Thermal storage

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Redislespud

New Member
Nov 18, 2012
7
I am looking at the Econobuner 200 model. I think that i can meet my needs with the 150 model but i am planning to have a thermal storage tank to extend the time between having to load the boiler. Is there any down side to over sizing the boiler if you have excess thermal capacity? Does anyone have any recommendations on what i should use for a storage tank? Im a newbe so any recommendations are much appreciated.

W
 

salecker

Minister of Fire
Aug 22, 2010
1,437
Northern Canada
Hi Redislespud
Welcome to the site.
I have the Econoburn 200.and 1000 gal of storage.I used two 500 gal propane tanks standing on end.
Today we are at -20c and we will burn about 6 hrs of spruce.
This is the first boiler system i have had,the boiler seems to work great,easy to operate my wife has no problems starting or tending the fire.
We have the system in it's own building,no mess,no chance of fire or carbon monoxide in our home.
Where are you located?I have a bunch of tanks.
Thomas
 

goosegunner

Minister of Fire
Oct 15, 2009
1,469
WI
Sizing and usefulness of storage depends on;

Heat loss of your home at design temps and type of emitters that you will be heating with?

I have a 200 with 1000 gallons of storage. I would say that would be the minimum I would want to connect to a 200.


gg
 

jebatty

Minister of Fire
Jan 1, 2008
5,788
Northern MN
Is there any down side to over sizing the boiler if you have excess thermal capacity?
Generally, "no," but I think moderation applies here as to most things. My system is over-sized: 140,000 btuh boiler, 1000 gal pressurized storage, shop calculated heat loss = 35,000 btuh at -35F, highest measured heat loss so far = 18,000 btuh in a 24 hr period.

Advantages: can charge storage from 120 to 190F in about 4-6 hours while also meeting demand and then meet demand from storage; need to burn every other day at the most, less often with mild outdoor temps; with a little care on loading (weighed wood burns makes this easy) boiler can burn full out and coast to fire out while bringing storage up to 190F and no idling.

Disadvantages: need to carefully plan plumbing (pipe size, circ gpm, pump head, etc.) to insure that system can deliver maximum output from boiler to storage and/or system; requires larger pipe sizes $$$ than a smaller boiler; need sufficient storage (thermal capacity) to accept boiler output.

If storage is intended to meet system demand between boiler firings, then you need to determine your heat loss btuh and size storage to be able to meet this demand during the times between firing your boiler. Example: if "normal" heat loss is 40,000 btuh and you want to fire once per day, then you need 40,000 x 24 = 960,000 btu available from the boiler/storage. Assume that your burn period is 4 hours, therefore boiler will meet demand for 4 hours and storage will need to meet demand for 20 hours. Needed btu's in storage at end of burn = 20 x 40,000 = 800,000.

If you need 140F water to meet your system demand, and you can heat storage to 190F, then you need about 2000 gal of storage to meet demand solely from storage (2000 x 8.34 x 50 = 834,100). If your system require hotter water, needed storage will increase, and vice versa. If you want storage to meet demand for a longer period, the storage will increase, and vice versa.

Incidentally, 800,000 btu's will require about 200 lbs of wood per burn (960,000 / 6,040 btu-lb / 0.8 efficiency). Efficiency will increase if the boiler/storage is in the space to be heated and efficiency may decrease if not. Btu's per lb of wood is based on 20% MC and 400F stack temp.
 

Redislespud

New Member
Nov 18, 2012
7
Thomas / All repys

Well first of all i have to thank all for the quick and helpfull reply's. I live on PEI Canada. I am not sure of my heat loss in the home. It is very well built and consists of almost 100 % concrete and steel construction. I guess i will need to do some number crunching.

So Thomas i take it that you need to sprayfoam the propane tanks? Are you willing to sell a couple of those extra tanks? How far are you from me?

Wade


Hi Redislespud
Welcome to the site.
I have the Econoburn 200.and 1000 gal of storage.I used two 500 gal propane tanks standing on end.
Today we are at -20c and we will burn about 6 hrs of spruce.
This is the first boiler system i have had,the boiler seems to work great,easy to operate my wife has no problems starting or tending the fire.
We have the system in it's own building,no mess,no chance of fire or carbon monoxide in our home.
Where are you located?I have a bunch of tanks.
Thomas
 

maple1

Minister of Fire
Sep 15, 2011
10,783
Nova Scotia
Hello Red Islander :)

There are all kinds of tanks in Moncton NB, if you can get there with a trailer. That's where I got mine:

http://www.triprovince.com/Resale-Yard.page

Scroll down & start planning. ==c

I'm just building an insulated box around mine. It's a work in progress. I'm getting very little heat off the boiler itself in my basement, & since the basement doesn't have any radiation in it I'm planning to make a door in one end of the box so I can open it up some in winter & let some heat into the basement from the tanks. The door will double as access to the tank drains and tank-to-tank piping if I need to get to them. So my tanks are boiler storage & radiation all in one unit.

EDIT: I did next to no number crunching. I just estimated how much storage to get from reading what everyone here is using, and balancing that with what would fit in my space. If arranged right, good sized storage is like a big forgiving bouncy cushion. With airbags.
 

Redislespud

New Member
Nov 18, 2012
7
I think I will only have room for 1000 gal tank. I have a friend that does sprayfoaming so i will most likely get him to insulate the tank. What else would be required to prepare the tank for use? Is there anything that i should look out for?

Hi Redislespud
Welcome to the site.
I have the Econoburn 200.and 1000 gal of storage.I used two 500 gal propane tanks standing on end.
Today we are at -20c and we will burn about 6 hrs of spruce.
This is the first boiler system i have had,the boiler seems to work great,easy to operate my wife has no problems starting or tending the fire.
We have the system in it's own building,no mess,no chance of fire or carbon monoxide in our home.
Where are you located?I have a bunch of tanks.
Thomas
 

salecker

Minister of Fire
Aug 22, 2010
1,437
Northern Canada
Hi Wade
I'm at the other end of the country.I did have mine sprayfoamed.The guy that runs the nozle dictates the quality of the job.If i did it again i would attach something to judge how deep the foam is.I had a welder weld some extra fittings on them.
I might add more storage in the future,it would be nice to get 24 hrs out of it.
Thomas
 

maple1

Minister of Fire
Sep 15, 2011
10,783
Nova Scotia
Sprayfoaming is good stuff, not much doubt about that.

But if there's any chance you might want to use some radiating heat from your tanks (like to keep your basement warm, or maybe wrap a bunch of pex around them to preheat your DHW), sprayfoaming will prevent that from happening. Just another consideration.
 

dogwood

Minister of Fire
Mar 22, 2009
825
Western VA
If storage is intended to meet system demand between boiler firings, then you need to determine your heat loss btuh and size storage to be able to meet this demand during the times between firing your boiler. Example: if "normal" heat loss is 40,000 btuh and you want to fire once per day, then you need 40,000 x 24 = 960,000 btu available from the boiler/storage. Assume that your burn period is 4 hours, therefore boiler will meet demand for 4 hours and storage will need to meet demand for 20 hours. Needed btu's in storage at end of burn = 20 x 40,000 = 800,000.

If you need 140F water to meet your system demand, and you can heat storage to 190F, then you need about 2000 gal of storage to meet demand solely from storage (2000 x 8.34 x 50 = 834,100). If your system require hotter water, needed storage will increase, and vice versa. If you want storage to meet demand for a longer period, the storage will increase, and vice versa.

Incidentally, 800,000 btu's will require about 200 lbs of wood per burn (960,000 / 6,040 btu-lb / 0.8 efficiency). Efficiency will increase if the boiler/storage is in the space to be heated and efficiency may decrease if not. Btu's per lb of wood is based on 20% MC and 400F stack temp.
The above succinctly put information and example should be in a "sticky". After completing heat loss calculations, anybody contemplating storage could use this info to readily calculate the size storage they need, in conjunction with how many burns a day to plan for. With a little extra work, looking at US Weather Data and degree days for your area, you could probably estimate out how many pounds of wood you might need to put up to dry a year or two in advance for your first year of burning. That is, after converting pounds into cords for the types of wood you have locally.

Nice work Jim.

Mike
 

Tennman

Minister of Fire
Mar 4, 2009
985
Southern Tenn
I totally agree dogwood. JB your post would make such a simple and useful spreadsheet for the next guy who asks this question. Making that spreadsheet is easy, but I don't know how you place it so you can download it from Hearth or a sticky. Good stuff JB.
 
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