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Low flow switches

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by Bob Rohr, Nov 6, 2012.

  1. Bob Rohr

    Bob Rohr Minister of Fire

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    I'm working on finding a dependable . 5 gpm flow switch. The switch on the left started our working well after a few weeks it started sticking in the on position after the faucet was turned off. I replaced it with a new one, installed an isolation relay, same problem.

    The one on the right, Harwil Q-12N is a different style switch, same .5 gpm. I installed it yesterday, I'll see if it holds up better.

    Attached Files:

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  2. Fred61

    Fred61 Minister of Fire

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    You think it's the switch as opposed to the water?
  3. goosegunner

    goosegunner Minister of Fire

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    Bob,

    How big of a buffer tank do you use for these setups?

    How do you control the exchange of water from main storage as the main storage temps decrease towards the bottom end of usable temp?



    gg
  4. Bob Rohr

    Bob Rohr Minister of Fire

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    Good question. I have a cartridge filter and a softener upstream of the feed to the switch and HX. looks clean inside, a bit of red color from my iron water.
  5. Bob Rohr

    Bob Rohr Minister of Fire

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  6. goosegunner

    goosegunner Minister of Fire

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    Bob,

    I would like to run a buffer tank as a staging area for my DHW and forced air coil. My main 1000 gallons of storage is in the shed. I would like to have the buffer tank drop down to a certain temp and then kick on a circulator to bring hot water to the buffer, stopping when it is hot again.

    The control confuses me, as my main storage depletes in temp.

    Maybe I should just run my return from the forced air coil to the top of buffer tank, then return from the bottom of buffer tank to main storage. That way every time the furnace calls for heat the buffer tank will get some new hot water.

    I typically burn when storage gets to +or- 140 so even at the bottom end I should get 120 or so in the buffer tank after forced air coil.

    gg
  7. Bob Rohr

    Bob Rohr Minister of Fire

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    You can control that with a solar differential control. The control "watches" various sensor locations and switches on a relay output. The control I use has two differential functions, 2 relays, in one control.

    The control turns on the boiler pump when the boiler is warmer than the tank, and a minimum of 140°F. A 3 way thermostatic valve/ pump controls return temperature to the boiler.

    The second relay powers pump 2 to move energy from tank to tank. I set the high temperature at 180F. You can play around with temperatures, of course. These controls also have variable speed function, so the pump speed modulates based on temperature, which reduces pump on off cycling.

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  8. Karl_northwind

    Karl_northwind Burning Hunk

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    check out GEM flow switches. used for some of the instantaneous boiler water heaters.

    karl
  9. goosegunner

    goosegunner Minister of Fire

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    Thanks Bob! That control looks like what I may need.

    gg
  10. goosegunner

    goosegunner Minister of Fire

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    Just thinking about it a littl more. I already have a taco zone controller that controls my primary/secondary manifold circulators. Do they make a solar differential controller that will send a low voltage signal to my taco panel?

    I don't think I would need the one with 120v outputs.

    gg
  11. Bob Rohr

    Bob Rohr Minister of Fire

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    All of the newer style microprocessor base brands that I have experience with have a 120V output. Resol, Steca, tekmar, Watts, etc. This allows you to wire directly to the control without a relay or relay box. One less component to wire and consume power is eliminated.

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