Is this too much for an eko 25. I live in Kansas so my winter's aren't quite as severe by low temperature as many of you. I want as much flexibility as I can get on loading my gasser. I live in a 1000 sq ft two story 1900 house with little insulation that has a very small basement. Is 1000 gallon storage too much to handle. Near as I can tell my max heat load is around 30 to 35000 btu/hr. I have base board heating. two years ago when I used propane I could use 9-10 gallon per day.
Is it a bad idea to use a 1000 gall propane tank for Eko 25
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SolarAndWood
Minister of Fire
I'm considering that same configuration. The downside for me is that it is twice the tank I have to purchase, install, insulate, allocate floor space to, etc. The upside is the flexibility of the burn schedule. It will probably take you 4 burns or so to charge the tank while you are heating your house if you let the temperature of your tank drop.
would that make it a challenge to keep storage temp up or would it be a situation where likely a person would be burning to recharge before tank temp got that low. unless you were gone for an extended time. Or is it better to have 500 gall storage to be able to keep up with it better.
mole
Member
Rugar,
I don't think it's to big at all. If we assume you heat your tank to 190deg max and your baseboard heat is "usable" down to 150F water temp, then you're storage capacity is about 333,000 BTU (1000galx 8.34lb/gal x40degF). That'll give you 10 hours storage on your coldest days, so the house will still be warm when you get home from work. I think you'll find that most of the time, (when your heat draw is much lower than 30,000btu/h,) you will be making the fire to recharge the tank, rather than to heat the house....and that's sweet because you can make the fire when it's convenient for you.
I don't think it's to big at all. If we assume you heat your tank to 190deg max and your baseboard heat is "usable" down to 150F water temp, then you're storage capacity is about 333,000 BTU (1000galx 8.34lb/gal x40degF). That'll give you 10 hours storage on your coldest days, so the house will still be warm when you get home from work. I think you'll find that most of the time, (when your heat draw is much lower than 30,000btu/h,) you will be making the fire to recharge the tank, rather than to heat the house....and that's sweet because you can make the fire when it's convenient for you.
stee6043
Minister of Fire
My only concern running 1,000 gallons of storage with an EKO 25 would be how long it takes you to recharge. I myself wish I had an EKO 60 some days. With my tanks down to 140 it takes me a good 2.5 full loads to get my tanks back up to usable temps. That's about 8-10 hours of burning. On week days that tends to keep me out of bed a tad later than I'd really prefer. And when the weather is REALLY cold (well below zero) I'm required to make a midnight run to the EKO 40 for a bonus load.
On the flip side...I don't think you'll get a full day of heat off 500 gallons assuming you really do have 30,000btu heat loss (which is a lot for a 1,000ft house!!).
On the flip side...I don't think you'll get a full day of heat off 500 gallons assuming you really do have 30,000btu heat loss (which is a lot for a 1,000ft house!!).
Nofossil
Moderator Emeritus
I think 1000 gallons would be fine. It's not that you have to get it up to temperature each burn, by the way. All you have to do is put enough heat into it to last until it's convenient to build another fire. You're right that a smaller boiler means it will take longer to heat the tank by any given amount, but that doesn't matter.
Whether you have 200 gallons or 2000 gallons, you'll need to run the boiler enough hours per week to make up the heat that the house loses to the outdoors. At 30,000 BTU/hr, that's 720,000 BTU/day (I agree with the above post that suggests that's WAY high for a 1,000 square foot house).
With an EKO 25, that's about 12 hours of burn time. That's what I need on a worst-case coldest day of the year. My average is about 6 hours per day. That's true regardless of storage. The more storage you have, the more flexibility you have about when to get those six hours in. With 1000 gallons, it could be a 12 hour burn every other day, or six hours each day whenever it's convenient.
By the way - I use water in my baseboards all the way down to 120, although if it's really cold out you need higher water temps than that to get enough heat out of the baseboards.
Whether you have 200 gallons or 2000 gallons, you'll need to run the boiler enough hours per week to make up the heat that the house loses to the outdoors. At 30,000 BTU/hr, that's 720,000 BTU/day (I agree with the above post that suggests that's WAY high for a 1,000 square foot house).
With an EKO 25, that's about 12 hours of burn time. That's what I need on a worst-case coldest day of the year. My average is about 6 hours per day. That's true regardless of storage. The more storage you have, the more flexibility you have about when to get those six hours in. With 1000 gallons, it could be a 12 hour burn every other day, or six hours each day whenever it's convenient.
By the way - I use water in my baseboards all the way down to 120, although if it's really cold out you need higher water temps than that to get enough heat out of the baseboards.
30,000 btu/hr....... Boy, that'd be nice! 
I think this old farmhouse of mine specs out at like, close to 80,000........ :O
And, it's not that big of square footage.... Can't remember right now... But almost surely less than 1500......
I think this old farmhouse of mine specs out at like, close to 80,000........ :OAnd, it's not that big of square footage.... Can't remember right now... But almost surely less than 1500......
35K sounds like a small load... divide it by the square footage then 35 btu/ square foot is a BIG number. Many of todays well insulated homes are coming in in the low 20's some in the teens with ICF or SIPs construction. Certainly look at ways to insulate and tighten up as a excellent payback on $$ spent.
The storage really depends on your participation level. The larger the storage, the longer the "coast" time. Sounds like you have more than enough boiler capacity to cover the load even at design day 35,000 btu/hr. So you have the ability to charge the tank with the home at full heat load.
Larger tanks do take longer to charge, and the heat loss goes up based on the amount of water and surface area. Where will you place 1000 gallons in a 1000 square foot home? You REALLY want the storage inside the heated envelop, even the garage is better than outdoors, if you can, to cut down on unusable losses.
What type of heat emitters do you have. If you have or will have low temperatue like radiant then you have a lot more useable BTUs from storage. Charge the tank to 180 or more and drag it down to 100F or less. With high temperature like fin tube you may need supply no lower than 160F to get enough output. So you have less "flywheel" in that 1000 gallons.
If you are going with an air coil in a furnace have it sized to use the lowest possible supply temperatures to leverage the storage. Coil manufacturers can help you with sizing and custom coils can be obtained in 3-5 days. happy heating.
hr
The storage really depends on your participation level. The larger the storage, the longer the "coast" time. Sounds like you have more than enough boiler capacity to cover the load even at design day 35,000 btu/hr. So you have the ability to charge the tank with the home at full heat load.
Larger tanks do take longer to charge, and the heat loss goes up based on the amount of water and surface area. Where will you place 1000 gallons in a 1000 square foot home? You REALLY want the storage inside the heated envelop, even the garage is better than outdoors, if you can, to cut down on unusable losses.
What type of heat emitters do you have. If you have or will have low temperatue like radiant then you have a lot more useable BTUs from storage. Charge the tank to 180 or more and drag it down to 100F or less. With high temperature like fin tube you may need supply no lower than 160F to get enough output. So you have less "flywheel" in that 1000 gallons.
If you are going with an air coil in a furnace have it sized to use the lowest possible supply temperatures to leverage the storage. Coil manufacturers can help you with sizing and custom coils can be obtained in 3-5 days. happy heating.
hr
Nofossil
Moderator Emeritus
I agree with Hot Water, but I ended up putting my storage outside. If that's the route you have to take, plan for LOTS of insulation. I'd suggest at least a foot on the sides and two feet on the top. You also want to be meticulous about packing / wrapping the insulation so that there's no air passages that would allow convection to carry heat from the tank to the outer layers.
Yes I have done outside tanks also, including in-ground concrete tanks. It's my least favorite location (in-ground) just too many areas to lose heat, cold ground, ground water, etc. Almost impossible to build a good waterproofed underground tank detail.
My tank is semi outside, a shed roof enclosure attached to the side of the shop. I have 4" of foam, and some scrap metal building film wrapped fiberglass, around it. I know it leaks more than I would like. I don't know that you could ever over-insulate an outdoor tank. I'm adding another 4" to mine before winter.
Understood that outdoor may be the only, or best option for some. Deal with insulation and infiltration to the best of you ability, and budget. I think the final wrap of InsulTarp or one of the bubble wrap products, taped at the seams would be a good exterior cover and water proofer.
hr
My tank is semi outside, a shed roof enclosure attached to the side of the shop. I have 4" of foam, and some scrap metal building film wrapped fiberglass, around it. I know it leaks more than I would like. I don't know that you could ever over-insulate an outdoor tank. I'm adding another 4" to mine before winter.
Understood that outdoor may be the only, or best option for some. Deal with insulation and infiltration to the best of you ability, and budget. I think the final wrap of InsulTarp or one of the bubble wrap products, taped at the seams would be a good exterior cover and water proofer.
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Nofossil
Moderator Emeritus
By the way - one other consideration for storage enclosures:
Consider how to keep ot the rodents. Mine is up against the side of the house in an attached enclosure. The little *
!!%^$#^$% mice tunneled through the blueboard that's against the house foundation to get around the ends of the shed walls. They then build little luxury condominiums in my insulation. Mothballs at the least might be good insurance.
Consider how to keep ot the rodents. Mine is up against the side of the house in an attached enclosure. The little *
!!%^$#^$% mice tunneled through the blueboard that's against the house foundation to get around the ends of the shed walls. They then build little luxury condominiums in my insulation. Mothballs at the least might be good insurance.
Eric Johnson
Mod Emeritus
I wrapped the exposed pex lines that go through my barn and greenhouse in foam, fiberglass insulation and then wrapped the whole works in wire mesh to keep the mice, squirrels, etc. from gnawing on the pex and generally fouling the insulation. Like most of us, they like to stay warm in the winter.
I think the 1000 gallons of storage is good, just be sure to super-insulate and have it in the house envelope,basement, etc. In my opinion, usually the larger the better, within reason. More flexibility.
My nieghbor proclaims the other day with a blank exhasberated look on his face "Mice.....You don't stop em(them)......@*@!!"
My nieghbor proclaims the other day with a blank exhasberated look on his face "Mice.....You don't stop em(them)......@*@!!"
Dune
Minister of Fire
Dunebilly said:
If you had a relatively small, well insulated building with an efficient heat delivery system such as radiant floor-- and if you had massive storage in relation to those modest heat needs, then in order to heat your storage up or get it back to temperature, you'd either need to do some long-tended lengthy burns (which could become inconvenient to plan/time or spend time tending), or need use a boiler that would be oversized in comparison to the building's heat needs.
Dune
Minister of Fire
Not to hi-jack this thread, but the co-gen system I am setting up is going to put out way more heat than I can use as it is being created. I have access to a 5000 gallon tank, so I figure I could run the generator until the tank is up to temp, then start it again when the tanks has room for BTUs, but I also have the option of making the tank smaller, if it would work better.
sgschwend
New Member
Good thread,
I am in the process of setting up a system for myself and friend. My system will be ready this year, buddies ran last year. With no storage his system ran very little, he even found times he needed to run his kitchen sink hot water to drain to help load the boiler. On a windy day the draft on the shielded chimney was high enough to keep the fire going which overheat the house (Greenwood). Our hourly load is in the order of 10-15K btu. We live on a large island in the PNW.
I was able to pick up a 500 gallon tank for each of us for $150 each, delivered. In our case I believe 500 gallons will be enough to load our boilers and make it easy to get a days worth of heating/hot water.
We will both need to have the tanks outside so the insulation comments are very useful, we have plenty of mice like creatures too.
I did see a comment in this thread about the tank slowing down the system response. "The simplified storage tank" thread suggests there is an easy way to manage which way the heated water goes giving the house the higher priority. The method is somewhat dependent on the physical layout of the system and the choice of pumps.
I am in the process of setting up a system for myself and friend. My system will be ready this year, buddies ran last year. With no storage his system ran very little, he even found times he needed to run his kitchen sink hot water to drain to help load the boiler. On a windy day the draft on the shielded chimney was high enough to keep the fire going which overheat the house (Greenwood). Our hourly load is in the order of 10-15K btu. We live on a large island in the PNW.
I was able to pick up a 500 gallon tank for each of us for $150 each, delivered. In our case I believe 500 gallons will be enough to load our boilers and make it easy to get a days worth of heating/hot water.
We will both need to have the tanks outside so the insulation comments are very useful, we have plenty of mice like creatures too.
I did see a comment in this thread about the tank slowing down the system response. "The simplified storage tank" thread suggests there is an easy way to manage which way the heated water goes giving the house the higher priority. The method is somewhat dependent on the physical layout of the system and the choice of pumps.
I will be placing my storage outside. I'm tempting the idea of vertical. Wouldn't there be less heat loss in a vertical setup. Minimal area to insulate on top and it can be built to look like a chimney on my small outdoor boiler room. Or is there not much difference in usability and efficiency of vertical vs horizontal.
Thanks for all your good info everyone.
Thanks for all your good info everyone.
Nofossil
Moderator Emeritus
Vertical is generally preferred to get more stratification, but in an outdoor installation it could result in more exposed surface area (loss out the bottom is minimal - better if that's a long side, I think).
As far as whether you can ever have too much - I designed a house once with enough storage for a whole heating season. Loss from storage increases roughly as the square root of capacity - doubling storage volume results in about a 40% increase in heat loss.
The point of diminishing returns is when heat loss from storage starts to become a noticeable percentage of total heat load (for outside storage) or when it results in too-high indoor temps (for indoor storage).
As far as whether you can ever have too much - I designed a house once with enough storage for a whole heating season. Loss from storage increases roughly as the square root of capacity - doubling storage volume results in about a 40% increase in heat loss.
The point of diminishing returns is when heat loss from storage starts to become a noticeable percentage of total heat load (for outside storage) or when it results in too-high indoor temps (for indoor storage).
Nofossil, Make sure im right. You feel the extra efficiency of a tank set horizontaly is more than the benifit of better stratificacion. From my classes in college I always thought the concept was you want the least amount of ceiling therefore reducing the area for the greatest heat loss. Your explanation makes good sense though. I by no means have the right answer. Stratification difference in the two layouts makes sense but is it so much reality. A tank set horizontaly should still have equal stratification, only difference is the layers are not as thick. with correct plumbing is the difference more or less a non signifficant issue. I'm asking the question for more clarification. I don't know the answer.
Nofossil
Moderator Emeritus
This is an area where I'd love to see more hard data.
You're right about minimizing ceiling area in a house, but that's in part because the open area inside the house allows convection cells to form and carry heat up to the ceiling. If convection is minimized, it's less of an issue. Heat loss by conduction isn't any different horizontally vs. vertically. There's a tradeoff between minimizing 'ceiling' area as opposed to minimizing total surface area. I don't have the numbers to say where that tradeoff is.
Stratification gets reduced by turbulence when there's flow into or out of the tank, and it's also lost via conduction in the water. The greater height in a vertical installation means that heat from the top layer has to travel muc farther to heat the water in the bottom. As a thought experiment, imagine stratification in a tank that's 6" in diameter and 20' long. I think it's safe to say that such a tank would get more stratification mounted vertically.
You're right about minimizing ceiling area in a house, but that's in part because the open area inside the house allows convection cells to form and carry heat up to the ceiling. If convection is minimized, it's less of an issue. Heat loss by conduction isn't any different horizontally vs. vertically. There's a tradeoff between minimizing 'ceiling' area as opposed to minimizing total surface area. I don't have the numbers to say where that tradeoff is.
Stratification gets reduced by turbulence when there's flow into or out of the tank, and it's also lost via conduction in the water. The greater height in a vertical installation means that heat from the top layer has to travel muc farther to heat the water in the bottom. As a thought experiment, imagine stratification in a tank that's 6" in diameter and 20' long. I think it's safe to say that such a tank would get more stratification mounted vertically.
This study, see link at bottom, from Denmark explains stratification and some of the concepts being used inside the tank. It is for solar storage but the concepts apply to wood boilers
I'm sure some of these ideas could be homebuilt.
If you have a system that can take advantage of those stratification layers and principles I think a vertical tank would work best.
If your system requires 180 supply and you run the tank at 180- 190, really the stratification levels don't do much for you.
In a typical Euro system they may use the upper, highest temperature, layer for DHW generation. It's rare to see any heating device, over there require over 140F supply. It may be code in some areas in fact. Early Euro imported boilers were set to a max. 75C (167F) on their controls. Some still are. So the next stratification level down would supply panel rads, which are more common than radiant floor in much of Europe.
Then the lowest level of temperature could supply a radiant floor with 100-120F supply.
Then of course the coolest part of the tank, the very bottom returns to the heat input device. Condensing boilers excel at low return temperatures, as do solar arrays, so that bottom cold temperature really drives the efficiency of the heat supplier up.
I think it would be hard to layer a 20" diameter horizontal tank as effectively.
I know long term heat loss from a large tank is hard to model. I've asked some engineers and tank manufactures to do that As the temperature is ever changing inside the tank at those stratification levels. Tanks can easily vary 30F or more from top to bottom. The heat loss changes as the temperature levels change and the ambient air and infiltration changes. Even in a lab setting with sensors every 2" on the tank it's hard to pin down exact numbers. So they tell me.
www.preheat.org/fileadmin/preheat/d...bo_Heat_storage_for_solar_heating_systems.pdf
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I'm sure some of these ideas could be homebuilt.
If you have a system that can take advantage of those stratification layers and principles I think a vertical tank would work best.
If your system requires 180 supply and you run the tank at 180- 190, really the stratification levels don't do much for you.
In a typical Euro system they may use the upper, highest temperature, layer for DHW generation. It's rare to see any heating device, over there require over 140F supply. It may be code in some areas in fact. Early Euro imported boilers were set to a max. 75C (167F) on their controls. Some still are. So the next stratification level down would supply panel rads, which are more common than radiant floor in much of Europe.
Then the lowest level of temperature could supply a radiant floor with 100-120F supply.
Then of course the coolest part of the tank, the very bottom returns to the heat input device. Condensing boilers excel at low return temperatures, as do solar arrays, so that bottom cold temperature really drives the efficiency of the heat supplier up.
I think it would be hard to layer a 20" diameter horizontal tank as effectively.
I know long term heat loss from a large tank is hard to model. I've asked some engineers and tank manufactures to do that
As the temperature is ever changing inside the tank at those stratification levels. Tanks can easily vary 30F or more from top to bottom. The heat loss changes as the temperature levels change and the ambient air and infiltration changes. Even in a lab setting with sensors every 2" on the tank it's hard to pin down exact numbers. So they tell me.www.preheat.org/fileadmin/preheat/d...bo_Heat_storage_for_solar_heating_systems.pdf
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