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Indoor Wood boiler and Gas Boiler question

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by Cobraal, Jan 26, 2011.

  1. Cobraal

    Cobraal New Member

    Joined:
    Jan 26, 2011
    Messages:
    3
    Loc:
    Hanover, Pa
    We moved into this house in 2003 and it had an indoor wood boiler hooked up to a propane boiler. The house was built in 1991, with the original boilers. There are 5 heating zones in the house and both boilers are in the basement of the 2 story house. All of the circulator motors are the same size (Taco 1/25hp), but the farthest run is to the second story master bedroom. From the basement level, this is about 30' high and 30-40' run to get to the room. Is this motor adequate to run that far of a distance?

    Second question:
    The downside to the wood boiler is that once the water temperature gets to be 190-200 degrees, a room may call for heat and drop the temp to 150, which then the propane boiler kicks on. Once the temperature gets hot enough the damper closes, but then the fire intensity is lowered, and when heat is called for the wood fire can't get going fast enough to heat the water and propane kicks on. Is there anyway to get more energy out of the wood boiler? Maybe to have it heat up water tank to store the hot water in? I could turn off the propane, but in the middle of night it is easier to run the propane.

    Third question:
    Tonight the wood boiler heated the water to 230-240 degrees and the relief valve opened. (lots of steam and water came out). I turned the heat zones on and the water started to circulate. However, the water in the propane boiler went from 230 to 150 and the propane kicked on. Yet the water in the boiler was still at 230. I felt the circulator motor that is between the two boilers and it was running. Shouldn't the temperature be equalized? Maybe that motor is internally bad? Should I replace it?

    Thanks for your help,
    Alex

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  2. kielka

    kielka Member

    Joined:
    Dec 23, 2008
    Messages:
    28
    Loc:
    Eastern Pa
    I have a kinda similiar set up. A Scandtec soloplus 40 wood gassifier in a shed and a oil boiler indoors and the two systems are tied together with a 3 spd taco circulator pump that runs continuously. my oil boiler temp is generally a few degrees cooler than my wood boiler and as long as there is wood in the boiler my oil boiler never kicks on. I have a 2100sq ft home with 4 zones for reference. does your tie between circ pump run continuously or is it only when a zone calls for heat? what temp do you have your propane to kick on at?
  3. Cobraal

    Cobraal New Member

    Joined:
    Jan 26, 2011
    Messages:
    3
    Loc:
    Hanover, Pa
  4. kielka

    kielka Member

    Joined:
    Dec 23, 2008
    Messages:
    28
    Loc:
    Eastern Pa
    First off I just want you too know I'm in no way shape or form a professional :) but anyway, what would you estimate to be the water jacket volume you have around your boilers? I think my wood boiler is about 55 and probably about 30 or so for my oil boiler. Going off of your pics I'm not visually seeing much water volume. which if that is the case could easily be and issue for the immediate loss of water temp.
  5. Cobraal

    Cobraal New Member

    Joined:
    Jan 26, 2011
    Messages:
    3
    Loc:
    Hanover, Pa
    The wood boiler is a tarm AD-24 that holds 40 gallons of water and the propane boiler has no storage area. Does that mean I should get water tanks to store the heated water or a larger boiler?
  6. afblue

    afblue Feeling the Heat

    Joined:
    Sep 1, 2009
    Messages:
    278
    Loc:
    Buffalo, NY
    What it sounds to be is you would definetely would benefit from a storage tank so the wood boiler can run and peak efficiency and dump the heat into storage, then it would give it enough time to let the wood boiler recover and start producing heat. The other thing to consider is you might need a different control logic, that wont let the propane boiler turn on so quickly.
  7. kielka

    kielka Member

    Joined:
    Dec 23, 2008
    Messages:
    28
    Loc:
    Eastern Pa
    From your description that is what I'm thinking. I'm looking into ideas for storage and it seems there is certainly a wealth of knowledge on all types of systems on here. For my current system which is lacking water storage, during the heating season I set my oil boiler to come on around 145*F. Which means that my wood boiler maintains a temp range of 175 to 200 for the system, depending on where I set it for the day. My oil boiler only kicks on if I forget to load the boiler and the temp drops way down.
  8. maplewoodshelby

    maplewoodshelby Member

    Joined:
    Mar 10, 2009
    Messages:
    114
    Loc:
    WV
    Your problem is that your not letting your system fully work to its potential. I have the same setup with the exception of you have broken the system up into more zones. I have two zones and recently (the past month one zone due to faulty zone valve that I now have locked open) and I am heating 5000 sq ft and dhw. My system also fluctuates like yours and routinely drops 30 degrees once the pump circulates. One other difference is that my circulator pump is kicked on by aquastat (water temp of wood boiler) and the only thing my thermostat controls is the draft. I have my aquastat set to kick on at 180. When water hits this mark it kicks the pump on regardless if the house is wanting it or not.
    My house stays comfortable 71-75 all thru the night with a load of wood at 9:00 PM and I dont get up until 6:00 am and there is always a nice bed of coals. My temps are typically in the teens at night and 30's during the day so not extreme. I was going to change my system with zones just like yours but after this winter and (new chimney, better draft) I'm not touching a thing. Simpler is always better. Dont get me wrong. The way you are zoned is great and I would probably stay that way if I were you. But you should not have that big of temp swing when only one zone is pumping in that size house. I would insulate all your pipes if they are not. The main thing is that you need to let your system fully work to its potential. Turn your propane boiler temp down to about 68 so that it will kick on if your fire is going out (and you dont freeze) but will not kick on with small fluctuations throughout the night. I use to let my propane kick on and it interefered with the operation of the system. Sure it would warm things up right away but over the long term it got things out of sync with the way a wood/water system works efficiently. The wood boiler needs to stay active all the time, when the propane kicks on, it effectively cuts out the wood boiler. Sure the wood boiler gets hot again but for my temps to stay steady I have to stick with one or the other. I use the propane for emergency only. I'm no expert but from what i read of others (loading wood frequently, using oil or propane assist, and poor performance) I am doing pretty good heating 5000 sq feet with a simple system and no adjustment
  9. maplewoodshelby

    maplewoodshelby Member

    Joined:
    Mar 10, 2009
    Messages:
    114
    Loc:
    WV
    I would also change that circulator between the wood and propane. Your temperatures should be pretty much the same so its probably not working right. When you overheated is it because all zones were satisfied. If thats the case you need to install an automag or wire it so a zone kicks on regardless if house is calling
  10. Huskurdu

    Huskurdu Member

    Joined:
    Jun 10, 2008
    Messages:
    138
    Loc:
    Southwestern NY
    In case you're taking a vote...... I have a similar set up and I turn my gas boiler down to 140-145 F during the winter months to keep it from kicking on while it waits for the hot water from my wood boiler to get to it. It's a 90 foot run from one to the other and it works very well that way. In the spring I turn the gas boiler back up when I'm not going to run the wood boiler any more.
  11. sgrenier35

    sgrenier35 Member

    Joined:
    Jan 8, 2010
    Messages:
    46
    Your gas boiler didn't cool down, because all the hot water from the wood boiler was going out to the zones and returning to the wood boiler, with little to no flow throught the gas boiler.

    The circulator between the wood boiler and the gas boiler should run 24/7 when wood boiler is above 135 deg. You should have a second aquastat on the wood boiler line that shuts down the propane boiler when the wood boiler wate is 140 +. This should help make things work better for you.
  12. willworkforwood

    willworkforwood Feeling the Heat

    Joined:
    Jan 20, 2009
    Messages:
    459
    Loc:
    Central Ma
    I don't have a big base of hydronics knowledge, but the system in the pics is somewhat similar to the way mine is piped. So, based on what I know about mine, it seems that (from the pics) the WB supply is being combined with the zone returns, all feeding into the GB return. So, that should normally cause the WB to always flow through the GB, and eventually equalize. But if there was a big wood fire going, no zones calling, and no overheat loop or zone, then that could have caused the boil-over. Then when the OP opened the zones, the flood of cold return water would have overwhelmed the WB supply, and immediately driven the GB temp way down. But it takes a while for the 2 to equalize again - hence the big temp difference is possible for a short period of time. But if this is true (and it may not be), then why now after working ok for 7 years? So perhaps something has changed or is kaput - maybe a zone that used to allow overheat flow is no longer working? JM(non-pro)O.

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