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Gasifier experts can you please tell me this one thing...

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by GS7, Sep 13, 2013.

  1. ewdudley

    ewdudley Minister of Fire

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    Here's another:

    http://www.termoventiler.eu/media/upload/LM21-60_Manual_E.pdf

    Page 5, "Installation with open expansion vessel". Note detail where expansion vessel is 2 meters above highest radiator.
    hobbyheater likes this.

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  2. hobbyheater

    hobbyheater Minister of Fire

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    No chemicals. The boiler heat exchanger is the lower than the storage and in 2011 was rust and sediment free , there is another drain at floor level 2 feet below the boiler heat exchanger when this drain is opened there is no sign of rust or sediment.
  3. heaterman

    heaterman Minister of Fire

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    What I'm saying is that once the loop is filled and purged, there is no "lift" involved. Only the head created by the loop piping itself.
    The "lift" up to the second floor, or wherever, is cancelled out by the "fall" of the water going back down. All the pump has to do is circulate the loop.

    Regardless of whether the system is opened or closed, a second floor loop WILL lock up if there is any air in the system at all. It will always find the highest point. That's why a good purge is mandatory.

    That being said, I'll repeat that in an open system great care must be taken to keep head pressure as low as possible. This decreases (not eliminates) the chance of suction boiling when fluid temps start getting above 180* or so.
    In a closed system the static fill pressure takes care of that problem. In an open system all you have to work with is the actual head/feet of height from the static water level to the inlet of the pump. This is why you'll notice for instance on a Garn piping diagram, the supply comes out of the top of the tank and they recommend actually mounting the circ as low as possible. In a Garn this will give you at least 4' of static head to work with. That's the pressure available at the suction inlet of the circ. The net positve suction pressure or NPSH to use the industry term.

    Back in the day of the Dead Men, it was common to run open systems and hang an expansion tank in the attic above the highest point of the system. This provided plenty of head for the pumps to work with and still does in situations where that design is employed. Those old guys could get 15' of head over a pump in the basement of the house easily.
    hobbyheater likes this.
  4. ewdudley

    ewdudley Minister of Fire

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    Speaking of which, looking at the Garn Jr I thought I saw something about the hatch being sealed. If so would there be an opportunity to use a raised open expansion vessel? How high could it be?
    BoilerMan likes this.
  5. BoilerMan

    BoilerMan Minister of Fire

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    And vented it on the roof! Just in case something failed and you got a boiling tea pot==c

    TS
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  6. tom in maine

    tom in maine Minister of Fire

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    I am putting together a small charging pump for Dick Hill to add water to his open system, which has been in service for over 50 years.
    He has no additives in there. There is an expansion tank up high in the building (single floor) that connects to the rest of the system through a 3/4" line. The water in the expansion tank has mineral oil floating on top to minimize evaporation through the open tap which is just a small diameter pipe. It is completely detached from domestic plumbing, so he manually tops it off every few years.

    He turns 95 in October and is still screwing around with heating systems.
    There is no hope for any of us!
    BoilerMan and hobbyheater like this.
  7. heaterman

    heaterman Minister of Fire

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    The mineral oil in the expansion tank is a good old trick and does its intended job pretty well. Seems like every generation of hydronic guys has to rediscover all these old methods.
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  8. heaterman

    heaterman Minister of Fire

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    They have the overflow designed so you could not connect an elevated expansion tank and completely fill the Garn. The factory's fear is that someone would seal up the vent pipe if they simply left a nipple welded onto the top of the unit for use as the atmospheric opening.
    Personally, I love to see the tank closed up and just have an opening like that welded to the top for use in connecting an open tank. It would work well in most cases. Unfortunately they have to design for people that don't really understand what is going on.
    BoilerMan, ewdudley and hobbyheater like this.
  9. ewdudley

    ewdudley Minister of Fire

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    Thanks for the info. Could be an interesting investigation for someone with a good handle on code compliance and who might be willing to void a warranty from time to time.
  10. maple1

    maple1 Minister of Fire

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    Anybody have any input (seat of the pants kind is good too) on whether the oil thing might help as an oxygen/air barrier too?

    All in all, I think my non-bladder expansion tank, sitting upright on the floor beside my storage, has faired fairly well after one year. I made a bit of a boo-boo on startup a month ago. I looked quick at a pressure guage, didn't see much, so I turned my autofill on while I did some cleaning & got my firestarter all ready figuring I might have had some air absorption in the expansion tank over the summer when I wasn't burning. Or something. I got a bit distracted, and by the time I came back around & shut the autofill off, it was up to 10psi. That was with storage & all stone cold. I didn't think to check the air level in the tank first - which I should have. Well, I did look quick but my float has sunk so I couldn't see it in the half-dark. Anyway, after getting my storage up to temp (but not fully charged), it was getting up to between 15-20psi. Yesterday I drained around 15 gallons of water back out of it to get my psi back down to where I like it, while things were hot. The water/air level was not quite halfway up the tank. A bit higher than when I started a year ago. I've never added any air since I got things up & going then. I thought of pouring some oil in back then, but then forgot about it. Now I'm thinking about it again.

    And, how thick of an oil layer should one aim for?
  11. Floydian

    Floydian Feeling the Heat

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    Maple1,

    I believe the oil is only used for an open expansion tank(highest point of system). I can't imagine wanting oil inside a closed pressurized but IDK with non bladder setups.

    Noah

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