Wood Stove Sizing

[Upnort]

Hello, I have heard different things from dealers and am here to see if there are more consistent answers. From looking at some past posts here, it seems that the size of stove box determines the amount of fuel which determines the burn time (along with species burned). And that cat stoves offer longer burn times because they can continue to burn on low (I know it's more involved than that, but but that's not my focus at the moment). Is the idea of a larger stove box still that the larger box means longer burn times for a non-cat stove?

I've posted before about sizing an f45 or f55 for a 1375-1400 sq ft home in Maine (just a bit inland from midcoast; just slightly over the "green zone" but in the colder "blue zone" of the 2023 Jøtul map). The dealer suggests the f55 is the right choice for a whole house heater where longer burn times are wanted. But another has said that that f55 might be too much. We would like a warm house in winter. If you can dial these stoves down to lower heat output, then wouldn't the bigger stove be a better bet? We've been deciding between the Jøtuls for their ease as far as non-cat stoves. If we were to go cat, we heard great things about blaze king models. We just want the best stove for our situation as you can't return the stove once it's bought.

The house is a 2-story 1990s cape--stairway in between the side of house on first floor, bedrooms above. Standard insulation, lots of windows in the living room where stove would be. We'd want a whole house heater tho we will have backup heat pumps for when temps are favorable. But power goes out a lot here. Chimney is interior masonry with an insulated steel liner that goes down to the clean out in the basement. Stove would be on first floor. Chimney is about 20 feet tall above stove surface if the stove is around 27-30 inches height. Stove pipe currently goes just over two feet then one 90° into the masonry chimney (but if we get a different stove, we would get a different pipe as needed). So just wondering about stove size right now and if the logic is true behind getting the larger stove [box] just means having the potential for a longer burn time. Right now, looking at deciding between the Jøtuls F45 or F55, but have been thinking more about a cat stove and then would only want to look at something that would work in the Blaze King line. Thanks!

 

[stoveliker]

Yes, larger box means longer burn time when comparing same heat output rates. Even for a high output of 50,000 BTU per hr (i.e. not dialed down) a larger box means you can sustain that output for longer.

But one has to look at the range of outputs a stove can achieve.
Burn times alone don't tell you much useful; one stove doing 20 hrs at 10,000 BTU/hr has nothing to do with another stove that does 10 hrs at 30,000 BTU per hr.

You're making good choices regarding the chimney (lined, insulated).

I'll let others comment on whether the f55 is good or not for you, but note that for stoves to be whole house heaters the layout of the house has to be conducive to that. Heat has to be able to flow well. The stove room will always be hotter than farther rooms.

 

[EbS-P]

From the EPA test reports low burn rate is 2 to 3000 BTU is different but the high burn rate of the F5 five is over 25,000 BTUs higher. You’ll need a damper and understand where the boost holes are.

 

[Todd]

A .39cu ft difference in usable fire box between the two is really not that much. I think either stove will work out for you and there probably won’t be a difference in burn times between the two. I pretty much have been burning my F45 all Winter with a 12 hour burn time schedule. The few times we had colder weather I went to an 8 hour schedule.

 

[Upnort]

A .39cu ft difference in usable fire box between the two is really not that much. I think either stove will work out for you and there probably won’t be a difference in burn times between the two. I pretty much have been burning my F45 all Winter with a 12 hour burn time schedule. The few times we had colder weather I went to an 8 hour schedule.

We're gravitating toward the F45 but are concerned it won't be enough to heat our house on colder days (especially if used as sole heat source). Also like the idea of the BKs. We thought the dealers would be some help, but some of their logic is all over the place and each one leans toward one stove or the other.

 

[Upnort]

We're gravitating toward the F45 but are concerned it won't be enough to heat our house on colder days (especially if used as sole heat source). Also like the idea of the BKs. We thought the dealers would be some help, but some of their logic is all over the place and each one leans toward one stove or the other.

Also: we haven't received much feedback on the BKs yet since our first focus was on the ease of the non-cat Jøtuls.

 

[Todd]

Blaze Kings are nice stoves and burn longer than any other stove but when it gets cold you need to turn it up like any other stove. If you plan on being away from home more than 12 hours at a time a BK would be a great option.

Rumor has it that the Jotul F35,45 and 55 are going to a new catalyst system along with a secondary air control. I’m not sure when but may be worth waiting for.

 

[BKVP]

It should be noted...as before, test methods influence numbers.

The Polytest snips here show a stove tested using ASTM3053. That is called the "cordwood method". In the cordwood method, the test runs (all of them) are over when 90% of the input fuel load has been consumed.

Btu's are calculated by (simplifying here) input ÷ burn time x HHV % efficiency.

Approximately 66% of cordwood stoves were tested in advance of the 2020 EPA deadline. In June of 2023, EPA announced the termination of ASTM 3053.

Now, let's move to other stoves tested to M28R. This method uses dimensional lumber and is called the Crib Fuel method.

Same simplified method above is used to get BTU'S.

HOWEVER, each test run is over when 100% of the fuel load is consumed. If two stoves are each tested to one of these two methods AND have the same fuel input in BTU's, the 90% vs 100% can and does influence published BTU'S.

If a particular stove design enables the stove to burn, say another 8 hours longer to consume the last 10%, the math above demonstrates how published BTU'S would be lower (influenced).

EPA has terminated the use of ASTM3053 and until a new FRM (federal reference method) is introduced, all manufacturers are going back to M28R. The tiny exception being units tested using an ATM (alternative test method) of which there are 2 or 3 at this time.

This is why we can all acknowledge that published numbers are neither real world nor extremely credible.

What is the best indicator to consider? Customer satisfaction! Many, many folks here are super happy with their stove choices. We hope many made their decisions after reading comments by consumers that own those models and help the wood stove community!

BKVP

 

[Upnort]

Customer satisfaction most definitely! That's why I'm here and gobbling up all the great info (& knowledge). Although I'm not certain I understand all the maths above (or anywhere; I teach writing :|).

I'm not sure I understand--and please pardon me here; I'm still learning "wood stove science"--why certain stoves made of the same material and firebox size might have different BTU outputs/ranges?

It might be the fF5 will be enough (?), but if a newer version might be coming out, that's intriguing. What time of year are new stove models released? If anything it might mean sales on current models, right?

I'm also liking what I hear about the BKs. Would those suit a cape house in Maine? And I can't find this on the BK site, but are they steel stoves with cast iron shroud? Which versions are NS loading? Any recommendations for a house with our setup?

Thank you everyone! We want to get the right fit and yeah, we're taking a bit of time to decide this, but now that we are closer to warmer temps, we have the luxury of being slow with our decision. What has been problematic is the inconsistency of the dealers we've spoken to. All good folks, but all seem to have different experience levels with different stoves and many use to dealing with older 'smoke dragons" and durable, but still decades older, stoves that almost everyone I know here in my section of Maine has. So sometimes the feedback they have is interesting but not necessarily that helpful for someone searching for a brand new stove. Thanks again!

 

[stoveliker]

The output ratings are the result of the engineering of the air/gas flow through the stove, which has to be done within the limits of EPA mandates, and the engineering of the heat transfer to the room (rather than up and out of the chimney).

Depending on how one does that, one can get the wood to burn faster and get more heat per hour, or slower and less heat per hour (and longer burn times). That defines the range of outputs.

BKs free standing stoves are all NS loading (though one can load any stove however one wants - but these are "deep" enough to have decnet split sizes NS).

All BK stoves are steel stoves (welded, no seams to maintain every decade). The Ashford has cast iron panels around that.

 

[BKVP]

Burn rates are determined by air to fuel ratio. If you allow more air into the stove, typically you have a higher burn rate. In wood stove parlance, it is Kilograms per hour (kg/h). A kilogram is 2.2 lbs. If a heater burn 2.5 kg/h, which would be very hot, the stove is consuming 5.5lbs per hour. Also keep in mind as others here have pointed out previously, marketing numbers are confusing.

Keep in mind that Btu's are from testing in a laboratory where all chimneys are the exact same length (actually they are dilution tunnels) and we can control the draft with fan systems. So turn up the fan, pull more air into the firebox and you can increase the burn rate and correspondingly the Btu's.

"Up to 65,000 Btu's" was common in stove marketing because when the firebox of fuel is fully engulfed, the thermocouples and scales would indicate, "that stove just hit 65,000", but it only did so for about 2 minutes. Without loading more fuel, it can't sustain that "up to" value.

And in catalytic enabled stoves, you must be very careful not to have designs that allow the catalytic combustor to exceed threshold temperatures. Protecting the combustor can and does also influence peak Btu output.

BKVP

 

[Newbie78]

I didn't see where anyone brought up building heat loss as a large factor in heater selection.

Just a thought...

Or maybe the OP described that adequately in the first post, idk 🤷‍♂️

Quality of fuel is paramount, I've learned.

 

[BKVP]

I didn't see where anyone brought up building heat loss as a large factor in heater selection.

Just a thought...

Or maybe the OP described that adequately in the first post, idk 🤷‍♂️

Explained or not, it is a factor that should always to taken into consideration! Good reminder!

BKVP

 

[Upnort]

Yes, thank you! The house has standard insulation. It's 1990s so not super tight but not classic Maine farmhouse pre-renovation either. New attic crawlspace & kneewall insulation will be added this summer. Lots of old fiberglass batts there now. Windows aren't great but won't be changed for a few years--they aren't failing. They're Anderson double-hung but could use replacement soon but realistically that's going to have to wait. Glass patio doors in living room. I know there are so many factors. And so many stoves!

The house came with an oldish (not sure how old but pre-2012 most def) Harman Oakwood woodstove nightmare. So that's what I learned on (grew up with fireplace). The Harmon is still here. I despise it. It's beautiful but finicky and not anything I want to deal with anymore so please no "hey keep the Harmon!" Because the Harmon is dead to me. We hardly used it after two seasons of headaches. Anyway, I really am looking for insight on best stove considering our setup. And was originally looking for ease of non-cat. The f45 or f55 Jøtuls. Or heard great things about PE/Alderleas but the Jøtuls seemed less maintenance-y? If we go cat--which considering the learning curve of the demonic Harmon-Nightmare, wouldn't be a big deal--we'd go with a BK model.

We will have heat pumps installed and those could work as sole heat except on really cold days and power outages which happen A LOT here. Like 3 in the past month, 1 with every storm. Sometimes lasting days tho this winter has been better and house doesn't immediately get cold. But having backup heat source that could heat us for awhile is ideal and possibly using it as sole heat source in middle of winter even when power is on sounds good too. (We have an old oil boiler at the moment--direct-vented [gross]--which will be removed when heat pumps are installed. We do not want to keep the oil boiler. The oil boiler is dead to me, so we are moving on: wood stove and heat pumps.)

Most likely? Stove will be used to offset what heat pumps might not handle fully tho these are going to be new heat efficient pumps meant for heating (yes also cooling) the home. But that could change. Nothing has been installed yet except a new insulated steel chimney liner in a clay-tile cinder block chimney. Liner is all the way to basement cleanout. Nightmare stove is still in place on first floor, brooding.

But! We don't have the heat pumps installed yet and we want to cover our bases. We also work and do not want to be reloading a fire more than at 8 hour intervals most days (& unless it's a -25+ day/night, but those aren't that common, tho they do happen, and then we'd just deal with it and load more often as needed). Ideally we'd like to keep the stove door closed more often than not.

So stove recommendations gladly welcome. New stoves and preferably of the options already listed (there are so many stoves so trying to narrow this down where I can: the Jøtuls and maybe PEs for non-cat; BKs for cat). People's feedback with experience or insight on such models would be awesome. Thanks!

 

[begreen]

The f45 or f55 Jøtuls. Or heard great things about PE/Alderleas but the Jøtuls seemed less maintenance-y? If we go cat--which considering the learning curve of the demonic Harmon-Nightmare, wouldn't be a big deal--we'd go with a BK model.

You're on the right track. Running any of them will seem like a dream next to the Oakwood and with lower maintenance too. We're on year 15 with the Alderlea T6. So far total maintenance costs have been under $200 and that includes buying a Sooteater for flue cleaning.

 

[Upnort]

I'm getting a bit more confused by the stove shop we have recently been in communication with regarding woodstove choices, how are chimney liner is installed, and information on particular stove models. All things you don't want to be in doubt about when you're talking with the stove shop. I feel like I'm getting different information and so I'm going to ask you all here because there seems to be a lot of knowledge on this forum.

We recently had installed an ultra pro steel chimney liner. We had it installed in December. We have not used our woodstove since that liner was installed because our woodstove is a Harmon Oakwood and we just wanted to get rid of it (please no focus on that wood stove; we no longer want it). We were planning on getting a new wood stove installed soon after but because of various delays, we just haven't had that done. Most of the delays now are because we're not sure which stove would be the best fit for us. Either way, it's been a very mild winter and we didn't really need to use a stove and we did not want to wrestle with the Harmon Oakwood. The chimney liner that we had installed was installed in our cinderblock, clay-tiled, center located chimney. Our chimney still has the clay tiles in it, but it now also has an insulated steel liner. The brand is ultra pro super.

The stove shop that we've been asking about the F45, F55, and blaze king models suggested that our liner needs a cap at the very bottom of it. I'm attaching a picture of what it looks like but keep in mind that the metal cover to our cinderblock chimney is just removed and set aside off picture. We do have one of those it's just not in the photo. What I think the stove shop was referring to was the fact that the liner itself goes all the way down to the cleanout. My understanding (and what our installer originally said) is that's because we would still use the clean out as the clean out, rather than going through the stove to clean the chimney. Our installer has since retired so I can't reach out to him. Anyway, I'm not certain, but when I look at manuals, especially on blaze King models, it looks like this is the recommended installation. Please let me know. Does a cap need to be placed on the actual steel liner itself? I mean at least when the stove is in use? But then it would be removed when you do the cleaning? I'm also going to put attach parts of the email I received in regards to stove size. (I also want to add that we currently have 26-27 inches of vertical stove pipe from our current stove before it turns into the chimney. So that might not be enough for a blaze king, tho we weren't set on a princess but one of the other models.) Thanks in advance!

 

[begreen]

As already discussed, the dealer is wrong. Some BK stoves are medium, 2 cu ft sized. But that is less relevant with a BK stove because they are thermostatically regulated. There are several folks here in the south that are burning in BKs.

The Oakwood cat experience could have been due to a few reasons. One is the downdraft design which tends to want the stove run hot so that the 'afterburner' kicks in. If draft is weak, say during mild weather, then these stoves can be balky. What you can do is equate the new stove size based on the Oakwood heating. How well did that stove do during different weather, like at 45º, 20º, and 0º?

Something is odd about the liner picture shown. Is this the view from the room? Where is the T snout through the thimble?

Past posting on this topic.

F45 or F55 for heating 1350-1450 +/- sq. ft house

Hello. We've searched the threads but are still wondering if a Jotul Greenville will be adequate for whole home heating our house or if the next size up would be best (F55). It's a 2-story cape, approx. 1350-1450 square feet. 1990's but still pretty drafty Maine house. Will an F55 be too much...

www.hearth.com

 

[Todd]

Yes, place a cap on the bottom of that liner or your draft may suffer. Take it off when you sweep the chimney.

 

[Upnort]

It's so frustrating when one of the only two dealers in the state that work with blaze kings seems to not really know what they are talking about.

The picture is of the clean-out in our basement (with the cast iron cover removed from the chimney; our thimble is on the first floor of the house where the stove is/will go). It's the end of the liner. We have never used the Harmon on this new liner (and we won't, as we are no longer using that stove). We had the liner installed because we didn't want just our clay liner. And we got the new liner installed in anticipation of a new stove. So I really want us to pretend that the Harmon Oakwood isn't there because it's really not a factor. We hardly used it and any issues that we had with it were all the documented ones that seem to be due to the design of that particular stove.. What we want is to be able to have a new stove installed correctly with the liner that we had installed this December. And we don't want any stove shop installer near our new chimney and liner if they're going to manipulate it in a way that should not be manipulated.

 

[Upnort]

Yes, place a cap on the bottom of that liner or your draft may suffer. Take it off when you sweep the chimney.

A cap would go on the metal liner itself?

 

[begreen]

Yes, place a cap on the bottom of that liner or your draft may suffer. Take it off when you sweep the chimney.

^^ This^^. The end of the liner needs to be cap to avoid draft dilution. Or it could have another tee there that is capped on the bottom and snout ends.

So I really want us to pretend that the Harmon Oakwood isn't there because it's really not a factor.

The question is, how wel did the Oakwood heat during various times of the winter?

 

[Upnort]

As already discussed, the dealer is wrong. Some BK stoves are medium, 2 cu ft sized. But that is less relevant with a BK stove because they are thermostatically regulated. There are several folks here in the south that are burning in BKs.

The Oakwood cat experience could have been due to a few reasons. One is the downdraft design which tends to want the stove run hot so that the 'afterburner' kicks in. If draft is weak, say during mild weather, then these stoves can be balky. What you can do is equate the new stove size based on the Oakwood heating. How well did that stove do during different weather, like at 45º, 20º, and 0º?

Something is odd about the liner picture shown. Is this the view from the room? Where is the T snout through the thimble?

Past posting on this topic.

F45 or F55 for heating 1350-1450 +/- sq. ft house

Hello. We've searched the threads but are still wondering if a Jotul Greenville will be adequate for whole home heating our house or if the next size up would be best (F55). It's a 2-story cape, approx. 1350-1450 square feet. 1990's but still pretty drafty Maine house. Will an F55 be too much...

www.hearth.com

Apologies--you were referring to the Oakwood in terms of sizing our new stove, and that makes good sense. Unfortunately, we can't really do that because we didn't really use the Oakwood that much. We just gave up on it. I don't know if it's correctly sized for this house. We did not install the Oakwood; it was installed decades before we bought the house. I think this is why I'm saying assume that we don't even have the history of a woodstove, since we didn't use the Harmon for a full season. So we're kind of taking this on as if we have a hearth set up but no stove in place yet and what would be the best stove for us. That's hard to determine so I guess I'm just wondering if it makes sense to have the F55 if it's true the difference would be in the burn time because it had a larger box stove. But it seems like with the non-catalytic stoves, that's not really how it works. That's more with the catalytic stoves. What the stove shop told me was the F 55 would be better if we wanted to have a longer burn time.

 

[begreen]

It's so frustrating when one of the only two dealers in the state that work with blaze kings seems to not really know what they are talking about.

I don't know how it can be any clearer when owners of BK stoves are correcting this misassumption. I suggest that the dealers contact the VP of the company for clarification. He is member BKVP here on the forums.

 

[Upnort]

^^ This^^. The end of the liner needs to be cap to avoid draft dilution. Or it could have another tee there that is capped on the bottom and snout ends.


The question is, how wel did the Oakwood heat during various times of the winter?

^^ This^^. The end of the liner needs to be cap to avoid draft dilution. Or it could have another tee there that is capped on the bottom and snout ends.


The question is, how wel did the Oakwood heat during various times of the winter?

I'm not sure what you mean by another T and snout ends?

Unfortunately, we can't use the Harmon as a measurement for how it heated the house during shoulder and through the heating season because we did not use the Harmon that much--it's just what was in place and we used it enough to know it wasn't a very good stove and that we wanted something different.

In regards to the Jøtuls, is the stove box theory (larger = longer burn times because more fuel can be added at one) correct?

 

[Upnort]

I just want to be clear that our cleanout itself does have a cap and that's that cast-iron cover. It's just not in the picture. So I want to make sure that when you say put a cap on the liner you mean on the actual metal liner and are not referring to a cast-iron cap that goes on (it is sort of a plate that just rests on two notches) the chimney cleanout entrance; it's just not in that picture because it was removed for the sake of the picture. Once again I apologize if I'm not getting something correct. I'm new at this and I really appreciate all the wise words you all have been sharing with me.