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Power failure protection

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by Tony H, Apr 11, 2008.

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  1. Tony H

    Tony H New Member

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    I am in progress of installing a EKO 40 in a remote shed about 75' from my house the system will start with no storage ( future) and will be connect to a sidearm for DHW and an exchanger in my gas forced air furnace.
    I am looking for the best / easiest way to provide for power outage overheat protection, I don't expect this to happen often as I live less than a mile from a power distribution plant and the power has only gone out for more than 5 min twice in the last eight years but as they say it only takes once to melt your boiler.

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  2. jebatty

    jebatty Minister of Fire

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    A computer UPS with a VA rating to handle your boiler/pumps and associated equipment should work work for short periods or longer if over-rated UPS is used. This will cut in to cover all power glitches and short down times. Also can replace UPS internal batteries with external deep cycle batteries to get longer run times. Test the system to make sure the UPS will handle a long run time without a thermal shutdown, as I think many are not made for extended operation, which is why using an over-rated UPS probably is better.

    With large external deep cycle batteries, the UPS charging system probably is sufficient to maintain the charge on fully charged batteries, but likely not sufficient to charge the batteries after they have been run down some, so use an external charger as needed. Also, deep cycle batteries have best life if you don't run them down more than to 50%

    Then a generator when you've got the time to start it up, if needed.
  3. trehugr

    trehugr New Member

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  4. Donl

    Donl Feeling the Heat

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    I think when you are planning a fail safe solution to protect a boiler from over heat you should take a look at all the potential failures that could cause an over heat situation. Power backup is a good idea however it won't protect the boiler from something as simple as a pump failure. Even power backup systems sometimes fail!

    My plans are to incorporate:

    1. a heat dump zone as a first line of defence.
    2. power backup to keep the dump zone in the loop if there is a power failure.
    3. a gravity feed zone with automag valve if all else fails.
    4. A plan as to how best to remove fuel from the boiler and cool it down.
    5. I'm still thinking about it.

    The plan should also consider that an over heat situation can occur when there is no one around to notice. Maybe some kind of alarm that could let you know on your cell phone or PDA.

    Don
  5. DenaliChuck

    DenaliChuck Member

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    I was thinking about a thermo-siphon loop to a tank above the boiler plumbed with a "normally-open" valve that has no other purpose except to collect btu's in an overheat situation.

    This would take care of a power loss (the valve opens in a power outage allowing the thermo-siphon to begin), but how to deal with a pump-failure?

    How many gallons would be needed for a Tarm 40?
  6. Tony H

    Tony H New Member

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    Having worked in the telephone and date field for many years I have seen quite a few UPS and backup system failures, I would use one but prefer not to depend 100% on it's proper operation. The automag is an open on power fail device if I recall correctly, so do you just setup a relay from an aquastat to open it for a pump failure or other overheat condition or what?
    Number 4. forging tonges, firesuit, heavy gloves and insulated fire can ?
    Tony
  7. jebatty

    jebatty Minister of Fire

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    I too wondered about the Automag on overheat, no power failure. Solution was to put a surface mount aquastat on the boiler supply line, set at 210F. The aquasat opens on rise and cuts power to the Automag, causing it to open and flooding the overheat loop.
  8. SE Iowa

    SE Iowa New Member

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    Just curious about those units that have built in storage like the Biomaxx and Garn and then the OWB's like central, etc. Do they have a little bit of built in protection b/c of the large amount (esp in the garn) of water surrounding the burn/gasification chambers? I would assume if there is a power outage that the dampers close, which would shut off the air supply and just let things smolder. Then, assuming you are not already at 200F, the temp of the water should not get too high, right?
  9. Tony H

    Tony H New Member

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    Thanks Jim that sounds like a resonable solution
    Biomass - seems like in reading the Garn setups have some type of overheat protection included in the design. I would assume even with the fire only smoldering if you can't move any water you woiuld be in danger of an overheat condition
  10. chuck172

    chuck172 Minister of Fire

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    Overheat, caused by pump failure or power out seems like it can cause a spooky event. This seems like a weak link in wood boilers. I like Jim's idea:

    "I too wondered about the Automag on overheat, no power failure. Solution was to put a surface mount aquastat on the boiler supply line, set at 210F. The aquasat opens on rise and cuts power to the Automag, causing it to open and flooding the overheat loop."
    Signature

    Jim
    Always tinkering . . .
    Tarm Solo Plus 40
    1,000 gallons storage

    Anyone have any other ideas that can provide peace of mind.
  11. Eric Johnson

    Eric Johnson Mod Emeritus

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    You kill two birds with one stone (or Automag valve, in this case) with that scenario.

    If you do that, wire the automag up to the same circuit that runs your pump. That way, a tripped breaker or any other power interruption on that line will open the automag, regardless of the status of the rest of the power supply to your house.
  12. chuck172

    chuck172 Minister of Fire

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    On the overheat loop. Do most people actually run about 25' of fin tube higher then the boiler? It seems there must be a more economical way.
  13. Eric Johnson

    Eric Johnson Mod Emeritus

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    You can connect your boiler to a big cast iron radiator or even a pressure tank like a hot water heater. You'll get much better thermosiphoning with those compared to finned baseboard, I'd think. I use a ci rad in the attic above my boiler room.
  14. chuck172

    chuck172 Minister of Fire

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    For overheat protection, what do you use Eric?
  15. Eric Johnson

    Eric Johnson Mod Emeritus

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    A couple of cast iron radiators in the attic above my boiler room and a 3/4-inch Automag. I also have a pumped dump zone into the greenhouse, but it's never kicked on.
  16. chuck172

    chuck172 Minister of Fire

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    Couldn't I just tee in to a heating zone with the automag ? As long as the loop is above the boiler, I should get gravity flow.
  17. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    Gravity flow (convection) isn't very strong, so if there is too much restriction in the loop piping, it won't flow fast enough to do you any good.

    Joe
  18. chuck172

    chuck172 Minister of Fire

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    I don't see why you would have any more restriction taping into an existing zone then you would in you stacked or lined up 25' of fin-tube.
  19. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    It depends on the zone. Some may have 4 feet of baseboard, then go back below the floor, then back up a few feet later for another 4 feet of baseboard, then back down, over a few more feet, and back up for another 8 feet (etc.). All those bends create restriction that can slow down the gravity flow. If it's one long loop with few bends, it should be fine.

    Joe
  20. chuck172

    chuck172 Minister of Fire

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    Right, that's what I had in mind. Thanks Joe.
  21. headrc

    headrc New Member

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    So now I have to ask ...what is an automag ....and how much do they cost. Designing my system seems to just more expensive all the time ......an additional $1800 for a generator takes me out of the running on a system. And this is something I do know ...we have power outages in my area frequen tly and they can last for 2-3 hours at a time. Having to have a backup power supply is smething I had not really thought about or factored the $$ in for .......sorry for being a novice again .....Thx, RH
  22. chuck172

    chuck172 Minister of Fire

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    headrc, boy are we in the same boat. Frustrating isn't it? I'm designing my system too. Seems like where ever I turn just more bucks. The automag is a zone valve that Tarm wants about $105.00. It's all part of the Gravity flow overheat loop. With this loop you should have about 25 ft. of fin-tube radiation.
    Do a search on overheat loop.
  23. Eric Johnson

    Eric Johnson Mod Emeritus

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    An Automag is a zone valve that opens when the power is cut. So if your power goes out in the middle of the night, the valve opens and allows hot boiler water to convect into a dump of some sort. A 40-gallon hot water heater, for example, probably has enough cool water in it to prevent an overheat if your boiler is up to temp and the circulator quits. You don't have to cool it off--just keep the temp below the boiling point. If piped correctly, a gravity dump like this takes the hottest water from the top of the boiler and puts it into a place where it can cool off, and replaces it with water at room temp, or below.

    An alternative would be a battery backup and inverter or small generator that can run your circulator during power outages.
  24. Bob Rohr

    Bob Rohr Minister of Fire

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    Other manufacturers offer normally open zone valves, Caleffi for one. And you don't have to mess with that funky 3 wire zone valve operator :)

    hr
  25. headrc

    headrc New Member

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    So how does this all work with heat storage?? Thx RH
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