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EPA wood furnace - Caddy

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by Beno, Sep 23, 2007.

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  1. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    If you're using an indirect for a "buffer" on the heating system, you can use it for both. The heat exchanger can put heat into it, but it can also take heat out of it.

    You can also add a small amount of pressurized storage by using an electric hot water tank, and just not connecting the power to it. Instant pressure-capable tank.

    Joe

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  2. mtnxtreme

    mtnxtreme Member

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    Eric, Are gasifiers worth the extra expense over non gasifying, I see Tarm and AHS offer both ways. I also see ou are a fan of separste units versus combo?
  3. Eric Johnson

    Eric Johnson Mod Emeritus

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    Since I bought one, I obviously think they're worth the extra expense. In my idea of a perfect world, everyone would buy a gasifier. However, the world ain't perfect and your circumstances might call for something different. The advantages of gasifiers are as follows:

    Half the wood consumption
    Little to no smoke

    The disadvantages:

    Higher cost
    Require dry wood

    I'd say that if you have a large amount of cheap or free wood at your disposal (into the foreseeable future) and you don't care about smoke (and don't plan to), then an OWB might not be a bad choice.

    As to separate vs. combination oil/gas and wood, my main complaint is that you're putting all your eggs in one basket. A leaky boiler means no heat until you replace it. If you have a dedicated boiler for each fuel, then you can easily switch back and forth as needed, and be sure that each one is burning its fuel efficiently. A combination arrangement always involves a compromise. And, if you were able to find a wood/oil combination that manages to burn both efficiently without compromise, then it's probably going to cost more than having one of each. And you're still in the same (sinking) boat if the thing springs a leak.

    If it happens during the heating season (when else?), you don't have the luxury of shopping around and thinking about your options. About your only option is to replace immediately--either with more of the same or a dedicated unit of some sort.
  4. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    As Eric said, redundancy is a good thing. Two boilers are better than one. It doesn't even have to be as big an issue as a leak. There are simple problems which might render one boiler inoperative until repair parts are installed. Do you want to call a service company on a weekend, paying a premium for emergency service, or just schedule the repair at a convenient time?

    Wood heat exchangers are different than oil/gas heat exchangers. The solid fuel heat exchanger sacrifices a certain level of efficiency for wider passages that are less likely to plug up... the oil or gas heat exchanger can be designed for better efficiency.

    Also, you don't want to know what happens when a decent-sized cinder wedges itself into an oil burner's end cone... You really don't want solid fuel and oil/gas venting up the same flue, on general principle.

    Put up a second flue and sit an HB Smith or a Crown (or other decent quality oil boiler - doesn't need to be fancy) next to the wood boiler. It costs a bit more, now, but it is more efficient, more reliable, and safer.

    Joe
  5. Beno

    Beno New Member

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    This thread became something very interesting and useful, more like Caddy EPA wood furnace vs Gasification wood boilers.
    I have 2 questions:
    1. With separate wood oil boilers, can you keep the oil boiler off and start it whenever you want or it must work in parallel with the wood boiler, as a backup whenever the water temparature is lower than a threshold? I'd like to have the full control of when the oil boiler kicks in (w/o damaging the oil boiler).

    2. I agree that hydronic heating provides a better comfort, and is healthier. What I need to find out is at what price. Let's take a 2 storey house having 3600 sq.ft.
    With Caddy wood/oil + Oil heater + Solar panels DHW + Air ducts = $5000 + $2000 + $5000 + $4000 = $16000.
    With TARM wood + Oil boiler + HRV/ERV ventilation + Radiant heating (in floor or panels) = $8000 + $2000 + $2000 + $10000 = $22000.

    I didn't add here the indirect water heater, which I assume is needed for either solar or wood boiler. I am not sure if the numbers are correct, so please feel free to correct me. Will the hydronic heating be at least 30-40% more expensive ?

    Thanks!
  6. Eric Johnson

    Eric Johnson Mod Emeritus

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    I can only comment on the boiler question. I have a gas boiler as a backup, and I shut it down when the wood is running, which is to say October through May. There's no reason to leave it on, and I don't ever want to be burning gas, so the best solution is just to flip the switch. For me, "backup" means it operates at my discretion. And that's without the benefit of a storage tank, at the moment.
  7. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    Yes. A simple switch will do it. If you want to get fancy, you can install a second thermostat (they even have non-adjustable ones) set to 50F or whatever, and use it to over-ride that switch. So, with the switch "on," the oil operates whenever the wood isn't running, based on water temp. With the switch "off," the oil won't operate, unless the house gets down to 50F, thereby protecting your house if you left in a hurry and forgot to switch the oil back on (eg, emergency trip to hospital).

    The numbers will depend on your local market in some cases. I think the 30-40% is a fair general estimate.

    Joe
  8. bbb123

    bbb123 New Member

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    I have a Tarm solo 45, this is my 3rd winter. I suggest hot water (I have baseboard) if you can go radiant you will never be unhappy with it. I've never felt warm in any hot air heated homes. I also have the Mitsubishi slim line series heat pumps for air conditioning, they work very nice also.
  9. Beno

    Beno New Member

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    Are you using the Tarm also for DHW ? I'll go to the expense of hydronic heating only if it can also assure year round hot water. Do you use the same 800 gal storage tank to supply hot water or you have an indirect for this?
  10. bbb123

    bbb123 New Member

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    I get my DHW from storage tank. It takes 5-7 days in summer between fires I wait till tank goes to 120 then reheat to around 160.
  11. Beno

    Beno New Member

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    I wonder if I can use the Caddy to preheat DHW with an air to water heat exchanger, like this one for example: http://www.heatexchangersonline.com/airtowater.htm .
    Maybe using a special duct connected to the hot air plenum that I manually open for air to water heat exchanger when is warm enough in the house.
  12. laynes69

    laynes69 Minister of Fire

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    It wouldn't work. Those are for boilers.
  13. Beno

    Beno New Member

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    I have a question about air conditioning. If I have the Caddy with electric backup, do I need anything else to connect to the Caddy, except of course the outdoor central air conditioning system? I've seen some systems that require an indoor coil/element to be connected to the furnace, and I wonder how will this work with Caddy? Many thanks, Beno.
  14. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    A standard split system will always have an outdoor condensing unit, and an indoor evaporator coil. The evaporator coil absorbs heat from the air, boiling the liquid refrigerant. The refrigerant vapor goes outside to the condensing unit where it is compressed back to liquid and dumps the heat to the outdoors. The liquid then travels back to the evaporator coil, in a continuous cycle.

    "Packaged" units put both coils in one box, meaning you run ductwork outside the house to the evaporator coil, then back in. It's a bad idea in most climates.

    If you're looking at central A/C, look for a two-stage or variable-speed system, and for one using R410A refrigerant.

    Joe
  15. Beno

    Beno New Member

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    I think of using an all year around ERV, like Venmar AVS DUO, which performs well enough during heating and cooling season. This may be enough, if not I can add later a split A/C, having 14 SEER or more.

    I have an additional question. Do I have to add in the utility room where the Caddy will be located a window? The Caddy will have its own OAK for air intake, and I rather not add a window, unless from your experience is a must (for safety?). Thanks again!
  16. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    You'd have to check local codes on that.

    Joe
  17. mtnxtreme

    mtnxtreme Member

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    On the oil/wood combo units, can you run the flue on the interior safely, or should you duct it outside and up an exterior wall.? Also how high, my house will be a 2 story farmhouse, am I limited in chimney height?
  18. Gooserider

    Gooserider Mod Emeritus

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    AFAIK, it is the case with ALL chimneys that you are best off going up through the interior as much as possible, so long as you use the proper construction techniques, clearances, materials and all that. The temperature difference between the flue gasses and the outside is part of what drives a chimney and keeping it inside will make it draw better. The "outside and up"installs are generally a compromise (usually on a retrofit) when the installer can't figure out a way to route the chimney inside. - exterior chimneys are sometimes known as "evil chimneys" because of their tendency to have draft problems (particularly on startup) and increased creosote buildup.

    In terms of height limits, it depends on the unit, the location, etc. but a two story house shouldn't be a problem, as most stoves will give optimal draw around 20-25', and be fine until well over 30'. Even if you do have an overdraft issue, there are ways to solve it, such as using a butterfly damper to slow things down a bit.

    Gooserider
  19. showmemike

    showmemike New Member

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    i would seriously advise anyone thinking of buying a u s stove product to reconsider. i recently tried to establish my environmental products business as a dealer for their furnaces. they had my money for about a week and did not ship my furnaces. i had to file a complaint with the better business bureau and the tennessee office of consumer affairs before they returned my funds.
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