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Plumbing diagram comments?

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by SIERRADMAX, Dec 2, 2012.

  1. SIERRADMAX

    SIERRADMAX Feeling the Heat

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    On a side note, My oil boilers supply manifold does have a L4006E high limit aquastat (I'm assuming as a failsafe?) Can't I adjust the L8148 to 140 degF setpoint? Then, it will always see 150 degF + water whenever P2 is circulating and not fire the oil burner?

    Sorry for all the questions.. Still learning this stuff.

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  2. SIERRADMAX

    SIERRADMAX Feeling the Heat

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    Nevermind, I won't be able to do that with a L4006E. It's a push button reset. I would be resetting everytime the oil burner turns on and gets to temp.
  3. ewdudley

    ewdudley Minister of Fire

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    Sorry here for causing confusion, my oil boiler has a single aquastat that serves as the high limit and failsafe, If you have a separate L4006 then you're good to go for safety.

    But if you use the relocated L8148 to turn the oil boiler on, it's going to turn the oil boiler right back off again when the oil boiler heats the supply manifold up to 160 (or whatever the hysteresis is). What many do is to have a open-on-rise contact at the wood boiler or at the top of storage that disables the oil boiler. When the wood boiler (or storage as the case may be) gets cool the contact closes and the oil boiler operates normally. It can be as simple as snap disk thermostat on the supply line of the wood boiler that you route the boiler T-T signal through.
  4. SIERRADMAX

    SIERRADMAX Feeling the Heat

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    I remember seeing those. so simple, then I CAN leave the L8148 in it's place....
  5. SIERRADMAX

    SIERRADMAX Feeling the Heat

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  6. ewdudley

    ewdudley Minister of Fire

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    I guess the switchover temperature would depend mostly on your goal, which could be anywhere from 'seamless comfort' down to 'quit your whining, at least the pipes didn't freeze!". I would go plenty low since once it switches over the oil boiler will heat everything up and keep things warm until you build a new fire.

    And another observation on the system schematic: when the system is in oil heat mode it looks like there is a parallel path through the Danfoss and/or wood boiler. Although it is inhibited by the weighted check there might be some unwanted flow nonetheless. Probably doesn't matter since the oil boiler normally comes on from standby and if you were going to run oil for an extended period of time you could just close the ball valves.
  7. SIERRADMAX

    SIERRADMAX Feeling the Heat

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    perhaps a motorzied valve can control this placed downstream of the ball valve on the returns side? Controled by a similar snap ring?
  8. ewdudley

    ewdudley Minister of Fire

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    The weighted check valve is supposed to prevent gravity float but allow pumped flow, but I've never been able to find in the specs what the opening pressure limit is.

    By studying the pump charts for IFC and non-IFC circulators I've concluded it might be on the order of 1 psi. So if P1 sees a small enough pressure drop through the oil boiler, swing check, elbows, pipe, and tees leading back to the point where the parallel paths join, the the weighted check will not open and everything is fine. It's reasonable to think so, but you could get fooled without better data to work with.

    So maybe just make sure there's a spot where a motorized valve could be added if it comes to that and wait and see. The worst that can happen is there will be some amount of flow through the wood boiler whenever the oil boiler comes on automatically, then the snap-disc thermostat will shut the oil boiler off and (depending on your control strategy) re-energize P2 until the snap-disc cools down, and so forth kind of stumbling along and more or less heating the house until you get home and shut the valves between the two systems.

    Also if P1 is over-sized it would definitely aggravate the situation. A Grundfos Alpha or a Wilo Stratos would help a lot in preventing the problem.
  9. I'm using a weighted check and it does keep the wood boiler side of the piping cold to the touch when the oil is running.
  10. SIERRADMAX

    SIERRADMAX Feeling the Heat

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    If I were to add future storage, what should I install & where so I don't have to rip apart the plumbing later?
  11. At the very least a couple of tees and ball valves on the supply and return.

    Tarm has a diagram that uses pretty much your proposed design as a starting point but adds in a 3 way valve on the return, another circ and a zone valve in place of the weighted check. You probably won't need the zone valve since you are not zoning with circulators.
  12. SIERRADMAX

    SIERRADMAX Feeling the Heat

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    If I use a P.A.B., can I install P1 further downstream on the return (closer to the oil boiler below primary loop return), keep P1 from circulating and have P2 serve as circulator to the zones? Will the PAB still function?

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