What is a Two-Stage Fuel Unit for Oil Burner?

Steve Garson

I am deciding on a replacement steam boiler (~500 sq ft) and notice that a number of manufacturers have an option of a Two-Stage Fuel Unit, but none of them say anything more.

What is this? Is it worth getting? Since I am making this investment for long term savings, I want to make sure I do it right.

Also, what burner would allow me to use an external air feed versus burning my warm air? Is this worth the money as well? or does the air going up the atmospheric damper nullify the benefit?

Thanks

Ken D.

Two stage

A fuel unit is an oil pump. On an oil burner, this is the device that draws oil from the tank and increases the pressure to 100 psi or more for proper oil atomization and combustion. The pumps come in single and two stage. This refers to the impellers inside the pump. On a single stage pump there is one impeller for both suction and pressure. this is a good choice if there is an above ground tank with the burner below the level of the oil in the tank with a relatively short distance between the burner and the tank. The two stage pump has two impellers, one for suction and one for pressure. This is a good coice for an under ground tank or any application where the oil in the tank is below the level of the burner or a longer oil supply line. The extra suction impeller gives extra vacuum or lift to move the oil. Which is best depends on the particular system. A single stage can be used for a system with an oil level below the burner as long as it is not too far below or too long an oil line run. A two stage can be used for a system with the oil level above the burner, but why go to the extra expense? With the oil above the burner, the weight of the oil will make the oil self feed so there is no need for a high vacuum. Oil level below means that the oil must be drawn out of tank so there must be a higher operating vacuum. Hope this helps.

Steve Garson

Excellent explanation. Thanks!