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Heat Storage and Exchangers

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by SteveJ, Nov 19, 2007.

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  1. SteveJ

    SteveJ Member

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    I have a Seton W-130 and a propane 225kBtu for a 3700 sqft off grid house at 9000ft

    Since the house is off grid, I am trying to minimize electricity - shut off as many circulator as possible.

    The Seton cycles on and off many times during the transitional periods (60 degree days and 30 degree nights).

    So, I would like to add a storage tank to the system.

    Currently the Seton uses a flat plate exchanger to pre-heat the DHW and then keep the existing gas boiler warm to minimize propane use and to use existing zone controls.

    There are three zones of radiant heating for the house.

    I was planning on building a tank like this

    Then I was going to use 3/4" L type copper for the heat exchange - 200 ft top to bottom for the Seton and bottom to top for the heating.

    I will probably add solar collectors later.


    Questions

    1. Tank storage location - Seton is in garage and propane boiler and DHW 40 gal tank in basement. I would like to have the tank in the garage with the Seton. Is there any convection issues with the tank one floor above the propane boiler?

    2. Tank structure - is anyone using a plywood tank with and EPDM liner with success?

    3. pH values - should the pH for the tank be in the range of 8.2 to 8.9 for the copper Hx?

    4. Has anyone used KiTec (Pex) as a successful water to water heat exchanger? If so, is about 3x the length of copper required?

    5. How do I minimize the electricity requirements of the system? Can I avoid the always on circulator pumps without using a differential controller?

    6. Any additional suggestions would be appreciated.

    It seems that the ultimate setup is the tank system from Sven at STSS - Does anyone use this system?

    Thanks,
    Steve

    Attached Files:

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  2. pbvermont

    pbvermont Member

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    I installed one of the STSS tanks and a Tarm for someone. I was so impressed with the tank that I went home and....built one for myself. I don't know why folks would build a rectilinear tank. Generally a round tank makes more sense. Spiral heat exchangers in a box? Cold corners? Skip the plywood and 2x4's. I built my tank in a day, including the trip to the store for materials. Its really just an above-ground swimming pool, built to whatever size you want...limited to some laws of physics of course.
  3. Eric Johnson

    Eric Johnson Mod Emeritus

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    There ar a lot of different ways to skin a tank, but I think pbvermont has the best DIY solution.

    On your questions:

    1.) If you're pumping water, I don't see any issues. If you're planning to rely on convection, then it's way more complicated than I can get my mind around.
    3.) Don't know.
    4.) My understanding is the pex and kitek need 3x as much length as copper.
    5.) I use circulators because of their response time, but I considered constant circulation and zone valves. But I'm not sure if that's more efficient.

    Why Type L copper? It's a lot more expensive, doesn't transfer heat any better (I don't think) and might or might not last longer than Type M.
  4. pbvermont

    pbvermont Member

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    answer to ph question: you are right on with the 8.2-8.9 range. Check the tank water in beginning and once a year using a ph meter. adjust using a 2 lb. box of baking soda usually (to raise ph of water in the 7 and under range).
  5. Eric Johnson

    Eric Johnson Mod Emeritus

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    Another thing to consider, especially if you have cast iron radiators, would be constant circulation and a four-way mixing valve. It works off a room stat (or an outdoor stat, if you prefer), and keeps the room at a constant temp by varying the flow through the zones. And uses almost no electricity.
  6. SteveJ

    SteveJ Member

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    Thanks everyone for the knowledgable responses.

    Type L because that is the spec from STSS. But I am always open to cheaper alternatives.

    Eric - the pump question - right now I have a Grundfos UPS15-58FC on until the Seton goes under 130 - so basically always on.

    I have on low speed so the draw is 0.5A or less. But off-grid anything that is always on is much worse than a bigger draw over a shorter period.

    So, I am playing around with my dump zone to get the heat away before boiling over - lots of knobs and adjustments without a storage tank.

    Also, I chose a rectangular storage over round storage due to foot print in the garage - round storage is much stronger and works better with spiral coils but the space issue will no work for me. Maybe a propane tank on end - but then there is not enough tank bottom area for the coile exchangers.


    Question

    With a storage tank the idea is to run the gassification boiler at full capacity until the tank is charged. How do you determine that point? That is, how do you prevent boilover when the storage tank reaches say 180 (tank will be about 650 gallons).

    Thanks again,
    Steve
  7. Eric Johnson

    Eric Johnson Mod Emeritus

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    Not having used one yet, I don't really know, but people I've talked to say that you quickly figure out how much firing it takes to get the tank to where you want it to be. They say things like, "The tank was 130 when I got up this morning, so I ran a load and a half of wood through the boiler to get it back up to 180." So I think you get a feel for it. Plus, your boiler isn't going to boil over when everything gets satisfied. If it's like mine, it will go into idle and you'll get a little smoke and lose some efficiency. So you can play around with it.
  8. trydave

    trydave New Member

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    Hi,
    I was looking at buying a Seton. DO you like it? How much wood do you use in a winter. Does it smoke alot? Basicaly are you happy with it? Thanks
  9. SteveJ

    SteveJ Member

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    CO 9000ft
    tryDave,

    This is my first winter with the Seton so I am not sure how much wood I will use.

    Several neighbors have Central boilers and went through 10 cords last winter.

    Smoke - not that much - like Eric said smokes in off cycle and right now mine is cycling too much.

    I am happy with the boiler. I am still trying to determine the ultimate setup and currently have the configuration shown below.

    Have you talked to Fred Seton? He is extremely knowledgeable and helpful and quick to repond.

    I am looking foward to the ThermaVolt add on from Fred when available. Should be about 1000W during the heating cycle - my batteries would love that.

    Steve

    Attached Files:

  10. trydave

    trydave New Member

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    Steve,
    Thanks for the reply. How many times a day are you loading? How much wood are you curently using(60 day-30 Day)? I would like to try and compar to my usage. I currently have a smoker but would like to upgrade. I have talked to Fred Seton but would like to hear from someone with one of his stoves.
    Dave
  11. SteveJ

    SteveJ Member

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    CO 9000ft
    Dave,

    I have had the W-130 hooked up since November 1 this year. So I don't have a good usage number.

    For instance from a cold house and cold start, today, I have used about 1/24 of a cord of beetle kill pine. 15 degrees F outside now.

    I have only been loading a few logs at a time to get a feel for it. So, right now I am loading about every four hours but could probably do a full load every 16 to 24 hours.

    What boiler do you currently have?

    Let me know if you have an idea of how to perform a good comparison.

    Steve
  12. antknee2

    antknee2 New Member

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    NY
    The Seton boiler is a amazing boiler once you understand that it works best when you start out with a full load of wood and a full heat load . After the boiler and wood are up to temperature the boiler has no problem of shutting down and extinguishing the fire completely ,it could stay that way for hours and then re-lite and burn clear in in a couple of minuets.My Seton boiler was bought used it had a major design flaw. It had so many air leaks ,that the original owner probably produced more steam than hot water, major bummer .I made custom door and draft damper gaskets and used high temperature silicon on other leaks . The good news is the Seton boilers refractory are cast in six separate pieces with steel reinforcing rods they seem to be built like tanks . The boiler really loves big unsplit logs cut to the width of the fire box, right from the forest floor , I don't see the need for seasoning with this type of boiler , never thought I say that . You will not believe how much hot water it produces per load of wood . PS my Seton has 360 gallons of heat storage capacity ,works like a dream. Anthony
  13. SteveJ

    SteveJ Member

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    Anthony,

    Do you have pictures?

    Especially detailing your air leak fixes?

    How did you hook the Seton to the tank and to the house?

    Thanks,
    Steve
  14. ISeeDeadBTUs

    ISeeDeadBTUs Guest

    So Anthony, how easy is it to obtain and replace individual firebox sections?
  15. antknee2

    antknee2 New Member

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    These little fixes totally tamed the beast . You could check for negative air leaks by using anything that generates smoke , I put the in-line induction blower on at full speed and have the high limit damper closed .Check around the entire boiler any ware the smoke gets sucked into the boiler is a leak that should be sealed , if you like perfect shut downs and complete control over water temp. I talked to Fred Seton he said has refractory sections in stock and there very easy to cast yourself .My piping arraignment is to hard for me to explain right now , but I will get to it. Any body know the secret to uploading pics?
    Happy Thanksgiving
    Anthony

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  16. Eric Johnson

    Eric Johnson Mod Emeritus

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    If make a post in "Fast Reply," you need to go into "edit" mode after the post is made to attach the pics. If you choose "Post Reply" when replying to a post, you can do it before you send it in.
  17. antknee2

    antknee2 New Member

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    Thanks Eic
  18. antknee2

    antknee2 New Member

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    How Cool living off grid , your way ahead of us on the east coast . I would love to know more about your system.
    Anthony
  19. SteveJ

    SteveJ Member

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    Anthony,

    Thanks for the pics...Nice sealing job!!!

    What is the material you used around the damper and door?

    Maybe we should start a Seton Thread.

    What would you like to know about my system?
    - I am using the Seton to pre-heat my existing propane boiler (which now never uses propane) - hooked up per instructions from Fred.
    - I am having boil-over issues using the main floor as the dump zone - I have the damper set at 180 and the dum set at 185 to prevent boilover.
    - I am sure I have air leaks - around the door hinge and damper - smoking during the off cycle
    - The system cycles a lot after the house is up to temp.

    _ I would like to seal like yours and am adding a storage tank to reduce the cycling.

    As far as off-grid
    - I have a 4.4kW Solar array and a 4kW inverter and a 3500AH 48 V battery bank


    Thanks again for the great pic and I am looking forward to your piping explanation!
    Steve
  20. antknee2

    antknee2 New Member

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    The gasket material you could find in any well stocked wood stove supply store , I bought a whole range of sizes an had to experiment with then for best fit . I used high temperature silicon to set the gaskets .As far as my setup I have two separate heat exchangers one is a flat plate 30 plates that feeds the main house an bypass's the tanks .The other heat exchanger is built into the 120 gallon Super Store stainless storage tank . The three tanks are hooked up in series with each other, with a separate circulator and low limit aqua-stat . As it turns out every part of the system mixes together and only needs to fired once a day[ so far ]. There are two unused heat exchanger in other two tanks , I will use them for solar backup and domestic hot water in the summer.PS the Seton has so much output that it heats the house and the tanks at the same time without even missing a beat. Hope this info is useful .

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  21. wouldchuckwood

    wouldchuckwood New Member

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    What brand of sealer did you use to hold the gaskets in place? Seems to me the door would be way too hot for the standard high-temp silicon we have at our local hardware store. I have a Seaton W-100, and it's about as air-tight as a mini-skirt.

    Thanks.
  22. antknee2

    antknee2 New Member

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    I hear you !!!! So far high temperature silicon with some sort of copper additive seems to hold the best , very easy to use . How long have you had your Seton in service ? Anthony

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  23. Tarmsolo60

    Tarmsolo60 Feeling the Heat

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    I just put the 957 gallon STSS tank online today. Mine came from tarm when I bought my boiler, I don't know if I overpaid. Looks like something you could build and save some money. I had pretty low wood consumption today compared to when I wasn't using storage. I think I'm going to like it.
  24. wouldchuckwood

    wouldchuckwood New Member

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    Thanks for the information. Well, "had in service" is the appropriate tense. I installed it last year, and loved the way it performed, but had a bit of a disaster last Thursday (see link). I'm waiting to hear back from Fred.

    Seton, Adobe, and Greenwood all use this same design, and I can't believe none of them use any gaskets at all!?! With such catastrophic consequences for having a smoldering fire, I would think they would be more concerned about eliminating the air leaks.
  25. Eric Johnson

    Eric Johnson Mod Emeritus

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    New Horizon, the importer of the EKO, claims up to 45 percent less wood usage with storage. That's a pretty big number. I hope it's accurate.
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