burn time

burn time

PostBy: ryan87gn On: Fri Dec 17, 2010 9:55 am

I know there are alot of variables involved, but is there a typical burn time one can expect from bit coal? I've got an outdoor nature's comfort 250 gallon furnace (yeah, wood furnace, seems to work fine with coal). Ran wood thru it a couple years. Easy access to wood, plus all the reloading has made this a pain and tough to justify. Switched to bit coal this year. Seems like if I build up a good pile of bit coal (building it up like a mound), it's out in the morning / evening when I go to refill. Half the time I have to restart the fire from scratch. I load it at 6 in the evening, top it off at 9 in the evening and refill 6 in the morning. This isn't alot better than wood. Plus, I spent ~ $300 for 1.5 ton of bit and I can't see that lasting a month. If it lasted 30 days, that would be ~ 100 lbs/day. Previous propane gas bills were $300-$400 per month. If I'm spending that on wood or coal, it can't be justified because of all of the labor. Help? Thanks.
ryan87gn
 
Stove/Furnace Make: Nature's Comfort
Stove/Furnace Model: 250

Re: burn time

PostBy: BigBarney On: Fri Dec 17, 2010 10:37 am

I have a boiler and run bituminous coal all year round so my

boiler has never been out since 2005. I load it up ( 25-75#)

2 times a day in the cold weather, in extreme cold <5* I

do an extra loading,in the summer once a day.

You need a deep bed of coal, mine is about 24" thick,

to keep a steady burn, controlled with the air inlet

and the draft controlled with a barometric damper to

steady out the draft.

Proper loading of coal is also important so that you burn

all the volatiles completely and have a clean burn of all the

fuel.

Usually these outdoor units have trouble with coal because

of the large grate area and poor ash removal, you'll have

to find these by trial and error.My boiler does not have a

shaker grate so I use a slide bar to clean the ashes off the

grate.

We nee some picture of the boiler and grate to better help you.

Size of house and heat loses are also important.

Hope this helps,

BigBarney
BigBarney
 

Re: burn time

PostBy: ryan87gn On: Fri Dec 17, 2010 11:23 am

You need a deep bed of coal, mine is about 24" thick, Ok will spread it out a bit more and stack height more even.
to keep a steady burn, controlled with the air inlet and the draft controlled with a barometric damper to steady out the draft. Boiler has a thermostat that kicks on the fan. Fan volume is adjustable.
Proper loading of coal is also important so that you burn all the volatiles completely and have a clean burn of all the fuel. Ash in the ash tray is fairly fine, but stuff that is out and still in the burner is not
Usually these outdoor units have trouble with coal because of the large grate area and poor ash removal, you'll have to find these by trial and error. Not sure what a shaker grate is. The inside of the unit is rounded in shape. holes in grate are probably 1" by 4" or so.
My boiler does not have a shaker grate so I use a slide bar to clean the ashes off the grate. If I open it up to add coal and all I have left are coals that appear hot, but if I stir it a bit to get more of the ash into the ash pan, they seem to go out quickly, then it's start over time.
We nee some picture of the boiler and grate to better help you. Will try to get that.
Size of house and heat loses are also important. 4 year old house, 2200sq ft living, same in basement unfinished. Went heavy on insulating the house.

Hope this helps,

BigBarney

Many thanks for the response!!!
ryan87gn
 
Stove/Furnace Make: Nature's Comfort
Stove/Furnace Model: 250


Re: burn time

PostBy: david78 On: Fri Dec 17, 2010 11:47 am

I have a Shaver 165; Nature's Comfort is the same basic design. I burned wood only the first two years; just started burning bit in it this year. It's not really an ideal appliance for burning coal IMO, for the reasons you state. The clinkers build up in the firebox with no good way of getting rid of them. And unless you limit the airflow, that fan forced draft gives the coal a lot more air than it needs. What I have been doing is burning a mix of coal and wood. I load wood on the sides, put a pile of coal on the grates and then some wood on top the coal. It seems to me that the burning wood helps the coal burn more completely, reducing the clinkers in size so they work down through the grate easier. Not saying this is the best or only way to burn coal in these boilers, so take this FWIW. I'm still experimenting. :gee: I'm certainly using less wood. I've thought about putting a spin draft in the loading door since bit likes some over the fire air. I also wondered if natural draft would be better than fan forced. The last load of bit I got was $105 a ton, so even though my wood costs me very little,it's worth it to reduce the wood cutting a little. If I had to pay much more for the coal, I'm not sure it would be worth the trouble.
BTW Shaver is selling a shaker grate for coal that will replace the regular grate in my OWB. Don't know the price or if it will fit yours. You could check with them.
david78
 
Baseburners & Antiques: Fuller & Warren Splendid Oak 27
Coal Size/Type: Nut

Re: burn time

PostBy: LsFarm On: Fri Dec 17, 2010 12:01 pm

Hello Ryan87,
There are a few items that may reduce your coal use.. What temperature is your combustion fan trying to maintain the water at?? if it is quite high, like 180*, you might do better with 160* or 150*.. usually this is still hot enough for heating your house.. that brings up a question: is your house hot water baseboard heated, or Hot Forced Air heated, and the wood/coal heated water goes through a water/air heat exchanger??

You also might try reducing the inlet area on the combustion blower, to limit the rate of combustion of the coal..

Most of the OWB units don't have enough heated surface area to extract the heat from a coal fire.. they depend on a roaring wood fire to transfer heat to the water.. Most coal boilers have a smaller, but deeper firebox, with the entire bottom of the firebox made up of shaker grates.. the grates are several sections of slotted cast iron, geared together, and when 'shaken' they rotate against each other, aggitating the ashes to fall down through the slots into the ashpan, and if the ash is hard and crunchy, the teeth will do some amount of grinding on the pieces of ash to reduce their size till they fall through the slots.

Fill in your signature a bit more,, where are you located?? Maybe someone on the forum is neaby.

Hope this helps..
Greg L
LsFarm
 
Stoker Coal Boiler: Axeman Anderson 260
Hand Fed Coal Boiler: Self-built 'Big Bertha' SS Boiler
Baseburners & Antiques: Keystone 11, Art Garland

Re: burn time

PostBy: ryan87gn On: Fri Dec 17, 2010 12:31 pm

Thanks guys...
-Will try more of a wood/coal mix. Agree with you on all the wood cutting. I love to cut, but this furnace loves to eat more than I love to cut!
-Will checkout Shaver's shaker grate. And thanks for the description on the shaker grate.
-I've got the temp on the boiler set high. My logic was that I wanted it to warm up quickly to warm the house up quickly when we're home and awake. If I get home at 5, and cut my temp back about 9, I don't have a ton of time to get the whole house up to temp. Bad theory?
-House is standard forced air heating. This comes into the house via water line to a water to air heat exchanger in my propane fired furnace.
-Located in the Akron OH area.
ryan87gn
 
Stove/Furnace Make: Nature's Comfort
Stove/Furnace Model: 250

Re: burn time

PostBy: wawrd1 On: Mon Dec 27, 2010 1:22 pm

I have the new 325G from Natures Comfort. I'm getting 36+ hour burn times heating in a similar situation as yours. The wood coal mix has been the winner for me. I'm burning Kentucky Lump coal with most pieces in the grapefruit size. I start with a bed of embers from a good wood fire, load wood on both sides of the grate, and add 2 scoop shovels of coal in the middle, then fill the stove with wood. After the load burns down to a bed of embers, I stir with a shovel to get the ashes to fall through and repeat the loading process. The coal I’m burning does not seem to produce clinkers and only smokes excessively when first loaded. After the coal is burning well the smoke goes to a lighter gray. Let me know how you are doing, I’ll share my experience as I am still experimenting also. This boiler has only been running for 3 weeks and I am still making adjustments.
wawrd1
 
Other Heating: Natures Comfort 325G Outdoor wood/coal boiler

Re: burn time

PostBy: ryan87gn On: Mon Jan 24, 2011 1:37 pm

I haven't been on in quite a while, but saw your note on my post. Wow is all I can say. I'll give that a shot. Right now with the real cold temps I've got it up to 8-10 hours. How high are you keeping the thermostat on the boiler itself? I've gotta be doing something wrong if you're getting those kind of burn times...thanks!!!
ryan87gn
 
Stove/Furnace Make: Nature's Comfort
Stove/Furnace Model: 250

Re: burn time

PostBy: LsFarm On: Mon Jan 24, 2011 5:53 pm

Keeping the water temperature in the boiler high, requires a lot more burning than a lower temperature. Plus, the hotter the boiler, the greater the heat loss to the outdoors and into the ground via the burried hot water tubing.. reducing the water temp by 20* should produce a noticable increase in burn times..

Your water to air heat exchanger doesn't need to be really hot, unless you are pushing the air through the exchanger quite fast.. Many of the coal burners on the forum use a variable speed fan in thier ductwork, and keep the fan speed slower, and the water temp lower, the air leaving the heatexchanger in the duct ends up being the same temperature, and the blasts of heated air in the house are reduced to a constant warm 'breath' of air rather than a body-cooling blast.. Not sure if this would help you or not, but worth a mention.

Greg L
LsFarm
 
Stoker Coal Boiler: Axeman Anderson 260
Hand Fed Coal Boiler: Self-built 'Big Bertha' SS Boiler
Baseburners & Antiques: Keystone 11, Art Garland

Re: burn time

PostBy: ryan87gn On: Tue Jan 25, 2011 2:22 pm

Greg, that helps tremendously. I had increased the temp on the boiler...probably within a couple months of getting it, thinking I needed that super hot water. I'll adjust it back down tonite and see what happens. It has seemed that by the time I went to refill (either in the early morning or late afternoon when getting home from work), the water temp was low, which meant low heat coming out of the vents, so I cranked the temp to try to heat the house quicker. Thinking about how you put it, if I can keep the thing lit and producing heat for several more hours, the low heat times would disappear as it would still have coal/wood in the burner when I went out to refill. Thanks!!!
ryan87gn
 
Stove/Furnace Make: Nature's Comfort
Stove/Furnace Model: 250