After last winter’s experience, I decided to start from scratch on the auger/hopper assembly. I varied the height several times through different burner designs. Now it looks like it was modified once too many times. The other main reason to rebuild the hopper assembly is the difficulty removing the burner from the boiler because it must stay balanced. I don’t remember exactly my thoughts at that point, I probably just had two wheels around the shop and was in a hurry.
So this fall I am rebuilding the hopper with a different auger drive system, and additional wheels and supports to make it much more robust and simple. The foundation of improvement in the new assembly is the ability to draw the parts in SketchUp as well as cut the parts with the CNC. Here’s a view of the cut out parts.
The parts laid out I call the saddle, angle iron, and side alignment plate.
The parts below are the angle iron plate with the side alignment plate. The angle iron plate is tabbed to fit into the slots of the side alignment plate, this way the parts are self aligning and jigging. Adding strength and ease of assembly. This makes the welding so much easier.
Finally here is the assembly on the welding table ready to weld, note the threaded rod, which also aids in the rigidity and ease of adjustment to make sure all the pieces are square and parallel prior to welding.
And finally the partially finished welded assembly, this assembly will be the foundation to cantilever the auger in the feed pipe as well as support the auger drive motor and gears.
The CAD designed parts combined with the CNC, combined with self jigging design for success make a nice finished assembly with light material for cost savings combined with good strength.
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.
The sprockets have been replaced and improved with key ways cut into the jack shaft and auger. This allows positive feeding without slippage. The jack shaft placement was constrained so adjustment of the chains is limited to what linkages can be removed or replaced with half links and adding a slack tension device on the slack side of the roller chain. With this complete the LCD problems appear to be fixed. Without proper tension the chain did not ride on the sprockets smoothly and the tension could take up suddenly adding a jerk to the system. Without this mechanical jerk in the system the motor can work more smoothly allowing the LCD to not get the power fluctuations that garble the display. The feed problems appear to be fixed but in the last test the unit ran for four days without fail and at this point although there is a marked improvement that time has not been surpassed. Next on the list is the hopper extension to allow feeding of two bags of pellets. This will allow 16 hours of run time without any software improvements.
Last 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.
After 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.
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.