# Square FootAge vs BTU Question



## AZ23 (Mar 17, 2014)

The XXV will heat 900 to 2300 sq feet.

P61 1300-3500 sq feet.

I know these numbers are rough and my house is around 2600-

So many factors - if your layout is open, where you are placing the stove, distributing the heat and moving it around the house.


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## DAKSY (Mar 17, 2014)

I'm in the Albany area of upstate New York, but I'm not sure where you are in relation to that.
A (rough) rule of thumb that we used in estimating the size of a unit for heating is the 30-40-50 rule.
Take the number of square feet you want to heat & if you have a duck's butt tight,
well insulated house, you will need about 30 BTU/Sf to heat it.
Moderately tight average insulation - 40BTU/Sf
Old windy farmhouse 50BTU/Sf (Minimum)
All of those numbers are OUTPUT. You will have to take the INPUT rating 
of your appliance & multiply THAT times the efficiency to get the OUTPUT.
So, 2600 x 30 =78K BTU OUTPUT  
2600 x 40 = 104K
2600 x 50 = 130K
So if your appliance is 75% efficient you'll need 104K BTU input to get 78K OUTPUT.
Bottom line? Gonna be tough to heat the entire place with one pellet burner.
You may have to close some rooms off or install more than one unit...


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## Lake Girl (Mar 17, 2014)

Most will recommend looking at the BTUs when deciding on what stove to purchase.  What is the average BTUs used by the furnace you have in place now.  I think there is a BTU calculator on-line http://www.calculator.net/btu-calculator.html

I'm sure others will chime in...


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## AZ23 (Mar 17, 2014)

Thanks. The reason I have been questioning is because I am down to either the p61 or xxv. I know it won't do all of the house but I want it to do as much as I can. So it's 50,000 BTU vs 61,000 - 2600 sq foot split entry home with stove in family room on lower level in corner exterior wall.


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## tjnamtiw (Mar 17, 2014)

Lake Girl is right about looking at your present source of heat.  BUT don't forget that a pellet stove is a 'space heater', not a whole house heater.  If you are expecting to have a nice, evenly heated house with a pellet stove, you will most likely be disappointed unless your daytime living spaces are central to the stove and only your bedrooms are more isolated.  That assumes you like sleeping in cooler temps. 
Look at a free standing unit rather than an insert (yes, I have 2 inserts) because fireplaces typically are at one end of the house and not centrally located.  In my case, I had no choice.  (read that as 'the boss wants them)..........


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## AZ23 (Mar 17, 2014)

My boss doesn't care haha. She says the p61 because it's larger output capability but I like the xxv as I hear it's quieter.


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## tjnamtiw (Mar 17, 2014)

The bigger the better.  You can always turn a big stove down but you can't, or shouldn't, turn a little stove up beyond its rating.  Some do and wonder why they shut down or even warp.


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## boo boo (Mar 17, 2014)

AZ23 said:


> My boss doesn't care haha. She says the p61 because it's larger output capability


 You now have no choice


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## Snowy Rivers (Mar 17, 2014)

Well,  have made this recommendation many times here at the forum,  Two Stoves

We have three on one floor of a 2400 ft ranch style house in NW Oregon

WE have one stove that's very small (Whitfield Prodigy 2)  One large Whitfield and a large Quadrafire
Running one stove hard enough to heat the entire house will result in parts of the house that's close to the stove getting too hot, and the distant rooms will be cold.

Using multiple units and not having to run them hard will give you a more even heat during the cold times, and during the milder weather one stove will suffice.

We use our little stove during moderate weather, the larger one when its colder and then two when its COLD, and possibly add the third (Quad) if needed, or allow it to come on by the stat and take up the slack.

I also believe that two are better, because when you rely on one stove, what do you do when the Snow is blowing sideways and your one stove goes KAPUTT ???? 

And it will not happen on a sunny day in May, ask me how I know this.

My honest suggestion is to think this over carefully and see if there is a way to install a second unit easily that will give you a good amount of synergism.

My spouse called huge amounts of smack when I set about doing three stoves, but the setup has worked marvelously over the past many years.

The family room has the one Large Whitfield, and the living room (farthest reaches of the house) has the Quad and the little Whitfield.

Yet during moderate weather, the little Whit can keep the entire house comfy.


One thing to consider is, i'ts a great idea not to have to run the stoves "Nuts to the bar" to keep the house warm.

Always go larger than you need for the total, then plan on running the stove in the lower to mid fire settings.
This keeps the thermal stresses on the unit far lower than if you have to run them hard.

The heat exchangers expand and contract a lot during duty cycles, and over time this takes a toll on them, especially if they are being subjected to a lot of heat.

We never run our stoves above the 1 or 2 setting (out of 5)


Just some thoughts.

Ms Snowy


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## TimfromMA (Mar 17, 2014)

The better your house is insulated, the more evenly your pellet stove will warm it. My stove is installed at one end of my house in the living room. The bedrooms are at the other end and there's only a 3 degree temperature differential between the living room and the farthest bedroom.


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## AZ23 (Mar 17, 2014)

How many btus do you have


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## Sniz (Mar 17, 2014)

go with a p68...no brainer over the 61 in your situation


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## TimfromMA (Mar 17, 2014)

AZ23 said:


> How many btus do you have


 My stove is rated up to 40,000 BTU's. Most nights, I run it on 3. The coldest nights I will sometimes set it to 4.


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## AZ23 (Mar 17, 2014)

I'm gonna go with p61


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## alternativeheat (Mar 17, 2014)

For the folks worried about over heating the stove,I suspect the computerization in the Harmons won't let them overheat. 

Did you ever try Stove Temp mode with the P43 ? Maybe stove temp 5 or even 6, feed rate 4 , blower on high. See what happens, because if that blows you out of the room you have it in the P61 will too and then some.


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## AZ23 (Mar 17, 2014)

So you are saying the lowest on p61 will be stove temp 5 on the 43?

What about the xxv


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## alternativeheat (Mar 17, 2014)

AZ23 said:


> So you are saying the lowest on p61 will be stove temp 5 on the 43?
> 
> What about the xxv


No I'm not saying that. What I'm saying is if the p43 cooks you out of the room and doesn't heat the house, then cooking the room more serves little advantage unless you can get the heat out of the room instead of you. Turning the p61 down, which, it will do, leaves you where you are at then, no ? The correlation is more like the P43 on full blast is about like the P61 on level 4.5- 5 actually. But just as a test have you tried stove temp up around 5 or 6 to see if the P43 can do a better job than it is in room temp. In your situation I think Room temp is getting squelched too soon before heat can get out in to the main house. Stove Temp offers a more steady output from the stove. I'm asking if you tried that ?

The XXV is a whole different thing as it mostly blows it's heat by convection, where the P43 and 61 radiate a lot of their heat. They still blow heat too but not the same % of the stoves capacity as the XXV.


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## AZ23 (Mar 17, 2014)

Hey, I do only use stove temp- I don't like room temp.

I use it at 4 or 5 and it does seem to move it upstairs. I am getting a fan installed in the main foyer to help move the heat.

You're right, I need to move the heat. Thanks for your input again.

I know the XXV is a diff ballgame but if I can move heat, I am wondering if the xxv will be better than the 43 or if the sure bet is 61


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## alternativeheat (Mar 17, 2014)

AZ23 said:


> Hey, I do only use stove temp- I don't like room temp.
> 
> I use it at 4 or 5 and it does seem to move it upstairs. I am getting a fan installed in the main foyer to help move the heat.
> 
> ...


OK, so if you up the P43 to 6 in stove what happens, what is the result besides using a few more pellets obviously ?


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## CaptSpiff (Mar 17, 2014)

AZ23 said:


> My boss doesn't care haha. She says the p61 because it's larger output capability but I like the xxv as I hear it's quieter.





AZ23 said:


> I'm gonna go with p61



You are a man of good judgement.


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## AZ23 (Mar 17, 2014)

Just cranked it to 5 and feed to 4.


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## alternativeheat (Mar 17, 2014)

AZ23 said:


> Just cranked it to 5 and feed to 4.


Ya, if you can stand it in the room the stove is in  then try more in a couple of hours. Also high fan. Then see how the house does in due time. It takes a bit of time. This is an experiment, so don't be afraid to turn the dial !

I can tell you this about the P61, on high fan it moves the heat out of the room it's in pretty well. However, mine is not in a corner install and I have room around the stove. On those really cold nights when the stove is cranking you don't want to sit right up close to it. We have chairs about 3 ft away and my inclination is to lean out slightly away from the stove rather than towards it..

Lately I've been running in stove temp myself because I think my probe for room temp is either messed up or catching some cool air. In stove temp I get even heat in terms of heating beyond the stove room. I'm happy with that but I do have to dial it up and down by the weather. When the weather warms I can switch back to room temp auto but meanwhile in stove temp it's using less pellets for sure and giving me really nice heat. At one point room temp was not flaring the flame up like is has been for a while now, so I just switched to stove temp and will deal with room temp on next years winter adventure when I've plugged some drafts up around here and found the probe a permanent home..


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## AZ23 (Mar 17, 2014)

That's good advice. I will see how it goes tonight. Do you think the xxv would move too


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## alternativeheat (Mar 17, 2014)

AZ23 said:


> That's good advice. I will see how it goes tonight. Do you think the xxv would move too


See how the P43 does bumped up before you get into all that.


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## AZ23 (Mar 17, 2014)

Room is very room and cozy. Love the strong heat. Upper level is not cold but not hot, don't have a thermostat around to compare


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## SwineFlue (Mar 17, 2014)

AZ23 said:


> I am wondering if the xxv will be better than the 43 or if the sure bet is 61



Looking at the manuals, the max feed rate of your P43 is 5.5 pounds/hour... the max of the XXV is 5.7      That's not a very big difference IMO.


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## AZ23 (Mar 18, 2014)

The room the stove was in ran on stove temp 5 feed rate 4 and high fan for a few hours. Upstairs living room and kitchen ended up being 74 when I went to bed.


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## Jocko1 (Mar 18, 2014)

Go bigger,  I just installed a p 61a in my house but if I could do it over I would have gone with a 68.  Price difference is minimal. I am heating 2500 square feet at around 70 degrees, give or take a few degrees in different areas, but when it gets in the teens I have to crank it all the way up.  I do have a 500 sq ft room that has ton of glass and skylights, I'm sure once I get proper window treatments that will help, but I do regret not going bigger.  I doubt a 61 a can handle 3500 sq feet in a cold environment.


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## alternativeheat (Mar 18, 2014)

AZ23 said:


> The room the stove was in ran on stove temp 5 feed rate 4 and high fan for a few hours. Upstairs living room and kitchen ended up being 74 when I went to bed.


 Well ok then . Do you still think you need a different stove?


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## AZ23 (Mar 18, 2014)

So I guess that experiment was good, so I am asking this q then - if you run the p61 at say 3 or 4 on stove temp to achieve what the p43 did last night at 5 -is that the only difference, or am I going to be burning more pellets  too

And lastly, do you think that switching up from p43 to xxv will only be cosmetic. If I am trying to have the option to get things really hot - then 61 is the choice?


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## alternativeheat (Mar 18, 2014)

AZ23 said:


> So I guess that experiment was good, so I am asking this q then - if you run the p61 at say 3 or 4 on stove temp to achieve what the p43 did last night at 5 -is that the only difference, or am I going to be burning more pellets  too
> 
> And lastly, do you think that switching up from p43 to xxv will only be cosmetic. If I am trying to have the option to get things really hot - then 61 is the choice?


 Was it not cold out last night up there? Does it get way colder than it was ?


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## AZ23 (Mar 18, 2014)

ya it can get much colder. It was about -10 with wind chill around -17 last night and today the same.


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## alternativeheat (Mar 18, 2014)

AZ23 said:


> ya it can get much colder. It was about -10 with wind chill around -17 last night and today the same.


 The P 61 will offer some head room for reserve when it gets colder. The xxv will heat differently and offer less reserve. The P61 is a moderate plus upgrade in heating power. The Xxv a modest step up. Not sure how the xxv convection heat would compare. Bottom line, the P61 is rated for your sq ft nicely. IMO you want a stove rated a bit over your houses sq ft, not less. Will it use more pellets? Most likely yes. Any time you make more heat you burn more fuel given closely equal efficiency. The P 61 I believe is 78% efficient. Not sure how the xxv is rated.


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