BTU Differences

[sig226!!]

Hello, I would first like to thank you all for the extremely useful information I have found on these forums so far. My wife and I have finally decided on a pellet stove to hopefully takeover for the furnace in heating our 1900 sqft single story home. We are debating between 3 stoves, the Accentra insert, P61A, and P68. My question is this, the P68 makes 7000 more BTU at max output than the P61A. While this is technically a difference, will I likely notice a difference when using the stove, or is it likely to help heat my home better than the less expensive P61? Secondly, if I were to go with the Accentra at 42000 BTU, will this 20000 BTU difference likely cause the stove to be noticeably less effective at heating my home. We care about about looks and the Accentra will look nicer, but lower heating costs are more important to us. Thank you in advance for your help.

Steve

 

[begreen]

Welcome Steve. The need for additional btus is going to depend more on the house than the stove. First and foremost,if you want to have better heating, tighten up the sealing of the house and beef up the insulation.

One way to figure what you need is to look at the past winter heating bills and calculate the average heating load in winter the current heating system. That should help guide you to the better fit for pellet burner size.

 

[sig226!!]

My house is reasonably insulated. I have propane now and I am averaging about $250 a month at $2 a gallon. So I guess about 125 gallons per month. I am unsure however how to transfer that into what type of stove I would need. I am unsure of the heating capacity of my furnace. I guess, do you think I will notice any difference between the 3 stoves or is the difference very minor?

 

[DexterDay]

The difference between the 61 and 68 is about a pound of pellets an hour. Which is minimal and if you need that many BTU's all the time, then burning pellets will not be much cheaper than burning oil.

To get 68,000 BTU, you need to burn 8.5 lbs an hour. Or about a bag every 4.5-5 hrs. So at an average price of $4-$5 a bag, your gonna be burning about 5 bags a day. That's $20-$25 a day x 30 days = $600-$750 a month.

Which is a little excessive. What type of furnace do you have now and what's it BTU rating?

The Accentra will likely be enough, if your insulation is about average.

I have a 47,000 BTU stove in my 2,180 sq ft Ranch and I only use the lowest setting. And at the max (coldest days) use 1.5-2 bags a day. But the average is about 1 bag a day.

Basically gonna heat the same up till 50,000. If you need the extra HP, the 61 and 68 will have it... but they have a hefty appetite, if left to eat what they want.

Welcome to the Forums.

 

[begreen]

Wow that is cheap propane. Delivered we are over twice that price.Have you checked what pellets are selling for locally? From the numbers I'm not sure you are going to see a lot of savings by going to pellet. If your ductwork is not fully insulated (supply and return), getting them sealed and insulated might have a better ROI.

A gallon of propane has about 91,500 btus. Let's guess that your furnace is 85% efficient. Are the ducts all insulated? If not, deduct another 15%. (this can be fixed for better efficiency) to arrive at delivered efficiency of 70%. In one month there are ~720 hrs. so you are burning thru approx .174 gallons/ hr of propane. Not bad at all. This equates to about 15885 btus/hr. Based on this you would be fine with the smaller Harman. You might need to supplement on very cold nights with the propane, but for the most part the pellet stove should be able to carry the load if the house has a relatively open floorplan. The difference will be that the pellet stove is an area heater and the central furnace system is a whole house system. How well the pellet stove will work out will depend on how well heat can convect throughout the house.

 

[sig226!!]

Thank you for the help. My cold air return is in the same room as where the stove will be located. So I should be able to circulate air reasonably well. My furnace is 80% efficient and my duct work is not insulated. From the sounds of it, if it turns out that I do need the max output of the 61 or 68 then it would be cheaper to run the propane furnace. Perhaps I will go with the accentra since it will look much nicer in my home anyway. Thanks again for all the help.

 

[DexterDay]

The Accentra would be my choice also. As for running the Furnace to spread the heat, it only works in like 2% of applications... You said your ducts are un-insulated? It will only cool the air trying to circulate it. It may equalize the temps a little.

 

[sig226!!]

Do you think if I insulated my duct work that my furnace would more effectively spread the heat?

 

[briansol]

single story and a large foot print means you need some air movement down the hall way. If the stove isn't aimed directly at pushing down the hall way, you might want to look into some fans, etc to help move the air down the hall.

my stove is

• Max. feed rate is 4.5 pounds/hour or 37,500 BTU/hour

and that's more than enough most the time to keep my house warm. some cold cold days (0s' and windy) it struggles to keep up. a quick bump of the furnace though, and it will hold it for a few hours.
and I NEVER run it on high because I don't have enough air. it just loads the burn pot with cake after a few hours so I only ever use med-high (4/5). (OAK hopefully coming this summer to remedy that!)

But my house is a split level, and the fireplace basically aims at the stair case up. the foyer at the top of those 6 stairs is the warmest place in the house. 3 step into the bedrooms form there, and its noticeably colder.

but that's fine by me. I like my sleeping temp a few degrees colder anyway.

you're not going to get that natural suck up to the foyer like I do though due to the length of the house.
but since you haven't said how your house is laid out, its pure speculation on my part

 

[sig226!!]

Yeah my house is a long rectangle with the stove being at one end. Even my furnace doesn't heat the other end of the house well. The duct work is poorly laid out and installed. Luckily the most lived in parts of the house are kept properly heated. So your speculation is pretty accurate. I'll definately be using fans though to help move air around.

 

[DexterDay]

Your best bet is to place the stove in the most central location possible

I wouldn't rely on the furnace helping. Your trying to move 70°-80° air. By the time its drawn through your HVAC, its gonna have a considerable amountof heat loss. It may help some. But your losing BTU to the system itself.

Central location and utilizing ceiling fans and/or through the wall fans will be a better route. IMO.

 

[kinsmanstoves]

Hello, I would first like to thank you all for the extremely useful information I have found on these forums so far. My wife and I have finally decided on a pellet stove to hopefully takeover for the furnace in heating our 1900 sqft single story home. We are debating between 3 stoves, the Accentra insert, P61A, and P68. My question is this, the P68 makes 7000 more BTU at max output than the P61A. While this is technically a difference, will I likely notice a difference when using the stove, or is it likely to help heat my home better than the less expensive P61? Secondly, if I were to go with the Accentra at 42000 BTU, will this 20000 BTU difference likely cause the stove to be noticeably less effective at heating my home. We care about about looks and the Accentra will look nicer, but lower heating costs are more important to us. Thank you in advance for your help.

Steve

If you burn a bag of pellets a day that is 40 pounds divided by 24 hrs = 1.6666 pounds per hour. 1.6666 times 8,000 btu (approx btu of a pound of pellets) = 13,332 btu per hour. Now this is input btu. You lose btu in the venting process. Do you need a 68,000 btu stove? All depends on the house but remember running the P-68 will burn over 8 pounds per hour.

Eric