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turning backup oil boiler off vs leaving it on

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by paulgrim1, Feb 21, 2008.

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  1. paulgrim1

    paulgrim1 New Member

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    Well I'm sure this has been addressed a million times. I have tried searching but not getting a clear answer. What are the pros and cons of running wood boiler parallel so that your existing boil says warm vs turning boiler off and letting it cool down to room temp. When the fire goes out and the storage is cool then the boiler fires up and has to come up to temp. The oil boiler in question is a 12 year old peerless cast iron. I wanted to hook it up so the boiler would automatically be turned off when w/b or storage is up to temp.

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  2. Nofossil

    Nofossil Moderator Emeritus

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    There's some room for debate on this, and different manufacturers / installers have differing preferences.

    In my view, there's a lot of waste involved in heating up the oil boiler when you don't need it. The hotter it is, the more heat it loses up the chimney and into the boiler room. This means that you burn more wood, and your wood boiler takes longer to deliver usable heat.

    If the goal is to keep the oil from coming on when the wood is working, you could use an aquastat on the wood boiler to disable the oil.

    I plumbed my wood and oil in parallel. Each has a circ pump with check valve. The oil will come on automatically if there's demand and no other heat source is available.
  3. paulgrim1

    paulgrim1 New Member

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    thats my plan . I guess I was wondering the affects of having the oil boiler sit cold for most of the winter. Is a little exter wood to keep the boiler warm and ready to go worth the problems you could get from not keeping boiler up to temp. I also thought just running the boiler at a low temp 120 might work but the your wasting oil. One more thing is the quailty of the oil sitting in a tank for a long time.
  4. steam man

    steam man Minister of Fire

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    You're opening up a can of worms here. However, I will start it off. As a steam engineer who operates and maintains large boilers, it is standard practice to "layup" any boiler that will out of service for sometime (if not emptied and dehumdified) with some means of keeping heat inside to prevent the temps from reaching the dew point. If you reach that point, soot will have very corrosive effects on the boiler not to mention it will turn hard and make cleanings very difficult. I believe you find that the case with small boilers also. Go to www.oiltechtalk.com discussion forum and look at the discussion on pin type cold start boilers. Techs generally hate seeing a boiler kept cold. I have similiar setup with an indirect heater that keeps the boiler operating enough to stay warm. Some wood boiler manufacturers recommend a series set up to circulate the wood boiler through the oil boiler to supply the zones. It will also keep the boiler hot. Some very knowledgable people here will say they turn their boiler off and have no ill effects. My thought is that if your boiler room is dry you shouldn't have as much of a problem. Some boiler controls will maintain a set low temp for protection, say 110 deg. While I currently burn wood in a stove and heat my DHW, I watch my oil boiler temp to make sure it stays warm. Once in a while I have to load it to get it up above room temperature. My next plan is to have a wood boiler tied in to the DHW heat storage, and radiant loops while my oil boiler will back up with baseboard heating. The OB will also be treated as a "heat zone" from the wood boiler when it is capable of suppling heat to supply the zones that don't have radiant floor heating. My thought is to maintain two separate systems
    that a "widow" can run.

    I'll venture a guess that you will hear different thoughts here. After that long winded reply, I'd say if you do decide to go cold, learn to keep your oil boiler clean as possible.
  5. Nofossil

    Nofossil Moderator Emeritus

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    Good point on condensation, steam man. I tend to think that everyone has a similar situation to mine, and I should remember that's not necessarily the case. My boiler room is in a dry heated basement, so the temps are stable and never approach dew point. In that situation, I have to believe that letting it stay cold is OK. and mine really does stay cold - months between firings. Keeping it warm from October through April when it's never going to be called on seems unreasonable.

    Perhaps a better long-term solution would be a tankless unit. My only needs are for backup DHW during 'shoulder' seasons, and backup heat when we go away during the winter.
  6. steam man

    steam man Minister of Fire

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    My basement stays warm also and I haven't seen any ill effects of letting go cold once in awhile. On the storage tank thread solar guy mentions the possibility of boiler leaks, probably with old gaskets on a sectional type boiler from going through cycles. At least you know the oil boiler is going to work when you need it. One would think that not running an oil boiler may save on wear and tear but it may not be the case.
  7. Eric Johnson

    Eric Johnson Mod Emeritus

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    Because of the way my system is piped, I pretty much have to go with a serial arrangement, whereby the wood boiler delivers hot water to the gas boiler vessel, from where it is pumped into the zones. To minimize the standby losses, however, I shut off the gas and cut the power to the gas burner, and then I plug up the chimney to avoid having heat go up the stack. This seems to work well. I never need to use the gas backup during the heating season, except when we go on vacation in the winter (rarely) and then it's not that hard to get it cranked back up.

    But I would wholeheartedly agree that you're ahead to plumb any wood boiler in parallel if possible.
  8. steam man

    steam man Minister of Fire

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    I think factors such as the boiler size, mass, water volume, whether the burner shutter closes off any openings for a draft will all have a big effect on the heat loss through the boiler. Each situation will be different.
  9. paulgrim1

    paulgrim1 New Member

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    To start off. I did start this post to hear everyones reaction. Because everyone I talk to has givin me different advice. Tarm dealer and Econo dealer, two differ. The oil tech that just serviced me boiler said to keep it warm. I guess I could run it cold and then replace it with a direct heat boiler. But to clarify my basement is dug out dirt and damp and the OB doesn't have a draft shut off (don't know what the name for it is) to keep the warm air in the OB.
  10. solarguy

    solarguy New Member

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    Paul,

    You got your answer from your oil tech, keep her warm which means series piping.
    If you don't I've got a hundred bucks down that says within 2 weeks she'll be a leaker....
  11. paulgrim1

    paulgrim1 New Member

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    My thanks to everyone I think I'll keep the OB warm. Wood is a lot cheaper then a new OB and having to reinvent the wheel. I guess the only problem I'll have is in the summer because I want to use solar for my DHW and wanted to bypass the OB tankless coil. If I do that the OB will run cold. I guess I could turn the OB down low and run the output from the storage thru the tankless coil on the OB. It only needs 120 and if the tank cools down the OB should kick on. Sorry just thinking outloud. when I get it finalised i'll post my pipe diag.
  12. solarguy

    solarguy New Member

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    One of the best things you could do would be to bag that tankless coil.
    You should set up an indirect fired hot water heater as another zone off
    your boiler. Solar wise, you should just put in a stand alone solar tank & forego
    loading your wood storage tank w/ solar. In doing this you benefit from solar
    for DHW production year round.
  13. paulgrim1

    paulgrim1 New Member

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    Solarguy. I have 620 gals of storage. Do you think 2 flat panels would be enough to heat the storage tank. I was going to have the output of the tank go to a super insulated electric hot water tank.
  14. solarguy

    solarguy New Member

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    >I have 620 gals of storage. Do you think 2 flat panels would be enough to heat the storage >tank. I was going to have the output of the tank go to a super insulated


    No 2 flat panels won't even come close in my opinion. Even if you only try to maintain a 20 degree difference in the tank, 120 to 140 it would take 103,000 btus. Based upon 6 hours of direct sunlight, no shade factor, a tilt of at least 35 degrees, you would need 120 sq ft of top quality collector, collectors that put out a minimum of 6000 btu's an hour.
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