# Gallons of water in outdoor boiler



## dwinch53 (Jan 25, 2013)

Good morning...Question...what advantage / disadvantage is there in gallons of water in outdoor wood boiler...looking at two stoves...Ridgewood has 120 gal and nature's comfort only has 80 gallons of water...need feed back please and thanks in advance.:msp_confused:


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## Encore (Jan 25, 2013)

More thermal mass means it'll hold it's heat longer before needing to be reheated. Some boilers hold closer to 500 gallons but those are pretty big. 

Depending on your home size, 80 gallons seems kinda small.


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## dwinch53 (Jan 25, 2013)

I will be heating apx 1500 sq ft...if there less water will I get a cleaner burn ?


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## jh35 (Jan 25, 2013)

dwinch53 said:


> I will be heating apx 1500 sq ft...if there less water will I get a cleaner burn ?



I'm not sure about cleaner but definitely more frequent cycling. Mine holds 114 gallons according to the manufacturer. 1000 sq ft living area, + basement and DHW. We hooked it up mid-November and with the latest cold snap I had to fill twice per day for sure but I was never close to out of a fire. I threw some pine and cottonwood in with the Ash last night and still had plenty left this morning.

I'm interested in the thermal mass too. If it shows worthwhile I'll think about adding storage in the basement. I haven't done any research yet.


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## leon (Jan 25, 2013)

dwinch53 said:


> I will be heating apx 1500 sq ft...if there less water will I get a cleaner burn ?



No,

You will not get a cleaner burn with a small boiler simply because 
it will be cycling on and off, opening and closing the automatic damper
creating a lot of smoke which is lost energy as the smoke is not consumed 
and simply wasted. 


The more water you heat the greater the thermal mass
and the hotter the firebox which will aid in combustion and 
draft and the reduction of smoke equals saved energy.

You can add thermal storage like the new horizons water storage tanks which 
are 490 gallons each and have a huge heat sink in the water volume and the 
tanks are insulated. 

The other thing to remember is you can have small very hot fire going
and keep a huge mass of water at temperature simply by throwing wood 
in the boiler occasionally to keep the fire going.

The more water you have the more useable energy you have from the thermal mass.

The forced draft aids in combustion and when the boiler gets up to temperature the 
easier it is to maintain the temperature simply because you have huge amount 
of water that will not cool down quickly.

It only takes small amount of combustion to bring the large volume of water 
back up to temeprature.


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## Guswhit (Jan 25, 2013)

IMO, I am looking at this as if it is a forced air system not a radiant. Imagine this, say you have 100 gal capacity for argument sake. Pump circulates water through system at a given rate through your heat exchanger, say 5 gpm, upon the return say you have 1-2 degree temperature drop in your loop with no load(ie no furnace kicking in blowing air through exchanger). So in theory it will take 20 minutes for you to circulate all 100 gal through the system 1 time dropping the temperature 1-2 degrees. So if you look at the system when there is a load on it and you are maybe getting a 10 degree drop for the time the furnace blower is syphoning heat off it is going to speed up the temperature drop in the mass of water, so the larger your mass of water the longer it will take before your OWB needs air to refire to temperature because it takes more minutes to circulate a larger volume. Yes, intial start up you will need more BTU's for getting up to temperature but after the first start you should find it easier to maintain a constant temp.


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## hondaracer2oo4 (Jan 25, 2013)

The more thermal mass the better. It will initially take a long time to get a lot of water up to temp but once it is there you are much better off. If you are doing a forced hot air system you are going to want a large thermal mass. You are shooting for around a 20 degree heat drop across the hx from the inlet to the outlet temp. Flowing at 5 gpm it brings the water temp down very quickly. I have a Hardy H4 feeding a 24x24 water to air hx. My temp drop is 25 from inlet to outlet. My water in the Hardy is 130 gallons. I wish I had twice that in water(which I could add with an external tank). If you are doing forced hot water the temp drop will be less and not be as drastic. I think 80 gallons is WAY to small. If you are heating 1500 sf I would suggest giong with either the 80 with additional storage or just the 120.


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## chugbug (Jan 25, 2013)

My medium size owb holds 300 gal


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## dwinch53 (Jan 25, 2013)

Thank you to all...makes since to me.


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## woodman6666 (Jan 25, 2013)

More water, more mass the better, my boiler has 3400 gallons way good.


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## Stihl310 (Jan 25, 2013)

I'm heating an 1800 sq ft house with approx 165 gallons on my boiler. Does fine however my house is only 4 years old and I put in spray in insulation so it's very tight.


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## hondaracer2oo4 (Jan 25, 2013)

Woodman, 

3400 gallons?! Whats your set up? What are you heating, with what, what size is your boiler etc?


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## Uncle John (Jan 26, 2013)

More water=Less fuel........:msp_biggrin:


Up to a point I guess. I don't know where that point is.
But I think it would be way up there.


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## vinced (Jan 26, 2013)

Google Garn wood boiler. They are the king of thermal mass. There smallest stove holds 1500 gallons. With a Garn the fire is not going all the time. You batch burn it to bring the water temp up when needed. If sized correctly, you should only have to have a fire every other day. This would be great with the strange outside temperture swings we seem to be getting the past couple winters. I've been planning on building my own and have been searching for steel to start the project. The only problem is steel isn't has cheap has it used to be!


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## woodman6666 (Jan 26, 2013)

vinced said:


> Google Garn wood boiler. They are the king of thermal mass. There smallest stove holds 1500 gallons. With a Garn the fire is not going all the time. You batch burn it to bring the water temp up when needed. If sized correctly, you should only have to have a fire every other day. This would be great with the strange outside temperture swings we seem to be getting the past couple winters. I've been planning on building my own and have been searching for steel to start the project. The only problem is steel isn't has cheap has it used to be!



I have personally been to the Garn testing facility and they have alot of good ideas the only problem I see is that if you are going to spend that kind of money on a system you are more than likely heating multiple buildings, houses etc. and when you do that the water temp goes down relatively fast which in turn leads you to filling that tiny firebox several times a day which I have no interest in. Funny when I brought up the amount of square footage I heat with my home made boiler and told them that I can go for 2 weeks between fills and their answer was ours pollutes less and for the amount of square footage I was heating you would have to have guy dedicated to filling their unit every few hours. I asked him if he wanted that job and he said no but alot of factories that buy their units just have one of the workers stop by the garn and fill it every few hours. 
I will say this when the Garn is burning it burns very hot and clean.


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## shawnw (Jan 26, 2013)

vinced said:


> Google Garn wood boiler. They are the king of thermal mass. There smallest stove holds 1500 gallons. With a Garn the fire is not going all the time. You batch burn it to bring the water temp up when needed. If sized correctly, you should only have to have a fire every other day. This would be great with the strange outside temperture swings we seem to be getting the past couple winters. I've been planning on building my own and have been searching for steel to start the project. The only problem is steel isn't has cheap has it used to be!


Maybe I'm missing something here but I'd rather start a fire once a year and stoke it twice day as opposed to screwing around with starting a fire a few times a week. Unless you have perfectly seasoned wood that's covered so well you never have snow/ice/water issues (which is quite difficult up here) it would be irritating at best to have to start a new fire multiple times per week. 

So seriously, what am I missing?


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## vinced (Jan 26, 2013)

shawnw said:


> Maybe I'm missing something here but I'd rather start a fire once a year and stoke it twice day as opposed to screwing around with starting a fire a few times a week. Unless you have perfectly seasoned wood that's covered so well you never have snow/ice/water issues (which is quite difficult up here) it would be irritating at best to have to start a new fire multiple times per week.
> 
> So seriously, what am I missing?



How about not having to worry about the boiler boiling over. No continueous fire you don't have to worry about something catching on fire. Cleaner, hotter burning, more efficent, don't have to be stuck every 8-12 hours stuffing wood in it. Thats just a few off the top of my head. Watch some of there videos and they show you how to start the fire and run it. It looks very simple and not much to go wrong.


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## vinced (Jan 26, 2013)

woodman6666 said:


> I have personally been to the Garn testing facility and they have alot of good ideas the only problem I see is that if you are going to spend that kind of money on a system you are more than likely heating multiple buildings, houses etc. and when you do that the water temp goes down relatively fast which in turn leads you to filling that tiny firebox several times a day which I have no interest in. Funny when I brought up the amount of square footage I heat with my home made boiler and told them that I can go for 2 weeks between fills and their answer was ours pollutes less and for the amount of square footage I was heating you would have to have guy dedicated to filling their unit every few hours. I asked him if he wanted that job and he said no but alot of factories that buy their units just have one of the workers stop by the garn and fill it every few hours.
> I will say this when the Garn is burning it burns very hot and clean.



I've never seen your boiler,but it sounds like you have a very good design. I've seen many installations of Garns in 3000sf or less and they work good. After getting them up to temperature they only have a fire every other day. Maybe when heating multiple buildings they aren't the most ideal. I never told anyone to buy a Garn, just to simply study that design.


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## shawnw (Jan 26, 2013)

vinced said:


> How about not having to worry about the boiler boiling over. No continueous fire you don't have to worry about something catching on fire. Cleaner, hotter burning, more efficent, don't have to be stuck every 8-12 hours stuffing wood in it. Thats just a few off the top of my head. Watch some of there videos and they show you how to start the fire and run it. It looks very simple and not much to go wrong.


My dad's CL6048 goes 12-24 hours without stoking. 24 is a solid ash bed, 12 is quite a few chunks left. Temp swings stay within 175-185 at all times (so no boiling?). It sits by itself out behind the barn with a big old wood pile next to it. Something catching on fire? What kind of a sales pitch is that? If you're that scared of something catching on fire you probably shouldn't be screwing around with fire (literally a fire!), or you need a better education when it comes to wood burning.

Continuous monitoring? How do you know when it's time to start a fire? Do you have to check? Sounds like some monitoring is involved with both.

Cleaner/hotter/more efficient is relative and a matter of opinion. 

Why do I care how hot it burns if it's deliberately modulating to maintain a temperature? 

Efficient? It's a wood boiler! If you want efficient put a stove in your house.

How do you describe cleaner? What's cleaner? You? The boiler? If you wanna talk about cleaner....I'm cleaner when I don't have to screw around with a slow-to-go new fire that smolders and belches smoke as I try to get it to take off. I'd say I spend less time loading a wood boiler twice a day then when I have to screw around with starting a new fire. Admittedly it's difficult to keep the wood dry this time of year. Most people have the same issue when you experience 300"+ of snow each year.

Now let me follow all of that up by saying I'm not against any unit. I'm sure there are quite a few perks to seriously large capacity systems with a ton of thermal mass. I just don't see how having to start a fire every few days is a perk. I'm the type of person that would rather keep my fire going and a open a window just to avoid having to start another fire.


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## beerman6 (Jan 27, 2013)

This thread has me thinking (and wishing we did not scrap that old 80 gallon water heater) that I should add a water heater in my basement to add to my OWB's water capacity?

I could even hook power to it to help with the first fire of the winter?

What do ya think?


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## vinced (Jan 27, 2013)

shawnw said:


> My dad's CL6048 goes 12-24 hours without stoking. 24 is a solid ash bed, 12 is quite a few chunks left. Temp swings stay within 175-185 at all times (so no boiling?). It sits by itself out behind the barn with a big old wood pile next to it. Something catching on fire? What kind of a sales pitch is that? If you're that scared of something catching on fire you probably shouldn't be screwing around with fire (literally a fire!), or you need a better education when it comes to wood burning.
> 
> Continuous monitoring? How do you know when it's time to start a fire? Do you have to check? Sounds like some monitoring is involved with both.
> 
> ...



First off, I'm not selling anything. I suggested the orginal poster to take alook at a Garn because it has alot of thermal mass storage to show that it is an advantage. How many square ft is your dad heating? He would only have to build a fire once every 4-5 days with 1500 gallons of storage. I can tell you did not watch any of the Garn videos, reseached how it works, or even operated a wood boiler. There is no "slow-to-go" fires because there is a draft blower. Simply crunch up some paper put in some scrap 2x4s or pallet latts light the paper turn on the fan and about 5 minutes latter load your wood. I have an old Aquatherm wood boilder and I've never had a problem starting a fire. In fact, there was a post last month about "the favorite way to start a fire in your wood boiler". Noodles from cutting big logs length wise is my favorite. Hot fire start to finish means cleaner burning and with all thermal mass you can transfer more of the heat from the fire to the water. Boil over? Well that tells me right there you have never run a wood boiler. Failing Aquastats, pumps, draft door solnoids, leaking door gaskets, and etc. can lead to boil over. Lastly, I don't come here to argue, just to give my 2 cents based on my experience.


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## vinced (Jan 27, 2013)

beerman6 said:


> This thread has me thinking (and wishing we did not scrap that old 80 gallon water heater) that I should add a water heater in my basement to add to my OWB's water capacity?
> 
> I could even hook power to it to help with the first fire of the winter?
> 
> What do ya think?



I think your on the right track, but 80 gallons would not be worth the effort. I've been told that to have extra thermal storage pay off you need at least 500 gallons depending on how big your heat load is. Everyone that I've seen that has added extra storage to there systems always says they would like more.


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## shawnw (Jan 27, 2013)

vinced said:


> First off, I'm not selling anything. I suggested the orginal poster to take alook at a Garn because it has alot of thermal mass storage to show that it is an advantage. How many square ft is your dad heating? He would only have to build a fire once every 4-5 days with 1500 gallons of storage. I can tell you did not watch any of the Garn videos, reseached how it works, or even operated a wood boiler.


I operate his boiler quite frequently. He heats a 2500 sqft barn, a 1500 sqft barn, his 1200 sqft house, and hopefully someday a new log cabin that we plan to build. It doesn't heat my personal property but I'm with him and on his land enough to know that I want one for my home as well.


vinced said:


> There is no "slow-to-go" fires because there is a draft blower.


There's no blower on a CL6048. It's a naturally drafting boiler.


vinced said:


> Simply crunch up some paper put in some scrap 2x4s or pallet latts light the paper turn on the fan and about 5 minutes latter load your wood.


I guess you didn't even read what I wrote. It's impossible to keep wood dry in our parts. It takes A LOT of 2x4's to melt the ice and snow off of a log before it will burn on its own. Know what you do in the meantime? Keep checking it, and making sure that it's still burning. To shelter all the wood he burns through each year we'd be building a ridiculously large storage area that simply is not feasible.


vinced said:


> I have an old Aquatherm wood boilder and I've never had a problem starting a fire. In fact, there was a post last month about "the favorite way to start a fire in your wood boiler". Noodles from cutting big logs length wise is my favorite.


We don't have any noodles around, guess we'll have to try them.


vinced said:


> Hot fire start to finish means cleaner burning and with all thermal mass you can transfer more of the heat from the fire to the water. Boil over? Well that tells me right there you have never run a wood boiler. Failing Aquastats, pumps, draft door solnoids, leaking door gaskets, and etc. can lead to boil over.


No, that should tell you I've been around a quality boiler. Are you a pessimist? Do you honestly expect everything to be worst case scenario? Better yet are you an opponent or a proponent of wood boilers? In the 5-6 years that my father has had his installed he has had ONE solenoid fail, and the fire went out because the draft door failed closed. It failed safe, the burn died, and the water temp dropped. I'm not saying that boil overs can't happen, but don't make it sound like this is the sort of thing people should expect on a weekly basis. That's like saying we should all drive diesels because in the event that a water pump fails the engine is less likely to overheat.


vinced said:


> Lastly, I don't come here to argue, just to give my 2 cents based on my experience.


Who's arguing? It's a discussion. I'm all for valid "arguments" that spark good discussion, but your comments in your first post come off as though wood boilers are the devil.


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## vinced (Jan 27, 2013)

shawnw said:


> I operate his boiler quite frequently. He heats a 2500 sqft barn, a 1500 sqft barn, his 1200 sqft house, and hopefully someday a new log cabin that we plan to build. It doesn't heat my personal property but I'm with him and on his land enough to know that I want one for my home as well.
> 
> There's no blower on a CL6048. It's a naturally drafting boiler.
> 
> ...



Against wood boilers? I said I own an old Aquatherm and have had it for 6 seasons. I also have welded and helped buid a homemade boiler for a friend, so I know them pretty good. Am I pessimist? Well maybe, but anyone who owns and operates a wood boiler should be well aware of the worst case scernios that could happen. I had mine boil over once when I didn't latch the door completely and I had to replace the Aquastat, put a new cartridge in the pump, and replaced a 3ft piece of pex. So it pays to have spare parts on hand. As far has keeping the wood dry, well I live in central Wisconsin where it will be -10F one day and 35F with sleet and rain the next. I burn 6-7 full cords a year and it all sits outside uncovered. I don't burn any wood unless it has been cut and stacked for at least a year. My boiler is in a 8ftx12ft shed and I have enough room to stack about 2 weeks worth of wood in there. After about a day or so the wood in the shed is very dry (it never goes under 60f in the shed). One last note, look at when I registered on this forum and how many posts I have. I read the posts everyday and I never post unless I know what I'm talking about.


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## beerman6 (Jan 27, 2013)

vinced said:


> I think your on the right track, but 80 gallons would not be worth the effort. I've been told that to have extra thermal storage pay off you need at least 500 gallons depending on how big your heat load is. Everyone that I've seen that has added extra storage to there systems always says they would like more.



The effort would not be much,pex is cheap and easy,but I get what you're saying.

I'll be looking for a cheap tank now.


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