Need a Boiler shut off for end of burn

salecker Posted By salecker, Aug 2, 2018 at 1:09 PM

  1. salecker

    salecker
    Minister of Fire 2.
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    Aug 22, 2010
    743
    195
    Loc:
    Northern Canada
    Hi All
    It looks like my way of burning for the last 8 yrs is going to change.
    In the past we would start a fire in the evening and burn flat out for 5 hours or so.This was an easy way to keep the storage in play.
    This winter i believe i will be by myself,it looks like my wife will be returning to Ontario for the winter maybe for good.
    So without a second person to rely on for starting and stoking the boiler i will have to start a fire and fill the boiler at various times during the day/night.At the moment the boiler doesn't have a shutdown once the fire is gone.This will be important now because i don't want the fan to run after the wood is gone,it will have a cooling effect that i can't afford.
    So has anyone added such a control to their boiler? Or any suggestions?
    Thanks Thomas
     
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  2. TCaldwell

    TCaldwell
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    Oct 26, 2007
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    Loc:
    860-868-9014 h 203 948 0864 c nw corner ct.
    I use a differential temp between flue and boiler storage, when flue temp decends below 10 degrees above the water temp, it shuts the draft inducer off.
    When I start a fire( turn on the inducer) with a momentary switch it activates a timer for 10 minutes, during this time the above temperatures are not monitored, this allows the flue temp to rise +10 deg differential. This ensures the fire is underway, if the differential isn’t met within the 10 minutes, it shuts the inducer off, possibly fire didn’t take.
    After the 10 minute time period and the differential is met the inducer stays on until the flue temp declines to within 10 deg above the boiler water temp at witch time the inducer shuts off signaling the end of burn.
    Typically for me water is 185, flue at 195, leaving very few coals, your optimum diff temp might vary.
    I use a eurotherm system and this is just some logic, math functions it has. A pid temp controller with 2 temp inputs, a math function for the differential, a timer and a relay would work.
     
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  3. S.Whiplash

    S.Whiplash
    Member 2.
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    Oct 28, 2012
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    Give Dale at Econoburn a call, I believe their new controller will shut down the fan after the burn is complete, you just have to replace your old control box.
     
  4. salecker

    salecker
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    Aug 22, 2010
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    Thanks i will see what Econoburn has out now...
    TC is your control something that you put together,or a purpose built unit.
    I would like something simple,i live 160KM's away from tech help and the nearest parts.
    Thomas
     
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  5. CountryBoy19

    CountryBoy19
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    Jul 29, 2010
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    The PID's I'm familiar with are just single input models. Can you elaborate a bit more about what type of PIDs can compare 2 inputs?
     
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  6. TCaldwell

    TCaldwell
    Minister of Fire 2.
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    Oct 26, 2007
    945
    99
    Loc:
    860-868-9014 h 203 948 0864 c nw corner ct.
    Most pid manufacturers have different levels of complexity and options available, my unit is a mini 8 made by eurotherm. Phone tech support is common and usually very good. Instrumart in Vermont is another good distributor with presales engineering help and lifetime tech support.
     
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  7. warno

    warno
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    Jan 3, 2015
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    I have a simple temperature controller with the thermocouple in my flue pipe. The relay in the controller is tied to the relay of a contactor. Once the thermocouple reads a flue temperature of less than 200 degrees it shuts everything down. It will not start up again until I hit the restart button with a new fire.

    Here's my control panel

    20161016_081612.jpg
     
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  8. salecker

    salecker
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    Aug 22, 2010
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    Loc:
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    Hi warno
    I assume you built it yourself?
    If so do you have a wiring diagram and list of components used?
    Fall is approaching fast here.Every year i watch people freak out once they realize they didn't get their summer list done.That might be me this year.I have been waiting a month and a half for a couple of day of rain so i can weld up the roof of the wood shed.8 yrs of bark,sawdust and wooden pallets isn't a good place to weld above if it is hot and dry.Then i need wood,i burnt my reserve wood last year because it was getting to old.
    So i am actually 2 years behind in getting wood.
    Thanks Thomas
     
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  9. warno

    warno
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    Jan 3, 2015
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    I just sent you a message.
     
  10. CountryBoy19

    CountryBoy19
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    Jul 29, 2010
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    Loc:
    Southern IN
    Can I get the same message?

    My thought is (no specific part numbers, just general idea): Momentary Push-button that controls a 1-shot relay (there are numerous types, you can do many interesting things with the diff types). That relay send coil power to a 2nd relay that controls the boiler power on/off. The 2nd relay can ALSO have it's contactor coil powered through the flue-temp monitor.

    Start-up goes like this: Push momentary button, this starts a timed-on process that energizes the main power relay, light the fire. If fire takes off and flue gasses rise to the set-point a 2nd power source will be sent to the main power relay. This way, when the timer cycle is over, as long as the fire is hot the boiler will remain on until it drops below the set-point again. If the fire dies out before the time is met the main power relay will never be energized through the flue-temp circuit and as soon as the time expires the boiler will shut down.

    You can add further controls via off-delay timed relays etc to keep your circulator pump from running until after the boiler gets going etc.

    It's also fairly easy to make a "self-latching relay" using a 3-phase relay. I just made one for a water storage tank that I want to fill autonomously when the level gets low. The low-level switch energizes the relay. But as soon as the low level switch trips again it would shut the fill off, causing short-cycling of the pump. I wanted some hysteresis built-in. There is a 2nd circuit that energizes the relay; this one runs series through the high-level switch, and then through the very relay it is powering, then to the coil of the relay. This way no power can go through the 2nd circuit until after the 1st circuit (low-level) energizes, but once the first energizes, the 2nd stays energizes until the high-level switch is broken. I hope that's not too confusing, I know pictures would make more sense.
     
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  11. warno

    warno
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    Jan 3, 2015
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    You described the exact setup i have in the beginning of this post. I have a push button, timer relay, flue temp relay, and contactor that everything runs through.

    And in the last part of your post, I too have a float switch but it doesn't power an auto fill it only covers water level in my boiler. If the water level drops before the float switch limit it shuts everything down. It is basically my main power. I've owned my boiler for going on 4 years now and have only added water one time. It's only a 125 gallon water jacket and it's as open system. I didn't feel the need for an auto fill on my system.
     
  12. CountryBoy19

    CountryBoy19
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    Jul 29, 2010
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    Loc:
    Southern IN
    Not to get too far off-topic but in my case it's not related to a boiler. I'm on a low production well that pumps into a holding tank. Domestic water demands are handled directly from the tank and when the water level drops it kicks the well pump on to bring the tank back up to full.

    The reason for the hysteresis (through the 2 float switches & self-latching relay) is to keep the well pump from short-cycling otherwise it will trip my pump monitor. The pump monitor checks for a variety of conditions including a dry well and short-cycling of the pump. If short-cycling occurs (mostly due to a "bouncing float switch") the monitor will automatically shut it down and it has to be manually restarted. The monitor is in an outbuilding 1/4 mile from the house so it's not easy to catch if it shuts down.
     
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