Remaining Issues
Posted: January 18, 2012 Filed under: Arduino, Homemade Boiler, Hopper and Feed, LCD display, Testing | Tags: flow testing, Magnehelic, Testing, Wind baffle Leave a commentLast night I went over the remaining issues with my girlfriend. So here is the list and the possible fixes and approaches to each item.
1) Smoke. There is still some remaining minor smoking issues. Possible fixes, better caulking, stronger fans, a wind baffle, burner redesign? Pipe cleaning? I think I will start with a wind baffle and some better caulking, next furnace will have a better gasket design. I also have ordered a Magnehelic to help determine the normal static pressure so that a baseline can be established and tested against. The boiler is working so ordering fans without more facts would be a expensive trial and error process.
2) Feed issues. There continues to be an occasional feed issue. So much so that today I am going to take the burner off the boiler and see if I can determine the binding issue. Possible solutions? Increase in torque, already ordered more sprockets.
3) LCD issues. The problem has been traced to the relay and I think needs some old fashioned power regulation, no doubt involving a capacitor to remove the spike when the relay is released. Possible fixes, ordered an LCD backpack to free up some IO and also allow only one power and ground to go to the LCD.
4) Hopper Extension. 3 bags per day means a bag every 8 hours, no all that conducive to being able to leave for a day long event.
5) Data logging. Tuning the machine is always the fun part and so dependable data logging needs to happen. I ordered a SD card writer. This should allow the internal Arduino software to work with the card independently of Windows XP which seems to have problems with continual or repeated Arduino upload. I also plan to test the upload and communication with a Linux operating system.
Back to work! Today I built the wind baffle and so after the auger is clear back to the experiment.
Good test for the boiler with -5°F overnight temperature
Posted: January 15, 2012 Filed under: Arduino, Homemade Boiler, Testing | Tags: Arduino, Arduino boiler control, auger feed, cheap heating, cost calculations, homemade chip boiler, pellets Leave a commentI restarted the boiler with a friend on Friday afternoon on the 13th of January. At present it is Sunday morning at 6:45. Thirty nine hours since starting, in that time the temperature has dropped to a low of -5°F which is the current temperature and the fuel usage has been a total of 5 bags. The house is still comfortable and has not shown any dip or problems in maintaining temperature. The only noticeable differences are two things. The lack of the oil fired boiler running which I can hear upstairs and always makes me a little twitchy. The second difference is the temperature of my office. My office is off the utility room which holds the furnace and so is normally quite warm after a cold night. Today it is the temperature the thermostat is set to maintain.
A few numbers, I paid $215/ton for the pellets, so the cost per 40 lb bag is $4.30. The hours per bag is approx. 7.8. This will need a longer time average to confirm but is probably a reasonably good number so in rough terms this is 3 bags per day for a cost of $12.90/day. I looked back to see if I had a furnace run time data which I did have a limited amount. On October 17, 2007 the furnace ran a total of 4.1 hours on a day that had a high of 51 and a low of 33 for a total Heating Degree Day of 22.7. (Heating Degree Days are calculated as (in °F) 65-(day’s max temp-day’s min temp)/2 or to restate 65-average temp) . Taking the furnace run time as 4.1 hours x nozzle rate of 1 gal per hour this translates to 4.1 gals usage for a total cost at $3.85 per gallon of $15.78 for one day relatively mild day. Yesterday’s HDD calculation using a high of 29 and a low of 11 yeilds and average of 20. So 65-20=41. Using a simple ratio of HDD/Furnace Run time would calculate to a furnace run time of 7.4 hours per day for a cost of $28.50 per day. Contrasting this with the pellet costs yields a savings of $15.60 for that one day.
So is that accurate? That was a lot of math using some not very exact calculations. The math was done correctly but Heating Degree Day calculations are notoriously rough. Many oil companies have moved onto more sophisticated methods and of course this is just a snap shot of one day. But as an reality check at this point I am confident 5 tons of pellets would easily get this building through the winter for a total cost of $1075. If I used 800 gals of oil throughout the heating season this would cost me $3080 at a cost of $3.85 per gallon. So yeah I think the numbers are reasonably accurate if not conservative. Wait until I try chips at a cost of $40/ton……too fun.
3rd Configuration
Posted: January 14, 2012 Filed under: Arduino, Homemade Boiler, Hopper and Feed, Testing | Tags: airbox, fuel usage, minor glitches, setpoint, zero temperatures Leave a commentAfter having the issues described in the last post the decision was made to reconfigure the feed for the third time. Hopefully the third time is the charm. The feed is now horizontal again with a reconfigured air box and single fan blowing along with the exhaust fan. The auger was extended into the burn area to allow the pipe to be mounted flush to the inner surface of the mounting plate and so that the auger will push the burning pile down the burner trough. After some minor glitches the burner is up and running. I made some minor changes to the software to allow the burner to run more at a lower temperature and changed the setpoint to 140°F from 135°F. Minor changes but all part of the tweaking and learning process.
The goal for this coming week will be to monitor the fuel usage and see if the system can keep up with the predicted below zero temperatures forecast for tonight.
New Airbox and feed
Back to the drawing board
Posted: January 8, 2012 Filed under: Arduino, Homemade Boiler, Testing | Tags: Arduino, homemade chip boiler, lcd display, LCD problems Leave a commentThe increased air from the second fan did improve the smoke and make the inlet fuel pipe even cooler. It also enabled me to have a viewing port to see if there is flame or if the fuel was adding as expected. But two things happened, the fuel did not flow out of the way so at the bottom of the pipe there was a scree field of pellets which did not move until the previously feed fuel had burned. This situation makes the feeding control very critical. The pace of the feed must be the same as the pace of burning. This alone makes the design unworkable, the process must be more robust than to require advanced combustion calculation, measurement or observation.
The second problem observed was the area of combustion across the pellet field is limited the area of the roughly trapezoidal shape that was formed. This area is significantly smaller than the area of the burner trough. Consequently two things are learned. One the area naturally formed by the falling pellets is insufficient to maintain the water temperature required for my needs, as evidenced by the boilers inability to get past a temperature of approximately 130°F. This alone also requires the redesign since the whole idea is to heat the house. The second conclusion is the area is directly related the heat making capability and thus sizing a burner to a house and feed system is probably quite doable. This seems obvious in statement however, I was thinking that factors such as air volume and burner efficiency would play a larger role. At this point I think I can tailor the BTU’s by burner size and design. I think I will start with the more modest goal of getting the damn thing to work for more than a day.
I’ll admit to being a bit discouraged, however, as January’s calendar said, ” Character consists of what you do on the third and fourth tries”.
To the side see a shot of the burner on the bench in my messy shop. You can see in this shot the approx size of the pellet field that would be burning vs. the potential size of the pellet field if the entire trough was filled.
More combustion air
Posted: January 5, 2012 Filed under: Homemade Boiler, Testing | Tags: Arduino, Arduino boiler control, homeade chip boiler, homemade chip boiler, welding Leave a comment
2nd Fan with slip joint connection
To increase the combustion efficiency a second fan was added. The smoke coming from the boiler was very thick at times and really needed more oxygen. So a second fan was added, to help add more air and help keep the chip feed area cool. The parts slip together and allow a quick look down into the burner area. This allows you to be able to visually check on the feeding, and the fire by simply lifting the fan. So far I am happy with the change and the biggest difference is the ability to see the feed rate appropriateness. Already I want to change the program to allow smaller bites less often because the fuel is backing up the feed pipe. Because of computer issues, the laptop I was using wouldn’t recognize the USB port the Arduino is plugged into more than one or two uploads, I am attempting to switch computers. The 2nd computer at my disposal is running Windows 7. Not nearly as easy to use as XP Pro that I am used to using in opinion.
So, I am having difficulty communicating with the Arduino. I may have to go back to the first computer. Ain’t computers grand? I am a lot happier with a welder and plasma cutter. My weight this morning was 193.8, down 1.9 lbs. Probably water weight although I have stopped drinking beer for a little while. Ham sandwich in every bottle so a friend once told me.
Burner Improvments
Posted: December 19, 2011 Filed under: Arduino, Homemade Boiler, LCD display, Testing | Tags: Arduino, Arduino boiler control, homeade chip boiler, homemade chip boiler, lcd display, LCD problems, welding Leave a commentA 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
Posted: December 17, 2011 Filed under: Arduino, Homemade Boiler, Testing | Tags: Arduino, Arduino boiler control, homemade chip boiler, lcd display, LCD problems Leave a comment
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
frugaltinker 