First off, thanks to all of you for the great infomation posted here. I just removed a Biasi wood boiler and intend to replace it with a gasification boiler, probably an Orlan EKO. My house is a 2-story plus the basement for a total of 4200 sq.ft. In addition to the two living floors we have heating zones in the basement for the laundry, spare bedroom and general use area. The house has 6" walls with fiberglass R-19 insulation and Anderson windows. I would like to go to the EKO-60 (205,000 btu) but I am concerned this may be too large for my application, based on their sizing charts. My question is, what are the consequences of going larger than may be necessary with my boiler sizing? I don't plan on having any water storage initially. Also, I may want to run heat to my detached garage in the future so I am thinking bigger may be better. We live near the Quebec border where -30*F is not unusual and daytime temps of 0*F are common in the winter. Any thoughts or advice would be greatly appreciated.
Boiler sizing question-Newbie needs help!
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A heatloss calc will tell you where you stand with regard to sizing. A boiler that is extremely oversized can cause excessive idling, which will produce creosote in areas not normally found in a downdraft... ie secondary combustion chamber, heat exchanger, and chimney. Not to mention reduce efficiency quite a bit.
If you plan on expanding in the future, or adding storage (which I recommend to anyone with any downdraft gasser) there's nothing wrong with putting in a boiler that might be oversized for your current heat load and detuning it a little to reduce the output by reducing the primary air a bit and by keeping the wood loads small enough to limit burn times to around 8 hours or so most of the time. I went through this exact scenario myself in our 4100 sq ft home with a heat loss calc around 110,000 or so. (actual 24 hour average is much less on an "average" winter day, say 35,000... and guessing around 80,000 avg at -15* design temps) The 200,000 Btu boiler worked well the first year when we ran without storage, though we did have to finesse it a little bit. Keep the hottest, but smallest fire in the upper chamber for as long as possible. This will require more tending when you are available to do so... but don't be afraid to load it up to get your 8 hour overnight burn... even 10 or more once in a while. You'll know if you are idling too much, because your turbulators will freeze up tight.
cheers
If you plan on expanding in the future, or adding storage (which I recommend to anyone with any downdraft gasser) there's nothing wrong with putting in a boiler that might be oversized for your current heat load and detuning it a little to reduce the output by reducing the primary air a bit and by keeping the wood loads small enough to limit burn times to around 8 hours or so most of the time. I went through this exact scenario myself in our 4100 sq ft home with a heat loss calc around 110,000 or so. (actual 24 hour average is much less on an "average" winter day, say 35,000... and guessing around 80,000 avg at -15* design temps) The 200,000 Btu boiler worked well the first year when we ran without storage, though we did have to finesse it a little bit. Keep the hottest, but smallest fire in the upper chamber for as long as possible. This will require more tending when you are available to do so... but don't be afraid to load it up to get your 8 hour overnight burn... even 10 or more once in a while. You'll know if you are idling too much, because your turbulators will freeze up tight.
cheers
flyingcow
Minister of Fire
We also get -30 usually in january, sometimes -40. but it's only for a few weeks at most. So you may have a few weeks, most likely 10 days of brutal cold. Don't shoot to size your boiler for those few days. i have a 1800sq/ft 2 story house, on top of a hill in northern maine. Same insulation value as your house. Have a 80,000btu oil boiler that would just keep up in the few days of bone chillin' cold. But it did keep up. Was always told not to have heating/cooling equipment short cycling. With that in mind, i went with a 100,000 btu wood boiler. Works great. BUT I would highly recommend doing a heat loss calc. Do a couple of 'em. Be well worth the time. Some one on this site will tell you which ones are the best. Good Luck
Gooserider
Mod Emeritus
With adequate storage, oversizing is not a big issue, without it, it can be, as stated above...
Do the heat loss calcs, and see what they suggest, keeping in mind that the "real world" output of a gasser is probably closer to about 75% of it's nominal rating - mostly because of the inherently cyclical nature of a fire, it only puts out the rated output for part of the time, so the average is closer to 75% or so...
One formula I've seen says do the heat loss, and go for the next larger size boiler. If the next size up is within 10%, go for the second size up. Seems like a reasonable starting point...
Gooserider
Do the heat loss calcs, and see what they suggest, keeping in mind that the "real world" output of a gasser is probably closer to about 75% of it's nominal rating - mostly because of the inherently cyclical nature of a fire, it only puts out the rated output for part of the time, so the average is closer to 75% or so...
One formula I've seen says do the heat loss, and go for the next larger size boiler. If the next size up is within 10%, go for the second size up. Seems like a reasonable starting point...
Gooserider
huffdawg
Minister of Fire
Not that my situation was the same for anyone else but I have tried 3 or 4 contactors to do a heat loss calc. on my place and shop . All of them just wanted the drawings for my place and didnt want to come over and actually take measurements ,see what the floor coverings were ,what way the house was facing ,if you have insulation between the 1st. and 2nd. floor and in your interior walls ect....
So unless a contractor comes over and actually has a look at all the different variables to do with your house ,you most likely wont get a very accurate heat loss calc. anyway.
But I guess a ball park figure is better than nothing.
I read this on the radiant design institute , and not that its gospel or anything but it might give you a rough estimate that you could get for yourself quite easily. If there is any merit to it.
Without a doubt the most common problem we see today
is the over sizing of the boiler, in all types of hydronic heating systems.
Several things have contributed to this problem. First is that insulation and construction values have changed dramatically in the last fifteen years. Heat loss requirements have went from an average of thirty five Btu. per square foot to less than fifteen Btu. per square foot. This has taken heat loss requirements for a three thousand sq. ft. house from over one hundred thousand Btu. to less than fifty thousand Btu.
Second is the fact that boilers have increased in efficiency from about seventy five percent to eighty five percent.
Third is that boiler construction has changed, today's boilers weigh about one half to one third of what they did twenty years ago. This contributes to higher fire side temperatures, and a lower boiler mass to absorb thermal shocks, leading to a shortened boiler life.
Fourth is the reduced amount of water in the boiler, many of today's boilers hold less than five gallons, often boiler cycles are reduced to three or four minutes, this can reduce efficiency to less than fifty percent. Installing a primary boiler loop with a secondary heating loop will not increase the boiler volume appreciably. Most radiant heating systems require less than two gallons per minute if only one zone is calling for heat.
Last and not least is the nature of the average plumber, who like all of us, if he has not run an actual heat loss on the structure, wants to make sure he is not under sizing the system. With increasing house sizes, shrinking boiler sizes and shrinking heat loss requirements, it is nearly impossible to guess the proper size of boiler.
With most residential new construction, sizing the boiler at twenty Btu's per sq. ft. of heated space is more than adequate, many of the more advanced construction methods are realizing heatloss under 10 Btu's per Sq. Ft..
Combo systems that hold twenty or more gallons of water are immune to these problems and over sizing has no effect on the efficiency or life of the heater.
All radiant systems should use a modulating boiler or a tank type heater.
( With most residential new construction, sizing the boiler at twenty Btu's per sq. ft. of heated space is more than adequate, many of the more advanced construction methods are realizing heatloss under 10 Btu's per Sq. Ft..)
Im curious does any of the members here that are in the know about heat loss calculations agree with the statement in brackets
Cheers Huff
If nothing of what I just posted makes sense its because I have had a few rhum and eggnogs!
So unless a contractor comes over and actually has a look at all the different variables to do with your house ,you most likely wont get a very accurate heat loss calc. anyway.
But I guess a ball park figure is better than nothing.
I read this on the radiant design institute , and not that its gospel or anything but it might give you a rough estimate that you could get for yourself quite easily. If there is any merit to it.
Without a doubt the most common problem we see today
is the over sizing of the boiler, in all types of hydronic heating systems.
Several things have contributed to this problem. First is that insulation and construction values have changed dramatically in the last fifteen years. Heat loss requirements have went from an average of thirty five Btu. per square foot to less than fifteen Btu. per square foot. This has taken heat loss requirements for a three thousand sq. ft. house from over one hundred thousand Btu. to less than fifty thousand Btu.
Second is the fact that boilers have increased in efficiency from about seventy five percent to eighty five percent.
Third is that boiler construction has changed, today's boilers weigh about one half to one third of what they did twenty years ago. This contributes to higher fire side temperatures, and a lower boiler mass to absorb thermal shocks, leading to a shortened boiler life.
Fourth is the reduced amount of water in the boiler, many of today's boilers hold less than five gallons, often boiler cycles are reduced to three or four minutes, this can reduce efficiency to less than fifty percent. Installing a primary boiler loop with a secondary heating loop will not increase the boiler volume appreciably. Most radiant heating systems require less than two gallons per minute if only one zone is calling for heat.
Last and not least is the nature of the average plumber, who like all of us, if he has not run an actual heat loss on the structure, wants to make sure he is not under sizing the system. With increasing house sizes, shrinking boiler sizes and shrinking heat loss requirements, it is nearly impossible to guess the proper size of boiler.
With most residential new construction, sizing the boiler at twenty Btu's per sq. ft. of heated space is more than adequate, many of the more advanced construction methods are realizing heatloss under 10 Btu's per Sq. Ft..
Combo systems that hold twenty or more gallons of water are immune to these problems and over sizing has no effect on the efficiency or life of the heater.
All radiant systems should use a modulating boiler or a tank type heater.
( With most residential new construction, sizing the boiler at twenty Btu's per sq. ft. of heated space is more than adequate, many of the more advanced construction methods are realizing heatloss under 10 Btu's per Sq. Ft..)
Im curious does any of the members here that are in the know about heat loss calculations agree with the statement in brackets
Cheers Huff
If nothing of what I just posted makes sense its because I have had a few rhum and eggnogs!
I'm by no means an expert on all the building methods that are out there, but I would tend to agree with what is in the brackets. We've been doing our share of heat loss calcs these days, and two things I have concluded -
1) The average home in America has an oversized furnace or boiler at design temps
2) Most heat loss calcs, including the IBR method, tend to be a little on the high side.
Wood boiler sizing is as much an art as it is a science. Too many variables to pin down boiler sizing perfectly, especially when trying to balance burn time and efficiency with these downdrafts. Thermal storage is by far the easiest way to make sure you're getting the most out of your system.
One thing to keep in mind is that every boiler is going to be "oversized" except on a design temp day. Just another reason to add heat storage.
cheers
1) The average home in America has an oversized furnace or boiler at design temps
2) Most heat loss calcs, including the IBR method, tend to be a little on the high side.
Wood boiler sizing is as much an art as it is a science. Too many variables to pin down boiler sizing perfectly, especially when trying to balance burn time and efficiency with these downdrafts. Thermal storage is by far the easiest way to make sure you're getting the most out of your system.
One thing to keep in mind is that every boiler is going to be "oversized" except on a design temp day. Just another reason to add heat storage.
cheers
Gooserider
Mod Emeritus
My personal take on it is that, unfortunately we seem to have a lot of "experts" that aren't as willing or knowledgeable as they should be - regardless of what they paint on the sides of their trucks, and what pieces of paper they get from the government... Therefore if you want it done RIGHT, you really ought to do it yourself... There is enough info and programs on the net to allow one to do a reasonably good Manual J heat loss calculation without all that much trouble - and without incurring a lot of costs...
Gooserider
Gooserider
ffspeed
New Member
Things may have changed a bit over the years since I went to school for heating and ac. But calculating heat loads and loss, isn't something you are going to knock out in five or ten minutes, and be any where near right. Even if there is a program to do the math, and has the charts and graft, it is still going to take some time.
Singed Eyebrows
Minister of Fire
I am relatively new here & no expert. That said, I feel storage is not an afterthought or an option, it is part of your boiler. There are used tanks that can be modified if funds are low. As was mentioned if you run storage a larger/oversized boiler isn't a problem, you just want to be sure your chimney can handle it though. Look at your gas/oil bills, how warm did you keep your house, how much warmer did you want it? This should give you some idea of demand. Did the Biasi keep up well. I hear they put out the heat with lots of creosote though, RandyBliz said:
Gooserider
Mod Emeritus
ffspeed said:
Didn't say it was an "instant" process, just that it could be done with the help of some of the tools on the net, and without an extraordinary amount of effort... And that even with the more rudimentary tools, the results are likely to be more accurate than the rule of thumb guesstimate that you seem to get from most of the "professionals" We got a new gas furnace and AC system a few years ago, (before I knew about Hearth.com) and had a very large number of "pros" come in - NOT ONE said anything about doing a heat load. Most were happy just to look at the label on the old furnace, and a couple guessed at the house size (didn't measure it) and did a rule of thumb guess based on that.... I didn't know what to expect then, but in retrospect I would have been distinctly underwhelmed...
Gooserider
Thanks for all the advise and info. I have spoken to a number of people I consider knowledgeable, including Eric Johnson, and have decided I am going to go with the EKO-40, rated at 137,000 btu. My Biasi boiler was rated at 120,000 btus and that would keep the house at 74*F easily in the winter. Before we had it my wife always complained the house was too cold then after getting it the house was too hot. We often had a kitchen window open and I often left a basement window open for fresh air and to get the smoke smell out. The Biasi was a good heater but the smoke when you opened the door was horrible. As far a creosote, it wasn't bad in the cold weather but in fall weather the thing was a creosote factory. I ordered my Orlan today and hope to have it up and running in the next couple weeks. I have grown to hate the sound of my oil burner coming on.
Good luck with your new boiler. Just a note, if smoke rollout was an issue before, you may consider getting a draft inducer with your Eko for reloading. A design issue common among some downdrafts is the stack exiting below the top of the upper chamber door. Without significant draft, smoke will definitely roll out. It's not something you can't work around, but it's definitely something to consider.
cheers
cheers
Piker, I did order a draft inducer with my new unit. Dave from Cozyheat was very helpful in discussing my setup with him and he suggested it as well. Thanks-Bliz
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