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Replacing Oil Boiler with Indoor Wood Boiler

OakLumber
OakLumber Member Posts: 18


Ok, I’ve read through a lot of discussions here, and still have a few questions about retrofitting an existing oil boiler with a new wood boiler. I apologize if some of my questions are duplicate, but I’m not a boiler expert. Anyway, some basic points and info:

1. 4500 sq foot home in Maine
2. In-floor heating throughout home.
3. Existing boiler is a Buderus, and the boiler and all controls are located in a mechanical room. Other than paying $6/gallon for oil, it is functional and works fine.
4. I have an endless supply of firewood available for just the labor, and yes, I’ve been cutting firewood for forty years so I’m aware of the work involved. There is room inside the basement right where the new boiler will be to keep all my firewood.
5. The new wood boiler will be a pressurized system, but will not be located in the mechanical room, and will be in the other end of the basement instead, about 40 feet away, but on the same level.
6. Having the systems working completely in parallel is not important to me. I’d be content to disconnect the old system and connect the new one (with shut off valves) and only connect it again if we were leaving for a couple of weeks and didn’t want the house to freeze.

Some questions:

1. There is a false ceiling in the basement, and I wanted to run the pipes from the wood boiler straight up and then through the ceiling and down again. Any problems with that?
2. To connect the new boiler, is it a matter of bringing the new lines down to the existing pipes that come out of the old boiler? Is there a problem with the new boiler being further away?
3. With an oil boiler, obviously I can just turn off the burner when it reaches temperature, but a wood boiler can’t do that. Is it typical to include a temperature controlled dump valve going to a floor drain to keep the water temperatures down?

I’ll have a qualified boiler person doing the actual plumbing, but want all my ducks in a row and build up some knowledge before I call anyone. If there is any more detail you need, let me know. Thank you!
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Comments

  • Hot_water_fan
    Hot_water_fan Member Posts: 621
    Are you including a large storage tank here? Usually these are paired with very large tanks - like hundreds of gallons of water.
    Ironman
  • Turbo Dave
    Turbo Dave Member Posts: 78
    Hello. Your question #3: On a similar system I had a customer complaint of the pressure relief valve blowing from overheat. I used a Tekmar user switch #480, along with a #402 house control and #552 thermostats, to raise all thermostats to maximum when the buffer tank (used to absorb and store heat when the wood boiler puts out more than the house demand) exceeds 175 degrees. In this way all zones become the heat dump. It works perfectly. An added benefit is the house control adjusts a mixing valve to match the supply temperature to the BTU requirement of the coolest zone, keeping temperatures within a degree throughout the home. The control could automatically fire the oil boiler when the wood boiler cools off. to prevent freeze damage.
    EdTheHeaterManrick in Alaska
  • OakLumber
    OakLumber Member Posts: 18
    I could do that if necessary, since I have the room. How is the size calculated? Do I take the size of the existing in-floor pipe capacity and the domestic water tank into account? What happens if the water in the storage tank also gets too high?
  • Hot_water_fan
    Hot_water_fan Member Posts: 621
    @OakLumber Idronics journal 10 HYDRONICS FOR WOOD-FIRED HEAT SOURCES has all the info :). Since you're using radiant floor, you'll be able to maximize the amount of storage available. The larger the delta T, the more storage will you'll have for a given volume.
    STEVEusaPA
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 12,149
    I wouldn't disconnect the oil boiler just tee into the existing line. If it was me, I would put isolation valves on at both boilers.
    EdTheHeaterManIronmanZman
  • Jamie Hall
    Jamie Hall Member Posts: 19,150

    @OakLumber Idronics journal 10 HYDRONICS FOR WOOD-FIRED HEAT SOURCES has all the info :). Since you're using radiant floor, you'll be able to maximize the amount of storage available. The larger the delta T, the more storage will you'll have for a given volume.

    But if you want a quick and dirty -- take the normal operating temperature of the boiler and the maximum allowable temperature of the dump -- I wouldn't go above 180 F and subtract. That will be the number of BTUs you can store per pound of water. Now divide that into the full power output of the boiler times the length of the burn on a full load, and that will give you a rough estimate of the number of pounds of water your dump tank needs to contain. Divide by 8 and that will give you gallons. Rough, but it will get you in the right ballpark, anyway.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Hot_water_fan
  • hot_rod
    hot_rod Member Posts: 16,557
    A lot depends on the type of wood boiler you are considering. The modern gasification units can turndown output quickly and a buffer or small kick space heater could be enough of a dump zone.  They have fairly small fireboxes compared to OWF type burners.

    The buffer is more for leveling out to cycles and to give you some “coast” time through the evening for example. Ideally you monitor and adjust the size of the burn to the load if you are around to do that
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • leonz
    leonz Member Posts: 530
    The simplest way to do it is to leave everything as is on the oil boiler and recirculate the water from the wood boiler between the two boilers continuously with a small circulator.

    In this way the only time the oil boiler runs when the wood fire goes out with the oil boiler only making 160 degree water.

    Adding a round storage tank that is used in solar heating systems would work well if you have room.
    The round tank comes with copper coils, lid, and side piece that can pass through a doorway and has a fitted high temperature liner.

    The copper coils are lowered into the tank after it is assembled and the liner is installed.

    The copper pipe connections come out through the holes that are pre drilled in the side of the round tank and avoid puncturing the liner.

    The coil lines are connected with the boiler line feeding hot water to the buffer tank.

    These tanks are offered by www.solarpanelsplus.com





  • OakLumber
    OakLumber Member Posts: 18
    The simplest way to do it is to leave everything as is on the oil boiler and recirculate the water from the wood boiler between the two boilers continuously with a small circulator. 
    Can you clarify this a little bit for me? Do you mean the oil boiler would be in series with the wood boiler? 
  • leonz
    leonz Member Posts: 530
    edited July 20
    I would be glad to,

    You can pipe it in series if you want to do it that way.

    One circulator is dedicated for the heating system,
    the other circulator is used as a method of temperature
    balance between both boilers in a separate loop between
    the two boilers.
    The third circulator only runs when the L6006L senses an overheat
    condition circulating water from the boilers to the radiator(s) to cool it
    and it flows back to the boiler sump.

    As long as the piping from the wood or oil boiler comes off the top or side of the boiler and then enters the sump of the wood or oil boiler to heat the water in the boiler you have a continuous loop of hot water circulating between the two boilers with no need for check valves.

    As long as the circulator plumbed on top of the boiler you choose to mount it on is pushing the water to the sump of the other boiler piped separately from the header pipe that is feeding the hot water to the floor heating system you will have a temperature balanced system.

    You would want isolation flanges to be able to change the circulators if one of them fails in the future.

    Essentially you need to picture it as an oval racetrack from the wood boiler to the oil boiler and back to the wood boiler with no other piping connected to it.

    You should have a strap on L6006L to turn on a circulator with an in line check valve for the dump zone using a small circulator wired to the L60006L that will only push water through the radiator(s) when the dump zone temperature is reached and sensed by the L6006L.

    You really want a huge hot water radiator to act as your dump zone to simplify the installation.

    A reclaimed salvaged and tested used hot water radiator as large as you can find or for that matter 2 of them will act as the dump zone for you so you do not have to worry about overheating the house-been there still do that, as I have no separate dump zone.

    If you have a bladder pressure tank already you will want to change it and install a larger
    one to maintain your point of no pressure change.

    I have a 15 gallon B+G steel compression tank, B+G Inline Air Separator and B+G airtrol valve for
    my heating system and I do not have to bleed air anymore and the 54+ gallons in the '
    system is shut off from the house potable water system.
    Invest in 2 of Dans books "PUMPING AWAY" and "CLASSIC HYDRONICS" and you will not
    have trouble putting in your wood boiler.

    One thing I must stress is that you use steel pipe for the close boiler piping NO COPPER, NO PEX, PEX FITTINGS OR RIGID PRO PRESS fittings!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
    The RIGID PROPRESS compression fittings will not tolerate high temperatures created by wood and coal boilers!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

    The fools that put in my coal stoker boiler used propress fittings and they made a rat's nest mess of things.

    I only want you to succeed and learn from my past mistakes of which there are many.

    Please send me a PM if you have more questions and we can e-mail back and forth or chat by phone.
  • OakLumber
    OakLumber Member Posts: 18
    Thanks everyone for all the info! Not ignoring you at all- just trying to come up with intelligent questions once I digest it.

    One thing I must stress is that you use steel pipe for the close boiler piping....


    Can you define close boiler piping? I would really prefer to use copper in the ceiling. How far from the boiler do I need to be to make the transition?
  • leonz
    leonz Member Posts: 530
    edited July 22
    Edit: 7/22/22

    The Major reasons I suggest that you use schedule 40 black iron pipe for the close boiler piping are these;

    A wood boiler like a coal boiler will continue to generate heat long after the air shutter is closed or
    if you have a runaway fire due to:
    (a) a mechanical failure
    (b) an air leak entering the fire box due to a bad door gasket or warped firebox or ash pit door
    (c) power failure that does not permit the solenoid to close
    (d) chimney fire due to creosote buildup (e)
    (e) a properly adjusted Barometric Damper being stuck shut due to creosote the black iron pipe is much
    less likely to leak because it offers more heat resistance to expansion
    (f) good threaded pipe joints on high quality pipe that are properly cleaned and doped should not leak.

    g. Steel pipe will be easier to tap into if you take the time to install 2 Tees, pipe nipples and ball valves
    in the hot header pipe coming from the wood boiler to let you tie in a big storage tank now or in the
    future.
    h. buying a hot water storage tank and installing it with the wood boiler eliminates the need to install a
    union to separate the hot header pipe later to add the hot water storage tank and a second drop and
    riser pipe for the hot water.
    i. hot water is thermal mass
    j. it takes less wood to burn to heat water that is already warm
    k. hauling less wood means less work and less wood ashes
    l. hot water storage is somewhat like a dam holding back water where the energy stored can be used
    m. if you invest in a large enough storage tank you would be able to just have one fire a day if the home
    is well insulated
    n. less work and less time messing with a fire that will always need fuel and tending



    ================================================================
    Hello OakLumber,

    You should probably use 20 feet of steel pipe in total from the wood boiler on both the hot water feed and cool water return for 40 feet of pipe and fittings.

    You also need bronze/brass transition fittings to prevent corrosion problems for the copper pipe.

    IF you pipe it as I suggested with a single dedicated loop to heat the oil boiler and return the water back to the wood boiler you will have 140+- foot loop of pipe in the ceiling and dropping down to both boilers.

    Do not forget that you will be running 2 lines in the ceiling one will be the hot water delivery header pipe to the oil boiler and the cooler water return header to the wood boiler sump tapping.

    Schedule 40 threaded pipe joints when properly chased with a pipe die and pipe tap, cleaned and pasted with pipe dope and teflon tape two threads back from end of the pipe will be fine.

    The pipe, pipe elbows, couplers and unions should be chased with a die and pipe tap and dipped in hot water with dawn dish soap to clean the threads and wiped with shop towel to dry them.

    You could probably use 1 inch black iron pipe and fittings for the hot side with the circulator to a storage tank like the ones I described with sweated bronze transition fittings to the copper coils and you will be able run 1inch pex from the tanks third coil to the oil boiler sump with a small circulator.

    If you pass on a storage tank you could use oxygen barrier pex for the cool water return to a steel riser pipe that is connected to the boiler sump tapping.

    You may want to be able to store the hot water you make for thermal mass and in the process you will burn much less wood too.

    Once you heat the thermal mass of water the storage tank will hold that thermal mass and keep it hot if you buy one of the round ones or one of thier steel rectangular fully insulated tanks.

    Water as thermal mass is like money in the bank and the larger the tank the more water you have to heat your home and you could heat it with 150 degree water.

    I burned wood and coal for 33 years in a hand fed boiler and switched to using a coal stoker boiler as its much less work and better heating. I would be glad to go into detail about coal stokers for you.










  • Robert_25
    Robert_25 Member Posts: 410
    OakLumber said:

    Thanks everyone for all the info! Not ignoring you at all- just trying to come up with intelligent questions once I digest it.

    One thing I must stress is that you use steel pipe for the close boiler piping....


    Can you define close boiler piping? I would really prefer to use copper in the ceiling. How far from the boiler do I need to be to make the transition?
    Copper is fairly expensive these days, but functionally it is fine for your boiler piping. My house was heated with a wood boiler for 30 years - it was piped in series with the oil boiler and had an aquastat that would dump heat to the largest zone in the house if the wood boiler got too hot.
  • OakLumber
    OakLumber Member Posts: 18
    Coal is a non-starter here, coming in at $450/ton. The equivalent in oak or maple is $250/cord if I bought it, and I harvest my wood myself anyway. I'm ok with sticking with wood.

    My long term goal is to get rid of the oil boiler anyway, so I think I'll plumb it in series and get used to the operation of the wood boiler and gradually phase the oil out. I'll probably keep a hundred gallons of oil in the tank as a backup, but I don't want to put any money into the existing oil boiler. I have an existing wood stove with a similar firebox, and that one holds a bed of coals for about 10 hours, so hopefully this is similar.

    I'm going to avoid the storage tank for now. Since I use floor heat, I'll probably use all I can send it, plus I already have a 100 gallon domestic tank. I have a heating zone going to the garage I never use, do I'm going to tie the overtemp relay to that, and add a second relief leading to a drain if that one can't keep up. I'll keep my eye out for a cheap used tank though, since it can't hurt.

    What do you guys use in the event of a power outage? Is there a mechanical device similar to a radiator thermostat that I can use to dump the hot water? Maybe that's already standard, I have no idea. I was imagining a valve in series that is closed whenever power is present, and then opens when I lose power and let the thermostat take control. This would only be necessary probably if the firebox is full and we just left.
  • Hot_water_fan
    Hot_water_fan Member Posts: 621
    edited July 24
    This has your answers: your power outage plan would work and there are other options too. I’d rethink the storage - your floors will not absorb nearly enough btus. It’ll save you time and wood!

    https://www.caleffi.com/sites/default/files/coll_attach_file/idronics_10_0.pdf
  • hot_rod
    hot_rod Member Posts: 16,557
    Copper add soft solder melts around 450F no reason to use steel, unless you have tools and experience threading 1-1/4 pipe?

    Piwer outages can work with a computer back up power supply running a single pump. Probably only need a few hours. Or a Thermo siphon loop worth a N.O., normally open zone valve

    All explained with pics and wiring in Idronics 10
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    ChrisJ
  • OakLumber
    OakLumber Member Posts: 18
    Reading deeper into this, I think I'll set the plumbing up to run in parallel with the old boiler based on the comments here and additional reading. It makes more sense. I'll look into a storage tank too.

    I've been burning wood for years, and although my house is very tight, I never had a problem with downdrafts or lack for draft air for the fire. But these stoves are a little different in that it has an automatic draft and damper, so I assume it will call for a more intense combustion on demand. Has it be necessary to provide outside air to the stove? If so, how did you achieve that?
    Hot_water_fan
  • Hot_water_fan
    Hot_water_fan Member Posts: 621
    @OakLumber great! How much oil do you typically use per year?
  • Labenaqui
    Labenaqui Member Posts: 50
    We did the same back in 1975 by convective coupling between our oil and ancient (still in use) wood boiler. A blog description will be found at https://www.boilersondemand.com/heating/our-unpowered-forced-hot-water-fhw-gravity-heating-system/.
    We aren't "massaging the woodpile" as much in recent years, but may have to this coming winter.
    BTW - Look at a Fuel Co-Op to cut your #2 Bill. We have our customers on one here in NH.
  • OakLumber
    OakLumber Member Posts: 18

    @OakLumber great! How much oil do you typically use per year?

    It's really doesn't apply here, because we never really made full use of the floor heating. We used two woodstoves for primary heat, and the oil boiler for domestic hot water. But now with oil at $6, it's time to pull the trigger on a wood boiler. At the end of the day, we'd be burning the same amount to wood anyway, and the overall heat would be more comfortable.

    We typically burn six cord of wood per year.
  • hot_rod
    hot_rod Member Posts: 16,557
    It will depend somewhat on how accurately your unit can control its temperature. Some have variable speed combustion fans, or fairly tight automatic dampers and they do not overshoot like older wood burners.

    Anytime you have combustion, a burner or fossil fueled, you need adequate combustion air. The mechanical codes and NFPA code detail the options. It depends on the size of the room where the burner is located.
    1/4" per 1000 BTU is a common requirement, for example, both a high and low opening. Duct that combustion air as close to the boiler as possible.

    Search around online for more info on sizing combustion air.

    I highly recommend a few CO detectors also, one in the room where it will be located for sure.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • leonz
    leonz Member Posts: 530
    Hello OakLumber,

    Have you picked a wood boiler yet or are you still looking?

    Just as a suggestion that will cost you much less money and heat as well or better than your wood stoves

    You should look at the ASHLEY console heaters by the US Stove company as a wood burning appliance instead of having 2 wood stoves.


  • OakLumber
    OakLumber Member Posts: 18
    We already have two high quality stoves. One is a Hearthstone Soapstone heater on the first floor, and a large 200,000 BTU heater on the basement. There is no way a single standalone heater could heat the house, which is why infloor heating was installed in the first place. But, it isn't cost effective when using oil.

    I've already got this year's and next year's wood split and dried, so we are already set up for the wood boiler. I'll put it where the 200k BTU stove is now, and do as much plumbing ahead of time as possible.
    Hot_water_fan
  • hot_rod
    hot_rod Member Posts: 16,557
    got a got a brand name or pic of the unit in the basement?  200,000 btu/ hr is a lot of heat energy to use and control. What is the heat load of your place. A buffer is making more and more sense if the wood boiler is way oversized. Burning them on low fire can lead to creosote formation.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Hot_water_fan
    Hot_water_fan Member Posts: 621
    @hot_rod 200kbtu but only 6 cords per year in Maine!
  • OakLumber
    OakLumber Member Posts: 18
    hot_rod said:

    got a got a brand name or pic of the unit in the basement?  200,000 btu/ hr is a lot of heat energy to use and control. What is the heat load of your place. A buffer is making more and more sense if the wood boiler is way oversized. Burning them on low fire can lead to creosote formation.

    It was made by US Stove, and I got it about 20 years ago. It doesn't look like they make that style of wood stove anymore, but I bought this one and one a little smaller for my shop. The big one has a large firebox, and it would go through an awful lot of wood If I kept it going steady.

    There are a lot of variables missing that you need to know for this to make sense. It isn't a super-insulated home, but it is very tight and very well insulated with high quality windows and drapes. We do all of the normal things anyone should do- keep doors closed in unoccupied rooms, put the boiler on a timer, etc. The stove in the living room is a Hearthstone Heritage, which is about 60k BTU.

    BTU ratings are misleading. We load up the big stove in the early evening to warm up the house, and the smaller one upstairs is idling all the time. It isn't like we are pumping wood through it all the time when no one is home. But the house is so massive and insulated that it just doesn't cool down much during the day. And once the sun is higher around March, a lot of heat is generated on sunny days.

    The key is the insulation and tightness of the home, which is why I asked about combustion air. I'm looking at the draft blower, and it looks like I could pipe external air directly to it and have a passive damper on it like a backwards dryer vent. That should help.

    When I say 6 cords, that's what I put in the basement with the stove. I probably dump another half cord in when it just starts getting cold so we take the chill off. It isn't exactly the same year to year.

    But this ignores the BTUs being used for domestic water, and the wood boiler will take care of all of this. And even if I have to store eight cord instead of six cord, I have an endless supply. Ten cord? I don't care. I don't play golf and I don't play tennis, so this is my workout. And if eight cord translates to about a thousand gallons of fuel oil, at $5k-$6k per year, the payback will be short.

    Does this make a little more sense? I admit there are unknowns. Using the floor heating full time means I have to heat the house when I'm not there, because I can't just start a raging fire when I get home and warm up the place. I don't know how running a stove steady over 24 hours compares to running it hard for a few hours. I guess I'll find out.
    Hot_water_fan
  • Hot_water_fan
    Hot_water_fan Member Posts: 621
    Does this make a little more sense? I admit there are unknowns. Using the floor heating full time means I have to heat the house when I'm not there, because I can't just start a raging fire when I get home and warm up the place. I don't know how running a stove steady over 24 hours compares to running it hard for a few hours. I guess I'll find out.
    It sounds rewarding! 

    For quicker response, are you able to add any panel radiators or any other low mass emitters? They could help for some of the rooms most used. 

    The short story is that the big, blazing fire is clean and efficient. Let the water buffer the load. 

    You might find this site interesting as well: http://www.nofossil.org/ - it’s got a live tracker which logs data from solar thermal, wood boiler, oil and propane if I recall correctly. Not very exciting in July though. 
  • hot_rod
    hot_rod Member Posts: 16,557
    You can work the math any number of ways. Here is an example of BTU content of various woods at 20% moisture content. So 6 cords times the wood content number times the efficiency of the stove. That give you an approximation of the homes heat load.

    Sounds like it is a non gasification type burner, so maybe 60% efficiency when burning a hot efficient fire.

    The newest gasification wood boilers with lamba sensors monitoring the O2 in the exhaust and adjusting the air flow can get into the mid to high 80% efficiencies.

    A moisture meter is a good investment, to maximize the wood.

    Or use an ohm meter. Drive two nails 1-1/4" apart 3/8" deep into the wood. Pull the nails and insert the meter leads. 3 megohms or higher is 20%. less than 3 megohms, you need more dry time. Typically no larger than a 6" log when split to dry all the way through.

    As for combustion air, a "fan in a can" is an option, if you don't want two 80 square inch openings (1/4"/ thousand BTU) into the boiler room :) Maybe a heat switch on the flue to start it up?

    People can wake up dead from lack of combustion air in a building :(
    Make sure you have this part thought through!
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Robert_25
    Robert_25 Member Posts: 410
    edited July 28
    @OakLumber What is the make/model of the wood boiler you plan to use?

    Generally speaking a conventional wood boiler paired with a modern house & radiant heat will spend a lot of time idling and produce a ton of creosote. A gasification boiler will burn much cleaner, but also require thermal storage for the best efficiency.
  • OakLumber
    OakLumber Member Posts: 18
    hot_rod said:



    People can wake up dead from lack of combustion air in a building :(
    Make sure you have this part thought through!

    Yeah, I've been using wood for a very long time, and it's always split and well seasoned. I cut it in winter, and let it lay there for a year before I drag it out and work it up (much lighter that way too). Never had a problem with creosote.

    Although the house is tight, I'm sure there is enough natural draft, or else I would be getting a lot of downdrafts and smoke. But in this case, instead of a steady fire, it will come in bursts and a directed draft from the outside would make more sense.

    I already have all the detectors in place.

  • OakLumber
    OakLumber Member Posts: 18
    Robert_25 said:

    @OakLumber What is the make/model of the wood boiler you plan to use?

    Generally speaking a conventional wood boiler paired with a modern house & radiant heat will spend a lot of time idling and produce a ton of creosote. A gasification boiler will burn much cleaner, but also require thermal storage for the best efficiency.

    I'm leaning towards the Royall boiler, probably the 6300. The floor space that the floor heating covers is about 8000 sq feet (includes the concrete basement floor), plus I'd like to use it for my shop and a greenhouse during the months of Feb-Mar.

    One problem is that I really don't know how much something like the basement floor offers for thermal storage. I have a big domestic water tank as well. I probably have to watch it for a month or so to see how much it runs.
  • Hot_water_fan
    Hot_water_fan Member Posts: 621
    edited July 28
    One problem is that I really don't know how much something like the basement floor offers for thermal storage. I have a big domestic water tank as well. I probably have to watch it for a month or so to see how much it runs.


    Extremely little thermal storage in the basement slab when paired with that boiler:

    Say 4" slab x 4000sqft. That's 1333 cubic feet. At 150 lbs per cubic foot, that's 200,000 lbs. Sounds like a lot! But the specific heat of concrete is about .2btu/lb/degree , so that's 40,000 btu per degree the slab changes. Maybe you take the slab from 70 to 80 degrees - that only stores 400,000 btus while the boiler has a firebox holding probably 5x that.

    The DHW tank doesn't contribute much at all: 100 gallons * 8.34 lbs/gallon * 1 btu/lb/degree F * 100 degree temperature change (from just above freezing) = just 83,400 btu.
  • leonz
    leonz Member Posts: 530
    If you have a garage my only other thought for your situation would be to take advantage of a Garn WHS1000 boiler to do all you want with it the year round and heat everything.

    You would not need to do a massive plumbing job in the home and you would only need to run a length of 2 pipe oxygen barrier pex closed cell foam tubing from the garage/hoop shed to the home and into the
    current boiler sump using one circulator for the loop from the basement to the GArn Boiler you could substitute a farmtek hoop shed for a garage if you do not have an unattached garage.

    www.garn.com
  • hot_rod
    hot_rod Member Posts: 16,557
    Every word boiler system is as specific to the job, there are many ways to pipe them 
    I have owned and operated both the Royall, an EKO, and a large homemade version at my shop and home. I was an Aquatherm dealer for a number of years and installed and worked on many Hardy was big in my area also, so I worked on those also

     You may fine that you spend a lot of time tending the fire unless you have some thermal storage. A dump zone is the other option and you need to be able to dump a full firebox worth of heat. So it then comes down to the size of the firebox in the unit you chose. If you go with a 200,000 unit I would buy or make a fan coil for a dump. Plenty of homemade versions from a car radiator with most any fan behind it. Kicks on at say 190F, off at 180F

    Ideally you would dump into a garage or shop where that energy could be useful.

    You can try and just parallel pipe them, see how it goes and leave a few tees to add storage or a dump if it becomes unmanageable.

    Typically the service calls are pressure relief valve blowing steam in the boiler room😉. Next you cool them down, refill and repurge the entire system.

    The common newbie mistake is not latching the door tightly and they run away from the owner and flash to steam. One occurrence usually gets folks attention. A boiler that size at 12 - 30 psi pressure, flashing to steam will be a sight to behold, try not to go there.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • OakLumber
    OakLumber Member Posts: 18
    Note that I'm not opposed to thermal storage- I just don't know how much I need yet. I really don't want to spend $4k on storage when it's just a blind guess. We've never tried using the floor heating to its potential before, and I first what to see how that works out. I am a process engineer and can record the temperature and device status over time and see exactly what it's doing. Will be an education for sure.
  • hot_rod
    hot_rod Member Posts: 16,557
    When you get a chance, the answer to all your questions are in this free journal
    https://www.caleffi.com/sites/default/files/coll_attach_file/idronics_10_0.pdf

    The sizing, piping, control wiring, everything but the plumber to do the work
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • OakLumber
    OakLumber Member Posts: 18
    hot_rod said:
    When you get a chance, the answer to all your questions are in this free journal
    https://www.caleffi.com/sites/default/files/coll_attach_file/idronics_10_0.pdf

    The sizing, piping, control wiring, everything but the plumber to do the work
    I’ve already downloaded several of those papers. There is very good information there that I’m still digesting. 

    But it’s the little things that are missing. I haven’t seen the Dayton draft blower in person yet, but it looks like I can attach a flanged piece of duct work to draw air from the outside. That would make a difference, since the boiler will be in a finished basement.    There are a lot of little details like this. And then I want to see how it reacts when it’s frigid cold for three weeks straight. That’s when it will pay off. 
  • leonz
    leonz Member Posts: 530
    edited July 31
    You do not know if you even need a draft inducer yet to do the same thing.

    Keep in mind the chimney can only have the wood boiler flue connected to it.

    You making it much harder than you have to live with a wood boiler in the basement of a fairly tight house.

    All you need is 4 inch PVC pipe coming from the outside away from the chimney you intend to use and dropping the PVC pipe down near the floor by the boiler to bring in combustion air but not so close that it will melt. You just need to be sure to glue a slotted drain cap over the outside pipe.
  • OakLumber
    OakLumber Member Posts: 18
    leonz said:

    You do not know if you even need a draft inducer yet to do the same thing.

    Keep in mind the chimney can only have the wood boiler flue connected to it.

    You making it much harder than you have to live with a wood boiler in the basement of a fairly tight house.

    All you need is 4 inch PVC pipe coming from the outside away from the chimney you intend to use and dropping the PVC pipe down near the floor by the boiler to bring in combustion air but not so close that it will melt. You just need to be sure to glue a slotted drain cap over the outside pipe.

    The boiler comes with a draft inducer and auto-damper, and I really didn't want a large hole dumping cold air in the room when it wasn't needed. But it's just about the same amount of work to run the pipe to the stove either way, so if I don't need to tie it to the blower, all the better. Just want to do the job right.

    Each stove in the house has a dedicated flue. It's pretty much a requirement.
  • leonz
    leonz Member Posts: 530
    You will have to plan on having a cold basement UNLESS you wall off the wood boiler with concrete block and place a pipe through the basement sill if there is enough open ground to pass a 4 inch pipe through and to make sure that the air inlet pipe is several feet above the ground to avoid its being plugged with snow.

    How tall is this chimney? Does it have a chimney extension or chimney cap?