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want feedback piping WOOD boiler gas mod/con backup via reverse indirect BUFFER tank

rainmaker Member Posts: 20
Hello! This is my first time, so bear with me. I am looking for advice on piping my home hydronic heating system so I've have been reading a lot of these forum threads and various other sources. I plan to post some detail info and a sketch separately to break it up and allow various replies to each...

(more in the next post)

Basically this is an old wood farm house in upstate NY that is getting some needed upgrades, like insulation, air-sealing, and removing the old oil furnace to put in radiant heating by indoor wood boiler with LPG propane gas modulating condensing boiler as backup. Since the place has an open basement ceiling, an open ceiling under the bathroom project and needed structural repairs in another ceiling, we are putting in staple up radiant pex. Toyed with idea of solid fuel renewables and found a great deal on refurbished wood unit and a discount on plumbing parts via a friend. We designed distribution, calculated heat loss, have sizes in mind so time to put it all together so I can order pipe, pumps and wire...

Have some experience with hydronic and radiant and very handy but lack a lot of hands-on experience or super detailed tech knowledge. like most I know just enough to get me in trouble... Huge respect for those that contribute their time and expertise! I'm impressed already by the technical and detailed replies to others.

Thanks in advance!



  • rainmaker
    rainmaker Member Posts: 20
    info on the house and radiant concept

    House is approximately 1400 SF, 2-story, detached, built 1850s, stone footing log floor balloon stud wood frame in upstate NY near Kingston in the historic Hudson Valley.

    Basement full height under 700 SF ground floor under 700 SF 2nd floor under Attic with new spray foam insulation at roof line.

    Heat loss measured before foam was huge, as any old drafty house.

    Next blower door test due after a few more air seal work...

    HEAT LOSS between 40-50 kBtu, but I'm convinced I can get it down even lower!

    Radiant design PEX stapled up to thick aluminum Joist-Trak @ 8"OC with batt insulation below each level (plus reflect barrier above basement).

    Distribution may only consume around 37kBtu estimated all in... which is why I may need to add future supplemental zone of higher temp radiators to make up difference, but I prefer not.

    Indoor WOOD boiler as primary, but more on that next since I want to install LPG gas mod/con backup first and tie in wood later... (my existing oil furnace is temporary heat and taking up the space of future wood unit).

    Backup source GAS mod/con was proposed Triangle Tube Prestige 110 but I did my homework and prefer to size as small as possible (finding many threads warning against over-sizing). Intend to go with Prestige 60 that just covers our extreme maximum worst-case and turn down ratio modulates to about 15kBtu.

    Zones calculated via Uponor app are 1-main floor 21kBtu, 2-upstairs bedrooms 15kBtu, #3-bathroom 3kBtu. MICRO-ZONE! time for a buffer tank for the gas unit to avoid short cycling.

    My original preference was pipe Primary/Secondary like the good manual says, and after debating zoning via pumps vs valves, am leaning toward ECM circulator variable speed delta-P like Grundfos ALPHA and 3 zone valves. Manifolds EP with integral flow balancing etc.

    DHW was going to be a SMART tank indirect. we have an old electric water heater 40-gallon that seems to keep up, and I'm heeding advice to NOT increase boiler size for domestic hot water, so idea was to increase to 50-gallon... until I warmed up to the idea of reverse indirect to also serve as buffer tank and also as hydraulic separation instead of closely spaced Ts on P/S loops.

    Now considering something like the ERGOMAX or Turbomax or even retrofitting the old electric DHW tank as dumb buffer...

    I welcome feedback on those decisions, but fully aware that these topics have been covered plenty before on previous threads! So proceed to the next line about the WOOD BOILER...
  • SWEI
    SWEI Member Posts: 7,356

    are you using plates?  Insulation?  Just curious.

    http://www.caleffi.us/en_US/caleffi/Details/Magazines/pdf/idronics_10_us.pdf will teach you more about wood boilers than you ever wanted to know.  I'd start there.
  • rainmaker
    rainmaker Member Posts: 20
    edited November 2013
    schematic drawings for wood boiler gas backup buffer tank options

    links to images of my crude sketches of a few ideas.

    i give a lot of credit to the Caleffi idronics 10 spiced up with some Siggy advice (the great Siegenthaler) and a lot of other good comments by others too...


    I'll describe the indoor wood boiler set up next...

    note: the wood boiler buffer is a challenge since there is only a narrow doorway to get down the hatch into the existing stone basement, so either multiple pressure tanks ganged with reverse return or a big fat unpressurized DIY water tub...

    Question: if pressurized storage, could the last buffer be a reverse indirect for DHW and mediate between gas mod/con and micro-zone in shoulder season bypassing the other wood storage but still be included in the wood capacity while burning?

    Am I asking too much?


    LINK-pressurized optA

    LINK pressurized optB
  • Ironman
    Ironman Member Posts: 7,373

    Lest start with the first step: what's the calculated heat loss? What did you use to get this? How many square feet is the house? How many lineal feet of tubing will you be able to install? What type of floors and covering will you have? Can you give brief discription of your windows, walls , insulation?

    Some suggestions:

    1. Don't even consider doing staple up WITHOUT heat transfer plates.

    2. Be prepared to probably have to add some other emitters to back up the radiant floor when it's extremely cold. But that depends on the answers to the above questions.

    3. Do NOT purchase non o2 barrier pipe - you'll regret it and pay more in the long run.

    4. Don't try to cut corners to save a few $$. You're installing a Mercedes Benz system; don't try to use Yugo parts. There are no short cuts to doing it right.

    5. Have it designed correctly by a knowledgeable pro before you start your installation. This is the most important step with the smallest percentage of the job cost yet most people want to omit it to save a few$$. They always pay more in the long run through poor performance and increased energy useage. Some pay the ultimate price in having to abandon it and install another system simply because it wasn't designed correctly. This leads me to a smilular suggestion:

    6. No what your total job cost is gonna be to do it before you commit. This includes what I stated above. If your budget won't allow you to do it correctly, then look at other options. But, please don't deceive yourself by thinking " this is all I have to spend, therefore, I'll make work at that cost". Be aware that the laws of physics will out-weigh the laws of economics every time. And I know of no other place where that applies more than hydronics.

    The folks here love to help if your willing to follow sound advice. So, please get back to us. And, after you supply some more info, be prepared for a few more questions. The better that you inform us, the better we can advise you.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • rainmaker
    rainmaker Member Posts: 20
    edited November 2013
    about that WOOD boiler:

    regarding the previous posts... we found a refurbished indoor WOOD BOILER.

    the smallest i could find (heat output capacity) was Itasca 85kBtu with 20 gallon water jacket. it has big threaded S&R ports with a thermostatic air intake damper.

    my understanding is that since this is almost double the output needed for heat load, then BUFFER tank is needed, so I'm shopping for used propane tanks to gang together as pressurized (and fit thru the narrow hatch to the cellar) or building my own EPDM lined tub as unpressurized storage and choose between external HX or submerge some copper coils...

    So ? How do I pipe the wood as primary source with storage to a low loss header and add gas mod/con backup that also needs a little buffer and all play nice?

    Could a reverse indirect DHW tank serve multiple purposes and transfer heat at the cross roads?

    Thanks again everybody!
  • SWEI
    SWEI Member Posts: 7,356
    Buffer tanks

    should be sized according to the maximum BTU output of the boiler from a full load of wood.  The BTU/hr rating determines the size of pipes and pumps, but the tank should have the capacity to absorb the full output of the boiler when there is a minimal load (e.g. a mild fall day where you need just a bit of heat to keep the place comfortable.)  The capacity of the buffer tank is determined by three things:

    The size (in gallons) of the tank.

    The maximum temperature of the tank.

    The minimum useful temperature of the tank (which depends on the emitter design and building heat loss.)
  • rainmaker
    rainmaker Member Posts: 20
    edited November 2013
    wish i found this post

    ... before i fooled around manipulating the other sketches!


    links to Siggy's article:


    scroll down to page 20 and 44...

    Any opinions about why I should do it that way versus the way I am proposing..?
  • rainmaker
    rainmaker Member Posts: 20

    Yes, using staple up heavy duty aluminum JOIST TRAK.

    You may see my subsequent replies with more info... yup, totally dove into idronics 10 publication.
  • Ironman
    Ironman Member Posts: 7,373

    You're definitely gonna need buffer due to the slow response of a natural draft wood boiler. I would suggest a minimum of 200-300 gal.

    On your drawings, you're showing a delta P Circe feeding all your radiant zones plus a high temp zone and then regulating each loop with telestats or zone valves. You'll have performance issues if you attempt it this way. The floor will need its own properly sized circ to prevent striping and give even heat. It's also not a good idea to try to zone every loop.

    A better approach would be to use a smart mixing valve or variable speed injection mixing based on outdoor reset and minimize the number of zones. If the reset curve is set properly, the thermostat(s) almost become unnecessary. The only thing that you may want to zone separately would be the sleeping areas.

    Also,a mod/con boiler doesn't need an external outdoor reset control, it's integral to the boiler. You'll still need the reset that I mentioned above because of the water temp from the wood boiler. But that's for controlling the temp to the floors, not the boiler output temp.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Zman
    Zman Member Posts: 7,569

    You really have a great start.

    A couple thoughts...

    How often will you use the backup boiler? It would be nice if it could run at low fire during a radiant load. Much more efficient. A properly sized fire tube mod con does not need a buffer.

    Another way to do it would be to set up the wood boiler storage tanks as boiler one and the mod con as boiler 2. They could be piped in parallel to a common header. A tekmar 2 modulating boiler controller could control a 0-10 vdc circulator between the wood boiler storage tanks and the common header.

    Do not use smart tanks for reverse indirect. They are carbon steel on the outside.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • rainmaker
    rainmaker Member Posts: 20
    reply to zoning and mixing

    yup, i grasp the benefit of ODR outdoor reset control and will attempt to figure that out when i get to the control module and wiring portion... but first i suppose the hardware layout is first step?

    I'll even tackle the zoning and pumping again later, once i understand the buffer and primary piping...

    But since we are on topic of zoning, a couple of questions:

    I like to zone each floor independently, (check out my breakdown in BTU sizing and areas above) and the idea of zoning #3 just the main bathroom for those rare occasions seems like a nice plus. We could sacrifice that desire for a better overall system, but for now would like to buffer down and keep the micro zone.

    Is that reasonable?

    Each zone is on one zone valve 3/4 going to manifold with maybe 5 or 6 loops tops, about 250-feet each. I'm trying to balance length as close as possible, reading all the Wirsbo and Uponor info...

    I hazarded a guess that it would work to pump supply after header along trunk pipe toward a future radiator branch, then 3-way mix down to temper radiant (with check-valve to keep flow toward floors) and branch off another 3 zones?
  • rainmaker
    rainmaker Member Posts: 20
    reply to basics

    Yes, transfer plates for sure (already going in nicely...)

    Calc heat loss based on Uponor software room-by-room exposure and construction type, plus comparing to rules of thumb and based on historic performance on oil forced air over a few winters, and also a blower door test measuring air changes at pressure.

    We have yet to test the "after" but work is in progress and since boilers only come in incremental sizes, it will either be too small or too big.. so thats why I'm using round numbers for now just to assess the overall design.

    Yes, Uponor HePEX Plus piping has barrier and intended to keep that portion pressurized and oxygen free (once I understand better where to put the vents and stuff)

    TOTAL TUBING LENGTH approx 2,200 Lin Feet over 2 floors total 1400 SF.

    old house has solid wood floor boards over joists (no subfloor)

    5" foam close cell roof insulation (R-30?), old walls fiberglass batt (exist), basement ceiling after radiant will get insulation too... Windows are old but have storm windows so poor mans double glazing (to replace in future). Still tackling all the air infiltration ... got heat loss from 68,000 down to 50,000 and shooting for even lower hoping for around 35,000 for 1300-1400 SF would suit this radiant nicely.

    I'll dig out the report for design temps, GPM flow rates, and Delta-T target each loop...

    Supply temps 160-F, Returns each loop around 130 to 140-F... seems hi for radiant?

    Yes, hydronics can be spendy but I aim to keep house for years and payback in comfort and energy savings.

    Willing to consult a paid pro, yet still looking to get most of design figured myself since I intend to install and maintain, and based on previous experience it can be very hit or miss with both engineers and contractors and client is still left wondering why and how to operate.

    Everybody has a different opinion anyway... so i remain open minded.

    Other info to your questions were posted in my other messages.
  • rainmaker
    rainmaker Member Posts: 20
    edited November 2013
    buffer tank size

    nice post here about sizing: (again thanks to you experts and Siggy!)


    Honestly, I'm still trying to understand the variables...

    As for the wood boiler buffer, I recall many sources mentioning formula something like BTU of water 8.3 per gallon per Delta-Temp degree rise, which is why pressurized looks appealing in both simpler piping and more range of heat input and draw.


    for example:

    500 gallons might hold 166,000 Btu to raise 140-F water up to 180-F...


    So if my wood boiler nominally 85k actually 80% at full blast net 68k to water storage, it would take a few hours to raise the 500-gal from 140 return up to 180... (not cold start but interim recovery) and drawing 35k emitted via radiant per hour would mean it would take about 4 hours of coasting time... yes?

    I'm sure the actual thermodynamics of concurrent heat and dissipation would change plus mixing and tempering but that helps me estimate that I might be able to plan my wood loads to burn time about twice that of what the time of heat demand... just for conceptual planning.

    Unfortunately my basement will only fit so much... unless i get brave and pipe insulated S&R out to the nearby barn and insulate the heck out of a huge propane tank salvaged from somewhere... hmmm...
  • rainmaker
    rainmaker Member Posts: 20
    parallel boilers

    How often? I like to think that most of heating season we will stoke the fire and only depend on gas (because we have LPG for cooking anyway) boiler if the flame goes out at night and storage tanks get depleted of extra heat or maybe grandma stays at house alone or a guest without any desire to load wood maybe seldom to very rarely... however during 'shoulder' seasons when we don't burn wood but need a little gas bump for DHW hot water... (but plan to do solar HW way down the road...)

    I'll look into the fire tube option you mention... i am totally open to ideas. was a fan of WM Ultra but now almost totally sold on TT prestige products.

    As for piping boiler sources in parallel to a common header... that IS conceptually what I am trying to do, so is there a better way?

    On my list is to understand the difference between variable speed circulator types and when it might be better to just size the pump to a fixed rate once flow is calculated and let controls work magic...
  • SWEI
    SWEI Member Posts: 7,356
    edited November 2013
    Buffer tank sizing

    for liquid or gaseous fuel boilers is based on those factors.  For a solid fuel boiler you need to look at the total capacity of a fully loaded boiler and use that combined with the tank ∆T.

    How many pounds of wood can you fit in the firebox?  Multiply the total BTUs in that load  http://chimneysweeponline.com/howoodbtu.htm by the efficiency of the boiler (percent) to determine how many BTUs the boiler will produce in a complete burn of a full load of wood.  If you burned 100# of 20% moisture wood like the example in the link above, yielding 6,200 BTUs per pound, you would have 620,000 BTUs to store.  This is not BTUs per hour, this is just BTUs.  Assuming for a moment that your floors can make use of 85ºF water on a mild day and the tank/boiler/PRV will allow 180ºF to be safely stored you have a ∆T of 95ºF for the tank.  620,000 BTUs divided by 95ºF can be stored in 6,526 pounds of water (almost 800 gallons.)  You can subtract the building load for a mild day over the course of a complete burn (BTU/hr x hours = BTUs) from the total if you want.  I generally start by assuming the possibility of overt stupidity on the part of a clueless future owner and assume they will need to store everything that is produced in a full load of the densest fuel they have around when the heating system is off.
  • TonyS
    TonyS Member Posts: 849
    You may want to consider

    Coming off the boiler with a direct loop to the heating system and then bleeding excess into the buffer tank. Then switch the loop back to the buffer tank when it comes up to temp. A relay and an aquastat could do this.

    Your boiler is already twice the size you require on the coldest day of the year. Whats going to happen the rest of the year? You will have to load up the boiler with enough wood to bring the buffer up to a temp you can heat with. My home is about the same as yours..design loss is 36000 at 0. We are at the end of November and still havent seen anything below 25 at night and we have been seeing 45- 50 some of these days.

    Last night I burned .....maybe 3- 12 inch split rounds in the wood stove and it is 79 degrees in here with sun shining in.  If it gets really cold where you are and stays that way for extended periods and your going to keep that fire going nonstop...go for it.

    It has been my experience living in south east PA  using an outdoor wood boiler then a indoor wood gasification unit and now finally a new epa quadrafire woodstove that by far and away the woodstove was my best idea.

    No matter how you get your wood, there is work and money involved and wood boilers just have to much loss when they are not wide open.

    Also be prepared for that unit to damper down when your buffer tank is maxed, it will still blow the relief valve and you will hate cleaning that filthy thing.

    Just my opinion based on my experience.

    Good luck
  • SWEI
    SWEI Member Posts: 7,356
    Wood boilers just have to much loss when they are not wide open

    Exactly, which is why you need to size the buffer tank as I described above.
  • TonyS
    TonyS Member Posts: 849
    The problem is

    using your 800 gallon buffer. 800 gallons of water x 8.33 gives us 6664 pounds of water that has to be raised in temp from room temperature to 85degrees just to start the heating process. Thats 15 degrees( if the room is 70 more if its in a cold basement) we need to raise this 6664 pounds of water, that requires in a perfect world 99,960BTUs.You can add another 50% to that for boiler loss and heat loss during heating the buffer. OK so we have now expended almost 150000 btus just to get our buffer hot enough to start heating. This is why I recommend a bypass on the buffer. So anyway lets say its night time and 50 degrees out and heat load is about 10,000 and hour. You have already burned enough fuel to heat for 15 hours just getting your buffer up to temp. I was lean on the buffer starting temp because your drawings show domestic prefeed going through the buffer which means your buffer tank is going to be starting out at 55 degrees( remember its well insulated so it will stay cold a long time) Now you need to bring that buffer tank up to 85 from 55... thats 30 degrees for 800 gallons of water. Wow do that math.

    All he needs to do is add 10,000 BTUs an hour to his house.  These systems really start to border on ridiculous for homes with low heat loads.

    If you have to have this system at least put in one modern wood stove in the home, it will give you much better control of your heat and use much less wood during those shoulder seasons.
  • SWEI
    SWEI Member Posts: 7,356
    I'm with you on the value proposition

    a modern wood stove (or two) is cheap by comparison

    But when it's done right, a wood gasifier paired with sufficient storage is wonderful.  It doesn't have to be complicated, either -- as the Garn owners like to remind us.
  • TonyS
    TonyS Member Posts: 849
    Two stoves

    Absolutely, wood stoves like boilers have a tendency to be over sized, then when it gets too hot you either open the windows or choke the fire, Two smaller stoves are better.

    One for the shoulders and two for the design.

    Another thing he needs to be clear about is Makeup air and chimney design. There are so many misconceptions about these two items. Google "outside air for woodstove"

    It gets downright humorous. Unlike the modulating gas boiler, where you get a bunch of professionals arguing the finer points..Wood brings everyone that's ever lit a fire into the discussion.. Farmers, mother earth news people, wood zealots and the list goes on and on.

    Outside air for combustion is a must...its all outside air but its much better for you to control it than let it find its own way in. Pipe it in stainless steel with a fireproof wall entrance, so if negative draw ever becomes a reality, it is no concern.

    Chimney lined with stainless liner same size as vent adapter and insulate with vermiculite. The more insulation the easier your life will be.
  • rainmaker
    rainmaker Member Posts: 20
    edited December 2013
    new version with wood storage bypass

    Thanks for the comments so far... Here is a new version (see link)

    Please comment if there is a better way to pipe the bypass to and from storage?


    My goal is to sequence like this:

    1. Wood fires and recirculates bypass until up to temp.

    2. wood circ to storage (normally open in case of power failure).

    3. DHW or SH heat call opens 3-way valve wood circ to buffer tank "header" until satisfied then disconnects and resumes to storage.

    4. If DHW or SH call but wood too cool then activate valve and storage circ to buffer.

    5. If both wood and storage too cool, then gas backup boiler fires.

    Due to hydraulic separation at central buffer tank, the heating zones can pump at their own rate as needed, as long as the tank is hot. The tank would recharge itself as needed also.

    (I still have to figure out control specifics, including ODR outdoor reset...)

    Is there a better way? perhaps thermostatic 3-way instead of off/on diverting...?

  • rainmaker
    rainmaker Member Posts: 20
    size matters

    So my plumbing parts sales guy is advising me that the Ergomax might require a bigger boiler or would not supply enough flow of domestic hot water...

    I'm waiting to hear back from Thermo2000 if the Turbomax is available with extra ports to do the buffer tank configuration in the middle, and whether the price will make it realistic.

    Any other ideas ? ...or this buffer idea might get tossed out.
  • rainmaker
    rainmaker Member Posts: 20
    another way to buffer

    Here is an example from Triangle Tube prestige manual:

    buffer the micro zone off a regular DHW indirect like a Smart tank.

    it is clever how the supply of the small load zone is from the return so it is already tempered...

    Then I could pipe regular primary secondary for the rest of the system and let each component function optimally.

    thanks again.
  • rainmaker
    rainmaker Member Posts: 20
    my latest revision... is this a good layout?

    Here is my latest version (with a lot of credit to Caleffi idronics_10).

    I have not given up completely on the buffer tank/ hydro-separator/ low-loss header, but decided to sketch an alternate layout that is more "conventional" using primary/ secondary closely spaced Tees for comparison.

    Link to piping diagram:

    Based on some good feedback about wood boiler storage, I feel confident that bypass might actually be redundant, so I'll plan on pulling hot water right off the top of the stratified tank as soon as it is available... hoping it won't have to heat up the whole thing before it is useful.

    I hope this piping allows either boiler to run independently, and each zone run independently also.

    DHW indirect domestic hot water is pumped as a zone also (after the Tees) so it can pull from either boiler source without interrupting that primary flow...

    The micro zone is pulled off the indirect tank on another loop to help buffer. Thanks to Triangle Tube piping examples in "Prestige Application Booklet".

    Anybody have any ideas to improve upon this layout?

    How would I control this thing? (I can post the idronics wiring schematic next...)

    3 thermostats total (2 zone valves shown and 1 micro zone)

    thanks again.
  • Weezbo
    Weezbo Member Posts: 6,232
    edited December 2013
    i am curious about something,

    as there shows no circ on the wood boiler and a circ headed at the buffer tank is the thermolec valve preforming its task on gravity and temp ?


    last year a friend of mine who fed his outside wood boiler ( an open to air) wood with a copious amount of cooking grease and used veggie oil moved the boiler near his brand new aircraft hanger and shop.

    he asked me to help him get some heat into his home thru the system in previous years thru a buffer (Water delivery truck with two 3/4"coils ,insulated and buried ) so i added an additional circ and bumped up the fitting sizes and piping on the wood boiler ...........

    plus a whole lot of balancing within the building and adding a toyotomi oil boiler within the building as a back up and to use in the shoulder seasons ....

    when he moved it to the hanger that was over 100 feet away and i could see while visiting the site as it was being built that the plumber friends of his had done nothing to up size the circs or near boiler piping to the tank and i checked the tank too and did not see that he had taken my advise on upsizing the coils ..

    so , how does the boiler move the heat effectively is it regulated by fan control at the burner ?
  • rainmaker
    rainmaker Member Posts: 20
    yes, there is also a circulator at wood boiler

    There is a circulator into the return of the wood unit.

    It recirculates on cold start for boiler protection, then checks to redirect flow out to tank when up to temperature.

    this simple diagram shows a Thermobloc unit by Caleffi which integrates check valve, circulator, 3-way bypass valve and temp gauges in one convenient package.

    There are other brands that do similar thing, like Termovar sold by Tarm (BioHeat USA).

    ... or if cost is an issue, I may just cobble my own assembly.

    Just something I learned by reading a huge list of wood boiler forums and specifications from reputable mfrs.
  • hot_rod
    hot_rod Member Posts: 22,103
    not bad

    Wood boiler pump block runs of boiler pump contact, OR

    I run that pump block with an I-solar plus control. Set collector min. (boiler min) at 140F, so it only powers on when the boiler is hot. sensor at top of boiler

    R2 runs the buffer tank pump on a delta T between tank top, and loop, similiar to i-dronics drawing

    P1 runs off the boiler pump relay

    P2, make it a delta p pump, always powered, and use a thermostatic valve on that load KISS

    P4 delta P powered always

    boiler is fired on by differential (solar) control, when buffer cools boiler fires

    DHW call fires dhw function in boiler

    The mix valve maybe runs from the boiler or a stand alone tekmar

    The control logic takes some time to work out. Write it all out down, use idronics for a guide Multi function solar controls work great. The i-solar MX LTE has some great features and virtual relays that you create to do what you need, so very flexible.

    I see Resol now has a wood boiler controller, have not tried one yet..
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • rainmaker
    rainmaker Member Posts: 20
    thank you HR ! ...please clarify?

    Help me understand, you were commenting on the latest sketch from Dec 12, correct?

    Which pump is delta-T, the one feeding wood boiler to storage?

    sounds like a good method to transfer heat efficiently without moving too much or too little depending on the variable rate of wood fire...

    How would the P2 pump operate from wood storage on primary loop, if it is delta-P (isn't it supposed to be hydraulically separated)?

    DHW would ideally feed from either source, which is why I propose to pipe it as a zone... so how is priority controlled? Lock-out other zones? Can it piggy back on the differential temperature relay to call but let the controller decide ..?

    If the TT Prestige 60 boiler backup is a good choice, then it would be great to use as much integrated control, IF possible...
  • rainmaker
    rainmaker Member Posts: 20
    ... can anybody help explain what he said?

    I am really appreciative of all this great advice!

    Can anyone help decipher what Hod Rod said in layman's terms?

    How does the DHW indirect get priority over heat and get supply from either boiler ?

    (and should it be piped on the primary loop instead?)

  • hot_rod
    hot_rod Member Posts: 22,103
    yeah, building a control

    package for that can be a head scratcher. You need a good understanding of how controls, relays, and logic work to sort through it. This is pretty advanced control wiring.

    In your case the control on the boiler can cover some of the functions the DHW pump can usually be driven from the boiler control. The signal to the mixing valve for the radiant possibly, also.

    Mixing various different controls can get complicated. In some cases you need to add isolation relays to keep different voltages sorted out. The boiler controls need to communicate with one another.

    On my system I used a couple solar, differential controls, for the wood fired control.

    Treat the wood boiler as the solar collector, sensor 1 goes on top of the boiler. The buffer tank becomes the solar tank, sensor 2 goes at the bottom. Simply when the boiler is warmer then the tank the pump fires up. when the tank is within 10 degrees of the boiler, for example, the boiler pump shuts down. You also can set a collector min. which allows the boiler to reach 140f before it fires that pump.

    A second delta T function moves the energy from the buffer to the P/S loop. There are some controls available that have two delta T functions in them, so 1 control pretty much runs the entire wood fired component.

    You need to know how to select and size wire, the sensors should use a shielded cable. the solar controllers need to wire to the two pumps with wire in flex or condiut, it gets parts and labor intensive.

    Then you need to know how to get into the control and adjust all the parameters to make it work properly.

    Can you find someone locally with the tools and knowledge to do the controls part?

    I can put you in touch with companies that build custom PLC controls to drive all this and have someone run sensors and make the connections.

    I don't know you will find anyone willing to talk you through this part. Sort of like asking your doctor to talk you through a surgery :)
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • rainmaker
    rainmaker Member Posts: 20

    Yes I get the temperature differential application for the wood portion. I guess I need to talk to product reps about specific control units.

    What about the indirect DHW priority? Do any differential boiler staging controls also give priority to DHW when using 2 different brands or types of boilers?

    Maybe I'll ask over at the other forum threads...

    Yes, I do have a good plumber that just did a geothermal ground source heat pump to radiant job down the road and another plumber that knows the house. But I intend to do a lot of the work myself (PEX is already going in) and as much homework as I can so I understand the system and later on know how to maintain it and why.

    I am an architect and have a lot of experience on the side as hobby / sport rebuilding engines and wiring both line and low voltage systems. not afraid to get dirty and interested in learning how to do this. this damn cold weather inspires me to get it right!

    Suggestions for specific controls or certain piping methods are very helpful. For example, would a triple acting aquastat help here or do I need to get more fancy with controls? Before this week I knew of them but had never taken the time to figure out what it actually does.

    How many designers even care about this stuff? Perhaps the more I learn now, the more appreciative I'll be toward the plumber on the next job... ;)

    If anybody is available to hire to help finish the design or consult on mine, please message me.

  • hot_rod
    hot_rod Member Posts: 22,103
    it is a small

    group of contractors that have a solid understanding of complex controls, especially microprocessor based stuff. I'd say the older "cap tube" type (analog ;) type controls are fading fast. Most heating equipment, even basic cast iron boilers now have microprocessors and circuit board.

    These days it seems the building automation speciality shops are best versed in building and maintaining complex control systems, especially if they are viewed or adjusted online. Alarm companies are also getting into HVAC controls.

    The first step, for me, is paper and pencil. Write down what has to happen when, what has priority, do both inputs ever run together? etc. You can't build it if you can't explain it. It helps to build the piping and control logic together. Not every piping layout is contol-able, at least not the way you might see it in your minds eye.

    tekmar has a lot of controls for complicated hydronic systems, and excellent training materials online. Many installers spend weeks learning tekmar controls. And that could be just one product category.

    The on board boiler control needs to be involved and integrated, it has the logic, and protection for the boiler, so don't bypass or ignore that.

    There is one control I have a fancy for that could probably run all this, four powered outputs, one dry contact. I think of it as a entry level PLC. it has some logic and function built in, but also a selection of virtual relays.

    So for example, chose relay one. Tell it to be either setpoint, differential, reverse acting, timer, parallel function. Then select the sensor, or sensors that it will respond to, determine and input the parameters it controls around, temperatures and differentials, timer or calander event, for example.

    In some cases multiple relays can share a sensor, or parallel one another. The relays are triac, so you can implement a "poor mans" speed control. One 0-10PWM output, and it can accept two Grundfos vortex sensors, flow and pressure. It can connect to a server and be viewed online.

    I have one on my wood/ solar heating system, but to be honest I'm using a fraction of it's functions. It's limitations seem to be the imagination and skill level of the installer, me :)

    I can PM you the installation manual and decide if it is something you and your crew are comfortable with.

    Remember it a bunch of switches (circuit board) in a plastic box, the ability to install it and make it work properly lies with the installer.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • rainmaker
    rainmaker Member Posts: 20
    yes please send control info

    yes, PM me the info for that controller.
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