storage and continous burning

That would kind of defeat the purpose of storage. If you're burning 24/7 you're going to idle the boiler. Storage is intended to do two things primarily - increase effeciency by eliminating idle and increase convenience by enabling you to burn "when you want to"....

I don't have storage yet. Do those of you with storage, burning hot, then burning out, find you have to re-start your fires frequently? I would guess you're using a LOT more kindling than you would without storage.
I see the benefits of storage. And I will put it in - probably next year. I'm just trying to understand the "costs" too.
Thanks. Happy burning!

I have the Econoburn 150 with 500 gallons storage. My demand is such that I utilize the storage through the shoulder months, but I'm guessing that my demand is about the same as, or very close to, the output of my boiler during the cold months. So....my storage is really not going to be as valuable in the winter as it is in Spring and Fall.

My B/B has max output of about 110kbtu plus I have a water/water domestic hot water maker soooo my 150kbtu wood boiler output is gonna be close to my demand.

I shut the gas off to my gas boiler 2 months ago and haven't used a ccf in that time! Storage saved me that money. PLUS the house is warm 24/7 now, when I used gas to heat the house it was COLD 24/7. That's worth a ton of money to me.

I guess the bottom line is that if your output is significantly more than your demand OR you want to utilize your wood boiler during the mild months w/o creating a lot of creosote then storage is well worth it. If you only want to run your boiler during the cold months and your output is very close to your demand then "I" wouldn't go with storage.

I am pleased with my storage situation, but wish I had 1000 gallons of it instead of 500. I also wish my house was tighter, wish my garage was insulated, wish the storage was better insulated, etc, etc, etc......

good luck,
np

maplewood said:

I don't have storage yet. Do those of you with storage, burning hot, then burning out, find you have to re-start your fires frequently? I would guess you're using a LOT more kindling than you would without storage.
I see the benefits of storage. And I will put it in - probably next year. I'm just trying to understand the "costs" too.
Thanks. Happy burning!

Click to expand...

Most of us with storage start a fire every day during peak heating season. Every two or three days in the shoulder season. I use very little kindling as far as I can tell. Three pieces of newspaper, three small pieces of kindling (6" long maybe), three or for small splits and then a few moderate size splits is all it takes for my fires to get going. It's quite easy once you get the hang of it.

With my work schedule I would never be able to heat with wood without storage. During winter I start a fire at 6pm or so with a small load, load the firebox 60% full at 7:30 or so....then fill it completely full at 9:30 and I'm done for the day. I have maybe 30-45 minutes of total time per day managing my fires. This heats 3200 square feet 100% on wood, all day long, at a much warmer temp than prior years when I was paying for gas....

great description Huskurdu. Unless you intentionally oversize the boiler and storage, storage does not play as big a big role mid-Winter.

Everybody has a shoulder season, some only have a shoulder season. Storage really shines in those cases.

However, any boiler can be more efficient with the addition of storage; don't forget that the fuel we use is quite variable. Using storage reduces those effects.

If you truly consume the fuel based on your load needs, then you will not be able to run 24/7 with storage. Yes, you can run and idle 24/7 while using storage, it would seem somewhat redundant and wasteful.

Peak heat load is about twice average heat load. If your boiler is just barely big enough to meet your peak demand on the coldest day, then on average over the course of the heating season it will be idling at least half the time. If you get any solar gain, it will be even more pronounced than that. Few people have a boiler that's sized that close to their peak load. I would argue that storage is helpful almost every day of the year.

nofossil said:

Peak heat load is about twice average heat load. If your boiler is just barely big enough to meet your peak demand on the coldest day, then on average over the course of the heating season it will be idling at least half the time. If you get any solar gain, it will be even more pronounced than that. Few people have a boiler that's sized that close to their peak load. I would argue that storage is helpful almost every day of the year.

Click to expand...

+1. I had roughly one week last year where the temps never broke above zero. During this time I had to fire my boiler roughly 20 hours per day. But that was only one week out of 6 months +/- of heating....

with a 1000 gallons storage i fire it when my tanks are low enough. when it gets real cold my boiler is sized really good to my load so it stays going 24/7 with minimal idle time, with storage i dont have to be right there to feed it if i get home from work late i just restart it. it gives me a buffer so to speak. im heating 3600 sqft hot water for 4 and my hot tub.

This thread is helpful for those out there who are thinking of putting in storage. So.. if I have this right... Storage is not that helpful during the coldest days if my Tarm 40 is matched to the heat loss on those days. Therefor storage is best for the days when it is not matched. Thus my question. If storage is mainly to be used to store the heat... then more is better because it stores more heat and then I can store more?... and then i go longer time periods without making a fire? So... how about people who have small storage? Is there anyone out there who has less than 500 gallons of storage? How is that working for you? Is it sufficient? What would my life be like if i had only 220 gallons of storage? Can i get rid of my overheat loop? Will it provide me enough storage to prevent idling on those less than coldest days? Will I have to match the amount of wood to this amount? What if the house had no demand... will 220 gallons take a full loaded Tarm amount of heat? Or would it take half a load to bring this amount of storage up to max temp?

Birdman said:

This thread is helpful for those out there who are thinking of putting in storage. So.. if I have this right... Storage is not that helpful during the coldest days if my Tarm 40 is matched to the heat loss on those days. Therefor storage is best for the days when it is not matched. Thus my question. If storage is mainly to be used to store the heat... then more is better because it stores more heat and then I can store more?... and then i go longer time periods without making a fire? So... how about people who have small storage? Is there anyone out there who has less than 500 gallons of storage? How is that working for you? Is it sufficient? What would my life be like if i had only 220 gallons of storage? Can i get rid of my overheat loop? Will it provide me enough storage to prevent idling on those less than coldest days? Will I have to match the amount of wood to this amount? What if the house had no demand... will 220 gallons take a full loaded Tarm amount of heat? Or would it take half a load to bring this amount of storage up to max temp?

Click to expand...

That's exactly the right list of questions.....

However, no boiler is perfectly matched to the load, so you will likely have some excess capacity on even the coldest days. With my EKO 25, I need to burn about 12 hours on the coldest days.

I think in general more is better, since it gives you more options about when to burn, and gives you more opportunities to skip days. You can calculate how much heat any given storage will hold:

storage btu = dt x gallons x 8.3

where dt is the difference between your lowest useful storage temp and your highest readily attainable storage temp.

If you had 220 gallons of pressurized storage with a useful range of 120 to 180 degrees, then the math is

60 x 220 x 8.3 = 109,000 BTU for your 220 gallon tank. I don't know what the Tarm puts out, but that's likely less than an hour's worth at full throttle.

Birdman said:

This thread is helpful for those out there who are thinking of putting in storage. So.. if I have this right... Storage is not that helpful during the coldest days if my Tarm 40 is matched to the heat loss on those days. Therefor storage is best for the days when it is not matched. Thus my question. If storage is mainly to be used to store the heat... then more is better because it stores more heat and then I can store more?... and then i go longer time periods without making a fire? So... how about people who have small storage? Is there anyone out there who has less than 500 gallons of storage? How is that working for you? Is it sufficient? What would my life be like if i had only 220 gallons of storage? Can i get rid of my overheat loop? Will it provide me enough storage to prevent idling on those less than coldest days? Will I have to match the amount of wood to this amount? What if the house had no demand... will 220 gallons take a full loaded Tarm amount of heat? Or would it take half a load to bring this amount of storage up to max temp?

Click to expand...

I wouldn't go so far as to say storage isn't helpful during "the coldest days". My storage is absolutely utilized 95% of the time I burn. Without storage I wouldn't be able to heat with wood, period. Extreme cold is the only time, in my system, that storage becomes somewhat underutilized. We're talking 20 below at night, below zero during the day.

I think 220 gallons would be less than useful assuming your Tarm 40 puts out something close to 130,000btu/hour. On an average heating day in winter (not shoulder season) I heat 1,000 gallons of water with roughly 5-7 hours of burn time every day with an EKO 40. I think a Tarm 40 would heat 220 gallons very, very quickly. And an average home would deplete 220 gallons of storage very, very quickly. Plumbing can be pricey. I wouldn't spend the money on a storage solution that wasn't going to really make you smile most days...

If I'm reading this correctly, it looks like there wouldn't be too much of an issue with oversizing the boiler for the heating needs of the house(within reason, obviously you wouldn't need an industrial boiler for an 800 SF house), as long as you put in enough storage to utilize all the heat from a full burn, and had the storage very well insulated. This would give the ability to skip more days, and ensure enough btus for any weather, including both DHW and heating. Is there a such thing as "too much storage"?

Is this correct, or am I missing a big part here?

karri0n said:

If I'm reading this correctly, it looks like there wouldn't be too much of an issue with oversizing the boiler for the heating needs of the house(within reason, obviously you wouldn't need an industrial boiler for an 800 SF house), as long as you put in enough storage to utilize all the heat from a full burn, and had the storage very well insulated. This would give the ability to skip more days, and ensure enough btus for any weather, including both DHW and heating. Is there a such thing as "too much storage"?

Is this correct, or am I missing a big part here?

Click to expand...

i do not know the answer, but i am interested. i have related questions about how long does a storage tank retain heat if it idles (both dropping from initial state but also dropping when return water mixes in).

i think the answer is that you would see diminishing benefits from a larger tank. the more time it sits the more it cools naturally no matter how much you insulate, and the more time there is for your colder return water to mix with and drag down the temps in the upper stratas of the tank. if i understand it right, the sooner you use your storage the more efficiently it will drive your radiators.

I hooked an older Tarm (MB55) to 250 gal storage with the hopes of adding more later. I can heat that amount of water with about 3/4 of a firebox load. If i load it full before going to bed my tank is still at 160 to180 in the morning. But it is not that cold yet, so time will tell, if i need to get up at night to load some wood, well it will be just like every other year.

semlin said:

i do not know the answer, but i am interested. i have related questions about how long does a storage tank retain heat if it idles (both dropping from initial state but also dropping when return water mixes in).

i think the answer is that you would see diminishing benefits from a larger tank. the more time it sits the more it cools naturally no matter how much you insulate, and the more time there is for your colder return water to mix with and drag down the temps in the upper stratas of the tank. if i understand it right, the sooner you use your storage the more efficiently it will drive your radiators.

Click to expand...

All true, but it's not too hard to insulate well enough so that heat loss is a minor issue. Mine only loses a couple of degrees per day. Of course if the storage can be installed indoors the heat isn't lost at all, though it might be delivered to places that you don't want it.

nofossil said:

semlin said:

i do not know the answer, but i am interested. i have related questions about how long does a storage tank retain heat if it idles (both dropping from initial state but also dropping when return water mixes in).

i think the answer is that you would see diminishing benefits from a larger tank. the more time it sits the more it cools naturally no matter how much you insulate, and the more time there is for your colder return water to mix with and drag down the temps in the upper stratas of the tank. if i understand it right, the sooner you use your storage the more efficiently it will drive your radiators.

Click to expand...

All true, but it's not too hard to insulate well enough so that heat loss is a minor issue. Mine only loses a couple of degrees per day. Of course if the storage can be installed indoors the heat isn't lost at all, though it might be delivered to places that you don't want it.

Click to expand...

I'm not quite as proficient at insulation as Nofossil....I will loose roughly 10 degrees per day on my tanks if they are sitting without being used. But as Nofossil says all of my heat loss is indoors. So it's not really "lost"...

couchburner said:

I am looking for a more even heat for my house instead of waking up and having to stoke the fire a bit to get things warmed up in the morning. At this point I am OK but as temps get closer to 0 it may be tougher to keep consistent heat. I'm not worried at all about idling(non gasser) and I dont like the idea of building fires everyday. Just wandering if storage will give my house more consistent and faster response heat. Also wandering if storage will work against me in that I am trying to keep more water up to temp thus burning more wood. I have water baseboards and heating nearly 5000 sq ft

Click to expand...

I don't know if this was answered.??? Before you put in storage, especially coupled with your concern of just burning more wood, you need to know if your boiler can go the extra btu output or if it is near max output during your most critical heat demand days as storage can be looked at as just having a larger area to heat.I have a non-storage gasser system and have to configure for long burn times so wood quality is imperative. If you have been using wood higher in moisture content you have been getting robbed in your efficiency and it you go to a larger heat demand by adding storage you will need to figure in added wood storage as well.

This is an interesting thread, and a subject that I have been thinking about a lot over the previous year's experience with my EKO 60 and 500 gal of storage (both indoors in the basement). I have a somewhat unusual setup, in that we are heating two houses - one a moderately insulated farmhouse, and the other a 70 ft barn converted to a house, with 11' ceilings and moderate insulation in half of it. I had previously used 3 hot air oil burners ~ 70K output each, to heat it. Overall, it is equivalent to about 3 normal homes, with the barn being twice as large as a regular house, and using about twice the oil of the farm house. I used 11 full cords of wood last season, which sounds like a lot, but in fact is pretty much in line with heating the equivalent of 3 conventional, moderately insulated homes.

I burn 24/7 in all but the warmest shoulder seasons. In my case, the heat storage is only about 100K BTU total (assuming 600 gal total including the boiler, with a 20 deg swing). Those BTU's from storage would only provide heat for a few hours under moderate conditions. Of course, at -20 deg, the boiler is running flat out, and just about keeping up. In most cases, I keep a hot bed of deep coals, and feed the furnace every 4-6 hours, which works out about right to keep a hot, clean fire going. If I maintain the bed of hot coals, it burns extremely clean, and gassifies beautifully whenever it comes on.

So it seems the issue of storage becomes one of the ratio of storage capacity to heat usage. In my case, even if I had 1,000 gal or more of storage, it still wouldn't be suitable to build intermittent fires all the time, as I could get at most perhaps 8 hours from the storage. OTOH, if I were heating only one house, reducing my load by 2/3, then 1,000 gal of storage could actually provide the necessary heat for 24 hours, and would be ideal. So there must be some mathematical ratio of total storage capacity vs. heat load, where using storage with intermittent fires is more advantageous that a more or less continuous burn.

Despite that, the relatively small storage I do have in invaluable, as it provides a kind of "thermal battery", drawing off heat if the fires gets low and before I can get it back up again, or in the coldest weather, providing a buffer. However, adding more storage tanks in my case wouldn't really accomplish too much, as I still could never add enough to be able to run off the storage for more than 12 hours or so.

Of course, the real solution is to reduce the required heat load through better insulation, and radiant heat delivery to utilize cooler water, which in effect is the equivalent of adding more heat storage. Anyway, the storage question is nuanced, and I think just assuming more storage is always the answer is not necessarily correct. It depends on the specifics of the situation.

Boilerman,

Yes I see your point about more storage not being best for your application, but what if, instead of 600 gal, you upsized the bolier(you said it's just about keeping up on the worst of days) used 1500 or even 2000 gallons?


Does anyone have experience using larger volumes of water, higher than 1000 gallons? If we were to assume 0% heat loss at the tank, 0% loss to well insulated piping, and so our only heat loss would be from the actual provided heat, would there be any drawback to even higher volumes of storage, provided the boiler could keep up with charging storage and providing the full require heat load?

karriON,

Yes, I could add more storage, and that is my point. If I try to articulate the problem a little more clearly, it seems there are 3 major ideas to reconcile in figuring an optimal system; 1 - the heating load, 2-the storage capacity and 3 - the boiler size.

In my case, my heat load is very high. At design temp, I am probably using right around 200K BTUH. Assuming half that load for more typical cold weather conditions, that would put me at 2,400,000 BTU for a 24 hour period, which would seem to be a convenient target. Dividing this by 20 deg and 8.35 lbs/gal, I would need a storage capacity of 14,371 gallons! Even dividing by 2 for 12 hours of storage, still means a 7,000 gallon tank, all of which means I would have to turn the basement into a 180 deg swimming pool.

Now, for a more reasonable design load of say, 25K BTUH, over 12 hours, would need 300,000 BTU. 1800 gal of water would provide that heat. So the more typical 1,000 gal of storage is useful in this situation, giving about 6 hours of full heat without firing the furnace, and more of course with lower temp radiant heat emitters.

After reconciling these two requirements, then the furnace output can be selected to charge the system within a reasonable time. For example, a 100K BTUH furnace size could charge the 1800 gal tank within about 3 hours.

So the issue seems to be the ratio of storage/load. In my case, it simply is not practical to provide sufficient heat storage for significant times without the furnace being needed. So in that situation, storage becomes less significant obviously, and at best can only buffer the ups and downs of the demand.

Put another way, in my first example for 12 hrs of storage with 100K of demand, or 1,200,000 BTU total, my 500+ gal with the boiler, approaches only 100K BTU, for a ratio of storage/load of 0.083. A 1000 gal tank would be about 0.16. However, in the more typical case in the second example of a 300,000 BTU load, a 1000 gal tank would have a ratio of about 0.56.

Storage is clearly very useful with the storage at about 0.56 of the total required heat output over the 12 hour period in that example. It is almost useless in my example, with a ratio of 0.08.

As I said, I am not heating engineer, or any engineer at all for that matter. I am sure someone who knows more has all these relationships fully worked out. I have been thinking about this for the past year of operating our EKO 60, and this seems to be a reasonable way to think about the storage requirements of a system.

Very Sensical BM.

I was picturing your heat load as being significantly lower than 200k btu/h.