Froling install question

[dogwood]

I am making my last car payment this month which will free up the money to buy our gassifier. I had been planning to purchase a Baxi (Tarm) Solo Innova 50 and have been planning our install accordingly. Due to some recent favorable financial circumstance, we can afford to finance a Froling Turbo 3000 50 unit instead, which we will acquire from BioHeat USA. Does anyone know what if any differences there may be in the install of the Froling rather than the Tarm. I've read Mr. Brownian's Froling Experimental Install posts a number of times. That installation looked both impressive and a bit daunting.

I saw on a UK site the output for the supply pipe was listed as 1.5 rather than 1.25 inches. Do I need to use the larger pipe to run between the boiler and the forced hot air furnace and DHW tank where heat exchangers will be? This may possibly make a difference in sizing an expansion tank as I have a longish run, about 50 feet, and then back, to the furnace and DHW. BioHeat's piping diagrams are the same for either unit and make no mention of a pipe size difference.

Are there more relays and electrical connections that need to be made to provide input for the many readouts the Froling provides? Is there anything else special or different I'd need to know about for the install? I have a thousand gallons of pressurized storage waiting, and am now sizing all the other components prior to purchase.

If anyone else out there has installed a Froling or has knowledge of their maintenance track record, I'd appreciate any input or suggestions. The potential life span of the electronics does worry me some. My old high end stereo components from the 1970's are difficult to get repaired or find replacement parts for. I really don't want to repeat that experience with the Froling. Heat and electronics are a poor mix as you probably know. On the other hand the Froling units look very well built and designed, so I think I'll take the plunge, unless one of you can scare the dickens out of me. Thanks.

Mike

 

[Gooserider]

The impression I've gotten so far is that lots of us have been drooling over the Froling, but I haven't seen many mentions by people that have actually installed them... From looking at the literature, my thought is that it shouldn't be that much different from any other boilers to hook up, but I haven't compared the install manuals to be sure.

As to the pipe size question, I would say that the first thing you need to do is figure out your optimal pipe size, which is essentially independent of the boiler, and plan on using it - along with whatever adapters are needed to get from the boiler ports to the pipe size you are using. A well designed boiler will have ports that are designed to accomodate the largest pipe size it might be used with, as you can always reduce down, while it is not normally possible to make a port bigger...

Also, note that some of the euro-boilers have metric or other non-US NPT threaded outputs, so you may need some sort of interesting adapter at the ports regardless - check w/ BioHeat, as I'm sure they will have the needed fittings.

Gooserider

 

[dogwood]

I was figuring on running running a loop of 1.25 pipe from the boiler to near the DHW and forced hot air furnace and back; and then probably separate 1.00 inch pipes off that to the flat plate DHW HX and the water/air heat HX in the furnace. I'll be using closely place tees on each separate loop's return to the 1.5 inch main loop and each loop will have their own circ pumps. Seems simple enough, but took plenty of time to figure out. The pipe sizing comes from the Bioheat piping diagrams on their site. Makes sense what you say about boilers having a larger port because you can only downsize, not upsize. I'm just a little concerned about getting in over my head if there are further complications to a Froling install over what you'd normally expect, which is complicated enough. I'm hoping Mr. Browning who has done a Froling install might comment as he would know if there are any. Thanks for responding. You folks are the best.

Mike

 

[DaveBP]

I'm inclined to think that if there's a 1 1/2" output port on the boiler that maybe that is the manufacturer's suggested optimum size, especially if you have a long round trip loop. The volume difference between 1 1/4" and 1 1/2" pipe is about 3 gallons per 100' (someone check my arithmetic). That's only about a pint of water worth of expansion difference. However, the larger pipe has perhaps half the friction to pump against. For a short hookup that might be not worth the price difference, but for a long run that can add up to a larger, more expensive circulator and a lot of pumping electricity over the years.
One of the pros on this forum, Heaterman, posted a list a while back for rules of thumb of efficient heat flow and 50KW (about 170,000 BTU) is right between 1 1/4" and 1 1/2" pipe. Longer runs favor larger pipe. And actually needing all the output regularly would suggest larger pipe, too.
This forum is scattered with tales of upsizing circulators to get enough heat out of their boilers when one size larger pipe probably would have saved some real money in the long term. Maybe someone who is competent at all the plumbing calculations (not me) could give you a more definitive answer and a real pump curve example.
I don't mean to be alarmist and I don't know what current pipe prices are running.

 

[dogwood]

Thanks Dave for your thoughtful response. I'll have to give BioHeat a call about that pipe size issue. I would like to avoid more powerful and electricity consuming circ pumps if at all possible. My idea is to get quality components now, but have reduced operating costs later, for when I'm retired and on a fixed income (only eight years away). The Froling or Tarm and wood heat in general will keep the propane barons at bay. I don't want to give the electric company an opening to exploit. Your input on how the expansion tank will only need to be one pint bigger in volume is quite helpful. I think I've enough info to do that expansion tank sizing calculation now. Circ pump and HX sizing will come next. I'll have to find that Heaterman post again. I do remember reading it. Thanks again.

Mike

 

[jebatty]

It's important not to start the thinking with the size of the pipe fittings on the boiler, 1.5" for example, and instead start the thinking with how many btu's your boiler is designed to deliver, how many btu's you need delivered to each of your zones, what size pipe you need to deliver the btu's, how much pump head will be in your shared pipe load, how much pump head in each zone, and the capacity of circulator(s) you need to move the desired btu's. Also keep in mind future needs, if any. You don't want to add zone(s) later and find that your main pipe supply is undersized. Remember that pump head increases by about the square of gpm's (double the gpm's and pump head is about 4x). There is a great advantage in sizing your pipes to actually meet your load demands, or boiler output capacity for the shared pipe load, rather than trying to meet your load demands by pushing more water through your pipes.

I' guessing that if the Froling has 1.5" fittings, it is designed to have an output up to about 220,000 btu, which translates to 22 gpm at delta-T = 20F, because that is the rated capacity of 1.5" pipe (gpm x 500 x 20). Other pipe sizes and capacities (these actually vary a little depending on whether copper, plastic or steel, but close enough for most purposes):

1/2 “ tube = 1.5GPM = 15,000BTU
3/4 “ tube = 4GPM = 40,000BTU
1” tube = 8GPM = 80,000 BTU
1.25” tube = 14 GPM = 140,000 BTU
2" tube = 22 GPM = 220,000 BTU
EDIT: 1.5" tube = 22 GPM = 220,000 BTU; 2" = 50 GPM

So, plan your system based on boiler capacity and heat loads and the required pipe sizes will be answered automatically. Good luck.

 

[Chris S]

Start your calculations at the Air handler. How many Btus/hr does your air handler coil require, and what is the head loss across the coil. That along with your other loads ( and possible future loads ) will determine your pipe size. Air handler hot water coils often have 3/4 copper connections, but need 1" pipe to feed them, so don't fall into that trap. For header sizing, we figure 1 1/2" pipe to be able to distribute 220,000 btus. , 1 1/4" pipe 140,000 btus. If you're in between, I would go bigger to avoid problems, and save $ on your circulator.
I attended a class once where the instructor stated that the size of the boiler supply pipe provided by the boiler manufacturer is the size pipe that should be used for distribution purposes. This is not always true, as boiler manufacturers will sometimes use one large size outlet ( 2") for instance over a whole line of boilers because it makes manufacturing easier. As I stated above, we've installed hydrocoils with 3/4 connections that are rated for 80,000 btu for example, and simply using a reducer ( increaser) fitting right off the coile is the key to getting the proper flow into one of these.
Finally, if your boiler is oversized for your application, you can only consume the amount of btus in your home equal to the amount of emitters, radiant, hydrocoil etc that you have installed, this sometimes warrants a smaller supply pipe than what the manufacturer provides.

 

[stee6043]

Are you planning on installing your storage right off the bat? Seems to me one of the big reasons the Froling is arguably worth the extra money is it's ability to manage storage temps (in addition to all the tricked out tuning it can do). I personally wouldn't wait to install the 1000 gallons you have. I couldn't stand seeing such a machine idle regularly....

If I may make one suggestion - install at least one extra set of inputs and outputs on your main loop when you do the install. Someday you're going to find a need for them and it'll save you lots of time...

 

[dogwood]

Chris and Jim, you've given me a lot of food for thought to help figure sizing. Thanks. The Froling is rated for 170.7 BTUs which does fall between the crack some on the pipe sizing chart info Jim provided. Other posts frequently mention the BTU claims are often overstated so maybe a lesser diameter supply pipe size would be sufficient. Maybe not with the Froling. When I lived in Germany if you got to the train station for the 4:00 train at 4:01 you could expect see the train pulling out. The Froling is manufactured right next door in Austria, so the BTU rating may be right on time too.

I am allowing for possible future expansion which is one reason why I am going with a larger unit than what I need. My home is 3000 sq. feet, fairly well insulated and sealed. My 80,000 BTU Lennox Pulse forced hot air unit can barely keep up with the heat load. It keeps cycling on and off on colder days. So I'm thinking, between keeping the house warm on the design low temperature day (17 degrees here in Roanoke), plus charging the thousand gallon tank, and allowing for adding a shop and another 680 square feet to the house, I should be OK. I am going to contact Ross at Nationwide coils as other posts suggest, about getting an oversized HX for the forced air plenum. There is already a cooling coil in there and maybe not enough room which is another mess to deal with. I might have to put it on the intake side of the furnace. I've though about putting a more powerful blower in the furnace, but that might make for trouble with the Lennox's designed purpose. The current blower is is 1/3 hp. I've done several heat load calculations and the 80,000 BTU figure is in the ballpark for the majority of them, so I can't figure why the system won't keep the house warm. So I am designing for more BTU's and want to make sure I don't undersize the boilers delivery system in any way.

Chris, pardon my ignorance, but are you using the terms "hydrocoil" and "air handler hot water coils" interchangeably. If your are, and are referring to the HX exchanger to go in the plenum I will make sure to use a one inch feed pipe to that connection. I wasn't sure what size fitting an oversized Water to Air HX could have, and had no idea a larger input pipe than to that fitting might be called for. You also mentioned going with the larger pipe size would save money on the circ. I am confused on this point. Wouldn't it be more costly to be pumping more water through larger pipes and a larger more costly circ pump called for. Maybe the better heat distibution would make for more efficiency and less operating cost?

I've also decided you HVAC and plumbing experts are geniuses. I'm fairly bright, built my own home, did all the electrical and plumbing too; but this pressurized wood boiler installation planning is giving me a run for my money. I'd better bear down and finish reading through the Siegenthaler book. The many posts on this site have been indispensable and very appreciated. I've read and saved an untold number for reference, including the ones above. Thanks again.

One more question. The boiler maintence person at work said that dedicated circulator pumps should be located on the return side of a heat exchanger rather than the supply side for better results, and that a HX coil in the plenum should be located below the cooling coil for better results. Anyone know if this is true. He said he actually has field tested results on the first claim. What do you think?

Stee6043, just caught your reply. Yes the storage is going in first. Good idea about putting in an extra set of inputs and outputs on the main loop during the install, I
hope to put in one of those hydronic clothes dryers in the future if I can find out if they work effectively and efficiently. I'll take your suggestion and do just that. Thanks

Mike

 

[jebatty]

The Froling is rated for 170.7 BTUs which does fall between the crack some on the pipe sizing chart

Don't know if this holds with the Froling, but with my Tarm, rated at 140,000 btu, it will put that out and maybe a bit higher at high burn. A load of wood is not in high burn though from beginning to end. I've come to a rule of thumb for my boiler that average output over a burn, to the point of low to middle coals, is about 70-80% of rated output.

As to going to 1.25 vs 1.5, I would go with 1.5 for my main supply and branch off to zones wit pipe size based on heat load for each zone. The 1.5 will reduce pump head and give you plenty of room to expand down the road. I installed my boiler too, and I undersized the pipe -- big mistake for extra work and cost, as I had to re-do it later.

 

[Chris S]

Hydroair= hot water air handler coils. The pipe size question was answered above ( less friction, less head.)
As to cycling, a properly sized system will run non stop on the design day- the coldest day of the year. Where I live we design for 70 degree indoor temperature when it's zero out, no wind. When it is actually that condition, the heating system should be running nonstop- thats what it's designed for. If it's able to cycle ( rest), it's oversized, and will not operate as efficiently as a properly sized system. This is because during the rest of the heating season it will short cycle. Short cycle= inefficient

 

[dogwood]

Chris, I never did understand the "cycling" off and on of the Lennox Pulse, maybe that's the wrong term. Even if you turned the thermostat up to 90 degrees the furnace would not turn itself back on until it was good and ready after going off, even when you were still not up to temp. I thought the cycling off had something to do with the Pulse technology which was touted for its efficiency. Consequently 70 degrees in the house was the best you could hope for and tough to maintain in the coldest weather. It would also take forever to get the house back up to temp if you were gone for a day and turned the thermostat down in cold weather. If we lived in Minnesota or Maine rather than Virginia we'd have been popsicles long since. And thanks Jim for the advice on pipe size and reduced pump head.

Mike

 

[Gooserider]

You also mentioned going with the larger pipe size would save money on the circ. I am confused on this point. Wouldn’t it be more costly to be pumping more water through larger pipes and a larger more costly circ pump called for. Maybe the better heat distibution would make for more efficiency and less operating cost?

Let me try a somewhat simplified explanation...

You don't necessarily pump more water with a bigger pipe, although your can... There is a sort of balancing act between pressure, volume / flow velocity and pipe size... If you need to move a given volume of water in specified time, then you can either move it at a higher pressure, which will result in a higher flow velocity, in a smaller pipe, or move it at a lower pressure and flow velocity in a larger pipe. Like most things that move, pushing fluids through a pipe generates friction, and the faster you try to move, the more friction and resistance you will encounter.

Bear in mind that the amount of heat you need to move is a function of the temperature differential, and the total volume of water, regardless of the pipe size - the volume of water you need to move does NOT change...

One of the key factors is "fluid velocity" or how fast the fluid travels through the pipes - easiest way to think of this is to imagine a little ball getting dropped into the stream so that it gets carried along at the same speed as the flow, how many feet per minute does it travel...

As a matter of practical application, there are definite limits to how fast you want your fluid to move, as going faster results in possible erosion of the pipes as well as increased flow noise, not to mention the extra energy consumption... On the other hand, roughly speaking, the bigger the pipe, the more it costs for a given length...

When fluid travels through a pipe, it encounters resistance, and that resistance is primarily a function of the speed of flow and the effective length of the pipe loop (Fittings all will have "eqivalent pipe length" values that have to be figured in along with the actual loop length to calculate the "effective length" of the loop) There are complex formulas to figure this out, or tables where one can look it up. The net result is what is referred to as the "head loss" of the loop - which is the equivalent to what the pump would have to do to push water straight up the same distance through that hypothetical "zero resistance" pipe. In order to move the fluid at the specified speed, the pump has to add that much pressure to the fluid in order to make it move.

If you look at the specs on a circulator, you will find what is called a "Pump Curve" - this tells you how much volume a given pump can put out given a specified head resistance - as the head pressure goes up, the pump output volume will go down. You need to choose a pump that preferably will be operating in the middle third of its pump curve (because that is it's most efficient range) and has an output in gpm at the head loss value that corresponds to your pipe loop and the required velocity.

Because a larger diameter pipe will need less flow velocity to get a given volume, it will have a much lower head loss value, so a smaller pump will be able to produce the required pressure needed to get the volume required.

Hope this helps,
Gooserider

 

[dogwood]

That was a great explanation Gooserider. Just the kind of information needed to help me understand what I am trying to do at this point. Thanks so much.

Mike

 

[jbird]

Hello, this is my first post but have been visiting this site for the last year. In fact, the reading I did here is what lead to the purchase of a gassification boiler.
The Froling boiler in the "experimental install" post is in my basement. If anyone is interested in in more pictures of the install or has questions please feel free to ask.
Being that I'm new to these things I could really only comment on how it was installed and how it works in my situation.

Thanks, Jon

 

[heaterman]

Mike, pipe size depends on the GPM you need to carry at a given head, not the fittings on the boiler. A rough rule for sizing to load would be 40,000btu=3/4", 80,000btu=1", 150,000btu=1.25, 210,000=1.5". Those numbers are based on head of no more than 6' per 100' of equivalent length and assume a temp drop supply to return of 20*. If you drop the 0000 off each of those numbers you will have the GPM each will carry. A 15-58 Grundfos will easily move all but the largest of those flows through 100' of equivalent length piping.

 

[dogwood]

Jon, thanks so much for replying especially this being your first post. I really got a kick of seeing a reply from the person who actually owns the "experimental install" Froling boiler. Made my day. How is the Froling working for you? I really am interested in anything you can share on how yours was installed, especially anything to with system sizing, pipe sizing, circ sizing etc, as that is what I am up to at present. Like you, I first read about gassification boilers here and became convinced these are the way to go. What convinced you to go with a Froling and are you pleased that you did? Does it seem to be worth the extra cost? Anything you might share about your set-up and day to day operation, or problems, would be valuable.

Earlier in the post I tried to find out if there were extra electrical connectors to sensors, or the like, to connect into the electronics for readouts. Are there any, or many, to your knowledge? I'd love to see any additional pictures you have of your installation. I've examined the ones in the "Experimental Install" posts a number of times. It's not too difficult to post them on this site. I had to download the Picasa 3 software described on the Boiler Room how to post pictures thread, to shrink the pictures down to postable size, but this only took a minute to do once I figured it out, which took over an hour. I'm sure others would like to admire your pictures as well. Otherwise I'd be more than happy to receive any pictures you'd be gracious enough to email to me at [email protected]. I'd be happy to post them for you too if you wished.

Heaterman, thanks for the pipe sizing and head info and the recommend on the 15-58 Grundfos. You all are filling in the missing info on my design and plans. I've read many of your posts, Heaterman, but did nor anticipate the good fortune of corresponding with you directly. This is really fun, on top of it being the being the major production it is. By the way, this is my nineteenth wedding anniversary today, and my wife is recommending we lay out the extra cash to get the Froling as it seems to be the best quality gassifier available in the U.S. She even wanted to get a 28 ton woodsplitter for our mutual anniversary gift. If you ever find a woman like that don't let her go.

Mike

 

[heaterman]

You are a very lucky man Mike. If you ever let that woman go I will lose all faith in and give up all hope for the male members of our species.:-S
Congrats on your annivesary. Mean Kathy Jean and I will hit 34 years of wedded bliss the first of August. ( I can say that safely because she is in bed sleeping) shhhh

Back to the topic at hand..........

The main thing to establish is your actual heating load. Pipe size, circulator model and all the other details hinge directly on that info.

 

[jebatty]

Heaterman, thanks for the pipe sizing and head info and the recommend on the 15-58 Grundfos.

I'm going to interpret Heaterman's info, which is very good. As to the Froling, at 170,000 btu output, using delta-T=20, flow is 17 gpm. Pump head at 100' equivalent is 3 ft for 1.5" steel pipe and 7.5 ft for 1.25" steel pipe. The 15-58 will move 15 gpm on HI at 3 ft of head and about 12 gpm at 7.5 ft of head on HI. In both cases the flow is on the bottom third of the pump curve. A Taco 007 is 19 gpm and 10 gpm, respectively.

If your heat load is 170,000 btu, both the 15-58 and 007 are undersized for the job.

Point being, again, calculate your actual heat load (including heat to storage), calculate your system pump head, and size your pipe and circulator(s) accordingly to deliver the gpm's you need to deliver the btu's you need.

As delta-T gets smaller, flows increase proportionately, and vice versa, assuming btu's stay the same (delta-T = 10, flow is 34 gpm for 170,000; delta-T = 40, flow is 8.5 gpm for 170,000). If you need or want to load your storage to closer than 20 degrees to boiler output, you will need to move a lot more water at 170,000 btu output to prevent idling. There is nothing perverse about some idling; just that operation without idling would be optimal.

 

[heaterman]

Do you need to move all the output of the boiler through one circuit or will that load be going to different points such as some storage and some for heating or DHW. Any conceptual drawing of your piping strategy? Maybe I missed it somewhere in these posts but is that 170K input of the boiler or output?

 

[jbird]

Dogwood, the boiler works extremely well. I'm sure from the previous post/pictures you can see the boiler was installed with 3 220 gal tanks. The tanks are all piped using 1 1/2" black iron. I will have to look tonight at the model number of the pumps (3) that were installed. The boiler has no problem heating the tanks from aprox. 130 to 190 in one full burn lasting about 5 hours. I was burning pretty much once a day to heat a 600 sq ft in-law apartment with radiant floor heat and a 1500 sq ft area with forced hot air. I’m currently in the process of ripping out the forced hot air system and installing radiant heat in the 1500 sq ft area right now.
As for the additional cost…. It was not all that bad. As an “experimental” install it is my understanding this was really the first Froling sold/installed in the US using the 220 gal tanks. Basically the boiler was discounted a bit and was not that much more than an equivalent Tarm.
To this point the unit has pretty much been flawless other than the occasional bridging of the wood during a burn. This tends to happen when I try and burn wood that may be a bit large or maybe funny shaped (like crotch wood). I just try and put these pieces on top to minimize the problem. It takes less than 10 minutes to get going and fill with wood. Then you walk away. Since the primary and secondary air is automatically adjusted you get a very uniform burn. Another great feature is the automatic smoke bypass. When you open the door the smoke is directed right up the chimney. Absolutely no smoke escapes in to the basement. You can add wood during a burn no problem.

Sorry for the long winded reply. I hope some of this is helpful. I’ll see what I can do about getting some more pictures.

Jon

 

[dogwood]

Heaterman, thanks. I'll have my wife read your post. She'll get a kick out it. Your 34 years of bliss is mighty impressive as well. My 5 heat load calculations seemed to cluster more towards the upper 80k range although some of the calculations I did using different avaiable on-line programs varied quite a bit. the highest was 102k, the lowest, using the program on the CD that came with the Siegenthaler book came in at 49k. Frustrating to say the least. I hope the Slantfin program comes back on line as several posts recommend it. Those calculations do not include what it will take to heat the 1000 gallons of storage I'll be using. I'm figuring all the rest of the output to go into that. There will be outputs for the storage, water/air heat exchanger in the forced hot air furnace, and for the DHW flat plate HX. I have drafted on paper a piping and electrical diagram which I will try to scan and post for input. As a challenge I was trying to come up with something simpler than the Simplest Pressurized Storage Design for a while, but that is a tough nut to crack, especially for an amateur, as I discovered after innumerable hours. Instead I have developed a cheap knockoff which may or may not work.

Jim- I have a week and a half off starting Thursday (first vacation in a year) in which to, among other things, figure out the true meaning of, and calculate all the things you mention in your post; pump head, gpm, pipe size and the like. With all the help in this post and the Modern Hydronic Heating book I think I might be able to do it. I will not permit any boiler, or personal, idling time to sneak in either. Thanks for an informative and very helpful post. Any idea if putting circs on the return side of heat exchangers has any advantage. I was going to put them right after the zones valves at the beginning of their respective lines on the supply sides before being advised otherwise.

Jon- Appreciate the input on your not longish at all, post. Good info about taking five hours to heat, and also raise the temp of your 660 gallons storage 60 degrees. How many hours did Mr. Brownian need to put in your installation. I figure I can muliply that by ten and that's the amount time I'll need to get the job done. Do you utilize the electronic readouts at all? And what are you burning? I understand the controlled burn makes burning softwood possible. Is that true in your experience? I just bought a tandem load of oak to cut to size, but have a bunch of hard locust and soft cedar left for fireplace use that I could possibly use for the boiler. Looking forward to posts of your pictures. Thanks for corresponding. Anything you'd care to share I'd be interested to hear, as well as others I'm sure. One more thing, my wife just asked "How much smoke do you get?".

Mike

 

[Gooserider]

Dogwood - save that Locust for the boiler! The cedar is poor to fair burning wood, and some say that it throws lots of sparks, so that is not unreasonable to put in the fireplace, or use it for shoulder season time in the boiler when you don't need as much output. OTOH, Locust is considered one of the best heating woods there is, as long as it's properly seasoned (which takes a bit longer than usual) - You will find it right up at the top of the BTU charts, at or above oak. It also is supposed to be very fast growing, and capable of re-sprouting from the trunk when you cut it down, so it doesn't need reseeding.

Gooserider

 

[dogwood]

You're right Gooserider, in all respects. And locust never rots. I recently cut up some locust logs from trees the electric company felled seventeen years ago, when they put in the lines for our then newly built home. The logs, other than loosing their bark, hadn't rotted a bit. I am concerned they may be too dry and might burn too hot. Another post suggested burning too dry wood with some greener stuff, so I think I'll mix the older stuff in judiciously with newer wood to avoid unreasonably high temps. I was hoping the Froling's automatic oxygen control function would moderate this possible problem.

Locust trees grow, and regrow, like weeds in Virginia, and are all over our land. Newer growth does have long and vicious thorns. I hope to fell and cut a few while I'm on vacation after that truckload of oak logs gets cut up.

Mike

 

[jebatty]

With your heat load calcs, look likes the Froling will produce plenty of extra BTU's for storage. 1000 gal of water at delta-T of 20 is about 165,000 stored BTU's.

I understand the controlled burn makes burning softwood possible. Is that true in your experience?

The wood the Tarm sees almost exclusively is pine -- red, white and jack. Burns hot, clean and smoke free, just like any other wood. I also burn aspen, almost the softest of the hard woods, and it burns fine. The general rule is, if it's wood, burn it. Locally available wood is mostly red oak, pines, paper birch, and aspen, with a little of a few others. Our wood comes from our own land, which is mostly pines and aspen. so that's what I burn. The key to success with all of these woods is well-seasoned, that is, dry.

I think using a mixture of woods has an advantage. Pines start fast, burn hot, with few coals -- good for the early high burn stage. Oaks start slower, also will burn hot, and good production of hot coals -- good to extend the high burn period with a more gradual burn down at the end, which results in lower boiler end-stage BTU output. In the high burn stage, plenty of BTU's for space heating, with excess to storage. In low burn, may be enough for space heating, or to top off storage, and then draw from storage as needed to supplement the lower BTU output.

The main difference I experience, other than as described, is the amount of ash. A 6-8 hr burn of pines produces about 1 cup of ashes; aspen considerably more; and oak less.