Good week of progress so far, I have on order the sealant to fix the remaining leaks in the chip boiler and have ordered the circulator pumps for to tie in the solar tank coil and the chip boiler. But to make progress toward completion I have to do more than sit in front of the computer writing about pump sizing and ordering materials. So time to get out the welder and add a good sized drain to the tank and create the ability to rotate the tank to make the sealant process successful. Pictures to follow.
On another note I am having trouble hooking up a 4 line LCD display, primarily because it seems to have different pinouts than a standard LCD and because it has two enable pins, one pin for each two lines. So more research is required on that.
Today my plan is to size the circulator pump from the chip boiler through the manifolds of the existing oil-fired boiler. The formula is: Q = h/(Cp*p*Delta T) Where Q is the heat transfer in Gallons per minute, Cp is the specific heat capacity, a constant based on the fluid, in this case water, p (really rho, I need help figuring out how to add greek letters and subscripts) and an assumed temperature drop or Delta T. Since it is my intention to run the chip boiler at 180°F and set the min temp on the oil burner at 130°F this will give me a 50°F temperature before the temp of the furnace requires it to fire. By leaving myself enough room I am hoping the Arduino controller and good temperature monitoring will preclude the oil boiler from firing. For the formula however I am going to assume a temperature difference of 20°F. So, again assuming a 30,ooo Btu chip boiler, a Cp for water of 1 BTU/Lbm/1°F, p (rho) the density of water, 62.34 lb/cu ft., Delta T=20°F and to convert BTU to gal/min 7.48 Gal/cu ft Therefore Q=30,000(7.48 gal/cu ft)/((1 Btu/lbm/1°F)(62.34 lb H2O/cu ft)(60 min/hr)(20°F)=2.9997 GPM
This formula gives the flow rate and now I need to calculate the pressure drop or head loss. The formula for this is:
HL = k x c x L x (f1.75) Measuring the distance to the proposed location of the chip boiler, I get about 18′ of piping to and from the existing boiler and approx 10 of additional piping in the boiler, assuming 4 elbows. Planning on using either 3/4″ pex tubing or 1/2″ copper. Using Table 1 in the above link either 3/4″ pex or 1/2″ copper will be acceptable for a flow rate of 3 gpm. I would prefer to use the 1/2′ copper since it is a relatively short run and will require less hangers and difficulty doing a nice neat job through the utility room. From Table 2 I see a equivalvent feet of 1.55 for each elbow so 4 x 1.55 ft= 6.2 ft From Table 3, k =.0159, From Table 4 Water at 180°F, c=0.933, finally the flow rate raised to the 1.75 power is 6.83. So the total length is 18+6.2+13=37.2 ft. I calculate a rough head loss of approx. H loss=.0159*37.2*.933*6.83=3.77 ft Use the graph to find the correct pump having the conditions of 3 gpm flow and 3.77 ft of head It looks like a Taco 003 or a Taco 006 pump will work just fine. After some internet research using my normal internet heating component supplier I will probably use a Grundfos UPS 15-58FC, 3 Speed Circulator pump, 1/25 HP, 115 V
The lower manifold shown in the right hand picture is the cold return from the zones. I am planning on adding the hot water from the chip boiler in at this point to prevent the oil-fired burner from starting. This will also increase the heat reservoir by heating the water in the furnace as well. Lastly I plan on adding a 4th zone onto the existing manifolds to take advantage of the existing 2nd heating coil in a solar hot water tank I have separately heated by solar evacuated tubes. This will give additional options for the Arduino to dump heat.
Hi! I decided to write a blog about the fun things I like to do and how it I like to apply those things to my life. I believe a balance is important, I feel it when I don’t have enough of something, exercise, money, sleep you name it. My goal is to do something about all of those things and more with a welder, an Arduino application and a sense of humor. My latest project is a homemade chip boiler that can burn either wood chips or pellets. The plan is simple, develop a boiler to heat the entire house on the cheap. The brains of the system is to be a Arduino microcomputer to control the boiler and the rest of the house in parallel with the existing oil fired boiler.
So the project is really split into two parts, the welding and design of the boiler and the control of the existing system and new boiler. The chip boiler is a continuous burn unit probably producing 20-30k BTU. Initial tests indicated 20-30k, I did these tests in the open air by weighing a pan of water and timing the time to boil. This was a very crude method so the prototype boiler may yield different results. The existing oil fired boiler is rated at 130,000 BTU. So to get the two systems to work together will require a different paradigm, one requiring the circulator pumps to work more intermittently and often .
But enough about the control theory for today, The prototype boiler is 90% welded up and has been tested for leaks. The boiler was started from an over the road truck’s fuel tank. The internal seams were never intended to be water tight and I am having trouble with welding up the all the internal weeps. The tank under my house’s water pressure of about 45 psi weeps, I am intending to call and get some information on tank sealing paints today. After a brief internet search I have seen several sealants that are intended to work with gas tanks for car restoration. I plan to call and see if they will work with a water application If this seems possible and good I plan to move onto the Arduino control application since I will no doubt be waiting a day or two for the materials to arrive and then apply the materials to the tank and wait the appropriate drying time. Please feel free to weigh in on any suggestions on sealing the tank.