Boiler size: does bigger mean more wood?

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nstueve

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So I've been looking around at boilers and have found several around. One is an oversized boiler. By oversized I mean a 300gallon boiler for a 2300 sqft house and garage. So if I can get this boiler cheap does this mean I automatically burn more wood since its obviously way oversized for this purpose... Or do I just get longer burn times and not much more wood???
 
I'm sure it will vary from boiler to boiler, but usually bigger boilers will burn more wood than a smaller one to heat up and maintain temp on the increased water capacity. However, it should maintain the water temp near your set point more easily so it will cycle less and give you longer burn times. I would guess you would burn 10-20% more wood with a large boiler over a medium sized one in the same set-up although... this is only a guess. Not sure what you plan to heat, but better oversized than undersized.
 
More water reserve means when the fire goes out you will still have heat in reserve. Saved btus in the extra water. I added an extra 120 gallons in storeage to mine with new but dammaged water heaters. Still looking for a larger insulated tank for more storage. Also means longer and more efficient burns.

On a 40 degree day it will go 8 hours between burn cycles. But as the temp drops the frequency increases.

Not 8 hours for a fill of wood but burning to heat the water to the idle setting. My boiler turns off at 195 degrees with 25 degree differential.

Sent from my SCH-R950 using Tapatalk 2
 
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So I've been looking around at boilers and have found several around. One is an oversized boiler. By oversized I mean a 300gallon boiler for a 2300 sqft house and garage. So if I can get this boiler cheap does this mean I automatically burn more wood since its obviously way oversized for this purpose... Or do I just get longer burn times and not much more wood???

I'm sure it will vary from boiler to boiler, but usually bigger boilers will burn more wood than a smaller one to heat up and maintain temp on the increased water capacity. However, it should maintain the water temp near your set point more easily so it will cycle less and give you longer burn times. I would guess you would burn 10-20% more wood with a large boiler over a medium sized one in the same set-up although... this is only a guess. Not sure what you plan to heat, but better oversized than undersized.

More water reserve means when the fire goes out you will still have heat in reserve. Saved btus in the extra water. I added an extra 120 gallons in storeage to mine with new but dammaged water heaters. Still looking for a larger insulated tank for more storage. Also means longer and more efficient burns.

On a 40 degree day it will go 8 hours between burn cycles. But as the temp drops the frequency increases.

Not 8 hours for a fill of wood but burning to heat the water to the idle setting. My boiler turns off at 195 degrees with 25 degree differential.

Sent from my SCH-R950 using Tapatalk 2

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Its more a case of being effective where if you filled the boiler firebox half full or more of standard firebrick not that half brick stuff you will be creating a thermal mass and be storing heat and having cleaner batch burns if you are willing to batch burn.
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inside boiler

my old northland boiler has a 50 gal water jacket ,the house is 1900sq feet. 6 to8 cords nov to april this boiler can handle 3 to 4000sq feet.k
 
I totally agree with better oversize than undersize but I never have bought into the water storage idea or the firebrick.
 
Boiler size

I feel like I over sized also when I bought mine (Shaver Pro 250) 4 seasons ago but it has had its advantages. I never intended to use the DHW in the beginning while I figured this thing out but once I did it was nice to know I could heat my DHW as well. I have 240 gallons of water sitting at 165 degrees most of the winter and the only time I feel like I am using a bunch of wood (more than normal) is when the temps are in that 0-5 degree range. of course last year we had about an entire month of that so I felt like I was shoving wood in that thing all the time. Actually it was just 2-3 times a day but I like to go out and poke at the fire so I spend a lot of time out there. I did take my DHW out of the loop during that extreme cold to relieve the boiler a little bit and that helped me maintain temp a little longer. I know a lot of people don't like Shaver but I had a pretty good experience with them and have made a few changes to the boiler to improve it. This summer I am going to take the sheet metal off and reinsulate a little better but I wouldn't ever step down in size. I do have 2 heat exchangers that pull about 180K BTU from the boiler so I know I have room to spare for a garage heater or barn one day if I want so oversized for now is just fine for me.
 
Yea there is a Shaver 250 that I could get locally and have considered it... I would considered the Shaver bigger than I need and this other local boiler is 60-100 gallons bigger. So, I know I'd definitely be over sized! Where are you located and how much wood have you used in the Shaver on average? I've heard that the have problems sealing the firebox to control air flow/heat output. Also heard that a new thermostat and a "flapper" need to be changed out as well as insulating it better. I don't mind a few DIY mods to a boiler as long as the problems get remedied and don't re-appear... We'd have a LP furnace as back up so not a huge deal if I needed to make repairs. I think we'll have about 300 gallons of propane in the house when we close on it next week. With money tight on a house closing I was hoping we could get a boiler in and not have to worry about filling the LP until next year since it will only run the stove and any extra the water heater needs past the boiler pre-heating.

I honestly don't care if it takes me 10-20% more wood if it allows me to fill only once a day. Cutting the frequency at which I need to fill is great since I have a regular 8hr work day and 1hr commute time. It's easy to think the boiler won't have someone to charge it for 10-12hrs regularly if I have errands after work.
 
Yea there is a Shaver 250 that I could get locally and have considered it... I would considered the Shaver bigger than I need and this other local boiler is 60-100 gallons bigger. So, I know I'd definitely be over sized! Where are you located and how much wood have you used in the Shaver on average? I've heard that the have problems sealing the firebox to control air flow/heat output. Also heard that a new thermostat and a "flapper" need to be changed out as well as insulating it better. I don't mind a few DIY mods to a boiler as long as the problems get remedied and don't re-appear... We'd have a LP furnace as back up so not a huge deal if I needed to make repairs. I think we'll have about 300 gallons of propane in the house when we close on it next week. With money tight on a house closing I was hoping we could get a boiler in and not have to worry about filling the LP until next year since it will only run the stove and any extra the water heater needs past the boiler pre-heating.

I honestly don't care if it takes me 10-20% more wood if it allows me to fill only once a day. Cutting the frequency at which I need to fill is great since I have a regular 8hr work day and 1hr commute time. It's easy to think the boiler won't have someone to charge it for 10-12hrs regularly if I have errands after work.

I like the Shaver quite a bit and it is one solid built no frills unit for sure. Mine was built before they used the fan with flapper so I bought a bracket and redid mine with a solenoid to accommodate the flapper style they are using now. I just did that modification last year so I am still figuring out how much of a savings that is worth. It appears to be working though because when that flapper shuts and seals off the fan I have very little smoke coming out of the unit. The second year I had mine I upgraded to a Ranco thermostat which gave me really good control over the water temp. In the dead of winter I run the water in the 165 degree range with a 10 degree offset. I also have LP as my backup and there was only one time last year that I remember using it because I wasn't ready to start a fire yet but the night temps dipped into the 40s or so. I only use propane in the summer now to cook with and heat my water since I don't like maintaining the boiler all summer when there are times I am gone on vacation and I don't feel like dealing with it when I get home. I am located in central Indiana so we can either have it be 50 in the winter or 5 like it was last year. I think with those few changes to an older Shaver you would have a pretty good reliable unit. If it helps you judge what you would pay I did give just over 6000.00 for mine and that was with the thicker firebox. That might be standard now I cant remember but it seemed like a good choice at the time.
 
A boiler being 'oversized' is not related to how much water it holds - it is related to how big the firebox is and the corresponding BTU/hr heat output, which is also related to the units heat transfer efficiency.
 
owb

A boiler being 'oversized' is not related to how much water it holds - it is related to how big the firebox is and the corresponding BTU/hr heat output, which is also related to the units heat transfer efficiency.

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The same theory applies to a coal boiler in a locomotive as well-small firebox and big water supply BUT incomplete combustion due to the duty cycle and overfiring with lots of smoke.

The locomotives that burned anthracite burned clean and had a high rate of combustion in the firebox because the coal was pure carbon.


If you have either a big firebox with a big water supply or a small firebox with a small water supply the need for high efffioiency in combustion still remains.

A fire box half filled with firebrick will act as a heat sink and the same heat sink also release heat back into the firebox and maintain a higher burn temperature as well with little smoke as the burn will be continuos with much less wood.
 
I have a central cl-40, 400 gallon storage heating a 1450sq ft house, small 2 car attached garage, a 24x30 detached, and my domestic hot water and I throw a heaping wheel barrel load in every day when I get home from work regardless of how cold it is. Less if its 30 or higher. I have a close friend with a 175 gallon shaver heating 1600 sq ft house and the first thing he has to do in the morning is hurry out and fill it up cause its almost out and he can't go anywhere after work cause by the time he hurries home, the fire is almost out again. Can't even go 10 hours. I left on a friday for a ski trip last winter and stacked a face cord in my firebox and came home Sunday to find out that I didn't need to put any wood in till Tuesday night. Bigger is DEFINITELY better! He gets a hotter burn and is always having chimney fires because of the combustion blower, so I guess one positive is he never has to run a brush down his chimney. I do mine twice a year to keep it from getting real bad. As mentioned above, the little guys have to work much faster creating a clean burn, but I like not having to stand there and make sure the fire doesn't go out. I'm learning that with wood heat, literally everything is relative and a don't think you are going to find one that burns half the wood as the rest, but the trade off is frequency of shoving wood in.
 
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Clean burn means efficiant burn, if you don't mind cutting extra wood and you don't tick off your neighbors or wife then bigger is better, I however have better things to do with my time than waste wood, and my wife likes to hang the laundry on the line, therefore loading the boiler with smaller quantities of fuel twice a day is what we try to do. Great point Leon about the firebrick, some of you guys should try it and you will find that even the old smoke dragons will burn cleaner and use less wood
 
My wife doesn't hang cloths on the line in the winter and the extra smoke is a misconception, plus i dont live in town so the neighbors all burn wood also. I surly don't burn more wood than the little guys, if anything it's less, noticeable amount less. What makes a clean burn more efficient than say a "dirty burn"? With hydronic heating, it's all relative. So back to the original post, bigger does not mean more wood unless you have a small or off brand boiler.
 
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