Over the summer and fall I have written and tested a number of programs to have the building blocks of a working program. I knew the key this year would be the ability to log data. Of course to log data and have it mean something you have to have good data. So I spent several days working the bugs out of OpenLog, which works but I would not recommend. I also spent some time figuring out a combination of moving averages which resultx in stable data.
Of course the integration process was a train wreck. The arrays used for moving average data smoothing were declared wrong so that bug had to be found and fixed. The Serial LCD needed to be replaced, and my soldering iron wouldn’t work. A few of the functions are timed and there were some issues with those functions. The code for Open Log was not robust enough, once I worked out all those issues, which took most of the weekend, it is finally ready to test.
I had a plow in the shop for repair and soaked up the spilled hydraulic fluid off the floor with some sawdust, actually pellets that got wet. So the hydraulic oil soaked sawdust is in the hopper to be burned. It’s burning now, so tomorrow I should have some excel data which will help me make decisions to improve the software. At this point I am not sure it will be valid however, it is really taking a long time to come up to temperature with the sawdust. Another data point.
Minor changes in the software that force the boiler to maintain a tighter range from the set point has cut the fuel consumption from 3 (40 pound) bags of pellets to 2 daily. These software improvements and a extension to the pellet hopper mean the boiler will now run 24 hours without needing additional fuel. The hopper extension adds at least another 40 lb bag of pellets capacity bringing the total capacity to approx. 2 1/2-3 bags. I haven’t measured only estimated.
The boiler set point is currently set at 135°F which seems to work just fine for the temperatures we have been having and the software is consistently running within4 degrees of set point. This range may seem excessive but seems to run just fine. The program is becoming more modular in that there is only one number to change, the set point. The set point currently is a variable declared in the setup section of the program but eventually the set point will be self adjusted by the program based on the outside temperature. Economy and efficiency by software optimization is the goal for this next week.
We have had a very mild winter in my opinion. The Heating Degree Day total for the month of Dec 2011 was 1091 as measured by the local weather station. The normal is 1209 HDD a difference of 118 HDD, not as much as I would have thought. The total for the month of January 2012 so far is 1140 with four days to go, with a normal of 1419. We’ll see how the month ends but if it continues as the average day it will be short approx the same number of HDD as last month,December. My interest in HDD is to see if there is a correlation to HDD and fuel consumption. There should be and if there is than the fuel economy is starting to improve. As I told a friend of mine, at this point the boiler is like a truck I used to own, 10 mpg going uphill loaded, 10 mpg empty going downhill….so seeing fuel consumption changing to track the weather will be the first step to seeing some optimization.
Software work on fuel economy and the extrapolation of costs for the upcoming remainder of the season is of great interest. The next step in fuel economy may be better insulation of the boiler and piping and will not be as simple as software improvements. But if I can get a correlation between the outside temperature and fuel consumption that is measurable then the software will be nearly optimized and further improvements will have to come from physical changes. This week sees a 40 pound bag and $4.00 improvement per day, $28/week, $112 per month. Next week’s goal: another $60/month. I am hoping for a total seasonal heating cost of $500 or less using $200/ton pellets. I will consider that a huge victory for heating a 2300 sq ft house with 3 garage doors.
I 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.
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.
The New Year practically demands resolutions and change for the better. So with that constant improvement theme in mind I am publicly stating my goal to lose 15#’s and so I am starting from 195.7. My second resolution is the constant improvement of the boiler. So here we go……
Auger feeding failure due to the motor stalling demanded the sprocket change on the auger motor feed assembly. The sprocket I chose doubles the torque available for feeding pellets. Since the shaded pole motor is constant speed the program had to change to double the auger run time. So taking the data I had gathered I changed the program in two ways.
I changed the times to accommodate the speed change demanded by the sprocket change and I changed the paradigm to have constant run time and vary the dwell or off time. The increased torque is a vast improvement and since the change it has had no problem feeding even adding an entire bag of pellets at one time.
A second advantage of the change is the improvement of the LCD display. I think that this problem is now fixed since the LCD has been running without garbling the characters for several hours, long past the time when the LCD would normally have failed. By increasing the torque the auger feed motor is running at less amp draw and so it feeds back less to the relays. I also grounded the relay in a more positive way.
I’m a big proponent of having some skin in the game. If you don’t you are fooling yourself. I learned that in the financial markets. If you can trade on paper you have a better chance of succeeding in the real world trading but when you have real money involved sometimes you can’t make the decisions needed.
That seems to be the case with the LCD display. After having worked out some basic electrical issues the display worked fine for 3-4 days with the relays tripping but no motors hooked up. Now that the motors are hooked up again it seems to be garbling the LCD. So, the only assumption I can make is there is some kind of electro-magnetic field or a bad ground that is interfering with the LCD. The motor is a shaded pole motor which has a large electromagnetic core which no doubt radiates interference for the controller. Below is a picture of a similar motor.As a fix I think I will twist the LCD wires so they are less of an antenna and see if using some tin foil to shield inside the project box as well as above the feed motor and see if I can improve the ground.
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.