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help with wiring wood boiler thermostat to run gas furnace forced air blower

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by rallen12, Dec 15, 2012.

  1. Downeast Farmer

    Downeast Farmer New Member

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    It was the heat exchanger in the plenum, not the boiler. Jeez, and English is my native tongue....

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  2. Downeast Farmer

    Downeast Farmer New Member

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    I'm a bit lost here and probably not asking this correctly because I don't really understand the discussion so far. I'd like to use my oil furnace with a heat exchanger from a biomass boiler. I'd like the normal function of the oil furnace to be preserved in case I can't tend to the biomass. I'd like a circulator to come on, get hot water into the heat exchanger, and only then for the blower fan to come on, both in response to a T-stat. Isn't this best? How do I do it? Put me out of my misery here....
  3. stee6043

    stee6043 Minister of Fire

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    This depends on how the user sets it up. Most OWB's run a single circ pump that runs 24/7 and the house thermostat only controls when the fan comes on in the furnace. Many of us indoor burners, especially those of us with storage, will have a circ that sends water into our tanks when the boiler is running at proper temp but we'll also have a second circ pump that sends water to our heat exchanger/load when needed.

    I personally control both the furnace fan and my second circ pump (for the heat exchanger) with a second thermostat and a relay. I only run water through the HX when there is a call for heat.
  4. Fred61

    Fred61 Minister of Fire

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    Run your circulator off the room thermostat and launch the furnace fan with a snap switch attached to the return line of the coil. That way you won't get a blast of cold air before the coil is up to temperature.
    GS7 and ewdudley like this.
  5. Downeast Farmer

    Downeast Farmer New Member

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    I'm just now getting to this!

    I'm not familiar with snap switches. Does this plumb into that return line, or is it surface mounted in the way a temperature probe might be? It'd come on at 140F or so, and then off at 120F; something like that? Any specific switch you could suggest?
  6. Tennman

    Tennman Minister of Fire

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    Boy, this is a blast from the past DF. Today I'm installing a RIBrelay solution to control my demand pump that's ~150' away from my furnace and house tstat. I bought what's called a Pilot Relay (RIBrelay PN - RIBU1C) that's activated by the tstat's 24VAC. It sends a signal via CAT5 out to the barn to turn on a Dry Contact Relay (RIBrelay PN - RIB01BDC). The Dry Contact relay is wired to a standard wall plug in an enclosure creating a relay controlled wall plug that I plug my Taco 0013 into.

    So now I have a remotely controlled 120VAC wall plug out in the barn. Relay cost was less than $80 for both from Grainger and they are solid state solutions (I think). I spent more on 500' of CAT5.

    When you started this post I didn't have storage, but now with storage I don't want to dilute the tank energy with a continuously running demand pump. Lots of ways to skin this and eventually I'm planning to go X300 network based control. But this was a solution I got working in a day. Don't know if this helps but back when I was asking questions on your thread I had no idea how to solve this.

    Best wishes and stay warm. Getting really nasty in Tennessee early this year!
  7. Fred61

    Fred61 Minister of Fire

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  8. Downeast Farmer

    Downeast Farmer New Member

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    Very slick, Tennman. I think Fred61's snap switch solution will be easier for my application, but I'm imagining other applications for yours--cool room temperature control out in the barn during berry harvest season, for example. I'm thinking of that x300 in the long run, too.

    Weather's not too bad downeast in Maine, yet, which is a very good thing because I'm still working on this boiler installation. I have a son in North Carolina who will be much colder tonight than me.
  9. Tennman

    Tennman Minister of Fire

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    Yeah Fred's solution is much simpler that what I thot you needed. I was thinking you were trying to control the pump/fan remotely like my current problem. I'll eventually be installing x300 controls using powerline network connectors. These RIB devices are cheap, simple, and reliable and can get me going fast.

    This morning northern Alabama was 10* colder than Barrow Alaska!

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