First year with Insert. Can Efficiency be improved?

[PlayWithFire]

This is the end of my first heating season with my Hampton HI300 insert. And I burned almost a full 7 cords, plus 204 gal of oil. I only have 2x4 construction, but R50 in the attic. The HI300 is in an external chimney and I have several mini fans that move the heat around the house. Now I know it was a long cold winter, but 7 cords seems like a lot for a 2100 sq/ft house. I already had an energy audit last year where they made sure the house was as tight as possible. I'm planing to add a block off plate inside the fireplace and insulate as best I can. Any other ideas on how I can improve my efficiency?

 

[begreen]

Just adding an insulated block-off plate and insulation behind the insert should make a noticeable improvement. Use Roxul mineral insulation.

 

[Beer Belly]

It was a cold winter, and it pretty much hit everybody's supply hard. As begreen stated, the Block off and insulation will make a difference, and there is also a learning curve with a woodstove....be patient, it gets a lot better.

 

[BrotherBart]

Seven cord through a firebox that size? You must have been stoking it like a locomotive.

 

[Grisu]

A block-off plate will certainly help and putting insulation behind the insert to reduce heat-loss from the back of the fireplace. However, what kind of wood are you burning? 7 cords of pine would only give you as much heat as ~4 cords of oak, which would be pretty normal in your situation. How long has the wood been split and stacked in a sunny and windy location? Did you measure its internal moisture content? What is the final setting of your air control once the insert is up to temp? Can you measure the temp of your insert? Do you have a 6" insulated liner in the chimney? How tall is it?

Finally, how much oil did you burn the winter before? That will tell us about the heating load for your house.

 

[begreen]

The winter before was exceptionally mild and may give a false sense of consumption. An average of the previous 3-4 winters would be better.

 

[prezes13]

I burnt about 3 cords of not the best wood most of it semi seasoned maple plus 120 gal of oil. I was heating 1200 s/f of 2 by 6 well insulated house. On the avarege I used to burn 300/350 gal of oil but the temp in the house was never higher than 72 with the stove I was avareging about 76. So IMHO 2100 s/f with an insert and 2/4 construction may not be that bad. I don't have a block off plate and I have 15 feet of not insulated ss liner in an outside chimney.

 

[begreen]

Put in a block off plate over the summer and I think you will notice the difference.

 

[PlayWithFire]

Seven cord through a firebox that size? You must have been stoking it like a locomotive.

When the temp got in the low 20s or lower, the insert had a hard time keeping up. So on those really cold days I was loading it every 2-3 hours.

However, what kind of wood are you burning? 7 cords of pine would only give you as much heat as ~4 cords of oak, which would be pretty normal in your situation. How long has the wood been split and stacked in a sunny and windy location? Did you measure its internal moisture content? What is the final setting of your air control once the insert is up to temp? Can you measure the temp of your insert? Do you have a 6" insulated liner in the chimney? How tall is it?

Finally, how much oil did you burn the winter before? That will tell us about the heating load for your house.

I burn 80% oak, 20% maple. It was "half seasoned" when delivered in late June. Stacked on North side of house in the shade, but plenty of wind. I don't have a moisture meter. Air control would be open about 15% when about 30Degs outside, 30% when 20Degs out, and 50% when in the single and neg digits. I have a temp gauge on the glass and it gets up to 700-800 degs when the pipe would say around 400 with IR, but hard to measure the pipe. Yes, 6" smooth wall flexible stainless, insulated, 25' liner. The year before I burnt 655 Gals of oil during the same time frame as I burnt 245 gal this year. Last year was my first year in the house.

 

[PlayWithFire]

Is wood worth it?
2012-2013 heating season 655 gal oil = $2300
2013-2014 heating season 245 gal oil = $865 + 7 cords at $160 each = $1985.

So I only saved $315 this year over last year using wood, plus a lot of time spent stacking and stoking. This winter was much colder then last, but looking at the numbers is still pretty depressing. I was expecting a much larger savings.

 

[Xikar]

For me the huge savings was not buying the wood.

 

[prezes13]

Might be a combination of under sized stove and not seasoned wood. Oak needs a lot of time to season. You might be able to season maple in one year but not oak.

 

[KB007]

When the temp got in the low 20s or lower, the insert had a hard time keeping up. So on those really cold days I was loading it every 2-3 hours.



I burn 80% oak, 20% maple. It was "half seasoned" when delivered in late June. Stacked on North side of house in the shade, but plenty of wind. I don't have a moisture meter. Air control would be open about 15% when about 30Degs outside, 30% when 20Degs out, and 50% when in the single and neg digits. I have a temp gauge on the glass and it gets up to 700-800 degs when the pipe would say around 400 with IR, but hard to measure the pipe. Yes, 6" smooth wall flexible stainless, insulated, 25' liner. The year before I burnt 655 Gals of oil during the same time frame as I burnt 245 gal this year. Last year was my first year in the house.

Can you describe your load/burn process? I may be mis-reading, but I'd like to have you describe from loading logs, just what you do with the air control.

 

[velvetfoot]

I know last winter was a lot colder, but doesn't look too good compared to previous year's oil consumption, unless the thermostat was set at 55 by the previous owner or you didn't have all the bills. I'm actually thinking that maybe those gallons are too small for your house and location, but that's just a gut feeling by an inexperienced person (me).

Using the numbers here: www.eia.gov/neic/experts/heatcalc.xls and inflating last year's oil consumption to 800 gallons, there's a wide disparity.


800 gals at 78% eff = 142,246,153 BTU
7 cords at 63% eff = 244,444,444 BTU

 

[Grisu]

When the temp got in the low 20s or lower, the insert had a hard time keeping up. So on those really cold days I was loading it every 2-3 hours.

I could not load my insert that quickly again because the firebox would still be half full with the previous load. The stove should also still be plenty hot; not need a reload.

I burn 80% oak, 20% maple. It was "half seasoned" when delivered in late June. Stacked on North side of house in the shade, but plenty of wind. I don't have a moisture meter. Air control would be open about 15% when about 30Degs outside, 30% when 20Degs out, and 50% when in the single and neg digits. I have a temp gauge on the glass and it gets up to 700-800 degs when the pipe would say around 400 with IR, but hard to measure the pipe. Yes, 6" smooth wall flexible stainless, insulated, 25' liner. The year before I burnt 655 Gals of oil during the same time frame as I burnt 245 gal this year. Last year was my first year in the house.

Oak needs a minimum of 2 years to season; I doubt yours was even half seasoned. Leaving the air control that wide open means you sent a lot of heat up the flue. The glass is not a good indicator of the stovetemp. I know it is hard with an insert but try to measure the stovetop. What you can try is to pull off the surround and remove the top of the air jacket to access the stovetop. Place a thermometer there (or use your IR). Burn it and try to get the temp there over 500 F (600 F to 700 F would be best). Search for the hottest spot on the front. Note the difference between those two spots at different times of the burn. After doing that for a few days you should have a good idea how a reading of e. g. 500 F on the front translates to how many F on the top. Put everything back as before and then use the spot in the front to measure the stove temp.

 

[begreen]

Is wood worth it?
2012-2013 heating season 655 gal oil = $2300
2013-2014 heating season 245 gal oil = $865 + 7 cords at $160 each = $1985.

So I only saved $315 this year over last year using wood, plus a lot of time spent stacking and stoking. This winter was much colder then last, but looking at the numbers is still pretty depressing. I was expecting a much larger savings.

That's comparing an exceptionally mild winter to an exceptionally cold one. You need to add 25-30% to your 2012-2013 season heating bill to be roughly equivalent to past winter's heating load or $2875-$2990. With a block-off plate and insulation I would expect your wood consumption in an average year to drop closer to 4-5 cords.

 

[Grisu]

I know last winter was a lot colder, but doesn't look too good compared to previous year's oil consumption, unless the thermostat was set at 55 by the previous owner or you didn't have all the bills. I'm actually thinking that maybe those gallons are too small for your house and location, but that's just a gut feeling by an inexperienced person (me).

Using the numbers here: www.eia.gov/neic/experts/heatcalc.xls and inflating last year's oil consumption to 800 gallons, there's a wide disparity.


800 gals at 78% eff = 142,246,153 BTU
7 cords at 63% eff = 244,444,444 BTU

Velvetfoot, I think your numbers are off. Oak has an average of 27 million BTU/cord. At 66% efficiency, that's 18 mBTU/cord. 18*7 = 126 mBTU.

2012-2013 heating season 655 gal oil = $2300
2013-2014 heating season 245 gal oil = $865 + 7 cords at $160 each = $1985.

Last winter you would have saved 400 gl of oil. Since this winter was colder let's assume you would have gone through 600 gl of oil in addition to the 245 gl you burned. 100 gl of oil = 14 mBTU. => 84 mBTU. Let's assume you furnace is 80% efficient, it adds up to roughly 67 mBTU. With other words you used almost twice as much wood as you should have (~4 cords).

My guess is that your wood is not dry. To get the insert up to temp due to the excess moisture you left the air open, thereby sending a lot of heat up the flue. I would check the chimney because that may be pretty dirty by now. Moreover, get the wood for the next two winters now. Ask for softwoods and ash as those have a chance to dry over one good summer. Other species leave for the winter 2015/16. You can also think about supplementing your wood with some compressed wood logs (like Ecobricks or Biobricks) or untreated lumber scraps.

For savings, look at the link that Velvetfoot posted: oil costs about $36 per mBTU of heat, wood at $200 per cord ~$14. Thus, wood will cost you less than half.

 

[Dix]

This winter was brutal.

I usually go through 5 - 6 cords, went through 8 this year, damn it.

BB, 7 is not out of line for up here this past winter,

To the OP ... I woild think that you will be working on your firewood supply for next season, and beyond. That will make a HUGE difference in your heating abilities .

 

[BrotherBart]

Yeah but you were feeding two stoves about the size of his his Dix. Physics comes into play here. To run that much wood through that stove the firebox would be stuffed with coals all the time and they would need to be scooped out to make room for more wood.

 

[Dix]

Yeah but you were feeding two stoves about the size of his his Dix. Physics comes into play here. To run that much wood through that stove the firebox would be stuffed with coals all the time and they would need to be scooped out to make room for more wood.

I have no Hampton experience, so I can't say.

I'll trust your judgement on this one..

204 gallons of oil ain't bad in this climate this past winter.

 

[BrotherBart]

2.4 cubic foot firebox Dix.

 

[velvetfoot]

Click to expand...

Velvetfoot, I think your numbers are off. Oak has an average of 27 million BTU/cord. At 66% efficiency, that's 18 mBTU/cord. 18*7 = 126 mBTU.

You are correct. To figure out how much energy the house used , you would multiply not divide by the efficiency. So, for the oil boiler, it would be 800 gal X 138,690 x .78 = 110,52,000. For wood,
I get 124,740,000. So, I'm totally wrong. Sounds comparable.

I've put 5 cords through a Quad 2700i. Not so much this year in the Hampton, 'cause I'm drawing down the oil tank so I can move it.

 

[PlayWithFire]

Might be a combination of under sized stove and not seasoned wood. Oak needs a lot of time to season. You might be able to season maple in one year but not oak.

I have wondered about it being undersised as it's rated for 2000 sqft and I have 2100 sqft. Yet at least 900 sqft are on the second floor and very little wood heat made it up there.

I'm sure at least half of the wood was not adequately seasoned. Hissing for first 10 mins in the fire.

Can you describe your load/burn process?

Starting with a small bed of orange coals I would rake the coals forward to make a pile right in front of the door. Then pack the stove as full as possible making sure to put the smallest piece on top of the coals. Close the door with the air control half open for 10-15 mins until I see a secondary burn coming from the tubes at the top. Then start to close it down maintaining a secondary burn. Usually I would leave the air control 15%- 25% open. Once it burned down to only coals (no flame), If in the low 20 I would sometimes open the air control 50% - 100% to get more heat and let the coals burn down until there was just a small bed. Repeat.

or you didn't have all the bills.

I moved into the house Dec 2012 and have all the bills since then. So the gallons of oil that I mentioned were used during Jan-Apr for both 2013 winter and 2014 winter. Yet for the 7 cords I started buring 24/7 on 10/27/2013 and stopped, just 2-3 weeks back.

Your right 2014 was much colder so it's hard to get a fair comparison. I did try to keep the temp the same in 2014 as 2013.

I could not load my insert that quickly again because the firebox would still be half full with the previous load. The stove should also still be plenty hot; not need a reload.

On a full load it would be down to coals with no flames by hour 2 and the heat output would drop significantly. So I would open up the air control to get more heat and use up the coals to make more room for another load.

With a block-off plate and insulation I would expect your wood consumption in an average year to drop closer to 4-5 cords.

That sounds Much better!

Last winter you would have saved 400 gl of oil. Since this winter was colder let's assume you would have gone through 600 gl of oil. 100 gl of oil = 14 mBTU. => 84 mBTU. Let's assume you furnace is 80% efficient, it adds up to roughly 67 mBTU. With other words you used almost twice as much wood as you should have (~4 cords).... My guess is that your wood is not dry.

Thanks for all the calculations guys. I'm always impressed by the knowledge on this forum. I'm sure damp wood is a problem. I'll try to take your advice about staying one winter ahead for seasoning. One of my 7 cords this year was a pallet of Biobricks. They were nice, yet, pricey and more like ¾ of a cord then the full cord equivalent that they calm.

What do you guys think about Holzhaufen to dry wood faster?

 

[Hills Hoard]

im no expert and am still learning but i know I use far less wood now that i am burning really dry quality wood. i dont have to over load the insert with with heaps of wood with the vents wide open to get as much heat...

 

[firefighterjake]

. . .

What do you guys think about Holzhaufen to dry wood faster?
. . .

General consensus is that they're neat to look at, when built properly can be quite stable and depending on how high you stack you may be able to get more wood in a smaller foot print, but in terms of drying out wood faster they're on par or not quite as good as traditional straight stacks. A few folks believe that it takes a lot longer to build (which is true for the first one or two), but when you get the hang of it they take about the same amount of time, maybe slightly longer to build.

I've built some in the past . . . more for the uniqueness. Wood in the center did not dry as quickly.