Control System

The control system is basically a way to control the burn speed of the wood, to keep the water temperature in the correct temperature range.  The speed of the burn is directly related to how much air is intorduced to the boiler, and since we have a secondary burn area, we can slowly burn the wood, and still get an efficient burn.

Before I did this, I thought this may be a difficult stage of the proccess, but it is really very easy.  There are three componens you will need though.

1- A 110v Elecric blower (I used the Dayton Blower 1TDP7, about $70 found here).

2- A solenoid and valve to close off the are (I used this one for about $13 and this for about $25).

3- A controller (again this is the one I used).  I also used a drywell to put the themometer in 

Once you have all the parts, it is easy to setup.  Just connect your blower to the inlet of your air injection.  I split this off with valves to control the ammount of air to the primary and secondar burn.  And then connect your solenoid with the shutoff valve.  They also sell a kit with all this together, but there is no need to pay extra for for the kit when this works just fine.


This is inside my shed, and a little hard to see, but the solenoid is connected to the valve using some wire, and this has worked just fine.


Once we have the blower and valve setup, we use the controller to turn it on and off, again this may seem complicated, but it is not.   You simply put the thermometer from the controller into the drywell in the boiler, and wire the blower and solenoide to the output of the controller.  The controller has a few settings, as it can be used for a heating system or a cooling system.  Just set it to heating, the max temperature you want your water, and the change (I set mine to max at 180 deg with a change of 30 deg).  This means it will heat up till the water hits 180 deg, then it will shut off until the water cools down to 150 deg.  I have noticed that even after the blower shuts off, the water temperature keeps going up because of all the heat that is built up in the hot coals and firebricks, so you won't want to have it much over 180.


4 comments on “Control System
  1. David says:

    I have not had enough testing in cold weather to know how long the burn would last, and it would really depend on what  you are heating (squar feet, and how well it is insulated).  But I suspect doubleing the width would get close to a 24 hour burn.  It also depends on the wood you burn.  I am using soft poor wood.  If you used better wood, then it would last much longer.

    from my experience, you don't need to pre-heat the air (primary or secondary).  But you need to keep the primary and secondary burn hot (insulated), and the primary exaust needs to run thorugh some hot coals to convert all the Co2(non flamable) to Co (flamable).  If you do this, the secondary burn should light.  You want to keep the burn as hot as you can until it has fully burned, then pull the heat out.

    I hope that helps.

  2. Dec says:

    Thanks David, I would expect to doule the width of the primary ,would your experience suggest this would give a 24hr burn? Nice mods on the video..why did the original primary air preheat tubes not work? It looks like ur preheating primary air using second burn chamber? I hope to partially preheat primary using an outer jacket on the last section of flue pipe.

  3. David says:

    Thanks for the comment.  The only reason why I went with a smaller primary burn chamber was to save on cost.  If I went bigger I would also need to go lager with the water jacket, which would add to the cost.  However I have found mine is too small, and I am working on a way to make a little better use of the space I have.  Also before you start building it, check out my youtube videos  (I have not updated my site to reflect a few important changes….

    As for the control system.  Currently I just have my blower setup to turn on when the water gets down to 160 deg and turn off at 190 deg.  Then I have my in floor heat circulation pump set on a timmer to turn on a few hours at night.  when it gets colder, I will just turn the time up on that.  I do the same thing with the circulation pump that heats my hot water tank.   I am sure there are better ways of doing this, but I a have not had time to work on that yet.

  4. Dec says:

    Hi, hope all is still going well with your boiler, t a very impressive system. So much so that yo have inspired me to take the plunge and replicate your build. On that note could ai ask you two questions,,,,the first is is there any reason why the primacy burn chamber is the size it is? Id like to go for a larger one to allow for fewer refills, even a sealed hopper to recharge every few days…? Is there anything you would do different given the choice.
    As far as control is concerned im looking to modify a central heating timer and use stats to maintain temp within these hours. Have you had amy thoughts on how you might control your system?

    Many thanks for sharing your work. All the best.


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