how much, and how long

[fabguy01]

I know that there are alot of variables, but just out of curiosity was wondering about other peoples setups. What type of boiler, how many gallons of storage, and how much time does it take to get your whole system up to full temp from room temp. Thanks

 

[SolarAndWood]

I've been going round and round with this as my tank has to go through a temporary hole in a wall that is getting finished this fall. My original goal was to completely eliminate the need for anything other than the wood boiler. So, big storage and a good size boiler to charge it conveniently. In the end, I think I have come to the opposite conclusion, use as little storage as possible to make the smallest boiler that will do the job always run efficiently. The big considerations for me were complexity, cost and floorspace. The downside of the small boiler/small storage strategy is that I will likely always have a fire going in the winter and if I am wrong about my heat demands or we have an extended cold snap with limited solar gain, I will have a penalty fire going in the wood stove as well. Not the end of the world for me and it keeps the system simpler, smaller and cheaper.

 

[Gooserider]

A second downside of the small boiler approach is that any boiler that is big enough for dealing w/ "design day" temps is going to be much to big to run efficiently during shoulder season temps... A moderate size boiler w/ a good size storage setup you don't really care about the outside temps as you are always going to be mostly charging the storage so you can always burn clean. The only thing the outside temps would affect is the frequency w/ which you would need to build your recharging fires.

This doesn't mean grossly oversizing the boiler - the advice I've gotten is that I should figure my design day heat load, and go to the next boiler size bigger than the minimum that would handle it.

Gooserider

 

[jebatty]

I know that there are a lot of variables, but just out of curiosity was wondering about other peoples setups. What type of boiler, how many gallons of storage, and how much time does it take to get your whole system up to full temp from room temp. Thanks

I only will address getting storage up to "full" temp, as my storage tank functions as a radiator to heat my shop. The tank is about 3/4 insulated, 1/4 exposed, with options to add or remove insulation as less or more heat is needed.

Tarm Solo 40, 1000 gal pressurized storage. A "normal firing" is 4-6 hours burn time. Typically bring storage from a low of 110F-120F to a high of 150F to 170F, depending on outside temp. If I'm going to be gone for several days, again depending on outside temps, I can easily bring entire 1000 gal storage to 190F.

Warm winter days: +20F to +40F -- one normal firing every 2-5 days.
Normal winter days: 0F to +20F -- one normal firing per day.
Cold winter days: -30F to 0F -- one normal to long firing per day (4-10 hours burn time, approx)

All of this is variable, as wind conditions, high or low within the temp range, cloudy or sunny, etc., all impact need for btu's. Also, I don't pay too much attention anymore to any of this. I just fire the boiler as needed to keep the shop warm.

 

[Duetech]

Great info jebatty. Length of burn time, length of time between burns and efficiency of burn time are the key factors for setting up a system with storage.

SolarAndWood, My system is not yours nor are our parameters the same. My preference is for a little larger boiler with a larger storage for optimum efficiency. Nofossil uses the concept of a smaller boiler but with large storage and does well. Overall, as Jebatty's usage breakdown shows, the larger storage can give you greater freedom from attending the fire as long as you don't oversize the storage.

 

[stee6043]

To answer one of your original questions - bringing the water in storage up from room temp to full temp should really only happen once a year. Unless you take some extended breaks from heating with wood, of course.

I heat with an EKO 40 and bringing 1,000 gallons of storage up to usable temps from room temp (without heating the home at the same time) is a good two/three day process. When you have 60 degree water in your tanks your mixing valve doesn't let much through. As a result the initial heating of the tanks is a slow process.

Once I'm running regularly (in the cold months) I have to burn roughly 6-8 hours per day to maintain constant usable heat in my tanks. I typically start a fire when I get home from work at 5PM, fill the firebox again at roughly 8PM and on the average winter day I'll have to throw another half load on before I go to bed at roughly 10PM. Last year there were two stretches of 2-3 days where I would actually set my alarm for 1AM and throw another load on. These were the days with lows in the -10 to -15 range and highs not much above zero, no sunshine.

 

[SolarAndWood]

SolarAndWood, My system is not yours nor are our parameters the same. My preference is for a little larger boiler with a larger storage for optimum efficiency. Nofossil uses the concept of a smaller boiler but with large storage and does well. Overall, as Jebatty's usage breakdown shows, the larger storage can give you greater freedom from attending the fire as long as you don't oversize the storage.

I'm not convinced you can oversize the storage especially if any heat loss goes into the building you are heating. However, there are escalating costs and diminishing returns. We are used to attending a fire 24/7 and don't really mind it. The choices I see are maintain a fire largely 24/7 in an 85K unit with 500 gallons of storage, a Garn 1500 and single fire or something in the middle with the 135K unit with 1000 gallons of storage. Each allows efficient operation of their respective boilers and has its benefits/drawbacks.

The biggest benefit in my mind of large storage is actually during the summer for DHW when I'm not maintaining a fire daily. However, that benefit is quickly overcome by solar dhw.

 

[in hot water]

At days end the storage size is really a personal preference choice. It serves multiple functions, overheat dump, off fire storage, possibly a shop radiator.

Once you combust the fuel the HX process is always working against you. Transfering the energy takes power, and brings heat loss along with it. Storing it adds additional loss. Then moving it out to the load costs loss in transfer. Eventually mother nature grabs it all back.

In a perfect world the boiler could adjust to an ever-changing load, shut down and start up as required without supervision.

I feel the biomass/ pellet boilers are extremely close to that goal. wood or solid fueled boilers, today are much better at limiting themselves when the load lightens or is satisfied. Dump zones really are not as big as a deal with todays equipment (operator error excluded) if you build the fire according to the projected load.

Vertical tanks make more sense, keep the hottest temperature up where the HXers reside, the cooler temperature low to drive the heat source (solar or wood) to it's best efficiency. Insulate to the best of your budget. Even with a fairly well insulated 500 gallon LP tank in my 1800 sq ft shop, I still over-heat at times.

Personally I think storage can be and is over done, but really, only you can decide what fits your installation and lifestyle, and what pros outweigh the cons.

There are formulas to help you run some what ifs before you breakout the tools and checkbook.

hr

 

[chuck172]

Correct me if I'm wrong but doesn't the size of storage relate directly to the length of burn time. That means it's just a matter of convenience whether you burn 4 hrs. to bring a 500 gallon tank up to temp or burn 8 hrs. to heat a 1000 gallon tank. Of course the 1000 gallon tank will last twice as long.

 

[sdrobertson]

Boiler - EKO 60
Storage - 2000 gallons pressurized (4 propane tanks standing on end)
One heating zone to air handler in NG furnace

I work 12 hour days (gone from house almost 14 hours) so my schedule is really different-I wanted to go 3 days without burning if possible

Below is a summary of most of last year(just a estimate as I didn't keep real good notes--burn times were around 14 hours)

Day----------Boiler/Storage-------------On/Off Duty(Work)
Friday-------Storage---------------------On
Saturday----Storage--------------------On
Sunday------Storage--------------------On
Monday------Boiler----------------------Off
Tuesday-----Boiler----------------------Off
Wednesday-Storage--------------------On
Thursday----Storage--------------------On
Friday-------Boiler-----------------------Off
Saturday----Storage--------------------Off
Sunday------Boiler----------------------Off
Monday-----Storage--------------------On
Tuesday-----Storage--------------------On
Wednesday--Boiler---------------------Off
Thursday----Boiler----------------------Off

This is a two week schedule that I work so this repeats itself throughout the year. On the last Thursday of the above schedule before my 3 day work weekend I have to burn as hard as I can and I get the storage up to 198 degrees at the top and the bottom is as close to 185 degrees as I can get it. Of course this burning schedule depends on the temps so I do adjust it accordingly. On the third day in really cold weather I'm really pushing it because of my air-handler needing at least 120 degree water so I may sneak in a burn.

 

[in hot water]

Correct me if I'm wrong but doesn't the size of storage relate directly to the length of burn time. That means it's just a matter of convenience whether you burn 4 hrs. to bring a 500 gallon tank up to temp or burn 8 hrs. to heat a 1000 gallon tank. Of course the 1000 gallon tank will last twice as long.

It depends on the load when you are trying to "charge" the tank.

If the building is at design day, or load and the boiler is sized exact then you really aren't adding to the tank at all.

On a mild no heat call, day, all the power of the wood load can transfer to the tank.

And anything in between see a portion of the boiler going to the load, and a portion to the tank. Which is where primary secondary piping applies nicely. Each "job" gets what the boiler can afford efficiently and accurately, no guessing as to what flow is going where, how, and why.

So the charge time depends on what is happening with the loads, be they DHW and or heat.

The best formula takes the loads into account when calculating the tank charge times. I posted Siggy's loooong formula here sometime last year. I will try to find it again. It really is the most accurate way to size, if you want to do the math.

Or the" two size" fits all 500, or 1000 gallon method.

hr

 

[Gooserider]

Correct me if I'm wrong but doesn't the size of storage relate directly to the length of burn time. That means it's just a matter of convenience whether you burn 4 hrs. to bring a 500 gallon tank up to temp or burn 8 hrs. to heat a 1000 gallon tank. Of course the 1000 gallon tank will last twice as long.

Somewhat, but it is also important to relate the size of the storage tank to the output of the boiler - the ideal is that you run the boiler flat out for the entire load of wood, and the storage tank would just reach it's max operating temperature as the boiler finished burning the load... Theory says that the boiler should never need to idle because it is putting out more heat than the load can accept... If it was just a boiler and tank this would be pretty easy to figure out; but in practice you have a bunch of other loads that are more variable in their demands (DHW, house heat, etc) that are going to be pulling heat as well, and that makes it harder to figure.

My take would be to say what size tank would ONE full load of wood take from "minimum useable" to "maximum operating" temps if there were NO other demands, and set that as the minimum size. That way you can accomodate any heating scenario. Once you add the other demands in, you can make the call as to whether to add a fractional load of wood to finish heating the storage, or let the fire burn out and live off whatever is in the tank until it drops to minimum useable again... (Remember, there is no rule that says you have to fully charge the tank during each burn cycle...)

Gooserider

 

[jebatty]

For some actual data on "how much, how long" where essentially just the tank is being heated, take a look at my three charts in Tank Heating

The second two charts also record the amount/weight of wood burned.

 

[chuck172]

No idling is the key. That about rules out no-storage. If I were to burn one full firebox of wood, depending on the heating demand, some heat would go to the heating load and some to storage.
More to storage when there is little call for heat or dhw.
Whether I have 500 or 1000 gallons depend on what how much time I'd like to invest in that burn. That's why I say storage amount is a matter of convenience.
With 500 gallons of storage, one load of wood, a TarmSolo 40, (140,000 btu's) I get little or no idling regardless of the heat load. I surly would be able to live on 1000 gallons of storage twice as long but I would have to adjust that burn time accordingly.

 

[SolarAndWood]

For some actual data on "how much, how long" where essentially just the tank is being heated, take a look at my three charts in Tank Heating

The second two charts also record the amount/weight of wood burned.

Your data and Nofossils are great. Reality is a nice compliment to theory when making these decisions. Have you come to any conclusions about how high you can efficiently heat your pressurized tank before you are just stuffing wood in the boiler? I assume your direct radiator approach is effective significantly below 120F?

 

[jebatty]

Have you come to any conclusions about how high you can efficiently heat your pressurized tank before you are just stuffing wood in the boiler?

With tank return temp about 160F and below, there is little or no boiler idling. As tank return temp continues to rise, idling will increase. In any system this is very dependent on gpm's moving and delta-T. At 8 gpm and delta-T of 20 (assume tank return 160 and boiler output 180), only 80,000 btu's will move, which means the boiler will cycle off if boiler output is higher than 80,000 btu's. As the charts demonstrate, actual boiler output is quite variable, depending upon the burn rate (related in part to stack temp) and the stage of the burn. Output will be highest in about the second 1/4 to middle 1/3 of the burn.

The charts also demonstrate the high level of tank stratification, even in a horizontal tank, at these flow rates. The tank heats very much top to bottom, keeping the lowest temp return water from the tank nearly until all the water above is heated. There is very little mixing occurring.

I assume your direct radiator approach is effective significantly below 120F?

This is very dependent on outside temperature. Top of tank 120F and bottom of tank much lower often still provides the heat I need. I also "modulate" the radiation performance by removing one 2' section of insulation (a 6" batt around the tank) or by adding 2'-4' of insulation on the otherwise open top of the tank. When it's really cold here (-20 to -30F and below), I need to heat the tank into the 180 range and even remove some insulation to get the heat I need for a comfortable shop (about 60-68F). Then if we get a fast warm-up, I can end up with 75-80F in the shop. Not bad, just have to open a window.

 

[DaveBP]

When it’s really cold here (-20 to -30F and below), I need to heat the tank into the 180 range and even remove some insulation to get the heat I need for a comfortable shop (about 60-68F). Then if we get a fast warm-up, I can end up with 75-80F in the shop. Not bad, just have to open a window.

Sounds like the next level of automation is a dump-scrounge garage door actuator and thermostat to raise and lower the batts. Goldberg Lite.

 

[SolarAndWood]

At 8 gpm and delta-T of 20 (assume tank return 160 and boiler output 180), only 80,000 btu's will move, which means the boiler will cycle off if boiler output is higher than 80,000 btu's.

So, when you heat your tank to 190, you are adjusting the flow from some minimum when the delta is large to some maximum when the delta is small to minimize power consumption and keep the boiler from idling? Is 190 as high as you go? Do other inefficiencies come into play when you get above boiler output temp?

 

[SolarAndWood]

When it’s really cold here (-20 to -30F and below), I need to heat the tank into the 180 range and even remove some insulation to get the heat I need for a comfortable shop (about 60-68F). Then if we get a fast warm-up, I can end up with 75-80F in the shop. Not bad, just have to open a window.

Sounds like the next level of automation is a dump-scrounge garage door actuator and thermostat to raise and lower the batts. Goldberg Lite.

Not far from what I'm thinking...several foam sandwich guillotine doors covering compartments. Maybe even just insulating blinds with magnetic strips.

 

[jebatty]

So, when you heat your tank to 190, you are adjusting the flow from some minimum when the delta is large to some maximum when the delta is small to minimize power consumption and keep the boiler from idling? Is 190 as high as you go? Do other inefficiencies come into play when you get above boiler output temp?

I don't make this too complex. I have an aquastat on the boiler supply line before the Termovar set at 160F "on." When the boiler is fired cold, hot water rises by thermo-siphon into the supply line until the aquastate is "on." The aquastat turns on a Grundfos 15-58 set at MED and continues to recirculate hot boiler water until the Termovar opens, which then shunts hot water into the system (to the tank). The 15-58 is "on" until the "off" differential (about 150-155) is reached. Flow (gpm) to the tank with the 15-58 relates to how much the Termovar is open.

I have a second aquastat set to "on" at 180F. This aquastat turns "on" a Taco 007 installed at the tank. So, as boiler output rises, gpm's will increase as the 007 turns on. The 007 is off at about 175F.

And that's it. At high boiler temp output, I get extra gpm's. This boost minimizes idling. It is a very simple "modulated" system.

I can't drive the tank any higher than about 190-193, as the Tarm shuts down the draft fan (idle) at about 185F or a little higher. After the draft fan shuts down, boiler temp will continue to rise some, usually to about 190 with 195 the maximum. So 190F hot water is about the hottest I can supply.

 

[fabguy01]

Have you come to any conclusions about how high you can efficiently heat your pressurized tank before you are just stuffing wood in the boiler?

With tank return temp about 160F and below, there is little or no boiler idling. As tank return temp continues to rise, idling will increase. In any system this is very dependent on gpm's moving and delta-T. At 8 gpm and delta-T of 20 (assume tank return 160 and boiler output 180), only 80,000 btu's will move, which means the boiler will cycle off if boiler output is higher than 80,000 btu's. As the charts demonstrate, actual boiler output is quite variable, depending upon the burn rate (related in part to stack temp) and the stage of the burn. Output will be highest in about the second 1/4 to middle 1/3 of the burn.

The charts also demonstrate the high level of tank stratification, even in a horizontal tank, at these flow rates. The tank heats very much top to bottom, keeping the lowest temp return water from the tank nearly until all the water above is heated. There is very little mixing occurring.

I assume your direct radiator approach is effective significantly below 120F?

This is very dependent on outside temperature. Top of tank 120F and bottom of tank much lower often still provides the heat I need. I also "modulate" the radiation performance by removing one 2' section of insulation (a 6" batt around the tank) or by adding 2'-4' of insulation on the otherwise open top of the tank. When it's really cold here (-20 to -30F and below), I need to heat the tank into the 180 range and even remove some insulation to get the heat I need for a comfortable shop (about 60-68F). Then if we get a fast warm-up, I can end up with 75-80F in the shop. Not bad, just have to open a window.

Wouldent it be eisier to put in awater toair HX with a fan on a t-stat?

 

[stee6043]

Have you come to any conclusions about how high you can efficiently heat your pressurized tank before you are just stuffing wood in the boiler?

With tank return temp about 160F and below, there is little or no boiler idling. As tank return temp continues to rise, idling will increase. In any system this is very dependent on gpm's moving and delta-T. At 8 gpm and delta-T of 20 (assume tank return 160 and boiler output 180), only 80,000 btu's will move, which means the boiler will cycle off if boiler output is higher than 80,000 btu's. As the charts demonstrate, actual boiler output is quite variable, depending upon the burn rate (related in part to stack temp) and the stage of the burn. Output will be highest in about the second 1/4 to middle 1/3 of the burn.

The charts also demonstrate the high level of tank stratification, even in a horizontal tank, at these flow rates. The tank heats very much top to bottom, keeping the lowest temp return water from the tank nearly until all the water above is heated. There is very little mixing occurring.

I assume your direct radiator approach is effective significantly below 120F?

This is very dependent on outside temperature. Top of tank 120F and bottom of tank much lower often still provides the heat I need. I also "modulate" the radiation performance by removing one 2' section of insulation (a 6" batt around the tank) or by adding 2'-4' of insulation on the otherwise open top of the tank. When it's really cold here (-20 to -30F and below), I need to heat the tank into the 180 range and even remove some insulation to get the heat I need for a comfortable shop (about 60-68F). Then if we get a fast warm-up, I can end up with 75-80F in the shop. Not bad, just have to open a window.

Wouldent it be eisier to put in awater toair HX with a fan on a t-stat?

I was having the exact....same.....thought.

 

[SolarAndWood]

And exhaust the fan outside? The problem is you have 1000 gallons of storage radiating directly into a space that no longer requires the heat. The only solution to that is open the window or super insulate the tank and build a way to control how much area of the tank is exposed to the space at any given time.

 

[jebatty]

Wouldn't it be easier to put in a water to air HX with a fan on a t-stat?

I don't think this provides any substantial benefit. Don't get the idea that I have to move much insulation or move it often. I have to move it maybe once every 2-4 weeks or so, and it takes about 2 minutes to do this. The main ideas of my system are to 1) move heat from the boiler to storage with no to minimal boiler idling, thereby achieving maximum full burn gasser boiler efficiency, and 2) heat the shop comfortably without any electrical power consumption.

The unit heater does nothing to accomplish either of thee goals. And for those of you with in-floor radiant heat with a concrete slab, you know how even the heat is. The big 1000 gal radiator storage tank is pretty much just like that, absolutely even, consistent heat, without drafts, hot spots or cold spots, and no electrical power to make it work.

 

[SolarAndWood]

The big 1000 gal radiator storage tank is pretty much just like that, absolutely even, consistent heat, without drafts, hot spots or cold spots, and no electrical power to make it work.

That is a pretty good argument for using cast iron radiators as well.