Burner Improvments

A friend and excellent engineer visited over the weekend and between us we decided to improve the burner a little.  The first change we decided to make was to add some insulation.    I measured the temperature around the outside of the boiler with a non contact thermometer at approx. 350°F in the area of the firebox.  The mounting plate that holds the burner was approaching that temperature as well.  The air box was lower but still this is an excessive temperature.  The Auger pipe was solid from the hopper to the burner unit and since I have both 4″ pipe and 4″ tube we decided to make a thermal break in the auger feed for additional safety.  The 4″ pipe even though it is surrounded by the air box eventually gets warm and since the feed auger has a fair amount of room between the auger and the pipe there is a certain amount of fuel that remains in the pipe and at shut down this can smolder.  So to remove this problem and make the unit more safe a redesign was initiated. Adding  insulation between the air chamber and the burner with the addition of a thermal break prompted us to take the unit apart, check it over and see how everything was faring as well as make improvements.  But of course after the burner and hopper were cut apart and on the bench more improvements were noted. Most of the improvements now fall into minor design for manufacturing type areas, maybe a little less welding and a little more tabbed nut and bolt assembly so minor changes can be made more quickly.  Of course being able to pull the auger feed away from the burner assembly without unbolting anything will be a big change and improvement.  I am going to make the air box bolt on as well.  Should be reassembled for another test on Wednesday.

Of course it wouldn’t be a weekend if we didn’t play with the software.  We added a For loop to the thermistor function to improve the accuracy.  I added an array to smooth the results using a moving average.  But most importantly we found the lingering problem with the LCD characters being garbled.  It was a wiring issue.  Now fixed it has run 24hours without a problem and I am confident it will stay fixed now.  The next step will be to add a capacitor if the problem resumes.  I am quite confident it will not be a problem however since it looks more solid even.  There is less flickering and more solid character display.  So all in all a fun and productive weekend.

Overnight run successful

Improved wiring and Arduino mounting, yes that’s a sparkfun box

Successful overnight run,  software required major tweaking but the boiler ran without involvement overnight.  I did supervise the process but nothing got hot or got out of the control parameters.  My only complaint at this point is chip economy.  The setpoint I chose was 160°F which is probably too high for the weather we are having now.  The overnight temperature was approx. 32°F  and so the circulator just didn’t use that much heat.  So I think I will add some software changes to the program.  The first to be the addition of a variable called setpoint so I can easily change the set point temperature.  Ultimately I need to add a outside temperature thermistor to the internal PC board so the Arduino can determine it’s own set point based on outside temperature.  Some other ideas are to relay the draft fan so the flames aren’t quite so robust all the time as well as physically remaking the burner unit to be smaller.  All in good time.  So far software changes are making a difference so I will try that first.

The flames look consistently great.  The burner is working really well.  Still having LCD problems and my main goal after getting the unit to run is building a second unit so I can make the unit run the Hot water thermostat as well as try to duplicate the LCD character problems.  Of course I could probably call the manufacturer of the LCD to see if they have any technical support.  That will be a Monday project.

Above is a picture of the somewhat improved but not final configuration.  At least the wires are neat and the smoking problems have been overcome.  The new door is pictured, and the burner flame.  A photographer I am not.

New Fire door with over center latches and fiberglass rope sealing

Electronics mounted

Arduino mounted in project box

Finally the electronics have been mounted in a project box which makes them much more portable and easy to use.  The LCD has been disconnected electrically from the relay for nearly 24 hours.  The relay may have taken enough power to cause enough voltage fluctuation to garble the LCD display which seems very sensitive to voltage fluctuations.  Of course this configuration will be much easier to work with, easier to move without worrying about wires and easier to keep clean and safe.  The Arduino is mounted so that the USB cable can be plugged in without removing the cover.  All seems to be working well, another milestone.  I think I will build a second one which I can use either as the thermostat or the boiler controller.  The project box part number 270-1809 was obtained at Radio Shack and the PC board inside was also obtained at Radio Shack.  The PC board is very easy to use with board that consists of many mini bus bars to make hook up and soldering easy, the part number is 276-168.Today’s goal is to deal with the smoking issues of the boiler.More update later.

Circulator controller now works!

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The Arduino thermostat/circulator controller has now been tested and works, I bought an Adafruit DS1307 RTC and am now displaying the time on a 20x4LCD display.  The relay board has been hooked up and now turns the circulator on or off according the time and temperature.  The circulator pumps hot water from the boiler through the second coil in the solar thermal storage tank to supplement any heat that may be required due to an inadequate solar collection day.   While the electronics now work nicely, the next step will be do put all the components in a neat case so that the project can be finished and mounted.  Let me know if you would like a copy of the code or have any questions.