What is the purpose of a two-pipe oil supply system?

The purpose of a two-pipe oil supply system is primarily to eliminate air and the need for bleeding the fuel lines. In this system, one pipe is used to deliver oil to the burner while the other pipe returns unused oil back to the oil tank. This design significantly reduces the chances of air becoming trapped in the fuel line, which can lead to inefficient burner operation or starting difficulties.

In a one-pipe system, air can enter the line, requiring the technician to bleed the line to remove the trapped air before the burner will operate efficiently. The two-pipe system avoids this complication, allowing for a smoother and more reliable operation, as the return line maintains a constant flow of oil and minimizes the potential for air accumulation.

The other options, while related to burner performance, do not address the primary function of the two-pipe system in the context of preventing air issues. Increasing pressure, improving fuel efficiency, and controlling temperature can be influenced by various factors, but they are not the defining purposes of why a two-pipe oil supply system is utilized.