ECN Forum Forums Photo Discussion Forums Photos for General Discussion Waste Vegetable Oil Burner

Electrical circuit. The core control of this burner still resides with the original Burner Controller. A variable output peristaltic pump is programmed to start on ignition and injects VO directly into a 'Y' inlet manifold at the gear pump inlet. It receives both VO and diesel oil. The solenoid valve fitted gives a positive VO stop to prevent diesel oil scavenging from the VO supply. Because the peristaltic pump is of positive displacement, the blend ratio is varied simply by changing its speed. Diesel oil is drawn in to make up the burner gear pump's fuel demand, fixed by the gear pump pressure and the nozzle size. Flow settings were obtained and noted in trials. Sequencing is by 230v x 30A relays, breaking into the existing burner controller terminals for the logic as shown. I have used two remote trigger timers for the delay circuits, as these are both accurate and robust. The latching circuit is a simple 2-relay design, which requires a manual intervention in a power outage. Considering the complexity of the operations this is a very simple circuit, but it has a disadvantage. A power outage during a burn would leave a high VO blend in the burner line. I am considering UPS as the perfect solution but the circuit as-built un-latches and needs to be reset if power is lost, giving me the option of a manual flushing procedure. To be honest, I'm not quite sure how to go about choosing a suitable UPS circuit and advice would be welcome. All the burner safety arrangements are retained of course.

The electrical arrangements as built. Labels are gloss photo-paper & were created on the PC. A fourth relay may be seen in the pic at far left, [blue terminals], as I have aleady begun to install a further PTC heater to the fuel line to try raising the fuel temperature and the % VO in the blend.

Schematic fuel supply. VO is pumped wherever possible to avoid mess. The VO tank is a 60 litre plastic drum housed in an insulated box. The VO in the drum is warmed to c. 40-45ºC using four x 15W x 230v lamps, wired in series/parallel for long life, which generate about 30W. This is to avoid fats clogging the VO line. The lamps are mounted on a float riding on the oil surface, bearing a thermostat and a guard grill. The tank is suspended on a weighing scale -it's the fuel gauge. I made a scale disc from photo-paper, marked in litres. VO is drawn from just under the liqid's surface, where it's warmer.

Float shows dimmed bulbs, [one's hiding]. Peristaltic pump, variable, 0.6 - 4.0 litres/hr. 'Santoprene' rubber pump-tubing - warning this rubber is not compatible with diesel oil. A disc thermometer aids setting the stat.