Ratiotrol valves are accurate and used for automatic control proportioning of oil and air flow. Ratiotrol valves maintains the balance between fuel and combustion air for complete combustion in burner. It is used to control burner from high-fire to low-fire and vise versa i.e., as combustion air is turned up or down, the Ratiotrol controls the oil to flow in proportion. Ratiotrols are available in two sizes.