It’s been a cold ride here in New Hampshire for a few weeks. However, like a campfire, on average we may end up less than average on HDD’s for the month. I say like a campfire, because it always seems that one side is too hot and one too cold to really enjoy it, however on average….It’s raining hard here today, so once again the snow is leaving. This will ruin the skiing and winter sports and yet it’s really too cold to enjoy summer sports. Winter in Northern New England has become a lot like southern New England. But that’s a different topic.
The pellets seem to be a pretty steady 14HDD per bag. And so a ton this time of year lasts about two weeks, maybe a little longer. We bought our first ton this year, I was using up old stock and we bought a ton from Tractor Supply, their brand. I am liking them a lot, they seem to not cause any ash build up problems at all. I will buy them again. If you add up all the bags used and divide by 50 bags/ton we are at 4.22 tons heating season to date, for a total cost of $947.39 at the cost of $224.50/ton.
Above is a scatter plot of Heating Degree Days (HDD) taken from Weather Underground data from the weather station in Springfield VT. Not exactly Newport, NH but close enough for this graph. It’s important to note that the beginning of October was quite nice which resulted in a fair number of days of timed burns, starting the boiler at 4 pm and running it until 9 pm for example. It quickly became obvious with Novembers below average weather that this would not result in satisfactory comfort and the boiler has been running continuously for most of the month. The trend-line looks like you would expect to see it, but the scatter data is quite varied. It will be interesting to see if this data correlates better as the winter continues.
The total pounds of fuel burned Heating season to date: 92 bags @40 pounds/bag= 3680 pounds vs. a total HDD to Date of 1444. Last year’s data for December indicates a HDD total for the month of 1069. This should result in 68 bags burned for the month for a total of 2720 pounds. Using $215 per ton this should be a monthly cost of $292.40 This is both heat and hot water. Be interesting to see at the end of the month how close the prediction comes.
You may remember I added a function to collect HDD data at one point, however it never seemed to work as well as it should have so I stopped using it, I am now considering reviving a variation of that function using an array for the max and min hourly numbers to get a more accurate HDD local number. I’ll post the code when I finish.
I know it’s early on the calendar but my focus is starting to shift back to my heating hobby. After two years of experimenting I have a proven performer with both the mechanical unit and the software I used last winter. I could change nothing and go through the winter fairly smoothly but there is always room for more improvement. So this is my plan: 1) Build a new unit very similar to the proven unit I have been using but with greater feed range capability to allow the unit to feed wood chips as well as pellets. By building a complete new unit I can always roll up the proven unit after the experiment is over and the data collected and resume heating without a hiccup. 2) Make slight modifications to the boiler to allow a larger interface plate between the feed unit and the boiler. This will allow a greater range of experimentation with burner designs. 3) Continue making small experimental changes to the working pellet unit such as a vibrator for ash removal, different burner designs, different draft designs. 4) Continue to make changes and improvements to the software. To start I would like three modes of operation. Continuous, run for some amount of time, and run until a set time. I changed the software to run to a set time by calendar date last spring but it was built into the software by date not menu or button choice. I would like to have the option of running for a few hours for both experimentation and also to occasionally heat hot water and be able to choose these options by menu. This fall I am sure I would like the unit to be able to take the chill off and then shut down. 5) Build a chip dryer. This is going to get to be a priority , I know the days are getting a little shorter and it is amazing how much less solar there is in the fall. Time to giddy up on that one.
I know I have to prioritize the work, and work as time and cash flow allows. But I think the first step will be to make a new interface plate and boiler opening. This will allow standardization for the next design and this work can be done while there is no particular need for heat. I went dumpster diving the other day and got a great new electrical box, so I guess I can get going on the that part of the new burner feed. I like free stuff. I may hit that dumpster again soon.
In the mean time it is still summer and there is still sailing weather.
Well of course there’s fire in the burner that’s how it works. After today however the Arduino should be able to sense the fire since I added a photo resistor, commonly known as a flame sensor, bought at a furnace supply store. With the Arduino’s ability to sense flame, the addition of automatic self starting should be enabled. The ability to determine if fuel is building up should also add safety to an already proven safe unit.
The sensor I obtained is a flame sensor used in a normal oil or gas fired burner. The flame sensor allows me to sense the light corresponding to a fire currently burning. The sensor cannot determine if the fire went out or if the flame sensor can no longer see it but functionally it makes no difference to me. I am interested in either condition and the response is the same to both conditions, turn off the fuel feed. If the fire went out, no need to keep feeding fuel, that will simply clog the feed chute and make a mess. If the fuel has backed up the feed chute so much as to shield the flame sensor, there is excess fuel, turn off the fuel feed. Physically the sensor is mounted to “look” through the back of the feed slide. This positions was chosen purposefully to determine if fuel was backing up.
Because the flame sensor is a resistor, I am using a voltage divider circuit to measure the voltage and then using the software to check the voltage with a if – then statement. The software determines if the voltage is high enough to indicate flame or too low indicating dark. I have been recording various sensor data to the micro SD over the heating season, so I will record the voltage overnight and we can see the range of data tomorrow. If anything this should be a good time of year for the test since the fire is needed to maintain the temperature in the building, it is mid 30’s F here today, but the fire is not required to be too vigorous since the temperature is not extremely cold.
Pictures and data to follow.
I went out on a customer issue the other day, I had to meet a locksmith at a customer’s house. After the job was done the locksmith who I have done business with for years and is a friend came back to the shop for a check and a beer. Naturally I showed him my home built boiler. He rent’s so he wasn’t particularly interested but mentioned he buys a 5 gallon can of off road diesel to bring home to heat his house every day. The price is about $3.77 per gallon which is about what the local oil company would charge to deliver. So if it’s the same price why not have it delivered? Because he doesn’t want to, or can’t tie up the $471.25 the fuel company would want for a minimum sale. That amount of fuel would last him about 25 days at his 5 gallon a day rate, maybe less time if the 10 gallon nights are accounted in as well. Since it was quite cold he was planning on buying two cans that night. He said the normal 5 gallons cost him $19/day. Rounding this to $20 for ease of math and multiplying by 30 days per month this is approx. $600 per month for fuel oil. We bought our third ton of of pellets for the heating season for $209 at Tractor supply last week. So our total fuel costs for the year are approx. $800 from November to mid February. What a difference! Not to mention I can’t imagine going to the gas station every day for fuel. What a pain. Having diesel trucks and fueling up at the same pumps I see many different people filling five gallon cans every time I fuel my trucks. I’m not the best at budgeting in the world, but I realize my blessings when I witness first hand how the paycheck to paycheck underemployed crowd deals with winter.
I’ve started calculating the Heating degree days with the Arduino program. It’s a pretty accurate look at the day’s heating requirements. I want to correlate those temperatures to fuel usage. I also have updated the CNC plasma cutter to the 5 start lead screw. Before I made the upgrades I needed to limit the cutter to a linear travel rate of 13 inches per minute to avoid vibration issues. After reassembly I tested the machine to 40 inches per minute with no problems. It may be even better than that I just got so giddy I quit testing. I am hoping this will significantly reduce the slag produced by the plasma cut. Not much motivation to take anything apart at this point. It’s just too damn cold out. It was -5°F this morning here, the HDD days yesterday was 65.5. Stay warm out there. I could back the tractor out of the shop and do some woodworking, maybe build the chip dryer…..
It may not be cabin fever, more just a general malaise. That midwinter everything is working and I don’t want to take it apart feeling. But I have several projects half done at this point. I am waiting for headers to install the Ethernet card so the Ethernet update project is on hold. The CNC plasma cutter is apart awaiting a new lead screw for the y-axis. This is to remove the vibration issues I have been experiencing. I am changing from a single start to a five start lead screw. I will lose one fifth of the resolution I have presently but that will still be plenty of resolution for this application. But the big news is I am finally going to move on building a new firebox. It’s time to retire the over the road fuel tank turned boiler. Well maybe not retire, just move onto a new home. Anyone want to buy this working boiler? I would consider selling the auger and burner feed as well as a combination. The unit is located in Newport, NH if you would like to see it working. It won’t be available until it’s replacement is built. It is after all heating the house, shop and hot water. But I am hoping to have the replacement built before the end of the heating season for some testing. If you are interested drop me an email at: email@example.com
A quick reminder of what the combination looks like, this has successfully burned pellets, chips and to a limited degree sawdust. Ideally you would be a person who can tinker as this is a prototype unit.
The software, Arduino and LCD display all very solid and work very well.
By adding Ethernet capability I can write the data I am currently collecting on the micro SD card to a browser directly. This means I could pull up Firefox and go to my Arduino’s IP Address and see the data. This will give me the ability to read the data from anywhere on my home network as well as anywhere I can get internet connectivity, potentially allowing me to review data from a smart phone remotely. Additionally I could control relays from a remote location as well. But for now the ability to ease the data collection and monitor the process remotely will be a great first step. First I have to buy an Ethernet shield. For those of you not familiar with Arduino this means an additional plug-in board that will stack on top of the Arduino pins.
Here’s a picture of just the Ethernet shield, the connection point you see on the front is the plug-in point for the Ethernet connection. This is a RJ-45 connector. I was able to get a 100 foot Cat 5 with installed RJ-45 connectors for $27 at Home Depot.
At present I have already have a prototype shield plugged into my Arduino Uno. This allows me to easily disconnect and update the Uno without disturbing any wiring connections. There are quite a few wiring connections for the RTC or Real Time Clock, the LCD display, the outside temperature thermister, the boiler water tank thermister, the Auger Feed pipe thermister as well as Relays to turn on the Auger motor and boiler tank water circulator. But when I attempted to plug in a prototype shield into the Ethernet shield there was interference with the RJ-45 connection point. The prototype shield would have grounded itself on the metal so I have ordered Stacking headers to extend the height above the shield. More when the headers arrive.
After writing a similar post on 1/15/2012 I find myself saying basically the same thing, after a -10F night the boiler has kept up. Additionally except for a 12 hour period when I made some boiler modifications the boiler has run continuously for 14 days. There are several differences however. The software is 100% better and controlling the temperature to within a few degrees. The burner is now a waterfall type burner that is much safer and runs more consistently. The hopper and auger setup is much more consistent and dependable as a worm and worm gear than the chain and sprocket setup from last year. Most significantly the burner has proved it can run on chips as well as pellets. During these colder nights it is more difficult for the burner to keep up with chips because of the density differences. The chips are much less dense and because of this the auger must feed significantly more of them. The auger motor may need to be changed to accommodate this burning however during weather that does not require so much energy the chips will burn just fine. I could have easily burned chips for most of December with no issues if they had been dry enough. Which brings me to my second topic.
A test plan. I have taken the Holidays off but it is now the new year and time to make some constant progress. To facilitate the test plan I want to make some incremental improvements in the software. The first change in the software is to gather more data to make better decisions. To do this I am going to first add the date and outside temperature readings to both the LCD display and the data collected. By knowing these I can correlate the feed times to temperature and see how close a relationship between them exists. Next I would like to total the run time of the auger per minute and correlate that to both outside temperature and fuel usage. Armed with this additional data I can then make various burner modifications and see the differences if any graphically. The data is good now but could be better. As you can see from the data below the software is not working properly now. The derivative portion of the formula is not contributing at all. This needs to be fixed in the software.
The PID control continues to work great, after 3 1/2 days the PID seems to be in good control. The graph shows a bit of variation but within 10 degrees which seems within bounds.
During this time period I used an average of 2.15 bags of pellets per day. At 40 lbs. per bag this is 86 lbs per day or 39.09 kg/day. At a cost of $216/ton. this is $9.28/day. I am hoping to reduce this to less than a dollar with chips but before I do, I intend to implement some more mechanisms to reduce fuel usage. More to come with the new year, Merry Christmas, Happy Holidays everyone.
After tweaking the Kp and making the Ki work in the software the graph speaks for itself. The software is controlling the temperature to the set point of 140°F within a fraction of a degree for the most part. This was the last difficult piece of puzzle. I did not use the PID function in the Arduino language, instead I wrote my own with a large part of the understanding of the code coming from the excellent description by Brett Bueargard who wrote the PID library, as well as assistance from a friend who helped me understand the problem better in a spreadsheet. I now have a burner that works dependably and is modular so that I can make changes and see if I can further improve the efficiency. I now have software which will hold the temperature without worry. I plan to add a proof of fire sensor next for the mechanical part of the project, and add the ability to set the Real Time clock in the software. Onward, ever onward, but for today I think I will have a beer!