish I could extend the burn times a little longer though. I'm burning osage orange now, which gives some serious heat and leaves plenty coals for overnight fires and easy morning relights

 

[agonyzhou]

I do have a user manual. It's also available online: https://downloads.hearthnhome.com/installManuals/MONTPELIER_II_WOOD_INSERT_OWNERS_7101_803.pdf

I'll admit my vision isn't great, but no where in this manual does it mention operating temperatures or where to measure temperature.

Temperature is only half the story; the other half is the duration of the hot temp. 1000F for 5 minutes is fine; but 1000F for over an hour will most likely damage something. The peak temp usually come at about one hour mark after the reload; if it is not too hot at that time then it will not get too hot.